+
Area of Study 2:EXPECTED LEARNINGTo revise homeostasis and immunity
+Quiz What are two differences between the endocrine and
nervous systems?
What are the 5 plant hormones and what do they do?
What is the main difference in the signal transduction pathway between amine/polypeptide and steroid hormones?
Describe the three lines of defence and the major parts/cells of the immune system involved in each
What is an autoimmune disease? What is an immunodeficiency disease? (definition and eg)
What is involved in an allergic response?
+Homeostasis
The maintenance of a constant internal environment despite changes in external environmentNB. Internal environment = The medium in which the body cells of multicellular organisms are bathed (i.e. extracellular fluid, interstitial fluid, plasma, lymph)
+What needs to be kept within narrow limits?
M.I.T.G.O.W.B + pH + wastes
Metabolites (eg blood glucose concentration)
Ions (eg salts)
Temperature
Gases (eg CO2 and O2)
Osmolarity (ie water balance)
Wastes (e.g. urea)
Blood Pressure
pH
+
Mechanoreceptors respond to mechanicalenergy (e.g. ear drum)
Thermoreceptors respond to heat or cold (e.g. nerve endings in skin)
Electromagnetic receptors respond to electromagnetic energy (e.g. ampullae of Lorenzini in sharks)
Photoreceptors respond to visible light and UV radiation (e.g. eyes).
Chemoreceptors respond to chemicalstimuli (e.g. olfactory)
Detecting signals from external environment
+Stimulus-response model
Response
Stimulus Receptor
Control centre
Effector
Transmission - nerves
Transmission – nerves or hormones
+Stimulus-response model exampleNegative Feedback
Increase in blood CO2
Receptor in arteries and
veins
Respiratory centre in
brain
Respiratory muscles in
lungsMore CO2 exhaled
Transmission - nerves
Transmission - nerves
Negative feedback – response counteracts the stimulus
+Two Types of Feedback
Positive Feedback Negative FeedbackOrgan or Gland Organ or Gland
Releases a substance to act on a system
Releases a substance to act on a system
System Acted Upon
System Acted Upon
Releases a secondary substance which acts on the gland or organ
Releases a secondary substance which acts on the gland or organ
Inhibits (stops) further release of the original substance
Promotes or encourages more of the original substanceto be released
+Feedback Loops
+Endocrine System
Uses chemical signals for cell to cell communication
Coordinates the function of cells
Response to an endocrine signal occurs within minutes to hours
+Endocrine System
Endocrine glands Release hormones into the bloodstream.
Hormones Chemicals released in one part of the body that travel through the bloodstream and affect the activities of cells inother parts. body.
+Hormones Cell to cell communication molecules
– Made in gland(s) or cells
– Transported by blood
– Distant or local target tissue receptors – can only communicate message to cell with the corresponding receptor (on cell membrane or within cytosol)
– Activate physiological response
– Negative feedback prevents hormone overproduction
+Types of hormones
+
Made in endocrine cells
Transported via blood to act at a site distant from the secreting cell or gland
Receptors on target cells
Long Distance Communication: Endocrine Hormones
+ Local communication: Paracrine and Autocrine Hormones
Act locally, either on the secreting cell or a neighbouring cell
Diffuse to target Autocrine – receptor on same cell
Paracrine – neighbouring cells
e.g. cytokines in immune system
+Neurocrine Hormones
+PheromonesChemicals released by animals to communicate with
other members of their own species
Can be used for: Attracting mates
Inducing mating activity
Marking territory
Signalling alarm
Marking food trails
+Plant tropisms
A plant growth response to an external stimulus Light = phototropism Gravity = geotropism
Thigmotropism = touchhttp://www.youtube.com/watch?v=1ZuZ_1cQnv4&feature=related
Growth towards the stimulus is a positive tropism
Growth away from the stimulus is a negative tropism
Responses rely upon chemical signals that initiate a signal transduction pathway in plant cells to produce a growth response.
