6 human health and physiology

8/10/2019 6 Human Health and Physiology

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IB Biology Notes by Adeel Ahmad 1

6 Human Health and PhysiologyDigestion

6.1.1 Explain why digestion of large food molecules isessential.

There are two reasons why the digestion of large food molecules is vital.Firstly, the food we eat is made up of many compounds made by other

organisms which are not all suitable for human tissues and thereforethese have to be broken down and reassembled so that our bodies can

use them. Secondly, the food molecules have to be small enough to be

absorbed by the villi in the intestine through diffusion, facilitateddiffusion or active transport and so large food molecules need to be

broken down into smaller ones for absorption to occur.

Summary:

1. Food needs to be broken down and reassembled.2.

Large food molecules need to be broken down into smaller ones.

6.1.2 Explain the need for enzymes in digestion.

Enzymes are needed in the process of digestion as they are the

biological catalysts which break down the large food molecules into

smaller ones so that these can eventually be absorbed. Digestion canoccur naturally at body temperature, however this process takes a verylong time as it happens at such a slow rate. For digestion to increase in

these circumstances, body temperature would have to increase as well.However this is not possible as it would interfere with other body

functions.This is why enzymes are vital as they speed up this processby lowering the activation energy required for the reaction to occur and

they do so at body temperature.Summary:

1.Enzymes break down large food molecules into smaller ones.2.Speed up the process of digestion by lowering the activation

energy for the reaction.

3.

Work at body temperature.


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6.1.3 State the source, substrate, products andoptimum pH conditions for one amylase, one proteaseand one lipase.

Amylase Protease Lipase

EnzymeSalivaryAmylase

PepsinPancreaticLipase

SourceSalivary

Glands

Chief cells in

stomach

lining

Pancreas

Substrate Starch Proteins

Triglycerides

such as fatsand oils

Products MaltoseSmall

polypeptides

Fatty Acids

and Glycerol

OptimumpH

pH 7 pH 1.5 - 2 pH 7

6.1.4 Draw and label a diagram of thedigestive system.

Figure 6.1.1 - The digestive system


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6.1.5 Outline the function of the stomach, smallintestine and large intestine.

The stomach is an important part of the digestive system. Firstly it

secretes HCL which kills bacteria and other harmful organisms

preventing food poisoning and it also provides the optimum conditionsfor the enzyme pepsin to work in (pH 1.5 - 2). In addition, the stomach

secretes pepsin which starts the digestion of proteins into polypeptidesand amino acids. Theses can then be absorbed by the villi in the small

intestine.

The small intestine is where the final stages of digestion occur. The

intestinal wall secretes enzymes and it also receives enzymes from thepancreas. However the main function of the small intestine is the

absorption of the small food particles resulting from digestion. It

contains many villi which increase the surface area for absorption.The large intestine moves the material that has not been digested fromthe small intestine and absorbs water. This produces solid faeces which

are then egested through the anus.

Summary:

Stomach:

1.

Secretes HCL which kills bacteria.

2. HCL provides optimum pH for pepsin.

3.

Secretes pepsin for protein digestion.

Small intestine:

1.

Intestinal wall secretes enzymes

2.

Receives enzymes from the pancreas.3. Has villi for absorption of food particles.

Large intestine:

1.

Moves material that has not been digested along.2.

Absorbes water.

3.

Produces faeces.


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6.1.6 Distinguish between absorption andassimilation.

Absorption occurs when the food enters the body as the food molecules

pass through a layer of cells and into the bodies tissues. This occurs in

the small intestine which has many villi that are specialised forabsorption. Assimilation occurs when the food molecules becomes part

of the bodies tissue. Therefore, absorption is followed by assimilation.

6.1.7 Explain how the structure of the villus isrelated to its role in absorption andtransport of the products of digestion.

