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Topic 6 Human Physiology (Note Vaccination and antibody production moved from unit 11 to unit 6)- Red text indicates the content of option D (Purple HL Opt D) Yellow is common material

Objectives

Expected outcomes o Required content

1. Describe the need for the ingestion of materials in the human diet

State with examples why some food substance s need to be ingested whilst others do not

Some nutrients cannot be synthesized by the human body and therefore need to be ingested as part of the human diet.

Certain amino acids and fatty acids are considered as being essential- meaning that they cannot be synthesized by the body. For example, the amino acid phenylalanine is an essential component of the diet whereas tyrosine can be synthesized with the help of enzymes (phenylalanine hydroxylase) from phenylalanine

Lack of essential amino acids in the diet means that certain proteins cannot be manufactured by the body

Some amino acids are considered to be conditionally essential- this means that at times of stress or illness, the body cannot synthesize them in sufficient quantities and therefore they need to be part of the diet

2. Describe the consequences of malnutrition

Discuss the biological consequences of malnutrition

Malnutrition means bad diet. This can be caused by the lack of certain substances in the diet or by having an imbalance or excess of a substance in the diet. Reasons for malnutrition include poverty, famine, war, overpopulation, large family sizes and poor infrastructure. Starvation leads to the breakdown of body tissue

Anorexia may lead to the breakdown of muscle tissue in the heart Overweight people are more likely to suffer from hypertension and type 11 diabetes A lack of essential amino acids or protein in the diet can lead to conditions such as

Kwashiorkor disease- this is a disease where the body is not able to synthesize certain proteins such as protein pumps, enzymes and antibodies it can lead to the buildup of fluid in the tissues, we call this edema

Dietary minerals are essential chemical elements and are needed in small amounts in order to keep the body functioning, these include calcium for bones, teeth and muscle contraction- deficiency results in muscle cramps and osteoporosis, sodium and potassium are needed for pH balance and nerve transmission- deficiency results in high blood pressure, iodine is needed for the production of haemoglobin and the transport of oxygen- deficiency results in anemia, Zinc is used as a cofactor for enzyme activity- deficiency leads to immunodeficiency, Iodine is needed by the thyroid gland- deficiency can lead to hypothyroidism.

Vitamins are a chemically diverse group of carbon compounds that cannot be synthesized by the human body, they are also needed in sufficient amounts. Vitamins may be water soluble such as vitamins B and C, or fat soluble eg Vitamins A and D. Note that the water-


soluble vitamins may be destroyed by the cooking of food Vitamin A is needed for the formation of visual pigments- deficiency leads to night

blindness. Vitamin D is synthesized by the skin using UV light, it is needed for the absorption of calcium- deficiency in the diet leads to the calcification of soft tissue and diarrhea, Vitamin C (ascorbic acid)is needed for the production of collagen, the maintaining of mucus membranes and a health immune system- deficiency may lead to poor immune system and scurvy

The vitamin C content of a substance may be determined through the titration of DCPIP/ iodine- this is a blue colored liquid that decolorizes in the presence of vitamin C. The vitamin C reduces the DCPIP/Iodine

Some mammals such as rats and mice are able to synthesize vitamin C, this led early scientists to believe incorrectly that scurvy only affected humans

Note that deficiencies of vitamins A and D and the lack of calcium in the diet can affect bone mineralization and this can lead to rickets and osteomalacia

3. Define PKU Discuss the cause and treatment of PKU PKU stands for Phenylketonuria is an inherited genetic condition that is carried autosome 12, the disease is recessive and caused by a base substitution on the gene that is needed to produce the enzyme phenylalanine hydroxylase, therefore the enzyme does not have the correct amino acid sequence when the gene is transcribed and translated.

The result of this mutation is that the amino acid phenylalanine (Phe) cannot be converted to tyrosine (Tyr). The Phe builds up in the brain and competes with other amino acids, this leads to poor mental development

To test for this disorder a doctor will conduct a heel prick test and measure the concentrations of Phe and Tyr

The treatment for this disorder lies in a strictly controlled diet which avoids dairy and the artificial sweetener aspartame

4. Describe the implications of a high cholesterol diet

Explain how HDLs and LDLs impact upon the treatment of cholesterol by the body

A diet that is high in cholesterol can lead to heart disease and atherosclerosis. High blood cholesterol is an indicator of a person being at risk of coronary heart disease

(CHD) High density lipoproteins (HDL) transport cholesterol out of the blood and to the lever

where it is broken down. Low density lipoproteins (LDL) deposit cholesterol in the arteries which leads to increased blood pressure and potential coronary heart disease

Foods high in saturated fats tend to be high in LDLs and therefore increase the risk of CHD5. Calculate the

energy Describe how a calorimeter may be used to determine the energy content of a food

The energy content of a food substance may be determined by the combustion of the food substance. This is often done by combustion in pure oxygen and measuring the


content of food

substance increase in temperature of a known amount of water. The apparatus used for this process is called a calorimeter

6. State the need for digestion

The digestive system is a long tube that connects the mouth to the anus, each organ has a particular function to play in the digestion process. Digestion is essential to life, many substances are too large or too complex to be absorbed in to the blood through the walls of the intestine and therefore will need to be digested- broken-down from their polymers by hydrolysis, using enzymes, into smaller more soluble monomers that can be more easily absorbed in to the blood.

Once absorbed the body is able to reassemble them into a useful form (assimilation). Substances that need to be digested include, proteins in to amino acids, starch in to maltose and glucose and triglycerides (fats and oils) which are broken down into fatty acids and glycerol. Digestion requires the use of enzymes.

7. Identify the key structures that are found in the digestive system

The digestive system consists if the following structures: Mouth, esophagus, stomach, small intestine (duodenum / ilium), large intestine (Colon, caecum), Rectum and anus. The accessory organs of the teeth, tongue, pancreas, gall bladder and the liver also play important roles in the digestive process.

Throughout the digestive system smooth muscle can be found. This muscle consists of circular and longitudinal muscle and is important for the pushing of substances through the esophagus and the intestines through the process of peristalsis. In the mouth food is mechanically broken down by the teeth, it is mixed with saliva containing mucus for lubrication, alpha amylase which starts the breakdown of starch in to maltose, lingual lipase which starts the breakdown of lipids, water, electrolytes and antibacterial compounds.

The food is rolled in to a bolus by the tongue. Food passes through the esophagus by the process of peristalsis.

Once in the stomach the food is churned and mixed with the gastric juices containing hydrochloric acid and pepsin. As food (chyme) leaves the stomach it enters the small intestine (duodenum) where additional enzymes are added along with bicarbonate ions from the pancreas and bile from the gall bladder. The digestive process continues and the products are then absorbed in to the blood through the villi- these are small structures that line the small intestine (ilium).

As the remaining substances enter the large intestine (colon) water is absorbed into the blood. The waste is then stored in the rectum until it is released from the anus (egestion).

8. Identify the State how the endocrine and Appetite is controlled by the hypothalamus; it releases appetite enhancing orexins


factors that control digestion

nervous system regulate digestion and the secretion of digestive juices

(neuropeptide hormones) which stimulate hunger Gastric juice secretion is controlled by three mechanisms: Cephalic stage- the nerves in

our sense organs see taste or smell food and send a signal to our brain (Medulla oblongata) this in turn sends a signal to the stomach vis the Vagus nerve, the stomach then releases gastric juice and the hormone gastrin, which stimulates the further release of gastric juice. The Gastric phase- this is a reflex that takes place when food enters the stomach, stretch receptors and chemo receptors in the stomach wall are activated and signal the Medulla oblongata, this then sends a signal to the stomach via the Vagus nerve to release gastric juice and gastrin. The intestinal phase, as chime (digested food) passes in to the duodenum there are changes in lipid content and pH, this causes a neuron response which signals the Medulla oblongata to reduce the stimulation of the stomach in the production of gastric juice, nerve signals from the duodenum also directly reduced the stomachs activity as do the hormones secretin and cholecystokinin which are released in to the bloodstream

9. Outline the structure of the stomach

Discuss some of the cells and tissues that make up the stomach

Mucus cells - also known as goblet cells, release protective mucus Parietal Cells – secrete hydrochloric acid which begins the digestion of peptides and

activates pepsin Chief Cells – secrete pepsinogen the inactive form of pepsin G cells – secrete the hormone gastrin which increases the secretion of gastric juice Secretion of gastric juice is accelerated by the presence of peptides in the stomach

10. Discuss the need for hydrochloric acid to be present in gastric juice

Describe the role of hydrochloric acid in the stomach

Hydrochloric acid secreted by the parietal cells in the stomach wall is important in the defence against invading microbes, it is important in the conversion of pepsinogen to pepsin and is also needed for some hydrolysis reactions

11. Discuss the serendipitous work of William Beaumont on digestion

Discuss how William Beaumont observed the process of gastric juice digestion by looking at an open gunshot wound

William Beaumont was an army physician who in 1822 observed the effects that gastric juice had on a man that had accidently been shot in the stomach. Over the time that Beaumont cared for the victim, he noticed that muscle tissue had fused with the tissue from the stomach. This also left a hole in the man’s stomach allowing Beaumont to access the gastric juice. Over a period of time Beaumont would experiment on the patient to observe the effect of gastric juice on the digestion of different food substances that would be placed in to the stomach of the patient. These experiments were key in our understanding of the process of digestion and the function of gastric juice.


12. Discuss the action of proton pump inhibitors in the regulation of stomach acid production

Discuss why a person may have the need to control the production of stomach acid.

In the event that a person suffers from a stomach ulcer or from acid reflux, they may need to regulate the production of stomach acid. This can be done by the use of proton pump inhibitors (PPI). This medication serves the purpose of blocking the enzymes that are needed to produce and secrete the acid in the parietal cells.

13. Discuss the actions of Helicobacter pylori in the stomach

Explain how certain bacteria are able to survive in the stomach

Helicobacter pylori is a bacterial infection that attacks the stomach wall causing a stomach ulcer. This bacterium is adapted to survive inside the stomach as it produces urea as a metabolic bi-product, it is also able to produce the enzyme urease which hydrolyses urea in to ammonia, this is an alkali which forms a protective neutralizing microenvironment around the bacteria

14. State the importance of circular and longitudinal muscle in the small intestine

Outline the structure of the digestive system and identify areas where smooth muscle is located

Discuss the role of circular and longitudinal muscle in the digestive system

Suggest how the contraction of the smooth muscle in the digestive system is regulated

Identify different digestive tissues from microscope images

Peristalsis is the wavelike movement caused by the contraction and relaxation of involuntary muscle. This occurs in the esophagus and throughout the digestive system. The esophagus is made up from an outer layer of longitudinal muscle and an inner layer of circular muscle. When we swallow the longitudinal muscle located in front of the bolus contracts and increases the diameter of the lumen in the esophagus. This provides space for the bolus to move in to. The circular muscle behind the bolus contracts and pushes the bolus along. This muscular contraction is regulated by neurons in the enteric/intrinsic nervous system which makes up part of the autonomic nervous system.

15. State the role that the pancreas plays in digestion

Identify the location of the pancreas

Discuss the role of the pancreas in the body and in digestion

Discuss the formation and secretion of the pancreatic juices

The pancreas is a small organ located behind the stomach. It plays a very important role in digestion through the production of pancreatic juices. These juices contain the enzymes amylase, lipase and trypsin (protease), it also produces elastase which also breaks down proteins, and it also contains bicarbonate ions needed to help neutralize the stomach acid as it enters the small intestine. The pancreatic juice is released in to the duodenum through the pancreatic duct. The release of the pancreatic juice is regulate d by the hormone secretin which is released by cells located in the duodenum.

Glands that secrete digestive juices and enzymes in to the lumen of the gut through a duct are referred to as exocrine glands an example would be the pancreas, we need to be able to recognize the components of an exocrine gland as seen under the electron


microscope. Acini are sac like cavities in the gland surrounded by secretory cells, the secretory cells have tight junctions between them in order to prevent leakage, these are formed from protein complexes that form between the cells

These secretory cells will also have many RER, Golgi apparatus and mitochondria, they will also have microvilli on the cell membrane.

