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Higher Human Biology. Unit 2: The Continuation of Life. Chapter 24: Regulating Mechanisms. Learning Intentions. Success Criteria. To know how the heart rate is regulated. Outline the principle of negative feedback

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Unit 2 the continuation of life

Higher Human Biology

Unit 2: The Continuation of Life

Chapter 24:

Regulating Mechanisms

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

Learning Intentions

Success Criteria

Mrs Smith Ch24 regulating Mechanisms

To know how the heart rate is regulated.

  • Outline the principle of negative feedback

  • Explain how heart rate is controlled with reference to the role of hormonal and nervous system


Unit 2 the continuation of life

Human Internal Environment

A human’s internal environment is the millions of body cells and the tissue fluid that bathes them.

For a healthy body, all body parts must work together keeping the internal environment within tolerable limits.

e.g. Human body must be maintained at 37°C to provide optimum conditions for enzyme controlled reactions

The features of the internal environment are controlled by homeostasis….

Mrs Smith Ch24 regulating Mechanisms


Homeostasis

Homeostasis

HOMEOSTASIS is the maintenance of the body’s internal environment within certain tolerable limits despite changes in the body’s external environment (or changes in the body’s rate of activity).

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

The value of Homeostasis

Homeostasis is of survival value because it maintains the body’s internal environment at a relatively steady optimum state.

If the body is exposed to extremely adverse conditions (e.g. freezing temperatures or absolutely no water) homeostasis will eventually break down, which in extreme cases can be fatal.

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

8. Negative Feedback Control

When a factor affecting the body’s internal environment deviates from its norm (or set-point) the body responds to correct the change.

Image source: www.hw.ac.uk

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

8. Negative Feedback Control

Receptors detect change and send messages to effectors.

  • The change in the factor is detected by receptors.

  • These send out nerve or hormonal messages which are received by effectors.

  • The effectors then bring about certain responses which counteract the original deviation from the norm and return it to a set point.

Image source: www.hw.ac.uk

  • This corrective homeostatic mechanism is called NEGATIVE FEEDBACK CONTROL.

  • It provides the stable environmental conditions needed by the body’s community of living cells to function efficiently and survive.

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

Sino-atrial node (SAN)

= Pacemaker

9. Control of Heart Rate: Pacemaker

Although the heartbeat is initiated by the pacemakertissue also known as a Sino-atrial node (SAN). However, heart rate is not set at a fixed pace. Heart rate can be altered by nervous and hormonal activity both of which exert control over rate (though not initiation) of heartbeat.

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

The Nervous System

The nervous system is a network of specialised cells that communicate information about an individual’s surroundings and itself.

It processes this information and causes reactions in other parts of the body.

Mrs Smith Ch24 regulating Mechanisms

Image source: www.drstandley.com


Unit 2 the continuation of life

The autonomic nervous system (ANS) controls involuntary responses to stimuli by the body.

Autonomic nerves serve

heart muscle

smooth muscle

Glands

all internal organs.

The ANS acts on these various effectors to maintain:

homeostasiswithin the body (parasympathetic branch)

response to stress – the "fight or flight" response (sympathetic branch)

Control of Heart rate.

The Autonomic Nervous System

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

Image source: www.biocomtech.com

Parasympathetic v Sympathetic

homeostasis

response to stress

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

The vagus nerve is the longest nerve in the body, and one of the most important. It sends commands to, and takes information from many important organs including the heart and lungs.

The Autonomic Nervous System:

The Vagus Nerve

People have two vagus nerves, one for each side, running roughly parallel from the medulla in the brain to the bowels.

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

  • Control of Heart Rate:

  • Autonomic nervous control

The heart is part of the autonomic nervous system. It has branches of 2 parts of the autonomic nervous system. These 2 pathways have opposite effects on heart rate (are antagonistic).

Heart rate is regulated by control centres within the medulla of the brain.

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

  • Control of Heart Rate:

  • Autonomic nervous control

The sympathetic cardiac nerves carry nerve impulses from the cardio-accelerator centre of the brain to the heart.

Causes an increase in heart rate

Thecardio-inhibitorcentre sends nerve impulses via the parasympathetic vagus nerve.