The structure of the villus is very specific. Firstly there is a great number

of them so this increases the surface area for absorption in the smallintestine. In addition the villi also have their own projections which arecalled microvilli. The many microvilli increase the surface area for

absorption further. These microvilli have protein channels and pumps in

their membranes to allow the rapid absorption of food by facilitateddiffusion and active transport.

Also, the villi contains anepithelial layer which is only onecell layer thick so that food can

pass through easily and be

absorbed quickly. The bloodcapillaries in the villus are veryclosely associated with the

epithelium so that the distancefor the diffusion of the food

molecules is small. This thin layer

of cells contains mitochondria toprovide the ATP needed for the

active transport of certain food

molecules. Finally, there is alacteal branch at the centre ofthe villus which carries away fats

after absorption.

Figure 6.1.2 - Intestinal villus


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Summary:

1. Many villi increase the surface area for absorption.2.

Epithelium is only one cell layer thick and so food is quickly

absorbed.

3.

Microvilli on the villi increase the surface area for absorptionfurther.4.

Protein channels and pumps are present in the microvilli for rapidabsorption.

5.

The mitochondria in the epithelium provide ATP needed for active

transport.6. Blood capillaries are very close to the epithelium so diffusion

distance is small.7.

The lacteal takes away fats after absorption.

The transport system

6.2.1 Draw and label a diagram of the heart showingthe four chambers, associated blood vessels, valvesand the route of blood through the heart.

Figure 6.2.1 - The human heart


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6.2.2 State that the coronary arteries supplyheart muscle with oxygen and nutrients.

The coronary arteries supply heart muscle with oxygen and nutrients.

6.2.3 Explain the action of the heart in termsof collecting blood, pumping blood, andopening and closing of valves.

The right atrium collects blood from the superior and inferior vena cava

and the left atrium collects blood from the pulmonary veins. This bloodthen flows into the right and left ventricle which pump the blood into thearteries. The direction of the blood flow is controlled by theatrioventricular valves and semilunar valves. When the atria contract

the blood flows through the atrioventricular valves which are open, intothe ventricle. At this stage the semilunar valves are closed so theventricle fills with blood. The ventricles then contract which causes a

rise in pressure. This rise in pressure first causes the atrioventricular

valves to close preventing back flow of blood into the atria. Then thesemilunar valves open allowing the expulsion of blood into the arteries.

As this happens, the atria start to fill with blood again. The ventriclesstop contracting leading to a fall in pressure which causes the semilunarvalves to close, preventing back flow of blood from the arteries. When

the ventricular pressure drops below the atrial pressure the

atrioventricular valves open again and the cycle repeats.

Summary:

1.

Atria collect blood from veins.2.

Atria contract, atrioventricular valves open.3.

Blood is pumped into ventricles.

4. Ventricle contracts, atrioventricular valves close and semilunar

valves open.5.

Blood is pumped into arteries, semilunar valves close.

6.

Cycle repeats.


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6.2.4 Outline the control of the heartbeat interms of myogenic muscle contraction,the role of the pacemaker, nerves, the

medulla of the brain and epinephrine

(adrenaline).

The heart muscle can contract by itself, without the stimulation of anerve. This is called myogenic muscle contraction. The region that

initiates each contraction is found in the wall of the right atrium and is

called the pacemaker. Every time the pacemaker sends out a signal, aheartbeat results. The pacemaker is under the influence of nerves and

adrenaline. One nerve carries messages from the medulla of the brainto the pacemaker and speeds up the beating of the heart. Another nervecarries messages from the medulla of the brain to the pacemaker and

slows down the beating of the heart. Finally, adrenaline (epinephrine) is

carried by the blood and once it reaches the pacemaker it signals it toincrease the beating of the heart.

Summary:

1.

Heart muscle can contract by itself (myogenic muscle contraction).2.

Pacemaker initiates contractions.

3. One nerve carries messages from the brain to the pacemaker tospeed up the beating of the heart.

4.

One nerve carries messages from the brain to the pacemaker toslow down the beating of the heart.