Note that digestive exocrine glands also include salivary glands, gastric glands Other exocrine glands that are not involved in digestion include the sweat glands and

sebaceous glands


16. State the role played by enzymes in digestion

Identify the key enzymes involved in digestion

State the site of production and the site of action for digestive enzymes

Identify the optimum conditions for digestive enzymes

Various enzymes are released into the digestive system to aide with digestion. These include:

Enzyme pH Source Substrate Product α amylase 7 Salivary

glands starch Maltose

pepsin 2 Stomach (chief

cells)

Protein Short peptide chains

pancreatic amylase

7 pancreas amylose Maltose

Trypsin 7 pancreas protein Amino acids

Pancreatic lipase

7 pancreas Triglycerides Fatty acids, glycerol

Elastase 7 pancreas proteins Amino acids

Nuclease 7 Jejunum Nucleotides Degraded nucleotides

Dextrinase 7 Small intestine

Starch Maltose

Maltase 7 Small intestine

Maltose Glucose

17. Describe the structure of the small intestine

The small intestine is made up of three parts, these are the duodenum, jejunum and the ilium. If a cross section of the small intestine is viewed under the microscope we will see 4 distinctive layers.

On the inner surface is the mucosa (containing villi), followed by a layer of connective tissue (submucosa), a thick layer of circular muscle surrounds the submucosa followed by a thin layer of longitudinal muscle. On the outside of the intestine is a protective layer called the serosa. Intestinal glands are embedded in the mucosa.

18. Explain the role played by

Identify the function and location of the villi

Villi are thin small structures (one layer thick) located in the jejunum and the ilium. They are small protrusions with a large SA/Vol ratio, they are responsible for the absorption of


the villi in the absorption of digested material

Sketch and describe the basic structure of the villus

Discuss the role of microvilli Identify the structure of a villus

from a microscope image

digested material. Each villus is folded to form microvilli- structures which increase the surface area of the small intestine many times over.

Each villus is formed from a single layer of epithelial cells which reduces the distance for molecules to diffuse. Villi contain a lacteal, which is part of the lymph system, capillaries are found close to the surface of the villi and are connected to a rich blood supply. Some substances such as lipids are absorbed by the lacteal others such as glucose and amino acids are absorbed into the blood (capillaries).

The villi have protein channels to allow facilitated diffusion and carrier proteins for active transport, they also contain many mitochondria to produce the ATP needed for active transport. Tight junctions between cells assist with the controlling of absorption, the capillary network reduce the distance needed for the diffusion of the nutrients. Pinocytosis is also utilized by the cells of the villi. (you should be able to recognize and label an electron micrograph of a villus)

19. Explain how different nutrients and minerals are absorbed through different methods of membrane transport

Discuss the processes involved in the absorption of nutrients by the villi

Identify the method of absorption for digested products

Discuss the role of the lymph system in the absorption of fatty acids

Various methods of absorption are used by the digestive system to absorb nutrients. Fatty acids are non-polar and can pass directly through the plasma membrane of the epithelial cells that line the villi (simple diffusion). Other substances such as fructose and water soluble vitamins are hydrophilic and therefore pass through protein channels through the process of facilitated diffusion. Glucose, amino acids and mineral ions need to be transported against their concentration gradient through the process of active transport. In breast feeding babies antibodies from the mother’s milk can be absorbed through the process of endocytosis. The absorbed materials will pass in to the capillaries and the bloodstream, whereas fatty acids will pass into the lacteal.

Substances that are not absorbed during the process of digestion are passed out of the alimentary canal through the process of egestion.

20. Produce and describe the action of a dialysis model gut

Dialysis tubing is cellulose tubing and is used to model absorption in the small intestine. A mixture of starch and glucose is placed in to the tubing and it is sealed and then placed into a beaker of water. The smaller glucose molecules can pass through the small holes in the4 tubing wall, starch is too large to pass through and first must be digested through the addition of amylase.

21. Discuss the economic applications of hydrolytic enzymes

A hydrolytic enzyme is an enzyme that catalyzes the hydrolysis of a chemical bond. Over 75% of industrial enzymes are hydrolytic, carbohydrases, lipases and proteases have a large economic value and are used in industrial processes such as the production of detergents, the paper industry, textiles.


22. Discuss the structure of the stomach

The stomach is a muscular bag that mixes the digesting food with gastric juice. Gastric juice contains mucus produced by the foveolar cells found in the gastric pits of the stomach wall. Chief cells produce the enzyme pepsin in an inactive form pepsinogen this is then activated by the presence of hydrochloric acid released by the parietal cells. The hydrochloric acid also kills bacteria which may have entered the stomach. The release of this gastric juice is controlled by the hormone gastrin, which is released by cells in the stomach and intestine.

23. Describe the action of endopeptidase

Endopeptidase is an enzyme that breaks down proteins by breaking peptide bonds between non-terminal amino acids. These enzymes are produced by the stomach (pepsin) and by the pancreas 9trypsin), they are very effective enzymes and therefore must be released in an inactive form (trypsinogen, pepsinogen). Pepsinogen is produced by the chief cells. It is activated by the release of hydrochloric acid from the parietal cells. Mucus protects the wall of the stomach from the effects of the hydrochloric acid and the pepsin.

24. Discuss why some substances are digested into their monomers, however cellulose remains in tact

Larger insoluble molecules need to be digested into smaller soluble molecules that can be absorbed in to the blood. Starch is made from alpha glucose and is digested by salivary and pancreatic amylase. Cellulose is formed from beta glucose and humans do not possess the necessary enzymes to break the beta acetyl linkage. Some animals are able to digest cellulose, but must rely upon bacterial in their intestine to release the necessary cellulose enzymes. Nonetheless cellulose is still an important part of the human diet as it forms fiber- needed for a healthy digestive system.

Fiber is indigestible material that passes through the intestine, the rate at which materials pass through the gut is directly linked to the content of fiber in the intestine. Low fiber intake may cause constipation and has been linked to bowel cancer

Cholera is caused by the bacterium Vibrio cholerae which is enters the body through contaminated food and water. The bacteria multiplies whilst in the intestine, the bacteria release toxins that are absorbed by the cells lining the intestine, these cells are then unable to absorb water, resulting in diarrhea and excessive water loss. Cholera infections can be fatal if not treated, treatment includes a dose of rehydration salts and antibiotics.

25. Discuss the role of the liver and the products of digestion

The liver also plays an important part in the digestive process through the production of bile. Bile is a yellow/green pigment that is produced by the liver and stored in the gall bladder. Bile contains bile salts, phospholipids and emulsifying agents, it also contains cholesterol, bile salts and bile pigments. Bile is produced by hepatocytes- cells in the liver. When needed it is secreted into the duodenum through the common bile duct. Bile contains bile salts which coats lipids and causes them to breakdown into smaller droplets


with a large surface area, this process is called emulsification. This allows the pancreatic lipase to breakdown the lipids ion to fatty acids and glycerol. The hormones CCK and secretin released from cells in the intestine stimulate the addition of bicarbonate ions and the release of bile from the gall bladder

26. Discuss how the liver deals with excess cholesterol

Describe the metabolic pathway through which excess cholesterol is converted to bile salts by the liver

Excess cholesterol is biosynthesized to produce bile salts, in the liver, these bile salts are amphipathic (has both hydrophilic and hydrophobic parts. The bile salts act as a detergent and aide the breakdown of lipids

Bile salts can be reabsorbed by the intestine and recycled, they are carried back to the liver with the help of albumin in the blood

Fiber is able to absorb the cholesterol and prevent the reabsorption of the bile salts, so a high fiber diet helps to lower cholesterol levels in the blood, bile salt synthesis is the bodies main way to excrete cholesterol from the body

27. Discuss the process of assimilation and the role played by the liver

Linking small intestine to the liver is the hepatic portal vein, digested products that have been absorbed into the blood will pass through this vein, this allows the liver to intercept blood from the gut and regulated the nutrient levels

28. Describe the general function of the liver

The hepatocytes will convert glucose to the insoluble molecule glycogen and vice versa Removes the amine group from the amino acids (deamination) Assimilates fatty acids forming lipoproteins, cholesterol and phospholipids Stores vitamin A, D and Iron in hepatocytes

29. Discuss the role played by the liver in the removal of toxins from the blood

Describe the role played by the liver and the tissues within in order to remove toxins from the blood and methods used to detoxify them

The liver has a key role in the removal of both metabolic and ingested it is able to detoxify them by converting them to less harmful products

Hydrogen peroxide- byproduct of metabolism broken down by catalase into oxygen and water

Alcohol- oxidized by ADH and ALDH and converted in to aldehydes and acetate Ammonia, the product of deamination- broken-down into urea

30. Describe the breakdown of erythrocytes and the role

Produce a flow chart to show the breakdown of haemoglobin

The components of the red blood cells (erythrocytes) are recycled by the liver in order to conserve the body’s resources. This is done in the following way

As red blood cells reach the end of their life cycle they rupture, macrophages called Kupffer cells located in in the liver engulf the components of the RBCs, the heme group is


played by the liver in this

separated from the globin, the globin is then broken-down into amino acids which are released in to the blood, the heme is reduced with the help of the enzyme heme oxygenase and converted in to the chemical biliverdin, the iron is removed and is then released in to the blood and transferred to the spleen or liver tissue for storage or to the bone marrow to be used in the production of new RBCs, transferrin is a protein in the blood that is responsible for the transport of iron. Biliverdin this is then reduced by biliverdin reductase to form Bilirubin, this is released in to the blood and carried by the blood protein albumin to the liver where it is conjugated (glucuronic acid is added to make it soluble) it is then released from the liver in to the intestine as part of the bile. Bacteria in the intestine produce derivatives of the bilirubin- this gives the feces its brown color

31. Discuss the role of hepatocytes in the liver

Describe the role played by hepatocytes in the absorption of nutrients and the production of plasma proteins

Hepatocytes are epithelial cells located in the liver, they are responsible for the absorption and storage of glucose, vitamin D, Vitamin A and iron

Bile is produced by the hepatocytes and released in to small canals called canaliculi, it then passes through to larger ducts on its way to the gall bladder and is then released in to the small intestine via the bile duct

Hepatocytes use their endoplasmic reticulum and Golgi apparatus to produce plasma proteins including albumin (transport protein) globulins (for transport and antibody formation) and fibrinogen (forms fibrin for clotting)

Hepatocytes also produce cholesterol for the synthesis of bile salts32. Describe the

dual blood supply of the liver

Describe the route taken by blood as it enters and leaves the liver. Compare the structures of capillaries and sinusoids

The liver receives oxygenated blood from the hepatic artery, and returns the deoxygenated blood through the hepatic vein

The hepatic portal vein (HPV) links the small intestine to the liver in order that the blood containing digested material may be intercepted, the HPV is similar in structure to a vein but is not considered as a ‘true’ vein. The HPV splits in to smaller vessels called sinusoids. The hepatic artery splits off in to smaller capillaries which supply the liver with oxygen and merge with the sinusoids


33. Discuss the health problems that affect the liver

Describe the conditions of cirrhosis and jaundice

Jaundice is a disease that is caused by the buildup of bilirubin it the blood, this leads to yellowing of the eyes and skin, the disease may be caused by hepatitis, gall stones, bile duct disease or cancer

Cirrhosis of the liver may be brought on by long term alcohol abuse, this results in the formation of scar tissue in the liver and the depositing of fat

34. Describe pulmonary and systemic circulation

Describe the need for a transport system in multicellular organisms

Identify the need for a double circulatory system in humans

Discuss the difference between a single circulatory system and a dual circulatory system

Multi cellular organisms cannot rely on simple diffusion alone to provide oxygen to all cells, they therefore require a circulator system. Humans have a dual (double) closed circulatory system, this means that one side of the heart (right) pumps blood to the lungs (pulmonary system) whilst the other side of the heart (left) pumps blood around the body (systemic system), in a double circulatory system, blood flows from the heart to the lungs, back to the heart and then around . Some organisms such as fish have a single closed circulatory system, blood flows from the heart to the gills and then around the body and then back to the heart. Advantages of a double circulatory system is that there is an increased rate of blood flow to the tissues and that the blood going to the lungs can be at a lower pressure. By ‘closed’ we mean that the blood does not leave the circulatory system. Some organisms such as arthropods have an open circulatory system where blood is pumped by the heart into the tissues, it then diffuses back into the circulatory system and returns to the heart.