+Plant hormones
+ Auxin
Indole acetic acid and related molecules
Photo-and gravitropism
Stimulates cell elongation
Made in the shoot apex
Travels down the stem
Apical dominance
Prevents leaf abscission (ie leaf shedding)
Enhances fruit growth
+Cytokinin
Cytokinins delay and even reverse senescence
Release buds from apical dominance
Stimulate cell division Cytokinins
Auxin
+ Gibberellins
Essential for stem elongation
Found as the toxin produced by some fungi that caused rice to grow too tall
Dwarf plant varieties often lack gibberellins
Gibberellins are involved in bolting of rosette plants
Promote cell division and elongation
Gibberellins are used to improve grapes
Gibberellins are involved in seed germination– gibberellins will induce genes to make enzymes that break down starch
+Ethylene gas
The smallest hormone
Important in seed germination, fruit ripening, epinasty (i.e. downward bending of leaves), abscission of leaves
Sex expression in cucurbits (i.e. pumpkins, zuccini)
+Abscisic acid (ABA)
Generally acts as an inhibitor
Important in water stress and other stresses
Causes stomatal closure
Prevents premature germination of seeds
Changes gene expression patterns
+Responding to light Plants possess light-sensitive enzymes –
phytochromes
Exist in two forms that interchange according to the light they are exposed to. active form (Pfr) at sunrise (i.e. red light) inactive form (Pr) at sunset (ie far-red light)
when exposed to red light the enzyme is able to catalyse a number of reactions within the cell, leading to altered transcription of genes in the nucleus, or activation of proteins already in the cell
influences responses such as seed germination, stem elongation, and formation of leaves, flowers, fruits, and seeds
+ Photoperiodism Photoperiodism is a biological response to a change in
relative length of daylight and darkness as it changes throughout the year.
Phytochrome, and other chemicals not yet identified, probably influence flowering and other growth processes.
"Long-day plants" flower in the spring as daylength becomes longer (e.g. spinach).
"Short-day plants" flower in late summer or early autumn when daylength becomes shorter (e.g. broad beans).
"Day-neutral plants" flower when they are mature.
+Signal transduction pathway
A mechanism linking a mechanical or chemical stimulus to a specific cellular response.
Communicating cells may be close together or far apart
+Cell communication
1. Production of extracellular signalling molecule (called a ligand) by a cell
2. Detection of this ligand by a receptor protein on or in target cell
3. Transduction of ligand through cell
4. Cellular response
5. Control or regulation of ligand or response
+2. Detecting the signalTo stimulate a response, hormones bind to specific receptor on OR in the target cell to form hormone-receptor complex
The cell targeted by a particular signal has a receptor molecule complementary to the signal molecule, or ligand.
Most amine and polypeptide-based hormones are not able to move through cell membrane – receptor proteins are on the cell membrane
Steroid hormones move through membrane and bind with receptors in cytoplasm
+ Receptor locations
Cytosolic or Nuclear– Lipophilic ligand enters cell– Often activates gene– Slower response
Cell membrane– Lipophobic ligand can't enter
cell– Outer surface receptor– Fast response
Figure 6-4: Target cell receptors
+3. Transduction
Converts the change in the receptor to a form that can bring about a cellular response.
This might involve a series of steps - a signal transduction pathway - that alters and amplifies the change.
Small amounts of signalling molecule can produce a significant response or even multiple responses due to amplification.
+3. Transduction
Once a hormone-receptor complex is formed, the way the signal is transferred depends on the type of hormone:
Amine and polypeptide hormones: Second messenger is produced that stimulates cell response.
Steroid hormones: hormone can enter the cell easily, binding
to receptor and initiating response. Tends to be slower, but longer lasting than second messenger response.
+Non-steroidal, lipophobic hormonesUsually involves the binding of extracellular
signalling molecules, like hormones and neurotransmitters, to receptors that face outwards from the membrane and trigger events inside the cell.
The binding of a hormone with a receptor often stimulates the action of a second protein (e.g. G protein), or an enzyme, within the cytoplasm.
This enzyme can then stimulate the activity of other enzymes to bring about a response.
+
+
+Steroidal, lipophillic hormones Lipid soluble hormone travels in bloodstream via a
carrier protein( insoluble in water) and passes through the cell membrane.
Binds to receptor protein found only in target cells. Hormone-receptor complex then enters the nucleus. Binds to specific regulator site for the targeted gene. Stimulates the gene to produce mRNA. mRNA is read by ribosomes to produce a specific
protein.