5. Adrenaline signals the pacemaker to increase the beating of the

heart.

6.2.5 Explain the relationship between the

structure and function of arteries,capillaries and veins.

Arteries have a thick outer layer of longitudinal collagen and elasticfibers to avoid leaks and bulges. They have a thick wall which is essentialto withstand the high pressures. They also have thick layers of circular

elastic fibres and muscle fibres to help pump the blood through after

each contraction of the heart. In addition the narrow lumen maintainsthe high pressure inside the arteries.


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Veins are made up of thin layers with a few circular elastic fibres and

muscle fibres. This is because blood does not flow in pulses and so thevein walls cannot help pump the blood on. Veins also have thin walls

which allows the nearby muscles to press against them so that theybecome flat. This helps the blood to be pushed forwards towards the

heart. There is only a thin outer layer of longitudinal collagen and elasticfibres as there is low pressure inside the vein and so little chance of

bursting. Finally, a wide lumen is needed to accommodate the slowflowing blood due to the low pressure.

Capillaries are made up of a wall that is only one cell layer thick and

results in the distance for diffusion in and out of the capillary being very

small so that diffusion can occur rapidly. They also contain pores withinthe wall which allow some plasma to leak out and form tissue fluid.

Phagocytes can also pass through these pores to help fight infections.

In addition, the lumen of the capillaries is very narrow. This means thatmany capillaries can fit in a small space, increasing the surface area fordiffusion.

Summary:

Arteries:

1.

Thick outer layer of longitudinal collagen and elastic fibres preventsleaks and bulges.

2. Thick wall withstands high pressure.

3.

Thick layers of circular elastic fibres and muscle fibres to pump blood.4.

Narrow lumen to maintain high pressure.

Veins:

1.

Thin layer with few circular elastic fibres and muscle fibres as blooddoes not flow in pulses.

2. Thin walls, nearby muscles can help push blood towards the heart.3. Thin outer layer of longitudinal collagen and elastic fibers as pressure

is low.

4.

Wide lumen to accommodate the slow flowing blood.

Capillaries:

1.Wall is one cell layer thick so distance for diffusion is small.2.

Pores allow plasma to leak out and form tissue fluid. Phagocytes can

also pass through pores.3.

Very narrow lumen so that many can fit in a small space.


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6.2.6 State that blood is composed of plasma,erythrocytes, leucocytes (phagocytesand lymphocytes) and platelets.

Blood is composed of plasma, erythrocytes, leucocytes (phagocytes andlymphocytes) and platelets.

6.2.7 State that the following are transported bythe blood: nutrients, oxygen, carbon dioxide,

hormones, antibodies, urea and heat.

Nutrients, oxygen, carbon dioxide, hormones, antibodies, urea and heat

are all transported by the blood.

Defence against infectious disease

6.3.1 Define pathogen.

Pathogen: an organism or virus that causes a disease.

6.3.2 Explain why antibiotics are effective againstbacteria but not against viruses.

Antibiotics are produced by microorganisms to kill or control the growthof other microorganisms by blocking specific metabolic pathways withinthe cell. Since bacteria are so different to human cells, antibiotics can

be taken by humans to kill bacteria without harming the human cells.Viruses on the other hand are different as they do not carry out many

metabolic processes themselves. Instead they rely on a host cell (ahuman cell) to carry out these processes for them. Therefore virusescannot be treated with antibiotics as it is impossible to harm the virus

without harming the human cells.

Summary:

1. Antibiotics block specific metabolic pathways in bacteria.2. Bacteria are very different to human cells so human cells are not

affected.3.

Viruses require host cell to carry metabolic processes for them and

so antibiotics cannot be used to treat viruses.

4. Harming the virus would harm the human cells.


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6.3.3 Outline the role of skin and mucousmembranes in defence against pathogens.