35. Identify the parts of the heart

Sketch a diagram of the heart and discuss the functions of each part

Compare the right and left sides of the heart

The heart is made up of 4 chambers that are separated by valves- these valves open to allow blood to pass through and close to prevent backflow thus allowing unidirectional blood flow. Blood is returned to the heart via the superior and anterior vena cava, it then enters the right atrium, passing through the tricuspid valve in to the right ventricle. Blood is then pumped to the lungs through the pulmonary valve in to the pulmonary artery. It returns in the pulmonary vein and enters the left atrium it is then pumped through the bicuspid (mitral) valve in to the left ventricle and then through the aortic valve in to the aorta. The tricuspid and bicuspid valves are called the atrioventricular valves and the pulmonary and aortic valves are the semilunar valves.

These valves ensure that blood flow is unidirectional. /the atria walls are thinner than the ventricular wall as they only pump the blood over a short distance. The left ventricle must pump the blood around the body at high pressure, so needs to have a thicker muscular wall than the right ventricle which pumps blood at lower pressure to the lungs.

36. Explain the role played by arteries in the transport of the bloodDescribe the structure of arteriesLink the arterial muscle and elastic tissue to the maintenance of pressure between pump cyclesState the role of veins in the transport of blood

Describe the function of arteries veins an capillaries in the transport of blood

Sketch the structure of an artery and identify the parts and functions

Explain the need for elastic and muscle tissue in the walls of the arteries

Sketch the structure of a vein and identify the key parts and functions

Discuss the role of valves in the regulation of blood flow

Explain the process by which blood is returned to the heart in the vein

Arteries carry blood away from the heart and veins towards the heart. Arteries from smaller arterioles, which connect to capillaries, these allow the exchange of substances between the blood and the tissues. The blood enters the venules which join to form the veins. An artery is made up of a relatively narrow lumen which keeps blood at high pressure.

The arteries have a thin layer of endothelial cells surrounded by a thick wall containing a layer of elastic tissue (elastin) and collagen which withstand high pressure and prevents leaking. A thick layer of smooth muscle surrounds the elastin these maintains the pressure of the blood between pump cycles of the heart and also help to distribute the blood- the elastin is stretched and then recoils the smooth muscle contracts and relaxes to control the rate of blood flow, a protective fibrous layer and be found on the outside surrounded by a layer of epithelial cells.

The veins carry blood back to the heart at low pressure. They have a larger lumen which reduces resistance to blood flow, a thin layer of epithelial cells, a thin wall containing a thin layer of elastin and a thin layer of smooth muscle the vein also has a fibrous layer and an outer layer of epithelial cells, valves can also be found in the vein these prevent backflow and therefore control the direction of blood flow, they also help to move the blood along the vein, this is helped further through the contraction of skeletal muscle.

In these two structures we refer to the inner layer as the tunica intima, the muscle layer is the tunica media and the fibrous outer layer is the tunica externa.

Capillaries are small vessels that link arterioles and venules they have a very narrow


State how valves in the veins prevent backflow

lumen (10um wide) that only allows one blood cell to pass at a time. They have a very thin wall that is made from a single layer of endothelial cells reducing the distance needed for diffusion, this combined with the presence of pores in the walls allows for efficient gas exchange and exchange of useful materials, they have a large surface area to volume ratio. Phagocytes also squeeze through the capillary pores in order to reach the site of infection.

37. Discuss the composition of blood tissue

Blood is made up of the following plasma/water; dissolved gases / CO2 / O2; erythrocytes / red blood cells; leucocytes / white blood cells; lymphocytes and phagocytes; platelets; hormones amino acids / albumin / antibodies; salts / minerals / ions other named solute in plasma apart from glucose, urea and plasma proteins;

38. Explain how substances are exchanged between blood and tissues as blood flows through the capillaries

Discuss the need for substances to be transferred between the blood and the tissues and vice versa

Discuss the process by which plasma leaves the blood to form tissue fluid and lymph

Identify health problems linked to the buildup of tissue fluid

Nutrients such as glucose and amino acids along with oxygen need to be able to pass from the blood to the tissues, equally waste products such as CO2 and urea need to pass into the blood from their tissues.

Much of this exchange relies upon the process of diffusion and for this to occur a liquid medium is needed. Plasma under high pressure is forced out of the capillaries at the arteriole end and in to the tissues where it is referred to as tissue fluid. This fluid carries the useful nutrients out of the blood through the process of ultrafiltration. At the venule end the pressure of the blood is much lower and the tissue fluid has a higher water potential than the blood. 95% of the tissue fluid moves back in to the blood. As it does it carries the waste products with it.

The other 5% of the tissue fluid will move in to the lymph system, which collects fluid to form lymph. The lymph system will return the fluid to the blood at various lymphatic ducts which can be found in the body. Lymph is circulated in the body the through the process of muscle contraction, lymph vessels also have valves to control the direction of flow.

If people are unable to move sufficiently or suffer from Kwashiorkor disease- a disease where the blood has a low amino acid level and therefore a high water potential, then the fluid can build up in the legs, this can cause damage to tissues and organs along with circulation problems.

39. Explain the role played by the SA node in the initiation of the

Explain the generation of a heart contraction

Discuss the pathway taken by blood through the heart during the cardiac cycle

The structure of the cardiac muscle allows for the propagation of nerve signals through the heart to stimulate contraction (systole) and relaxation (diastole) of the heart muscle

The Sino-atrial (SA) node, also called the pacemaker is a myogenic (impulses originate in the muscle cells which contract without the need for nerve signals) region of the heart located in the wall of the right atrium. Signals from the SA node pass across the atria


heartbeatDescribe how the electrical signal that originates from the SA node propagates through the heart

stimulating contraction (atrial systole) the impulse also travels to the atrio-ventricular node (AV) located at the base of the right atrium, which delays the impulse slightly (0.1 sec) to ensure that the atrial systole has completed before the ventricular systole begins.

The signal then travels along the ventricular bundle branches (bundle of His) to the nerves called the Purkinje fibers. This stimulates the contraction of the ventricles from the bottom up. Note that the electric signal cannot pass directly from the atria to the ventricles

As the heart contracts there are various electrical and pressure changes that take place in the heart, this can be seen on an ECG. As the signal travels across the heart the muscle cells depolarize this means that they become more permeable to sodium ions which changes the electrical current across the cell membrane, this causes an action potential which stimulates the muscles to contract. The ions will then be pumped out of the cell and it repolarizes, this constant polarization and depolarization is referred to as auto-rhythmicity.

The cardiac cells have a Y shape branches and the cells have interconnecting cytoplasm (gap junctions), they also have intercalated discs which stabilize the cell structure, this allows for a faster depolarization wave and the cells contract as if they are one cell. When the cells are repolarizing they will initially become hyperpolarized- this means that the charge across the membrane is more negative that when polarized eventually they will return to their resting potential. Note intercalated discs are formed when two myocytes are close together forming a gap junction, they can be seen under the microscope as irregularly shaped dark bands and have the function of holding the cells in position and allowing for the transmission of the impulse (they are located in the arms of the ‘Y shape’)

Describe the cardiac cycle


0.10 0.2 0.3 0.4 0.5 0.6 0.7 0.8

0.10 0.2 0.3 0.4 0.5 0.6 0.7 0.8

Atria l Systole

atria contractblood enters ventricles

Ventricular Systo le

ventricles contractblood enters arteries

Diastole

atria and ventricals both relaxblood enters atria and ventricles

Pres

sure

(kPa

)

ECG

PCG

Nam e

Even

ts

Time (s)

0

5

10

15

20

ventrical

a trium

artery artery

atrium

ventricalatrioventricular

valves closeatrioventricular

valves open

sem ilunarvalves close

sem ilunarvalves open

P wave- shows atrial systole

QRS- shows ventricular systole

T- Shows ventricular diastole


40. Describe the role of the autonomic nervous system in relation to heartbeatDescribe the action of epinephrine (adrenaline) on the heart

Discuss the factors that influence the heart rate

Discuss the action of the autonomic nervous system on heart rate including the role of the medulla

The heart rate is controlled by the autonomic nervous system and by the endocrine system. The medulla located in the brain stem, is the part of the brain that is responsible for controlling the heartbeat by sending nerve impulses to the heart.

Pressure receptors (baroreceptors) in the arteries (aorta and carotid) and chemo-receptors in the carotid arteries detect changes in the blood pressure and acidity, they are linked via nerve endings to the cardiac control centre in the medulla.

If the blood pressure is too high, a correction signal is sent from the medulla to the SA node via the Vagus nerve (parasympathetic system) which at the SA node will release the neurotransmitter acetylcholine to slow the heart rate. If the pressure is too low the medulla will send a correction signal via the cardiac nerve to the SA node. The cardiac nerve will release noradrenaline/Norepinephrine to speed the heart rate up.

41. Discuss the action of epinephrine/adrenaline and noradrenaline on the heart rate

Discuss the effect of caffeine on heart rate

Adrenaline/epinephrine speeds up heart rate, it is released by the adrenal gland located on top of the kidneys, and this hormone is released at times of stress to prepare the body for the ‘fight or flight’ response.

This hormone stimulates androgenic nerve cells in the heart tissue, this intern activates the ‘G protein’, with the G protein stimulates the production of cAMP from ATP using the enzyme AC, the cAMP activates PKA a kinase enzyme which stimulate the pacemaker cells to absorb calcium ions (Ca2+) causing an increased heart rate. The cAMP is then broken down by the enzyme cAMP PDE.

Caffeine competes for the active site on cAMP PDE preventing the cAMP form being broken down, (competitive inhibition) this results in an elevated heart rate.

42. Discuss the work of William Harvey in overturning theories developed by Galen on the movement of blood in the body

William Harvey discovered the flow of blood around the body. He demonstrated that valves in the veins and the heart controlled the direction of blood flow (unidirectional), He showed that blood was not consumed by the body but actually circulated through it, he predicted the existence of capillaries and falsified the theories put forward by Galen who proposed in the second century that the liver made blood for the veins and that the heart made blood for the arteries- Galen’s theory was accepted until 1628.


43. How has our understanding of the heart helped with the development of modern surgery techniques

As our understanding of the circulatory system has increased the number of corrective surgery procedures have also. There were significant developments in heart surgery during the second world war, Dwight Harken performed numerous successful surgeries to remove shrapnel from the hearts of soldiers, prior to this it was believed that the heart was too complex to operate on. This led to further rapid advances in surgical techniques including open heart surgery and keyhole surgery.

44. Discuss the causes, problems and solutions of cardiovascular disease

Cardiovascular problems can be caused by numerous factors, such as bad diet (high fat) and genetic predisposition. Other lifestyle choices such as smoking and drinking alcohol can also influence the health of the heart. Atherosclerosis is the buildup of plaque on the surface of the artery due to high cholesterol. Improved low fat diet and exercise along with activities to control stress such as yoga can reduce the effects of heart disease,

45. Discuss the causes of occlusion of the coronary arteries

Coronary occlusion is a blockage of the coronary artery. This can result in a blockage or a clot/thrombosis which can lead to a coronary heart disease and a heart attack. Angina is due to a partial blockage of the coronary artery. If this occurs a coronary bypass may be necessary, for less severe cases medication such as Glyceryl trinitrate (nitrates) which widens the artery, beta blockers which slow the heart rate or calcium channel blockers which relax the smooth muscle in the arteries. Diet and exercise can also help to reduce the causes of coronary heart disease.

