Human Nervous System in Use

8/2/2019 Human Nervous System in Use

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11. Coordination and Response

Content11.1 Nervous system11.2 Receptors11.3 Reflex action11.4 HormonesLearning outcomesCandidates should be able to:(a) state that the nervous system - brain, spinal cord and nerves,serves to coordinate and regulate bodily functions;(b) identify, on diagrams of the central nervous system, the

cerebrum, cerebellum, pituitary gland and hypothalamus, medulla,spinal cord and nerves;



(c) describe the principal functions of the above structures in terms ofcoordinating and regulating bodily functions;(d) describe the gross structure of the eye as seen in front view and in

horizontal section;(e) state the principal functions of component parts of the eye inproducing a focused image of near and distant objects on the retina;(f) describe the pupil reflex in response to bright and dim light;(g) outline the functions of sensory neurones, relay neurones and motorneurons;(h) discuss the function of the brain and spinal cord in producing acoordinated response as a result of a specific stimulus (reflex action);(i) define a hormone as a chemical substance, produced by a gland,carried by the blood, which alters the activity of one or more specifictarget organs and is then destroyed by the liver;

(j) state the role of the hormone adrenaline in boosting the bloodglucose concentration and give examples of situations in which this mayoccur;(k) describe the signs (increased blood glucose concentration andglucose in urine) and treatment (administration of insulin) of diabetes

mellitus.



Human Nervous System

Central and

Peripheral



A General

Sense…



Peripheral Nervous SystemSensory Division

• Sensory neurons carry messages toward the CNS fromsensory receptors all over body.

• Sensory receptors act as “energy transducers.” Atransducer is a device for converting a non-electricalsignal into an electrical one. In this case, the electricalsignal produced is the action potential of a nerve.

• Sensory receptors are in sense organs, such as eyes,ears, mouth, nose, skin… and different regions of thebrain respond to different signals.



Nervous System Cells

• Called neurons

• Neurons have long axons that enablethem to transmit signals. Many neuronstogether are called a nerve.

• Each nerve has a dorsal root (info into theCNS) and a ventral root (info out fromCNS to body).



Anatomy of a Neuron

• Cell body – main part

• Dendrite – receives action potential (stimulation) fromother neurons

• Axon – branches from cell body, where the action

potential occurs• Axon terminal – end of an axon

• Myelin sheath – lipid layer for protection over neurons thatallows for increase in speed of signal transmission; made

by Schwann cells• Nodes of Ranvier – gaps in myelin sheath along the axon,

where most Na+ pumps are located

• Synaptic Cleft – gap between neurons; between the axonterminal of 1 neuron and the dendrite of a 2nd neuron



The Patellar Reflex



Central Nervous System (CNS)

BRAIN• About 1.4 kg, 2% of body weight

• About 100 billion neurons

• 12 pairs of cranial nerves are connected tothe human brain – Example: Pupil reflex in response to bright

light, to avoid damage to retina. Nerves thatcontrol this reflex are connected to the brain.

– Others: blinking, Hering-Breuer reflex



My brain is inside my head.

It makes my body work.It makes me think and feel.It keeps my heart and lungs working.

The brain makes sure our hearts keep beatingand our lungs keep working without us havingto think about it. Part of the brain makes our

muscles work. The biggest part of the brainmakes us think, see, hear, feel and taste.



There are five important parts of the brain:Cerebrum, the biggest and heaviest part. It is the

thinking part of the brain.Cerebellum at the back of the brain below thecerebrum, controls balance, movement and co-ordination.

Brain stem ( medulla oblongata), connecting thebrain and the spinal cord, controls all the bodyfunctions like breathing and circulating blood.Pituitary (pit-you-it-airy) gland, is tiny but produces

and releases hormones, which help you grow andhelp change children into adults.Hypothalmus (high-poe-thal-uh-muss) regulatesthe body temperature.



We each have a backbone, called a spine.Inside it there is a spinal cord. The spinal cord joins the brain at the top of our neck.

All through our body there are nerves which

connect to the spinal cord. This is called thenervous system.Messages from the nervestravel to the spinal cord, which sends them to

the brain. Neurons are long, wiry cells thatcarry electrical messages through the nervoussystem and the brain.



The messages come from eyes, skin, nose,ears, tongue.

The brain works out what the messages are sowe know what we are seeing, touching ,

hearing and tasting, and if something hurts orfeels good.