The skin forms a physical barrier that prevents pathogens from enteringthe body as the outer layer is very tough. In addition the skin contains

sebaceous glands which secret lactic acid and fatty acids which createsan acidic environment on the surface of the skin preventing the growthof pathogens.

Mucous membranes form another type of barrier against pathogens.

Mucous membranes are soft and moist areas of skin found in the

trachea, nose, vagina and urethra. These membranes are not strongenough to create a physical barrier but they do have mucus which

contain lysozyme enzymes that digest the phagocytes. Also, the mucus

can be sticky such as in the trachea, and trap the pathogens which are

then expelled up the trachea and out of the body by muscles within thetrachea.

Summary:

Skin:

1.

Forms a physical barrier.2.

Sebaceous glands secret lactic acid and fatty acids.

Mucous membranes:

1.

Mucous contains lysozyme enzymes.2.

Mucous can be sticky and trap pathogens.

6.3.4 Outline how phagocytic leucocytesingest pathogens in the blood and inbody tissues.

Phagocytes are found in the blood and ingest pathogens. They do so by

recognising pathogens and engulfing them by endocytosis. Enzymeswithin the phagocytes called lysosomes then digest the pathogens.

Phagocytes can ingest pathogens in the blood but also within body tissue

as they can pass through the pores of capillaries and into these tissues.


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6.3.8 Discuss the cause, transmission andsocial implications of AIDS.

Cause: HIV causes AIDS (acquired immunodeficiency syndrome). A

syndrome is a group of symptoms that are found together. HIV destroys

a type of lymphocyte which is vital for antibody production. Over theyears, less active lymphocytes are produced which leads to a fall in the

amount of antibodies. Pathogens that would normally be easilycontrolled by the body in healthy individuals can cause serious

consequences and eventually lead to death for patients affected by HIV.

The immune system is considerably weakened.

Transmission: HIV is transmitted through body fluids from an infectedperson to an uninfected one. This can occur through vaginal and anal

intercourse as well as oral sex if there are cuts or tears in the vagina,

penis, mouth or intestine. It can also be transmitted by hypodermicneedles that are shared by intravenous drug abusers. The small amount

of blood present on these needles after their use may contain the virusand is enough to infect another person. Another way of transmission is

through the placenta from mother to child, or through cuts duringchildbirth or in milk during breast feeding. Finally there is a risk oftransmission in transfused blood or with blood products such as Factor

VIII used to treat hemophiliacs.

Social implications: Relatives and friends suffer grief. Families can

also suffer from a loss of income as the person infected by HIV can losetheir wage if they are unable to work and are refused life insurance.Also, HIV patients may find it hard to find partners, employment and

even housing. Finally, AIDS can cause fear in a population and reducesexual activity.

Summary:

Cause:

1.HIV causes AIDS.

2.

HIV destroys a type of lymphocyte vital for antibody production.3.

Overtime there are less active lymphocytes.4.

The body becomes very vulnerable to pathogens.


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Transmission:

1.Through vaginal and anal intercourse as well as oral sex if cuts ortears are present.

2.

Through hypodermic needles shared by drug users.

3.

Through placenta from mother to child.4.Through cuts during child birth or in milk during breast feeding.5.

Through transfused blood.6.

Through blood factors such as Factor VIII used to treat

hemophiliacs.

Social Implications:

1.Grief suffered by relatives and friends.2.Families can get poorer.

3.

Can be hard to find a partner, employment and housing.4.

Can reduce sexual activity in a population.

Gas exchange

6.4.1 Distinguish between ventilation, gasexchange and cell respiration.

Ventilation is the process of bringing fresh air into the alveoli andremoving the stale air. It maintains the concentration gradient of carbondioxide and oxygen between the alveoli and the blood in the capillaries

(vital for oxygen to diffuse into the blood from the alveoli and carbon

dioxide out of the blood into the alveoli).

Gas exchange is the process of swapping one gas for another. It occursin the alveoli of the lungs. Oxygen diffuses into the capillaries from the

air in the alveoli and carbon dioxide diffuses out of the capillaries and

into the air in the alveoli.