46. Describe

thrombosis and hypertension

Thrombosis is the coagulation or clotting of blood in the blood vessels, people who do not move for long periods of time may result in having thrombosis in their veins due to the slow movement of blood through the veins

47. Describe ways

in which to monitor heat rate

A doctor may use a stethoscope to monitor the heart rate, this allows the doctor to see if there are any irregularities in the heart beat including any additional heart sounds which may indicate valve problems

The radial artery in the wrist, carotid artery in the neck and femoral artery in the leg are all good locations to measure pulse rate

48. Discuss the Systole is the contraction of the heart muscle and diastole is the relaxation. As the signal


pressure changes that occur during the cardiac cycle

passes from the SA node across the atria, the atria contract (atrial systole). The pressure insider the atria increase above that of the ventricles and blood is forced out of the atria and into the ventricles through the atrioventricular valves. The atria then relax (atrial diastole) and the ventricles contract (ventricular systole), the pressure of the ventricles is greater than that of the aorta or of the pulmonary artery and blood is forced through the semilunar valves. We can describe these changes using the following:

Atrial systole- contraction of the atria Isovolumetric contraction- pressure in the atria falls and increases in the ventricles

closing the atrioventricular valves (Lub sound) Rapid ejection- blood is forced out of the ventricles in to the aorta and pulmonary artery Reduced ejection- the ventricles are at lower pressure but still able to force blood out Isovolumetric relaxation- pressure falls in the ventricles causing the semi lunar valves to

close (Dub sound) Rapid ventricular filling- ventricles relax and pressure falls further causing the AV valves to

open an fill with blood from the atria (passive process) Diastasis- the passive filling of blood slows and the cycle repeats

49. Describe the use of artificial pacemakers

In the event that a person has a defective SA node or is unable to generate or regulate their heart beat, an artificial pacemaker may be inserted in to the SA node. This artificially regulates the heart rate or corrects the heart rate if it becomes irregular.

50. Describe fibrillation

Fibrillation is the irregular and uncoordinated contraction of the heart muscle. The event that a person enters a state of fibrillation a device known as a defibrillator may be used, this fires an electrical shock across the heart that resets the rhythm. Portable defibrillators known as AEDs are now available in many public places.

51. Discuss the implications and causes of high blood pressure (hypertension)

Hypertension is simply abnormally high blood pressure. It may be caused by obesity, high LDL intake, high trans-fat intake, high salt diet, alcohol, smoking and caffeine consumption. Other factors include genetic predisposition, age, gender and ethnicity.

Consequences of hypertension include, heart disease, kidney damage or stroke Treatment includes, exercise, lot fat and low salt diets, medication


6.3 Defense against infectious disease

Objectives Expected outcomes o Description52. Define the role

of the skin and the mucous membranes as the primary defense against pathogens

Identify the different components of human skin

Stet the role of the skin, in terms of sensitivity, temperature regulation and forming a protective barrier

Discuss methods used by pathogen to enter the body through the skin

The skin is the organ that covers the human body. It acts as a defense mechanism against harmful pathogens and separates our internal environment from our external environment.

The skin is made from a number of layers. The epidermis is a thin layer of dead cells which are tightly welded together and act as a defense barrier. They are constantly replaced by cells from the dermis which lies below the epidermis. The dermis is a network of woven collagen fibers which provide structure and flexibility, you also find capillaries in this layer. The lower layer of the skin is the hypodermis, here we can find sweat glands, hair follicles and fat storage tissue.

53. Explain how cuts in the skin are sealed through the action of blood clotting

State what is meant by blood clotting

Name the factors that are involved in blood clotting

When our skin or cells are damaged it is important that the cut is sealed to prevent the entry of pathogens and the loss of blood. This is achieved by the clotting of blood. Blood clotting is also known as coagulation and is essential to prevent excessive bleeding. Platelets (small cell fragments in the blood produced by the budding of megakaryocytes in the bone marrow) and thrombin (inactive as prothrombin until needed) are key players in the clotting process. They form a mesh to prevent further loss of blood cells. If a clot forms inside the body we call it thrombosis- this can be deadly as it cuts off the blood supply to vital organs.

54. Describe how clotting factors are released form the

Explain the process of blood clotting and how platelets release clotting factors

Identify the process of blood

The clotting process (coagulation cascade): When tissue is damaged it causes the platelets in the blood to change shape

and become sticky forming a platelet plug (Extrinsic pathway) Injured tissue and platelets release the clotting factor prothrombin activator


plateletsExplain how the cascade results in the rapid conversion of fibrinogen to fibrin

clotting as a cascade effect Explain the conversion of

prothrombin to thrombin and fibrinogen to fibrin

Discuss deep vein thrombosis and identify the possible effects of unwanted clotting on the coronary artery

Describe hemophilia

and calcium ions (calcium ins need for the activation of clotting factors) (Intrinsic pathway)

Prothrombin activator converts the blood protein prothrombin into thrombin this then converts soluble fibrinogen to insoluble fibrin (Common pathway)

The fibrin forms a mesh over the cut and traps red blood cells and platelets forming a clot

Bleeding stops The mesh hardens and shrinks as new replacement tissue grows The enzyme plasmin (found in blood as plasminogen) is activated to dissolve

the clot (fibrinolysis) The clotting cascade is a series of reactions designed to prevent internal

clotting. If a clot is formed in the veins, we refer to this as deep vein thrombosis. This can be fatal, as it prevents the blood flow to major organs such as the lungs. In the event that a clot forms in the coronary artery, it could lead to cardiac arrest.

Hemophilia (Xh) is a recessive sex-linked inherited disease that causes the lack of clotting factors and therefore blood is unable to clot. This means that if a person cut themselves they will continued to bleed and will need to seek medical help. Sever hemophiliacs can suffer from internal bleeding also.


55. Describe the external and internal defenses against pathogens

The skin along with mucus membranes act as a defensive barrier to prevent the entry of pathogens in to the body, the oils that the skin produces along with tears contain enzymes which destroy pathogens. Mucus traps dirt and bacteria, ciliated cells help to move the bacteria out of the wind pipe. Stomach acid destroys pathogens and urinary flow also adds to the first line of defense, the cough reflex also. These forms of defense along with the humoral immune system are nonspecific and will attack all pathogens we say that they are part of the innate immune system. Once in the body the pathogens are exposed to the active immune system immune system.

Typical exam question and answer- Describe how the body can defend itself against pathogens

56. Define antigens and state that every organism has unique molecules in the surface of its cells

State what is meant by antigen Give examples of substances

that may be classed as an antigen

State that every organism has antigens that are unique molecules in the surface of its

Antigens are anything regarded by the body as being a foreign body that initiates an immune response they are usually protein markers that are found on the surfaces of cells, they may stimulate the production of antibodies as part of an immune response. Antigens are unique to a particular organism. Protein markers are found on all cells, the immune system is able to recognize the antigens as being self (part of a person’s own proteome) or non self (foreign). The part of the antigen to which the antibody attaches is called the epitope.


cells57. Explain that

some pathogens target specific species however other can cross the species barrier

Define pathogen Give examples of pathogen of

the bacterial, virus and fungal variety

Explain that pathogens often target specific species however some able to cross the species barrier

A pathogen is defined as being an organism or virus that causes disease, for example E coli (Bacterium), H5N1 (Virus) and Aspergillus (Fungi), Many pathogens will target a specific species, however some can quite easily cross the species barrier. Pathogens may be spread in sir, water, food, skin contact, body fluids, sexual contact, and blood contact.

An example of a prokaryotic disease is Borrelia burgdorfen which causes Lyme disease. It is transferred by ticks, and symptoms include a red circular rash and flu like symptoms

58. Describe the function of phagocytic white blood cells and explain why their action is considered to be a non-specific response

Draw and label a phagocyte Identify the different

components of a phagocyte and link this to an immune response

Explain why the action of phagocytes are considered to be a non-specific response

Explain the role of macrophages in an immune response

Phagocytes are one category of white blood cell that t are attracted to pathogens, they are nonspecific and work by engulfing pathogens through the process of phagocytosis (a form of endocytosis), this forms a phagosome. Lysosomes inside the cell will fuse with the phagosome and the hydrolytic enzymes will digest the pathogen. Phagocytes are present in the blood, they will concentrate at a point of infection and are able to leave the capillaries and enter the tissues by squeezing through the capillary walls. Lysosomes containing digestive hydrolytic enzymes will fuse with the phagosome and digest the pathogen. The waste products are excreted form the phagocyte through exocytosis. Phagocytes include neutrophils, monocytes, macrophages, mast cells and dendritic cells. Macrophages are deposited in the lymph nodes around the body and are often the first to encounter a pathogen and present the antigen to helper T cells.

59. State that white blood cells release histamine and identify the function of this substance on the bodyState the negative effects of histamine

Outline an immune response Explain the role of histamine in

an immune response State the negative effects of

histamine in an allergic reaction

Explain the action of antihistamines in medication

When pathogens enter the blood they will initiate an immune response, this often starts with the release of histamine from a type of cell called the mast cell which are located in the tissues around the body. Histamine results in inflammation, this results in vasodilation allowing other cells to get to the site of infection and fluid secretions which helps to rid the body of toxins produced by the pathogens. Sometimes histamine can lead to an allergic response, this is caused in response to an allergen which results in the over release of histamine, this can cause skin, nose and throat irritations and swelling. The body naturally produces adrenaline to counter the effects of this, however, a doctor may prescribe antihistamine which block histamine receptors (H1) reducing the effects of histamine.


production in response to allergens

60. Describe how a cell mediated response is initiated

Discuss the role played by antigen presenting cells

Discuss the role of helper T cells

Discuss the action of cytotoxic T cells

In an immune response: Innate barriers such as the skin, mechanical and chemical are breached Mast cells release histamine. Note- there are many different types of T and B

lymphocytes, -lymphocytes are white blood cells that are initially produced and stored in the lymph nodes before migrating to the bone marrow and thymus gland where they mature.

Macrophages engulf the pathogen and present antigens (Antigen Presenting Cells) Major histocompatibility proteins (MHC) found on the membranes of these cells present the antigens/fragment to specific naïve T lymphocytes which bind to the antigen on the APC cells (CD4 helper T cells produced in the thymus gland. the CD4 glycoprotein on the surface of the T cell identifies the antigen)

When the correct T cell has been identified (Clonal selection) the APC will release the cytokine interleukin 1. The naïve/helper T cells are activated and produce interleukin II which activate specific T cells and specific B lymphocyte cells causing them to divide (proliferation by clonal expansion).

The T cells may also bind directly with inactive B lymphocytes cell and activate them.

The T cells differentiate to form Cytotoxic T cells (CD8 cells)- which locate the pathogens and release the chemical perforin which destroys the invading cells through cellular lysis and Memory T cells which remain in the blood in case the antigen is encountered again.

Once activated Naïve B cells will clone and either become memory B cells- in preparation for a secondary encounter with a pathogen, or grow and become antibody producing Plasma cells. The plasma cells proliferate rapidly producing large quantities of the specific antibody (immunoglobulin) which leave the cell by exocytosis and flood the body- the RER and Golgi apparatus is quite extensive in these cells.

There are different types of antibodies (Igs) these include IgM which is important for agglutination, IgG for opsonisation/ neutralization- this is the only

61. Explain how B lymphocytes are activated by T lymphocytesDescribe the proliferation of activate B cells and distinguish plasma cells from memory cells

Explain how T cells activate B cells

Describe the proliferation of active B cells

Describe how some B cells become plasma cells and others become memory cells

62. Identify the function of antibodies and explain how they are produced by plasma cells

State the general function of antibodies (immunoglobulins)

Identify the main types of antibodies and state the properties of each


antibody that can cross the placenta during pregnancy, IgD is found on the surface a B cells, IgE is an anti-parasite, IgA is found in bodily secretions, tears, colostrum etc. Immune responses may be innate (nonspecific) of adaptive/humoral (antibody producing)

If a response generates the production antibodies, we say that it is active immunity

If it antibodies enter the body through injection or breast milk we say that it is passive.