The brain at birthAt birth a baby's brain contains 100 billionneurons. As the baby experiences things andlearns, the brain continues to develop.



Hormone: A chemical substance produced in the bodythat controls and regulates the activity of certain cells ororgans.Chemical substances having a specific regulatory effecton the activity of a certain organ or organs. The termwas originally applied to substances secreted by various

endocrine glands and transported in the bloodstream tothe target organs. It is sometimes extended to includethose substances that are not produced by theendocrine glands but that have similar effect.



Hormones travel via thebloodstream to target cells

•The endocrine system broadcasts its

hormonal messages to essentially all

cells by secretion into blood andextracellular fluid. Like a radio

broadcast, it requires a receiver to get

the message - in the case of endocrine

messages, cells must bear a receptor for the hormone being broadcast in

order to respond.



Regulation of hormonesecretion

• Sensing and signaling: a biological need issensed, the endocrine system sends out a signalto a target cell whose action addresses thebiological need. Key features of this stimulusresponse system are: – · receipt of stimulus

– · synthesis and secretion of hormone

– · delivery of hormone to target cell

– · evoking target cell response

– · degradation of hormone



Endocrine vs. exocrine

Hormone

Endocrine gland

ENDOCRINE GLANDS

pineal gland

thyroid gland

pancreas(islets)

testes (male)

hypothalamus

pituitary gland

thymus gland

adrenal glands

ovaries(female)



ADRENAL CORTEX (ZONA GLOMERULOSA)



Adrenaline is a hormone secreted by the adrenal gland, it is also called Epinephrine.Adrenal Gland is either of the two small dissimilarly shaped

endocrine glands,one located above each kidney. Adrenaline helps the body

to adjust tosudden stress.

When a person becomes angry or frightened,the adrenal gland release adrenaline into the blood.The hormone causes changes in the body to make it moreefficient for "fight or flight".Adrenaline increases the strength and rate of the heartbeatand raises the blood pressure. It also speeds up theconversion of glycogen into glucose, which provide energyto the muscles.



Adrenal MedullaAdrenalin

Prepares the body for "fright, fight or flight" and has many effects:

Action of heart increased.

Rate and depth of breathing increased.

Metabolic rate increased.

Force of muscular contraction improves.

Onset of muscular fatigue delayed.

Blood supply to the bladder and intestines reduced, their muscular wallsrelax, the sphincters contract.



Noradrenalin

Similar effects to adrenalin:

Constriction of small blood vessels leading to increase in blood pressure.

Increased blood flow through the coronary arteries and slowing of heartrate.

Increase in rate and depth of breathing.

Relaxation of the smooth muscle in the intestinal walls.



Adrenal CortexCorticosteroids

Glucocorticoids (e.g. cortisol, cortisone, corticosterone)

Utilization of carbohydrate, fat and protein by the body.

Normal response to stress.

Anti-inflammatory effects.

Hypersecretion of cortisol results in Cushings Syndrome.Mineralocorticoids (e.g. aldosterone)

Regulation of salt and water balance.

Hypersecretion of Alderosterone decreases the potassium in the body(affecting nerve impulse transmission and leading to muscular paralysis).



Negative feed back: A feedback in which the systemresponds in an opposite direction to the perturbationIt is a self-regulatory system in which it feeds back to the

input a part of a system’s output so as to reverse the directionof change of the output.The process reduces the output of a system in order tostabilize or re-establish internal equilibrium. There are severalnegative feedback in biological system to regulate andmaintain homeostasis.Some of which are the regulation of hormone synthesis,blood glucose levels, body temperature, and baroflex in bloodpressure.



Negative Feedback Loop• Blood glucose in the bloodstream drops

• Cells require glucose to meet the energy demand • Body detects this change in the variable with a particular receptor designed for this function• These receptors send impulses/signals to Integrating Center • The IC receives inputs from the sensors/receptors, processes the info, then sends a effector signal

• Effector signals travel to their target tissue and initiate a corrective response• In this case, the corrective response is the secretion of more glucose into the bloodstreamIC



Together, the nervous and endocrine systems coordinate

functions of all body systems.

NERVOUS SYSTEM VS. ENDOCRINE SYSTEM

NERVOUS

neurotransmitters hormones

ENDOCRINE

muscle contractions andglandular secretions

metabolic activities of cells

acts in milliseconds acts in seconds to minutes tohours to days to months

brief effects long-lasting effects

Human Nervous System in Use

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