Causes a decrease in heart rate

Mrs Smith Ch24 regulating Mechanisms

Image source: http://courses.scholar.hw.ac.uk


Two antagonistic pathways

Two antagonistic pathways

  • The sympathetic and parasympathetic pathways are antagonistic to one another. i.e. They have an opposite effect on heart rate.

  • An increase in the number of nerve impulses conducted to the to the pacemaker by the sympathetic nerve causes an increase in heart rate.

  • An increase in the number of nerve impulses conducted to the to the pacemaker by the parasympathetic nerve causes a decrease in heart rate.

Causes an increase in heart rate

Causes a decrease in heart rate

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

Image source: www.rch.org.au

B. Control of Heart Rate:

Hormonal Control

The adrenal glands produce the hormone adrenaline, which also affects heart rate.

During exercise or stress….

Sympathetic nervous system causes the adrenal glands to release adrenaline

At pacemaker: adrenaline causes an increase in the rate of cardiac impulses

Increase in heart rate

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

Learning Intentions

Success Criteria

Mrs Smith Ch24 regulating Mechanisms

To know how the heart rate is regulated and the effects of exercise on the cardiovascular and respiratory systems.

  • Analyse graphs showing distribution of blood to tissues at rest and during exercise

  • Calculate cardiac output under different conditions


Unit 2 the continuation of life

Vigorous exercise can cause huge changes of the body’s internal environment.

The metabolic rate increases in the muscles that are working hard.

need more oxygen

need more glucose

produce more CO2.

The body adjusts to meet these demands and returns to normal a.s.a.p

Experiments show (see Torrance p188) high levels of CO2 acts as the stimulus to trigger this. But severe lack of O2 can also cause this.

Control of the Heart. C. Exercise

Breathing rate & depthincreases to increase ventilation this promotes O2 uptake and CO2 removal

View the Scholar animation: http://courses.scholar.hw.ac.uk/vle/scholar/session.controller?action=viewContent&contentGUID=92be7024-6e80-a2da-455b-e306b499a29a

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

Carbon dioxide as the stimulus

Experiments show (see Torrance p188) high levels of CO2 acts as the stimulus to trigger an increase in breathing rate. The graph below shows the results!

Only the ‘abnormal’ air type 2 is found to cause breathing rate to increase sharply. It is concluded that it is the high level of CO2 in the ‘abnormal air that acts as a stimulus triggering increased rate of breathing.

Mrs Smith Ch24 regulating Mechanisms


Carbon dioxide as the stimulus con t

Carbon dioxide as the stimulus, Con’t

  • Further experiments show

    • Depth of breathing also increases in response to inhalation of air rich in CO2.,

    • In a person under going strenuous exercise it is the increased level of CO2 in the bloodstream that acts as the main stimulus for bringing about an increase in rate and depth of breathing.

Oxygen as a stimulus

  • It is worth noting that experiments also show that severe lack of oxygen will eventually also cause an increased rate and depth of breathing.

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

The effect of Exercise on the Respiratory System: Homeostatic control: Part 1

  • Chemoreceptor's in the carotid arteries and aorta are sensitive to the concentrations of CO2 in the bloodstream. A rise in CO2 levels during vigorous exercise causes these sensory cells to send an increased number of nerve impulses to the respiratory control centre in the medulla.

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

The effect of Exercise on the Respiratory System: Homeostatic control: Part 2!

  • This region of the brain responds by sending a greater number of nerve impulses to the intercostal muscles and diaphragm. The subsequent increased activity of these structures brings about an increase in rate and depth of breathing.

  • Excess CO2 is removed and the internal environment is kept within tolerable limits.

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

High CO2 concentration

SUMMARY: The effect of Exercise on the Respiratory System: Homeostatic control

More nerve impulses sent to respiratory control centre in medulla

Chemoreceptors in cartoid arteries & aorta detect CO2 concentration

More nerve impulses sent to intercostal muscles and diaphragm

An example of negative feedback control

Breathing rate & depthincreasescausing a return to normal CO2 concentration

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

ml/min

beats/min

litres

1000

B. Effect of exercise on cardiovascular system

Stroke volume = volume of blood expelled by each ventricle on contraction

Heart rate (pulse) = number of cardiac cycles per min

Cardiac output = volume of blood pumped out of a ventricle per min

All of these increase with exercise and even more with strenuous exercise

The stronger the contraction the higher the stroke volume

Cardiac output

Heart rate

Stroke volume

=

X

Mrs Smith Ch24 regulating Mechanisms

To convert ml to litres


Unit 2 the continuation of life

Task!!!