Note that normal body cells infected by a pathogen can also act as an APC, B plasma cells (antibody producing) have a large nucleus and an extensive endoplasmic reticulum network in order to produce sufficient antibodies.

Natural Killer Cells (NKC) target infected cells and tumor cells, they release perforin and cytotoxins for apoptosis (cell destruction).

B cells may fight against more than one antigen at the same time, we describe this as a polyclonal response.

The body may also increase its temperature (fever) in order to denature the enzymes in the bacteria. https://www.youtube.com/watch?v=wYPlc6-nnzU

63. Describe the structure of an antibody

An antibody (immunoglobulin) has a 4 chain structure. It consists of 2 heavy chains and 2 light chains that are held in position by di-sulfide bridges, this provides the antibody with a flexible ‘Y’ shape. Each antibody has a specific variable region and a region that is common to all antibodies. It is the variable region that provides the antigen binding site.

64. Link long term immunity to the persistence of memory cells

Discuss what is meant by long-term immunity

Compare the antibody production of a primary and secondary response

Give examples of disease for which immunity can be developed

Long term immunity means that we have previously been exposed to an antigen and that we have memory B lymphocytes that will be able to produce the necessary antibodies should we encounter the same pathogen again.

Also referred to as a secondary immune response, the memory B cells can proliferate very quickly and therefore can flood the body with the necessary antibodies much faster than the slower primary immune response. Chicken pox is a prime example of this in action.

https://www.youtube.com/watch?v=wYPlc6-nnzU


65. Explain how vaccinations works

Define vaccination Give a brief account of the

history of vaccinations Discuss why there is not a

vaccination for every disease

Vaccines are a form of artificial immunity. The concept of vaccination was first addressed by Edward Jenner in 1796. He took the puss from the sores of a person with cow pox and infected a young boy. He later infected the boy with small pox- a deadly disease. The boy did not fall ill from the small pox due to the fact that the cow pox virus had similar antigens and his immune system, was able to produce the necessary antibodies.

This was the first vaccination and led to the eradication of smallpox from the planet. Now there are many vaccinations, the patient is exposed to weakened or inactive antigens which evoke an immune response and the production of antibodies. The memory B cells will then be able to produce the correct antibodies should the person ever be exposed to the real disease, this will initiate a secondary immune response and will result in the proliferation of the memory cells allowing g rapid antibody production. Thus the process gives a person immunity or resistance to a specific disease.

Some viruses and bacteria evolve quickly or exist in multiple forms and as a result it is difficult to produce a vaccination. Equally some diseases attack our organs and therefore are difficult for the immune system to get to.

The Polio vaccine has also had a great success and technically this disease should have also been eradicated, however resistance of some people to take the vaccine, logistical problems and political ‘red tape’ have limited the success of this vaccination program

66. Describe active immunity as the production of antibodies (specific immunity)

Define active immunity as the production of antibodies (specific immunity)

Define passive immunity Discuss the difference between

natural and artificial immunity Compare and contrast active

and passive immunity, with examples

Active immunity involves the production of antibodies by an organism itself, it is a specific response that targets a specific antigen.

Passive immunity is when the antibodies are acquired by some other means, for example through the placenta IgG passes from mother to fetus in this way, in colostrum (breast milk) or by antibody injection. The body does not produce its own antibodies in this case.

Natural immunity is quite simply when the organism is exposed to an antigen naturally and produces the antibodies as a result, or the organism acquires the antibodies from the mother.

Artificial immunity is when the organism is deliberately exposed to the antigen eg through inoculation with a vaccination.

For example natural immunity may be due to the exposure to a disease such as chickenpox and artificial immunity may be due exposure to the polio vaccine


(Sabin vaccine).

67. Explain the action of antibiotics and state why they are effective against prokaryotes whilst not effecting eukaryotes

Define antibiotic Outline the history of

antibiotics State examples of antibiotics

and identify their action on bacteria

Antibiotics are a group of chemicals derived from microorganisms that can inhibit the growth of bacteria.

Antibiotics were first discovered by Alexander Fleming in 1928 he serendipitously discovered that a fungus growing on a bacterial plate was preventing the growth of bacteria, he had discovered penicillin.

Antibiotics exist in a number of forms a Bactericidal antibiotic prevents the development of the cell wall or the formation of the cellular contents, this group include penicillin and daptomycin. A Bacteriostatic antibiotic stops bacteria from multiplying by interfering with bacterial protein production, DNA replication, or other aspects of bacterial cellular metabolism. Some Bacteriostatic antibiotics are tetracyclines, sulphonamides,

Streptomycin inhibits the translocation step of protein formation by binding to the small subunit of the ribosomal RNA and blocking the metabolic activity.

68. Explain why antibiotics are not effective against virusesExplain with examples how antibiotic resistant bacteria have evolved

Discuss why antibiotics are not effective against viruses

Explain how the overuse of antibiotics has led to antibiotic resistant strains

Explain what action is being taken to fight the growing numbers of antibiotic strains

Antibiotics target the metabolic pathways and are only effective against living pathogens, as viruses are considered to be nonliving and therefore antibiotics have no effect as viruses have no metabolic pathways to block. Note as humans have different cell structures and different metabolic pathways antibiotics do not interfere with human cells.

The overuse of antibiotics has led to the evolution of antibiotic resistant strains eg MRSA. Bacteria have a high reproductive rate and therefore a high rate of random mutation, if an antibiotic resistant strain develops and antibiotics are used this will reduce competition for the resistant bacteria as those sensitive to the antibiotic will be destroyed and they will therefore be able to establish colonies, which may not have happened if antibiotics had not been used.

Over time MRSA has become resistant to multiple antibiotics. To reduce the risk of additional antibiotic strains developing many countries reduce the use of antibiotics by making them only available on prescription.

Other precautions include, not using antibiotics to fight viral infections, not using mild doses of antibiotics over a long period of time, completing fully a course of antibiotics, using a combination of drugs to fight bacteria, discontinue the practice of including antibiotics in animal feed as a preventative measure.


Note that as viruses have no metabolic pathways and few enzymes to block, they use host cells to produce their metabolites, therefore any drug that interferes with virus metabolism would also affect humans.

69. Explain how monoclonal antibodies are produced by hybridoma cellsDiscuss the practical uses of monoclonal antibodies

Discuss the commercial uses of antibodies

Explain how monoclonal antibodies are produced

Discuss the role played by monoclonal antibodies in a pregnancy kit

Antibodies can be produced on a commercial scale through the process of monoclonal antibodies (mAB). A mouse is injected with the epitope (antigen). Antibody producing B cells (plasma cells) are extracted from the spleen of the mouse and fused with melanoma cells (cancer cells to maximize cell division) this forms a hybrid (hybridoma), the hybridoma is cloned in order to produce the antibodies which are then purified before use.

Practical uses of these antibodies include, pregnancy tests (HCG detection) and diagnostic tests in medicine such as the detection of HIV. They can also be used to detect malaria and cardiac enzymes (an indication of a heart attack).

Monoclonal antibodies can also be used to detect blood group and tissue type, Monoclonal antibodies could potentially be used to target cancer cells by attaching cancer treating drugs. They can be used in the treatment of rabies (injection), Ebola and malaria, they can also be used to attack T-cells in order to reduce the chance of tissue rejection after a transplant. Equally the serum (part of the blood containing antibodies) can be extracted from the mouse directly.

70. Would penicillin be allowed today- discuss the work of Florey and Chase test on the safety of penicillin

Inspired by the work of Fleming with penicillin, Florey and Chase set out to develop a pure extract of penicillin, they realized the potential applications of this new ‘wonder drug’ in their test on the safety of the drug they used mice and Guinea pigs, they found the antibiotic was toxic to Guinea pigs but effective on mice. It was then administered to human patients after just one animal test, even though the results and safety concerns were still unclear.

Early samples of penicillin were impure and may have contained toxic contaminants, some of the early patients suffered adverse effects from the drug.

If some of the tests had been done today it is possible that the drug would not be permitted to be used on the human population.

71. Discuss the effects if HIV on the immune system and its

HIV can be transmitted through blood contact and transfusion, through the sharing of infected needles and through sexual intercourse. The virus can also pass across the placenta, be transferred in a blood transfusion and by blood products (clotting factor VIII) which is used to treat hemophiliacs.


transmission, link to a reduction in active lymphocytes and number of antibodies produced. Link also to AIDS

The HIV virus attaches to the CD4 protein found on the surface of T lymphocyte cells, the virus then inserts itself in to the cell and is duplicated many times over. The virus then attacks other T cells.

The reduction in active T cells results in lower antibody production and the increased vulnerability of the person to other pathogens due to a weakened immune system.

When the active T cell count has fallen below 200 T cells per mm3 of blood a person is diagnosed as having AIDS.

Note, HIV is a retrovirus, this means that the RNA that is found in the virus capsid (protein case) is transcribed in to DNA in the T cell, the enzyme reverse transcriptase, produced by the virus catalyzes this. This makes it more difficult to treat the HIV virus.

Although there are now drugs that will control the effects of HIV, the disease still has no cure. Social impacts of the disease include discrimination, changes to family structure, reduction in the workforce and the social exclusion of family members.

72. Discuss international measures to compact global pandemics such as bird flu

A pathogen may lead to an epidemic if localized or a pandemic if global. Global measures are often taken by the UN and other global bodies to restrict the movements of people from an infected area to a clean area. People who have traveled to an infected area may be quarantined as a precaution. Medical staff dealing with patients should ensure that they were the necessary protective equipment and that they clean themselves fully with antiseptics after exposure. Examples of these measure were seen with the Ebola outbreak in West Africa.

73. Discuss how our understanding of immunity has aided our understanding of vaccinations

As our understanding of immunity has developed we have learned that the antigen which an organisms is exposed to does not necessarily need to be active, this means that the body can be exposed to weaker forms or fragments/ toxins of the disease. Macrophages will ingest the antigen and present it to the T-helper cells which bind to the macrophages and are activated. Alternatively the antigen may bind to receptors on the B cells, T-cells will then bind to the B-cells and activate them. The B-cells undergo proliferation (mitosis) and produce antibodies to fight the pathogen. Memory B-cells ensure that a secondary and more rapid response can be initiated with future exposure to the pathogen. Booster injections may be needed to top up the immune system.


74. Explain how human vaccines are produced

Animals have widely been used to assess the effects of a vaccine such as the Polio vaccine. This has caused problems due to contamination of the vaccine with other pathogens and due to the fact that animal tissue does not respond in the same way as human tissue. More modern techniques of human cell cultures (cell lines). Rubella is one such vaccination that has been developed using cell lines. The virus was cultivated to grow at lower temperatures (30oC) as a result it grows poorly at the human body temperature. This means that people can safely be injected with the weaker form of the virus in order to initiate an immune response.

75. Discuss the success of the WHO in eliminating the threat of smallpox and explain why this is difficult to do for other diseases that we have effective vaccines for

The elimination of smallpox from the globe was a phenomenal success for the vaccination programme. The last reported case was in Somalia in 1977. Since then organizations have tried to repeat the success with other vaccines such as polio and prevent epidemics and pandemics, this has not always been possible due to global conflict, reluctance amongst people to take the vaccine, the remoteness of communities and the rate at which the disease mutates.

MMR is a mixture of vaccines that is given to infants to reduce the chances of getting mumps, measles and rubella. Exposure to the vaccine reduces the chances of the diseases causing deafness, blindness and heart problems. There is some resistance amongst groups to accept vaccine as it is believed that too many vaccines may actually weaken the immune system if exposed to other diseases.

There may be side effects from vaccinations for example the whooping cough vaccine is suspected of causing encephalitis. Some people may have allergic reactions to the vaccine and others are sensitive to the preservatives (eg mercury) of the vaccine.