Cell respiration releases energy in the form of ATP so that this energycan be used inside the cell. Cell respiration occurs in the mitochondria

and cytoplasm of cells. Oxygen is used in this process and carbondioxide is produced.


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6.4.2 Explain the need for a ventilation system.

A ventilation system is needed to maintain the concentration gradientsof gases in the alveoli. Diffusion of gases occurs due to the concentrationgradient of oxygen and carbon dioxide between the alveoli and the

blood. The body needs to get rid of carbon dioxide which is a product ofcell respiration and needs to take in oxygen as it is needed for cell

respiration to make ATP. There must be a low concentration of carbondioxide in the alveoli so that carbon dioxide can diffuse out of the bloodin the capillaries and into the alveoli. Also there must be a high

concentration of oxygen in the in the alveoli so that oxygen can diffuse

into the blood in the capillaries from the alveoli. The ventilation systemmakes this possible by getting rid of the carbon dioxide in the alveoliand bringing in more oxygen.

Summary:

1. To maintain the concentration gradients of oxygen and carbondioxide in the alveoli.

2. The body needs oxygen to make ATP via cell respiration.

3. The body needs to get rid of carbon dioxide which is a product ofcell respiration.

4.

Oxygen needs to diffuse from the alveoli into the blood. Carbon

dioxide needs to diffuse from the blood into the alveoli.

5. To do so there must be a high oxygen concentration and a low

carbon dioxide concentration in the alveoli.6.

A ventilation system makes this possible by getting rid of the

carbon dioxide in the alveoli and bringing in more oxygen.

6.4.3 Describe the features of alveoli thatadapt them to gas exchange.

Even though alveoli are so small there are huge numbers of them which

results in a large surface area for gas exchange. Also the wall of the

alveoli is made up of a single layer of thin cells and so are the capillaries,

this creates a short diffusion distance for the gases. Therefore this allowsrapid gas exchange. The alveoli are covered by a dense network of blood

capillaries which have a low oxygen and high carbon dioxideconcentrations. This allows oxygen to diffuse into the blood and carbon

dioxide to diffuse out of the blood. Finally, there are cells in the alveolar

walls which secrete a fluid that keeps the inner surface of the alveoli


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moist, allowing gases to dissolve. This fluid also contains a natural

detergent that prevents the sides of the alveoli from sticking together.

Summary:

1. Great numbers increase the surface area for gas exchange.

2.

Wall made up of single layer of cells and so are the walls of thecapillaries so diffusion distance is small allowing rapid gas

exchange.

3. Covered by a dense network of capillaries which have low oxygenand high carbon dioxide concentrations. This allows oxygen to

diffuse into the blood and carbon dioxide to diffuse out of theblood.

4.

Some cells in the walls secret fluid allowing gases to dissolve. Fluid

also prevents the sides of alveoli from sticking together.

6.4.4 Draw and label a diagram of the ventilation

system, including trachea, lungs, bronchi,bronchioles and alveoli.

Figure 6.4.1 - The ventilation system


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6.4.5 Explain the mechanism of ventilation of the lungs

in terms of volume and pressure changes caused

by the internal and external intercostal muscles,

the diaphragm and abdominal muscles.

Inhalation:- The external intercostal muscles contract. This moves the ribcage upand out.

- The diaphragm contracts. As it does so it moves down and becomes

relatively flat.- Both of these muscle contractions result in an increase in the volume

of the thorax which in turn results in a drop in pressure inside thethorax.- Pressure eventually drops below atmospheric pressure.

- Air then flow into the lungs from outside the body, through the

mouth or nose, trachea, bronchi and bronchioles.- Air continues to enter the lungs until the pressure inside the lungs

rises to the atmospheric pressure.

Exhalation:

- The internal intercostal muscles contract. This moves the ribcage

down and in.- The abdominal muscles contract. This pushes the diaphragm up,

back into a dome shape.