+
+4. Response
the transduction process brings about a cellular response.
can be one of many different cellular activities, such as: activation/inhibition of a certain enzyme rearrangement of the cytoskeleton regulate protein expression through activation of specific
genes. Open or close protein channels, etc
Once the cellular response is initiated, the ligand is degraded by cell enzymes
+Summary
+Summary
+The nervous system
This communication system controls and coordinates functions throughout the body and responds to internal and external stimuli.
Maintains homeostasis by detecting change and coordinating action of effector organs
Responsible for unidirectional, fast communication
brain
Spinal Cord
Cerebellum
Cerebrum
Medulla Oblongata
The Central Nervous System (CNS)
Consists of the brain and spinal cord
+The peripheral nervous system (PNS)
Nerves extending out to the rest of the body from the CNS
Includes all sensory neurons, motor neurons, and sense organs
+Nerve cells: NeuronsThe basic functional unit of the nervous system.
Send impulses to and from the CNS and PNS and the effectors (muscles/glands)
+ Types of Neurons
+The nervous systemSensory receptors monitor changes in the
environment
Afferent or sensory nerve cells transfer messages to the central nervous system (CNS)
Efferent or motor nerve cells transfer messages from the CNS to effector organs
(See Jacaranda diagram)
+Nerve impulses
Information is transferred in the form of an electrical impulse
The cell membrane of a nerve cell is polarised i.e. there is a difference in charge between the inside and
outside of the cell
+Neuron at rest: Resting potential
A condition where the outside of the membrane is positively (+) charged compared to the inside which is negatively (-) charged.
Neuron is said to be polarized.
+How is resting potential maintained?
Ion Distribution
+Nerve impulses: Action potentialAs an impulse moves along an axon, the
permeability of the membrane changes
Positive sodium ions move into the neuron Potassium ions move out of the neuron The inside of the membrane is positively (+) charged
compared to the outside which is negatively (-) charged.
This is called an ACTION POTENTIAL
+Nerve impulses
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html
+Neuron Communication: SynapsesA synapse is the junction between two nerve
cells (e.g. axon bulb of one neuron and the dendrite or cell body of a second neuron).
A very small gap, called the synaptic cleft, lies between the two neurons.
Molecules called neurotransmitters relay messages across the synaptic cleft between the two neurons. The communication between neurons is chemical in nature.
+Neuron Communication: Synapses
+Neuron Communication: Synapses
Communication across the synapse involves:
Release of neurotransmitters (e.g. actylcholine) from secretory vesicles of presynaptic neuron
Exocytosis of neurotransmitter across the presynaptic membrane and release into the synaptic cleft
Attachment of transmitter to protein receptors on the postsynaptic membrane, opening protein channels, leading to stimulation of the neuron or effector cell
Deactivation of neurotransmitter by enzymes and reabsorption into presynaptic neuron
http://www.youtube.com/watchv=HXx9qlJetSU&feature=related
+Reflex arc
An involuntary response that is processed in the spinal cord not the brain.
Reflexes protect the body before the brain knows what is going on
Definitions
Immunity The ability of the body to fight infection
and/or foreign invaders by producing antibodies or killing infected cells.
Immune System The system in the body responsible for
maintaining homeostasis by recognizing harmful from non-harmful organisms and produces an appropriate response.
Foreign Invaders
Pathogens Cellular or non-cellular
agents that cause disease/immune response.
Antigens Compounds, usually
proteins, on the outside of pathogens that can trigger the immune system to respond.
+Major Parts of the Immune System
1. Blood - White Blood Cells in particular.
2. Lymphatic system - vessels carry a type of fluid named lymph, which bathes the tissue of the body and also is a ‘transport network’ for immune cells.
3. Lymph nodes - the centre of activity where lymphocytes (a type of white blood cell) are continually circulating from tissue in the body, to the lymph nodes and back again by using the bloodstream and lymphatic vessels.
4. Thymus Gland – Produces T Lymphocytes
5. Bone Marrow – Produces B Lymphocytes
•Self= cells and other substances that are a part of the organism and carry “self” markers (i.e. MHC markers) •Non-self = organisms, cells and other substances that are not part of the organism and carry antigens
What is self and non-self?
Major Histocompatibility Complex
• Simple terms: Major Histocompatibility complex is a cluster of genes that produce proteins that form the markers on our cells. These markers are known as MHC Class 1 molecules.
• Each person’s MHC markers are different
MHC
Inside the cell...