In some cases, the vaccine has not been properly prepared and as a result people have actually contracted the disease from the vaccine itself.

Vaccines do increase life expectancy and protect vulnerable groups such as the young and elderly. Economic benefits will result as the population becomes more disease resistant.

76. Analyse data of disease distribution


77. Present a case study of an epidemic or pandemic

o

78. Discuss why some blood groups can be given to some people whilst others can’t

Red blood cells (erythrocytes) like other cells have protein markers (antigens) these may be recognized as self or non-self, and if non-self will evoke an immune response. Cells from Blood group A have the A antigen, B the B antigen, AB both A and B antigens and blood group O is without the A or B antigen. Due to the lack of antigens blood cells that are blood group O can be given to anyone (universal donor) and AB can accept blood cells from anyone (universal acceptor). To add to this there is also the rhesus protein this also acts a s an antigen and gives rise to the positive (rhesus factor present) and negative (rhesus factor absent) blood groups. O rh negative is the universal donor and AB rh + is universal acceptor. Blood typing is done to identify a person’s blood group, a sample of blood is exposed to antiserum A, B and O. This allows a medical technician to look for signs of agglutination (clotting) and therefore assess a person’s blood group.

79. Explain how ventilation maintains the diffusion gradients in the alveoli and tissues

Explain the importance of a gas exchange system in a multicellular organism

Explain how diffusion gradients are maintained with a gas exchange system

Explain why it is essential that a diffusion gradient is maintained in both the lungs and in the tissue

Multicellular organisms cannot rely on diffusion alone in order to supply the needed nutrients to all cells. They therefore need a transport system and ventilation system in order to supply oxygen and remove carbon dioxide.

A good ventilation system will have a good blood supply in order to maintain a high concentration gradient this is maintained by the constant movement of blood.

This gradient is needed to ensure that there is a constant exchange of gasses between the blood and the ventilation system. In order to assist with this the human alveoli have flattened and very thin walls to allow for rapid diffusion, have a large surface area for greater diffusion, have a moist lining as the oxygen needs to first dissolve before it can diffuse, they have a dense capillary supply (also a single cell wall to reduce the distance for diffusion) to carry the oxygen away from the lungs in the blood. They also have elastic tissue to reduce damage from over inflation.

80. Describe the pathway of air as it passes in to

Trace the pathway taken by air as it enters the lungs

Identify the structures of each

Air enters the body through the nasal or the oral cavity, it then passes past the pharynx and the larynx down the trachea, the trachea then splits into two principle bronchi which then split to form smaller bronchi and bronchioles.


the lungs respiratory component Identify possible diseases that

can effect each organ/tissue in the respiratory system

Located at the end of the bronchioles are the alveoli, where the gas exchange takes place. Despite the body’s innate defenses, we do get infections throughout the system, these include laryngitis, pharyngitis, bronchitis, pleurisy and pneumonia. The infection tends to be named after the part of the body that it infects. The trachea produces mucus and has ciliated cells to move this along with any trapped dirt and pathogens. Trachea and bronchi also have C shaped cartilage to prevent the airway closing and maintaining air flow.

81. Describe the role and structure of type 1 pneumocytesState the role of type 11 pneumocytes in the production of a surfactant

Define pneumocyte State the role of type 1 and

type 11 pneumocytes Define surfactant and explain

its importance in the respiratory system

Pneumocytes are the cells that form the alveoli. There are two types of these cells type 1- is the cell that is needed for gas exchange it has a larger surface area and is unable to replicate itself by the process of mitosis. Type two- is a smaller cell that has elastic properties, it releases a chemical surfactant, which acts as a lubricant and reduces the surface tension (stickiness) of the pulmonary fluids. Type two cells can self-replicate through mitosis and will replace any damaged type 1 pneumocytes with type two, this process therefore reduces the surface area that is available for gas exchange.

82. Explain how pressure changes are brought about during breathing and how they result in the movement of air, in

Describe the process of inhalation and exhalation

Link changes in the size of the thoracic cavity to changes in pressure in the lungs

Ventilation is the movement of air in to and out of the lungs, as this happens pressure and volume in the chest increase and decrease, air will then flow from high pressure to low pressure. During inhalation the dome shaped diaphragm will contract and move downwards, the external intercostal muscles contract and move the rib cage outwards and upwards. This increases the size of the


and out of the lungsDescribe the different muscles that are involved with inspiration and expiration and identify any antagonistic pairings

Identify the key muscles involved in breathing and recognize antagonistic pairs

Discuss the role played by the internal and external intercostal muscles during breathing

thoracic cavity and creates a vacuum (reduced pressure), the air pressure outside of the body is higher than inside the body so air rushes in and the lungs inflate. When we breathe out the diaphragm relaxes and moves upwards, the internal intercostal muscles contract and the ribs move downwards and inwards. This increases the pressure in the thoracic cavity, the pressure inside the chest is greater than the pressure outside of the body and air is forced out.

83. Explain how epidemiological studies have developed our understanding of lung cancer

Epidemiology is the study of the distribution of a disease, in this case lung cancer is studied. Lung cancer is the leading cause of cancer related deaths globally. The disease is much more common in smokers and people who have previously smoked than in people who have never smoked. Studies have shown that there is a link between the number of cigarettes a person smokes and the occurrence of lung cancer. The pattern of lung cancer follows smoking trends- although there is a lag, increasing number of women taking up smoking has led to an increase in the disease. Countries that have a high rate of tobacco consumption, such as the USA also have a higher rate of lung cancer.

Scientific research has led to a change in the perception of governments and the public towards smoking

84. Discuss the causes and consequences of emphysema

Emphysema is a chronic obstructive pulmonary disease (COPD) a condition in which the alveoli in the lungs are damaged and enlarged, this reduces the efficiency at which oxygen diffuses in to the blood and as a result causes breathlessness (dyspnea). It is defined as a chronic (long term) illness with irreversible effects. It is caused by smoking and pollution, some rare cases may be genetic. The disease often results in the formation of scar tissue as the lungs try to repair themselves. Along with shortness of breath, symptoms also include wheezing, coughing that worsens with physical activity. Treatment includes Broncho-dilating medication and steroids. Many patients need to wear an oxygen mask, antibiotics are often given due to the increased risk of infection. If untreated the disease may lead to heart failure.

85. Interpret a respiratory chart for an athlete at rest and during

Tidal volume and lung capacity can be determined from a lung volume chart.


exercise86. Explain how

ventilation rate may be measured

Ventilation rate may be measured with the use of spirometer or a respirometer, this is a device that measures lung volume, it can be used to measure the health of your ventilation system or to assess the severity of a lung disorder. Minute volume is a measure of how much air enters the lungs in one minute. It is calculated by using the following formula.

A greater lung volume allows more air to enter the body and a greater volume

of oxygen to diffuse in to the blood per breath. Greater alveolar area means a lager surface area for diffusion, greater capillary area means that oxygen can be carried away from the lungs faster and more oxygen can be absorbed by the blood.

87. Describe the oxygen dissociation curve

Discuss how oxygen is carried in the blood

Each molecule of haemoglobin is able to transport up to 4 molecules of O2 The amount of oxygen in the blood can be measured according to its partial

pressure- this is quite simply the amount of pressure exerted by oxygen alone

When levels of O2 are high, for example in the alveoli, there is a high partial pressure (PO2) of O2 and oxygen quite easily binds with haemoglobin. When the amount if oxygen is lower a lower PO2 is also lower and the haemoglobin has a lower affinity for oxygen- this means that in areas of the body where O2 is low for example the tissues, oxygen will not bind to the haemoglobin and will be released into the blood and surrounding tissues. We call this relationship dissociation

Foetal blood has a higher affinity for oxygen than haemoglobin and is able to take up oxygen at lower partial pressures for example in the placenta, where oxygen dissociates from the maternal blood and is picked up by the foetal blood- we say that the dissociation curve shifts to the left

Myoglobin is found in the muscles; it has a very low affinity for oxygen at low partial pressures and will give up its oxygen over a narrow PO2 range, thus releases the oxygen so that it can be used for aerobic respiration

88. Discuss the Carbon dioxide is transported by the blood in different ways


transport of carbon dioxide in the blood

Some of the CO2 (25%) binds with the haemoglobin and is released when the blood reaches the lungs

The remaining CO2 (75%) diffuses in to the red blood cell where the enzyme carbonic anhydrase combines it with water to produce carbonic acid.

The carbonic acid freely dissociates to form hydrogen carbonate ions and hydrogen ions

Hydrogen carbonate diffuses out of the RBCs through carrier proteins and in to the plasma. At the same time chloride ions pass in to the RBCs and bind to the haemoglobin, this has a buffering affect and maintains the pH (we call this movement of chloride ions a chloride shift)

Blood proteins also help to buffer the plasma, maintaining the pH between 7.35-7.45

89. Describe the Bohr shift

Discuss how different levels of CO2 lead to a difference in the affinity of haemoglobin for oxygen

CO2 is produced by respiration, in the tissues this increase in CO2 levels lowers the pH of the tissue fluid and the blood

This lower pH has the effect of shifting the O2 dissociation curve to the right, this lowers the affinity of the haemoglobin for O2 and it is more likely to and release the O2 to be used by the respiring tissue, we call this effect a Bohr shift


90. Discuss how the rate of ventilation can be controlled

Discuss the action of the autonomic nervous system on ventilation rate

The medulla oblongata is the respiratory control centre of the human body, for here messages are sent to the respiratory tissues in order to influence the rate of ventilation.

Chemoreceptors and baroreceptors (pressure sensors) located in the aorta and the carotid artery detect changes in pH, CO2 and O2, they communicate with the respiratory control centre in the medulla oblongata via afferent nerves

The respiratory control centre communicates with the intercostal muscles and diaphragm via efferent nerves

This will increase and decrease the rate of ventilation accordingly Therefore when we exercise the PO2 will fall and the pH of blood will rise,

these changes are detected by the baroreceptors and the chemoreceptors in the heart and neck, these receptors signal the respiratory control centre which in turn will stimulate the intercostal muscles and the diaphragm to move faster and thus increase the rate of ventilation

Through the process of negative feedback, as O2 and CO2 levels return to normal signals are sent to the respiratory control centre and the ventilation rate will return to normal

91. Discuss the effect of altitude on the rate of ventilation and gas exchange

As altitude increases the concentration of oxygen in the atmosphere decreases. Thus, the PO2 also decreases.

The blood oxygen level is therefore reduced and the body is in a state of hypoxia (low oxygen level). The body compensates for this by increasing heart rate and ventilation rate

Symptoms of this include, altitude sickness, headaches, nausea, dizziness, loss of copiousness and rapid pulse rate

Acclimatising will compensate for this by the production of more red blood cells, myoglobin and mitochondria, in order to make the respiratory system more efficient

Populations that live at high altitudes have evolved through natural selection to have larger chests, denser alveoli, more RBCs and a greater affinity for oxygen

92. Outline the State the main structures The central nervous system is made up of the brain and the spinal cord.


organization of the nervous system

found in the nervous system Peripheral nervous system are the nerves that branch from the CNS. The PNS is made up of the voluntary and the autonomic nervous systems, the autonomic system is further divided in to the sympathetic and the parasympathetic. The voluntary system is made up of sensory, relay and motor neurons.

93. Discuss the structure of a nerve

Describe the action of efferent and afferent nerves.

A nerve can be described as a bundle of neurones. The peripheral nervous system links the CNS to the rest of the body and consists of afferent nerves which carry a signal from the receptor to the CNS and efferent nerves which carry the signal from the CNS to the muscles and organs.

A typical nerve would consist of endoneurium- connective tissue surrounding nerve fibres, perineurium- connective tissue enclosing a bundle of nerve fibres and epineurium- the outer sheath of a nerve trunk. The central nervous system (CNS) is made up of tracts- myelinated nerves within the CNS, white matter- myelinated neurones within CNS and grey matter unmyelinated neurones in the CNS.