- Both of these muscle contractions result in a decrease in the volumeof the thorax.- As a result of the decrease in volume, the pressure inside the thorax

increases.- Eventually the pressure rises above atmospheric pressure.

- Air then flows out of the lungs to outside of the body through the

nose or mouth.- Air continues to flow out of the lungs until the pressure in the lungshas fallen back to atmospheric pressure.


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Nerves, hormones and homeostasis

6.5.1 State that the nervous system consists of thecentral nervous system (CNS) and peripheral

nerves, and is composed of cells called neuronsthat can carry rapid electrical impulses.

The nervous system consists of the central nervous system (CNS) and

peripheral nerves, and is composed of cells called neurons which carry

rapid electrical impulses.

6.5.2 Draw and label a diagram of the structure of amotor neuron.

Figure 6.5.1 - A motor neuron

6.5.3 State that nerve impulses are conducted from

receptors to the CNS by sensory neurons,

within the CNS by relay neurons, and from the

CNS to effectors by motor neurons.

Nerve impulses are conducted from receptors to the CNS by sensory

neurons, within the CNS by relay neurons, and from the CNS to effectorsby motor neurons.


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6.5.4 Define resting potential and action potential(depolarization and repolarization).

Resting potential: the electrical potential across the plasmamembrane of a cell that is not conducting an impulse.

Action potential: the reversal and restoration of the electrical potentialacross the plasma membrane of a cell, as an electrical impulse passes

along it (depolarization and repolarization).

6.5.5 Explain how a nerve impulse passesalong a non-myelinated neuron.

Sodium is found in greater concentrations outside of the cell while

potassium is found in greater concentrations inside the cell. Sodium-

potassium pumps exist in the plasma membrane to maintain the theconcentration gradients and the membrane potential. Nerve impulses

have a domino effect. An action potential in one part of the neuroncauses another action potential in the adjacent part and so on. This isdue to the diffusion of sodium ions between the region of the action

potential and the resting potential. It is the movement of sodium and

potassium that reduce the resting potential.

If the resting potential rises above the threshold level, voltage gated

channels open. Voltage gated sodium channels open very fast so that

sodium can diffuse into the cell down its concentration gradient. Thisreduces the membrane potential and results in more sodium channels

opening. Sodium ions are positively charged and so the inside of the cell

develops a net positive charge compared to the outside of the cell. Thisresults in depolarization as the potential across the membrane is

reversed.

A short while after this, voltage gated potassium channels open and

potassium ions flow out of the cell down the concentration gradient.Since potassium ions are positively charged, their diffusion out of the

cell causes a net negative charge to develop again inside the cell

compared to the outside. The potential across the membrane isrestored. This is called repolarization.

Finally, the concentration gradients of both ions are restored by the

sodium-potassium pump. Sodium is pumped out of the cell while

potassium is pumped in. The resting potential is restored and the neuronis ready to conduct another nerve impulse.


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Figure 6.5.2 - Synaptic transmission

Summary:

1.

Action potential reaches the end of a presynaptic neuron.2.

Voltage gated calcium channels open.

3. Calcium ions flow into the presynaptic neuron.4. Vesicles with neurotransmitters inside the presynaptic neuron fuse

with the plasma membrane.

5.

Neurotransmitters diffuse in the synaptic cleft and bind to

receptors on the postsynaptic neuron.6. The receptors are channels which open and let sodium ions into

the postsynaptic neuron.7.

The sodium ions cause the postsynaptic membrane to depolarize.

8.

This causes an action potential which passes down the

postsynaptic neuron.9. Neurotransmitters in the synaptic cleft are degraded and the

calcium ions are pumped back into the synaptic cleft.


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6.5.7 State that the endocrine system consistsof glands that release hormones that aretransported in the blood.

The endocrine system consists of glands that release hormones that aretransported in the blood.