MHC marker protein recognised
BANG!!R.I.P.Edward
Non-Self
How does the body fight pathogens?
The Body’s THREE lines of Defense
FIRST LINE
SECOND LINE
THIRD LINE
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Pathogen Invades Tissue
Non-Specific Defences
Barriers to EntrySkinMucousSecretionsNatural Flora
Physiological MechanismsFever
Chemical Mechanisms Complement proteins Interferons
MechanismsPhagocytes (granulocytes,Macrophages), Natural killer cells (cytotoxic)
Inflammation Mast cellsRelease of Histamine
Specific Defences
Second line of defenseFirst line of defense
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Pathogen Invades Tissue
Non-Specific Defences
B-cells T-cells
Specific Defences
Third line of defense
Plasma cells – produce antibodies
Memory cells – remember antigen
Helper T-cells (Th) - stimulate B cells
Cytotoxic t-cells (Tc) kill body cells infected with a pathogen
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ANTIGENS: Any substance foreign to the body that triggers a response from the immune system, such as producing antibodies in order to neutralise it.
- Usually made up of proteins but can be polysaccharides
- All have unique shapes
- A way to remember:antigens = antibody generators
- Antibodies are generated to attack thepathogen behind the antigen being detected
Antigens.
Antibodies/Immunoglobulins
The third line of defense involves the production of antibodies:
Y-shaped protein molecules
Produced by B-cells
Made up of variable (recognizes antigen) and constant regions.
Function: Recognize antigens, bind to and deactivate them.
+ANTIGENS AND ANTIBODIES.
http://www.youtube.com/watch?v=Ys_V6FcYD5I
+IgG IgA IgM IgD IgE
Approx. Concentration in serum (mg/mL) 12 2 1 0.04 0.000.02
Ability to cross placenta yes no no no no
Present in saliva and tears no yes no no no
Present in milk yes yes no no no
Active against viruses yes yes some no no
Active against some bacteria yes yes yes no no
Involved in allergy reaction no no no no yes
Immune Response Summary
Antigen
Helper T - Cell
Active Cytotoxic T-Cell Active B - Cell
Kills Infected Cells Memory T- Cell Plasma Cell Memory B-Cell
Antibodies
Deactivates Antigens
Displays copy of antigen on surface of cell
Cellular Immunity Humoral Immunity
+Clonal selection
+Acquiring immunity
Long lasting vaccines
Short lasting vaccines
+Autoimmune Diseases
Autoimmune diseases cause antibodies in the immune system to act against the body’s tissues!
There are 80 different types (e.g. MS, Chrohn’s disease etc)
The cause is unknown…
BUT, it is genetic and can pass through your family.
An autoimmune disorder may result in:
-The destruction of body tissue
-Abnormal growth of an organ
-Changes in organ function
+Immunonodeficiency diseases
Immunodeficiency refers to a malfunction or deficiency in one or more components of the immune system.
PRIMARY IMMUNODEFICIENCY:Disorders where part of the immune system is missing or not functioning properly. Most are genetic disorders.
SECONDARY IMMUNODEFICIENCY:Same as Primary Immunodeficiency, but is caused by a secondary nature, e.g. caused by another disease, drug treatment or environmental exposure to toxins (e.g. HIV leading to AIDS)
+Allergies
Overreaction of immune system to harmless antigens (e.g. dust, pollen etc)
Mast cells are immune cells involved in allergic responses. Circulating basophil cells are also involved in allergic responses, but to a much lesser extent. Both kinds of cells contain large granules of histamine.
IgE binds to mast cells and, to some extent, to basophils. IgE antibodies are made against antigens such as dust, pollen and plant spores.
If a person contains IgE antibodies for a particular antigen, they are said to be sensitised to that antigen.
If the person is further exposed to the same antigen, cross links are
formed between the antibody on the mast cells and the antigen. These antibody–antigen cross links trigger mast cells to release active agents such as histamine (which causes contraction of smooth muscle.
+Quiz What are two differences between the endocrine and
nervous systems?
What are the 5 plant hormones and what do they do?
What is the main difference in the signal transduction pathway between amine/polypeptide and steroid hormones?
Describe the three lines of defence and the major parts/cells of the immune system involved in each
What is an autoimmune disease? What is an immunodeficiency disease? (definition and eg)
What is involved in an allergic response?
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