Interneurons also known as association neurones are relay neurones which link the PNS with the CNS.

94. Describe the structure of s nerve cell- including the nodes of Ranvier

Draw and label a sensory and motor neuron

Identify the function of each component of a neuron

Identify the function of the nodes of Ranvier

Nerve cells have the following features: Axon - a thread like fiber along which the impulse travels, Cell body (soma) - the part of the nerve cell that contains the nucleus, Dendrites – branches of the nerve cell that form synapses, Myelin sheath - a protein and phospholipid layer that insulates the axon, Nodes of Ranvier – gaps in the myelin sheath, Schwann cells-these are the cells that produce the myelin. There are two main types of neurons, motor and sensory. A sensory neuron will rapidly carry an impulse from a sense organ to the CNS in response to a stimulus. A motor neuron rapidly carries an impulse from the CNS to the effector muscle, this results in contraction of the muscle and movement.

95. Explain how neurons transmit electrical impulses link to sodium and potassium ions

Describe a nerve signal an electrical impulse

Identify key neurons in the body

Link the generation of a nerve impulse to sodium and

A nerve cell generates an electrochemical impulse, it is caused by the generation of an action potential, this is similar to the generation of an impulse in cardiac muscle.

An action potential is caused by the change in electrical charge across the membrane of a nerve cell. Electrically charged. Ions are able to pass across the semipermeable membrane of the nerve cell.


Define saltatory conduction and link this to myelinationDefine resting potential and action potential, polarization and depolarizationDescribe how a threshold potential is reached and link this to nerve impulses

potassium ions State the process of a normal

neuron response Explain what is meant by

salutatory conduction State what is meant by

polarization and depolarization and link this to myelination

At rest the inside of the cell has a negative charge (-70mV) compared to the outside of the membrane, we call this the resting potential the sodium potassium pump maintains this- note the resting potential is the point when the neuron does not conduct an impulse and there is a Net negative charge (-70mV) across the membrane. At rest we say the nerve is polarized.

When the nerve is activated by a stimulus such as pressure, an action potential (impulse) is generated. The stimulus causes the membrane of the nerve to open voltage gated sodium channels increasing the cells permeability to Na+, the electrical charge across the membrane moves towards -55mv due to the influx of Na+ ions and we say that the nerve is depolarized.

At -55mV more sodium channels open and there is an increased influx of Na+ ions. This causes the electrical charge to move towards +30mV and an electrochemical signal passes along the axon.

The sodium channels then close and the voltage gated potassium channels reopen, potassium ions flood out of the cell (efflux) moving down a concentration gradient. This causes the electrical charge to fall (repolarization), initially the charge falls too much -90mV and we say that the cell is hyperpolarized.

To return to the resting potential the cell actively pumps K+ ions into the cell and pumps Na+ out (2K+ in 3Na+ out using ATP).

Eventually it will get back to the resting potential -70mV. The time taken to get back to the resting potential is the refractory period.

As the depolarization wave moves along the nerve the process is repeated many times in adjacent parts of the neuron. In cells that are myelinated, the action potential jumps from node of Ranvier to node of Ranvier, we call this salutatory conduction.

An action potential will only be generated at -55mV, this means that any changes in electrical charge below -55mV will not generate an impulse, we say that this level is a threshold potential and only when we reach the threshold do we get an impulse (all or none).

96. State the role of synapses as, a junction between

State that were two or more neurons meet a Explain how a nerve signal is transmitted across a synapse

A response to a stimulus requires more than one nerve, where these nerves meet a synapse (junction) is formed, this allows the nerves to communicate without actually touching.

In order that the two nerves are able to communicate with each other a


neurons and neurons and receptor/effector cells Explain the role of neurotransmitters in presynaptic and postsynaptic neurons

Identify the function of a neurotransmitter

Discuss how neurotransmitter are regulated in the body synapse will form

neurotransmitter (Eg acetylcholine) is released, this is done when the action potential in the first nerve propagates to and depolarizes the presynaptic terminal membrane (the end of the first nerve- presynaptic knob) this causes the voltage gated calcium channels to open and Ca2+ ions flood the cell.

This influx of Ca2+ causes vesicles containing the neurotransmitter (acetylcholine) to move towards and fuse with the presynaptic membrane and be released from the cell by exocytosis. The neurotransmitter diffuses across the synaptic cleft (fluid filled space between the terminal membranes - 20nm across) and the neurotransmitter molecules bind to receptors on the post synaptic terminal membrane (start of second nerve).

This causes the voltage gated sodium channels to open and sodium ions move in to the post synaptic neuron, the action potential then continues. The neurotransmitters will then detach from the receptors and some of this is degraded by enzymes (acetylcholinesterase AChE), some however is reabsorbed by protein channels in the presynaptic terminal membrane, it is then repackaged and reused. The Ca2+ is pumped out of the presynaptic cell back in to the synaptic cleft.

97. Discuss the action of neuron-inhibitors

Give examples of substances that can interfere with nerve transmission

Discuss associated problems with the nervous system

Certain substances can interfere with or imitate the effects of neurotransmitters in the synapse.

Many medications and illegal drugs have an effect upon the release of neurotransmitters for example cocaine may have the following effects on the nervous system, increased nerve transmissions, it can cause the release of neurotransmitters without the need for a nerve impulse, it can prevent the reuptake of the neurotransmitter, cause the presynaptic cell to release a higher amount of the neurotransmitter or even prevent the neurotransmitter from being released.

Other substances that interfere with neurotransmission include opiates, nicotine and alcohol. Nicotine imitates the effects of acetylcholine and stimulates the nervous system. Alcohol reduces the absorption of calcium by the presynaptic membrane reducing the release of neurotransmitters.

98. State the role of acetylcholine as a neurotransmitter

Acetylcholine is neurotransmitter used by the spinal cord neurons to control muscles and by many neurons in the brain to regulate memory.

In most instances, acetylcholine is excitatory. It is produced by the combination of chlorine from the diet with an acetyl group which was produced during


aerobic respiration. The acetylcholine acts on the post synaptic membrane and then is rapidly

broken down to form chlorine and acetate by the enzyme AChE, the products are reabsorbed by the presynaptic nerve and recycled.

99. State the action of pesticides on the blocking of synaptic transmission at cholinergic synapses

If a receptor uses acetylcholine as a neurotransmitter, we say that it is cholinergic. Pesticides contain organophosphates (OPs), they interfere with the activity of the enzyme acetylcholinesterase (AChE) - which breaks down acetylcholine. This causes a buildup of the neurotransmitter, this results in the overstimulation of muscles leading to cramps and paralysis. OPs act as noncompetitive inhibitors for the acetylcholinesterase enzyme.

Other active ingredients in insecticides include neonicotinoids, these chemicals bind irreversibly to the cholinergic receptors on the postsynaptic membrane, reducing the effectiveness of acetylcholine, this too can result in the paralysis or death of an insect- it may affect humans but to a lessor effect as we have fewer cholinergic receptors.

100. Interpret oscilloscope traces of nerve impulses

A nerve impulse can be mapped using an oscilloscope trace

Objectives Expected outcomes Description101. Identify the key glands in

the endocrine system Define hormone and

endocrine system State the function of

hormones and the need for them in the body

Identify key endocrine glands and the hormones that they produce

Identify the different types of hormones

The endocrine system is collection of ductless organs that secrete hormones directly in to the blood stream, where they are absorbed by the blood and transported around the body to target tissues and target cells (effectors).

Hormones are considered as chemical messengers, they are produced by the endocrine glands and are transported by the blood around the body.

Hormones tend to be slower than the nervous system and often have longer lasting effects. There are a number of endocrine glands located throughout the body. They include the thymus, adrenal, thyroid, pancreas, ovaries, and testes, pineal and pituitary glands.

Hormones may be steroid based eg testosterone and estrogen,


peptide based eg, insulin and ADH or tyrosine derivatives such as thyroxin.

Peptide based hormones are produced from amino acids in the cytoplasm of the cells, they are needed in small amounts and are fast acting. These hormones are water soluble and cannot pass directly through the cell membrane. They must first bind to receptors on the surface of the cell membrane, this binding stimulates a cascade effect causing secondary messenger (G protein) to be released inside of the cell, the secondary messenger is able to activate or inhibit enzymes in the cell

Steroid hormones are made from cholesterol, they are therefore lipid soluble and able to pass directly through the phospholipid bilayer of the cell membrane, they are slower acting and needed in large amounts. Steroid hormones work by passing through the cell membrane and binding to receptors in the nucleoplasm forming a hormone receptor complex, these complexes act as transcription factors and therefore regulate gene transcription

Tyrosine derived hormones contain the amino acid tyrosine an example of this hormone would be the thyroxine released by the thyroid gland

102. Describe the role of the hypothalamus in a hormone mediated response

The hypothalamus is located in the brain has the job of inking the nervous system with the endocrine system, it controls secretions from the pituitary gland

The hypothalamus is linked to the pituitary gland via neurosecretory cells which release chemicals, it is also liked via portal veins which can carry transmitters

The pituitary gland located at the base of the brain consists of the anterior (front) ant posterior (back) lobes. The posterior pituitary releases the hormones ADH and oxytocin, the anterior pituitary releases thyroxine, FHS, LH and growth hormones

ADH is released by the posterior pituitary gland. It is first synthesized in the neurosecretory cell in the hypothalamus, where it then passes along axons connected to the pituitary gland and is stored in the nerve endings. Osmoreceptors in the hypothalamus


detect the water levels of the blood, if it is too concentrated ADH is released from the nerve endings in the pituitary gland and this hormone acts on the kidney nephrons and collecting ducts causing water to be reabsorbed in to the blood plasma, making the urine hypertonic. When the blood is too dilute the release of ADH is inhibited and less water is water is reabsorbed in to the plasma making the urine hypotonic

103. State the role of insulin and glucagon in the body and identify the cells that produce them

State the need to control glucose levels in the blood

Identify the hormones that are secreted by the pancreas to control glucose level

Identify the stages involved in the release of insulin and glucagon and identify the cells in the pancreas that are responsible for producing them

The desired glucose content of the blood should be around 5mmol/L. If glucose concentration falls below this level it is detected by cells in the pancreas, α cells in the pancreas release the hormone glucagon, which is transported by the blood. This hormone stimulates the liver cells to breakdown stored glycogen in to glucose and release it in to the blood stream.

If glucose is too high the β cells in the pancreas release insulin which is transported in the blood and stimulates the liver cells and muscle cells to absorb glucose and convert it to glycogen which the tissues then store.

These hormones are broken-down by the target cells once they have acted upon them. These hormone producing cells are found in the islets of Langerhans located in the pancreas.

Once the blood sugar level returns to normal the release of the hormones stops. This is called homeostasis and is a form of negative feedback.

Both insulin and glucagon are synthesized in the RER, vesicles ‘bud off’ the RER and migrate to the Golgi apparatus where further modification of the hormone occurs. Vesicles then form from the Golgi and migrate to the plasma membrane where they fuse with the membrane and are released by exocytosis- ATP is required for this process.

104. State the role of thyroxin and link this hormone to metabolism and the control of body temperature

Identify where and how thyroxin is produce

State the function of thyroxin on the body

State the effect on the

The thyroid gland is a butterfly shaped gland located in the neck, it releases hormones that involved in growth, development and metabolic regulation.

Thyroxine has a number of functions in the body, this is aided by the fact that it lipophilic, meaning that it can pass through the cell


body of an underactive/overactive thyroid gland

membrane directly Thyroxin (T4) is one such hormone that that controls metabolic

activity. Released in an inactive form thyroxin is converted to the active triiodothyronine (T3) by the cells and organs such as the liver.

Thyroxin is important for growth, maintaining body temperature and development.

Changes in the blood, such s temperature are detected by the hypothalamus, if temperature is too low, the hypothalamus detects this and then sends a chemical signal (thyrotrophin releasing hormone TRH) to the anterior pituitary gland which then sends a chemical signal (thyroid stimulating hormone TSH) to the thymus gland. This then stimulates the addition of iodine atoms to the TSH to form thyroxin (T4 also known as TH) which is then released in to the blood.