6.5.8 State that homeostasis involves maintaining the

internal environment between limits, including

blood pH, carbon dioxide concentration, blood

glucose concentration, body temperature and

water balance.

Homeostasis involves maintaining the internal environment between

limits, including blood pH, carbon dioxide concentration, blood glucoseconcentration, body temperature and water balance.

6.5.9 Explain that homeostasis involves monitoringlevels of variables and correcting changes in

levels by negative feedback mechanisms.

Homeostasis involves maintaining the internal environment betweenlimits, including blood pH, carbon dioxide concentration, blood glucose

concentration, body temperature and water balance. Blood and tissue

fluid (derived from blood) make up the internal environment. Thisinternal environment varies very little compared to the external

environment which varies greatly. Negative feed back is used to keep

the internal environment between limits. It uses the nervous andendocrine system to do so. It has a stabilising effect as any change from

a set point level will result in an opposite change. The levels ofproduction of for example blood glucose, feed back to affect the rate ofproduction. If blood glucose levels rise above the set point, this will feed

back to decrease production and reduce the level back around the set

point. A decrease in blood glucose levels below the set point will resultin an increase in production so that the levels increase back to the setpoint. Small fluctuations around the set point will not cause any

response. Negative feed back is only triggered when there are significantincreases or decreases from the set point.


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Summary:

1.Homeostasis maintains the internal environment between limits.2.

Negative feed back is used to do so. Any change from a set point

results in an opposite change.

6.5.10 Explain the control of body temperature,including the transfer of heat in blood, and

the roles of the hypothalamus, sweat glands,

skin arterioles and shivering.

The hypothalamus is responsible for monitoring the temperature of theblood which is normally close to 37 degrees. If there are significant

fluctuations from this set point, the hypothalamus sends signals(messages carried by neurons) to different parts of the body to restorethe temperature back to the set point. This is done through negative

feedback.


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6.5.11 Explain the control of blood glucoseconcentration, including the roles of glucagon,

insulin and and cells in the pancreatic islets.

Blood glucose concentration does not have a specific set point like blood

temperature. Blood glucose levels drop and rise through the day and sothe body usually tries to keep blood glucose levels around 4 to 8

millimoles per dm3of blood. Once again, negative feedback is used todo so. There are responses by target organs which affect the rate atwhich glucose is taken up from the blood or loaded into the blood.

Response to blood

glucose levels abovethe set point

Response to blood

glucose levels belowthe set point

cells in the pancreaticislets produce insulin.Insulin stimulates muscle

cells and the liver cells to

take up glucose from theblood and convert it into

glycogen. These are then

stored in the form ofgranules in the cytoplasmof cells. Also, other types

of cells are stimulated totake up glucose and use it

for cell respiration instead

of fat. All of theseprocesses lower the levelsof glucose in the blood.

cells in the pancreaticislets produce glucagon.

Glucagon stimulates the

liver cells to convertglycogen back into

glucose and release this

glucose into the blood.This raises the glucoselevels in the blood.


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6.5.12 Distinguish between type I and type IIdiabetes.

Type I diabetes Type II diabetes

The onset is usually early,sometime during

childhood.

The onset is usually late,sometime after

childhood.

cells do not produceenough insulin.

Target cells become

insensitive to insulin.

Diet by itself cannot be

used to control the

condition. Insulininjections are needed to

control glucose levels.

Insulin injections are not

usually needed. Low

carbohydrate diet cancontrol the condition.

Reproduction

6.6.1 Draw and label diagrams of the adult male and

female reproductive systems.

Figure 6.6.1 - The male reproductive system


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Figure 6.6.2 - The female reproductive system

6.6.2 Outline the role of hormones in the

menstrual cycle, including FSH (folliclestimulating hormone), LH (luteinizinghormone), estrogen and progesterone.

The menstrual cycle:

1.

FSH is secreted by the pituitary gland and its levels start to rise.This stimulates the follicle to develop and the follicle cells to secret

estrogen.