Some people have an overactive thyroid gland (hyperthyroidism), this results in weight loss, increases appetite and increased heart rate.

Others suffer from an underactive thyroid gland (hypothyroidism) this causes fatigue and intolerance to cold. The causes for these disorders may be genetic, caused by an autoimmune disease or a diet lacking iodine.

People with thyroid problems may develop a swollen thyroid gland (goiter).

Note that the presence of TH in the blood inhibits the production of further TRH from the hypothalamus, which in turn reduces the release of TSH by the pituitary, which in turn reduces the amount of TH released by the thyroid gland. This is an example of negative feedback.

When body temperature is too high TRH release is further inhibited in the hypothalamus

105. State the role of leptin in the body

State the role of leptin in the body and identify the site of production

Leptin is a hormone that is released by adipose tissue (fat storage tissue), its function to suppress hunger.

It therefore regulates energy intake in order to maintain body


Identify the consequences of over/under production of leptin

weight. The leptin acts upon cells located in the hypothalamus which in

turn act to suppress hunger. The amount of leptin produced by the body changes with the

amount of adipose tissue that we have. Too much leptin may result in leptin resistance and therefore in obese people the effect of leptin may no longer suppress hunger.

Too little leptin may lead to delayed puberty, childhood obesity and a suppressed immune system.

This disorder may be caused by a genetic mutation, treatment would be leptin injections.

106. Define circadian rhythm (body clock) and link to melatonin production by the pineal gland

Explain what is meant by circadian rhythm

Describe the function of melatonin in the body

Describe the location function of the pineal gland

The circadian rhythm is also known as the 24-hour-cycle (body clock), it is a self-regulatory pattern, although it can be influenced by external factors such as day and night.

The circadian rhythms control sleep patterns, it is believed that there is a genetic link to our circadian rhythm.

The pineal gland is a small pinecone shaped gland located at the base of the brain. It is believed that the pineal gland responds to light (the optic nerve signals the hypothalamus (suprachiasmatic nuclei cells SCN) which signal the pineal gland) the pineal gland releases the hormone melatonin in low light levels.

It is believed that melatonin influences the activity of other hormones in the body and can therefore control activity. It believed that this hormone also influences breeding cycles in animals. Melatonin is often taken as a sleep aide and as a treatment to prevent jetlag. Melatonin is broken-down by the liver cells.

107. Link the production of testosterone to the Y chromosome and the development of embryonic gonadsState the role of testosterone in the development of primary (pre-natal) and secondary sexual characteristics

Describe the function of testosterone

Link the production of testosterone to genes on the Y chromosome

Link the production of testosterone to the

Male embryonic gonads develop due to the presence of a single gene on the Y chromosome (SRY) this gene codes for the protein testes determining factor (TDF) which stimulates other genes for male development. Testosterone is the hormone that causes the development of male genitalia and of the male secondary sexual characteristics during puberty it is produced by the testes- the primary characteristic being the production of sperm. Testosterone


development of embryonic gonads and primary and secondary sexual characteristics

Sketch and label the male reproductive system

is also linked to sex drive and to aggression. The male reproductive system is made up of the testes, epididymis, vas deferens, seminal vesicles, Cowper’s gland prostate gland and urethra and penis.

The male condom is a method of contraception used to prevent pregnancy, it is also very effective in the prevention of the transmission of sexually transmitted disease. It is a mechanical method that involves covering the penis with a rubber barrier. This prevents the entry of semen into the vagina and therefore prevents the fertilization of the ovum by sperm. Some people do have allergies to the chemicals used in condoms, they do sometimes fail so people become over confident on them, and there is pressure in some religious groups not to use them as it interferes with a natural process.

108. Link estrogen and progesterone to primary (pre-natal) and secondary sexual characteristics in girls

Identify the function of estrogen

Identify the site of estrogen production

Link estrogen to the formation of primary and secondary sexual characteristics

Sketch and label the female reproductive system

The hormone estrogen and progesterone are responsible for the development of female characteristics. These are released during pregnancy by the mothers ovaries, in the absence testosterone, the placenta will then take over the release of these hormones. This causes the development of the female genitalia. During puberty the female releases higher levels of the estrogen and progesterone, resulting in the development of the secondary sexual characteristics.

Note- you may be asked to draw the female reproductive system; this should include the ovaries surrounded by (not touching the fallopian tubes which are linked to the uterus. \the cervix muscle is found at the base of the uterus and the vagina as the opening to the reproductive system.

109. State the role of hormones in the menstrual cycle and give examples of positive and negative feedback

Name the hormones involved in the menstrual cycle and state their action

Plot a graph showing hormone levels throughout the menstrual

An ovum is released from the ovary once a month (day 14 of the menstrual cycle) an underdeveloped ovum is referred to as an oocyte. Menstruation is the process by which blood and tissue debris is discharged from the uterus on a monthly cycle. The menstrual cycle involves the action of a series of hormones which are released at differing levels throughout the cycle. FSH (Follicle stimulating hormone) is a hormone that is released from the


cycle Discuss with examples

what is meant by positive feedback

Discuss with example what is meant by negative feedback

pituitary gland day 1-5 (when progesterone and estrogen levels are low), its role is to stimulate the development of the follicle, the Graafian follicle develops, this is a fluid filled structure containing the ovum whilst in the ovary prior to ovulation FSH is also needed for the development of the ovum, it stimulates the follicle cells to release estrogen. LH (luteinizing hormone) also released form the pituitary gland (mid cycle day 10-14) it has the job of maturing the ovum and stimulating ovulation it also stimulates the development of the corpus luteum (developed from the remains of the Graafian follicle after the discharge of the ovum) LH causes the reduced production of estrogen and an increased output of progesterone from the corpus luteum. If pregnancy occurs the corpus luteum will remain active for a few months, if pregnancy does not occur the corpus luteum will degenerate. Estrogen (a group of hormones- estradiol being the most relevant in the menstrual cycle) is released by the follicle and is needed for the development of the endometrium (mucus membrane lining the uterus), it inhibits the release of FSH and stimulates the release of LH. Progesterone is released by the corpus luteum and stimulates the maintenance of the endometrium. In the event of pregnancy production is taken over by the placenta, the hormone will also prevent further ovulation and the release of FSH and LH. In the menstrual cycle there are examples of positive and negative feedback.

Positive feedback- initially the release of estrogen increases the release of FSH

Negative feedback, the release of estrogen later in the cycle hinders the release of FSH. The presence of progesterone inhibits the release of FSH and LH.

Hormone activity can be shown on a graph: Day 1-4 follicular phase- menstruation and the development of the follicle. Day 1-14 ovulatory phase- the body prepares for ovulation which occurs when LH reaches its maximum level, usually on day 14. Day 15-28 luteal phase, levels of progesterone and estrogen fall leading to menstruation.


110. Discuss the limitations that William Harvey faced in his research into reproduction in the absence of the microscope

William Harvey studied embryology and proposed the following- that the ovum is developed by the uterus if semen does not enter the uterus then the fetus will be delivered. Harvey stated that the fetus will be gradually built up from its parts. He thought that fertilization was due to a magnetic attraction between the semen and the ovum. He did not have access to a microscope (as they had not been invented) so may have formed different conclusions had he been able to access better technology.


111. Discuss the causes and treatment of type 1 and type 11 diabetes

Diabetics are unable to regulate the glucose content of the blood and this elevated glucose level may damage cells and tissues. The additional glucose in the blood also hinders the reabsorption of water in the kidney nephron and thus results in the production of excessive urine. There are two main types of diabetes Type 1 often called childhood diabetes is when a person is unable to produce insulin to control the glucose level this can be caused by damage to the βcells and is often due to an autoimmune disease. The treatment for this disease is to monitor blood glucose levels and inject insulin. Stem cell research is currently be developed to replace the damaged cell. Type 11 diabetes (late onset) is caused by an inability to produce sufficient insulin or by a lack of insulin receptors on the target cells and a decreased response leading to insulin resistance. It is often linked to obesity. A person with this disease should have controlled diet and only consume foods with a low glycemic index (slow release starches) have regular meal times and eat moderate portions of food to avoid blood glucose fluctuations. Note that insulin producing cells are found in the islets of Langerhans located in the pancreas.


112. Discuss the role of hormones when used in the contraceptive pill

The contraceptive pill is a method of birth control that prevents ovulation; it involves the manipulation of the levels of progesterone and estrogen in the body, the hormone levels are kept high in the body which prevents the release of FSH and LH whilst at the same time maintains the endometrium. People who take the pill may experience side effects such as high blood pressure and should undergo an annual medical checkup. The contraceptive pill does not prevent the spread of sexually transmitted infections (STIs).

113. Discuss how hormones are manipulated during IVF treatment

In vitro fertilization (IVF), women are given hormones to disrupt their natural cycle, gonadotropin FSH and LH are given to stimulate the development of multiple ova. Human chorionic gonadotropin (HCG) will be given to help the ova to mature. The ova are then harvested and washed with sperm from the father (or donated sperm). If fertilized the zygote is incubated in order to form a blastocyst. The embryo is then inserted in to the uterus. The embryo can be screened for genetic disease and only healthy ones are used.

114. Discuss hormone replacement therapy

Hormone replacement therapy has been used to relieve the symptoms of menopause and as a treatment for osteoporosis. As a woman enters menopause her normal levels of estrogen will fluctuate, this can result in hot flushes, night time sweats and vaginal dryness. Estrogen pills are given as part of systematic hormone therapy. This therapy was once thought to also reduce the chances of heart disease and dementia, however further studies have shown that in some individuals it may actually increase the risk of heart disease and stroke, it is also suspected that the treatment may lead to a higher chance of developing breast cancer and blood clots. A person undergoing this treatment should have medical checkups every 6 months.

115. Identify a hormone deficiency disease and discuss the implications and treatment of this disease

There are a number of diseases linked to hormone deficiencies. One such disorder is Growth Hormone Deficiency (GHD), this is caused by a lack of Growth Hormone (GH) secreted by the anterior pituitary gland. This results in reduced growth patterns and slower


maturation (delayed puberty), this hormone targets receptors in the liver causing the liver to release an insulin-like-hormone which stimulates the development of bone and cartilage along with increasing muscle mass. Causes for this disorder include, congenital defects, mutations, trauma, illness and tumor formation. In many cases the hormone levels will normalize as the child enters adulthood, however many cases require daily injections of recombinant human growth hormone (rHGH). The contribution of this hormone towards muscle mass has led to the hormone being abused by athletes in order to enhance performance.

116. Discuss why some athletes illegally take anabolic steroids

Anabolic steroids are chemical that have long term effects on athletic performance, they are known to improve an athlete’s strength and power. These drugs affect the metabolic pathways in the body and interfere with neurotransmitters. Use of these drugs can lead to kidney problems or failure, liver damage, Enlarged heart, High blood pressure, Changes in blood cholesterol, quite often resulting in stroke and heart failure.

117. Discuss the use of oxytocin and prolactin in the control of milk secretion

When a baby suckles at the nipple sensory neurons communicate with the hypothalamus to stimulate the anterior pituitary gland to release the hormone prolactin. This hormone causes the breast tissue to secrete milk

Oxytocin is a hormone produced by the hypothalamus and stored in the posterior pituitary gland ready for release, once released it stimulates the contraction of the epithelial cells around the mammary alveoli to contract and release the milk, we call this the milk ejection reflex, this is stimulated also by the suckling baby but may also develop as a conditioned reflex

118. Is obesity a disease- discuss the research in to the use of leptin on patients with clinical obesity

There is much debate as to whether obesity is a sickness or a lifestyle choice. Many people may become obese due to an underactive thyroid, lack of leptin production or genetic disposition. As many other diseases such as type 2 diabetes and coronary heart disease are linked to obesity there is a need for obesity to be taken more seriously.

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