2.Estrogen then causes the follicle cells to make more FSH receptorsso that these can respond more strongly to the FSH.

3.

This is positive feedback and causes the estrogen levels to increase

and stimulate the thickening of the endometrium (uterus lining).4.

Estrogen levels increase to a peak and by doing so it stimulates LH

secretion from the pituitary gland.5.

LH then increases to its peak and causes ovulation (release of eggfrom the follicle).

6.

LH then stimulates the follicle cells to secrete less estrogen and

more progesterone. Once ovulation has occurred, LH stimulatedthe follicle to develop into the corpus luteum.

7.

The corpus luteum then starts to secrete high amounts of

progesterone. This prepares the uterine lining for an embryo.


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8.

The high levels of estrogen and progesterone then start to inhibit

FSH and LH.9.If no embryo develops the levels of estrogen and progesterone fall.

This stimulates menstruation (break down of the uterine lining).When the levels of these two hormones are low enough FSH and

LH start to be secreted again.10.

FSH levels rise once again and a new menstrual cycle begins.

6.6.3 Annotate a graph showing hormone levels in

the menstrual cycle, illustrating the relationshipbetween changes in hormone levels and ovulation,menstruation and thickening of the endometrium.

6.6.4 List three roles of testosterone in males.Roles:

1. Stimulates the development of prenatal genitalia.2. Stimulates the development of the male secondary sexual

characteristics such as growth of the skeletal muscle and pubic

hair.3.

During adulthood it maintains the sex drive.

6.6.5 Outline the process of in vitro fertilization (IVF).Process:

1.

For a period of three weeks, the women has to have a drug injectedto stop her normal menstrual cycle.

2. After these three weeks, high doses of FSH are injected once a day

for 10-12 days so that many follicles develop in the ovaries of thewomen.

3.

HCG (another hormone) is injected 36 hours before the collection

of the eggs. HCG loosens the eggs in the follicles and makes themmature.

4. The man needs to ejaculate into a jar so that sperm can becollected from the semen. The sperm are processed to concentrate

the healthiest ones.5. A device that is inserted through the wall of the vagina is used to

extract the eggs from the follicles.


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6.

Each egg is then mixed with sperm in a shallow dish. The dishes

are then put into an incubator overnight.7. The next day the dishes are looked at to see if fertilization has

happened.8.

If fertilization has been successful, two or three of the embryos

are chosen to be placed in the uterus by the use of a long plastictube.

9. A pregnancy test is done a few weeks later to find out if any of theembryos have implanted.

10.A scan is done a few weeks later to find out if the pregnancy isprogressing normally.

6.6.6 Discuss the ethical issues associated with IVF

Arguments for IVF Arguments against IVF

Many types of infertilityare due to environmentalfactors rather than

genetic which means that

the offspring would notinherit the infertility.

The infertility of the

parents may be inheritedby their offspring passing

on the suffering to thenext generation.

The embryos that are

killed during the IVFprocess cannot feel pain

or suffering as they do not

have a developed nervoussystem.

More embryos are

produced than neededand the ones that remain

are usually killed which

denies them the chance ofa life.

Suffering caused by

genetic diseases can be

decreases by screening

the embryos beforeplacing them into the

uterus.

Embryologists selectwhich embryos will be

placed into the uterus.

Therefore they decide the

fate of new individuals asthey choose which ones

will survive and whichones will die.


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Since the IVF process is

not an easy oneemotionally and

physically, is costly, takes

time and there are no

guarantees, parents whoare willing to go through it

must have a strong desireto have children and

therefore are likely to be

loving parents.

IVF is not a natural

process which takes place

in a laboratory comparedto natural conception

which occurs as a result ofan act of love.

Infertility can causeemotional suffering to

couples who want to havechildren. IVF can take

away this suffering forsome of those couples.

Infertility should be

accepted as Gods will and

to go against it by usingIVF procedures would bewrong.

6 human health and physiology

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