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

Try this calculation! These figures actually show the effect of exercise on cardiac output for the average adult human!

Mrs Smith Ch24 regulating Mechanisms


Effect of exercise on cardiovascular system

Effect of exercise on cardiovascular system

  • The cardio-accelerator centre in the medulla sends impulses via the sympathetic nerves in the heart making it beat more often and powerfully.

  • This increase in both heart rate and stroke volume brings about the increase the total cardiac input needed to boost delivery of oxygenated blood to respiring tissues and to return deoxygenated blood to the lungs.

  • During very strenuous exercise, the cardiac output of an average person can increase by X5. This is mainly due to the increased heart rate.

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

Control of local distribution of blood

  • All parts of the body require an adequate supply of blood to function efficiently. But the demands by each part are not constant.

  • At rest the ‘vegetative functions’ (digestion, urine production etc.) are promoted.

  • When the body undergoes ‘strenuous activity’ much blood is diverted to the skeletal muscles (for extra O2 and glucose).

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

Increase in CO2 concentration

Control of local distribution of blood

During exercise…

Chemoreceptors detect CO2 concentration

Nerve impulses sent to cardio-accelerator centre in medulla

An example of negative feedback control

Nerve impulses sent to arterioles in working muscles causing arteriole wall to relax to increase blood flow

Nerve impulses sent to arterioles in abdominal organs cause muscles in arteriole wall to contract to restrict blood flow

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

Distribution of blood to tissues during exercise

During exercise blood flow to various parts of the body changes.

Mrs Smith Ch24 regulating Mechanisms


Task torrance tyk pg192 qu 1 3

Task: Torrance-TYK pg192 Qu 1-3

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

Learning Intentions

Success Criteria

Mrs Smith Ch24 regulating Mechanisms

To know how the heart rate is regulated and the effects of exercise on the cardiovascular and respiratory systems.

To know how blood sugar levels and body temperature are regulated.

.

  • Explain how blood sugar level is controlled by the hormones insulin, glucagon and adrenalin.

  • Analyse glucose tolerance curves of normal and diabetic subjects


Unit 2 the continuation of life

DNA replication

Regulation of Blood Glucose Concentration

Blood sugar level must be kept within a certain range to provide the energy needed by cells for:

  • Synthesis of DNA, proteins and other complex molecules.

  • Active uptake of ions.

  • Muscle contraction.

Cells are therefore constantly using up the blood sugar.

To ensure a regular supply regardless of food consumed the body uses homeostasis!

Mrs Smith Ch24 regulating Mechanisms

Image source: library.tedankara.k12.tr


Liver as a storehouse

Liver as a storehouse

  • About 100g of glucose is stored as GLYCOGEN in the liver. Glucose can be added or removed from this reservoir if stored carbohydrate depending on supply and demand.

Mrs Smith Ch24 regulating Mechanisms


Control of blood sugar insulin and glucagon

Control of blood sugar: Insulin and glucagon

  • Insulin and glucagon are two hormones that control how much glucose (sugar) is in the blood

  • These hormones are made in the pancreas.

  • Your pancreas contains small groups of cells called the islets (or islands) of Langerhans.

Mrs Smith Ch24 regulating Mechanisms


Pancreas

Pancreas

  • When you eat a meal, the amount of sugar in your blood rises. The cells in your pancreas react by making more insulin.

  • When your blood sugar levels are low, the cells in your pancreas react by making more glucagon.

Mrs Smith Ch24 regulating Mechanisms


What does insulin do

What does insulin do?

  • After digestion, glucose enters your bloodstream.

  • The Islets of Langerhans in the pancreas detects an increase in blood sugar level.

  • These cells produce the hormone insulin, which is then transported to the liver in the bloodstream.

  • Insulin activates an enzyme to catalyse the reaction

    glucose glycogen

  • This decreases the blood sugar level.

  • Glycogen, a long chain carbohydrate, is stored in the liver until it is needed e.g. when you are sleeping

Mrs Smith Ch24 regulating Mechanisms


What does glucagon do

What does glucagon do?

  • Glucagon stops your blood glucose level from dropping too low.

  • When you exercise, your body uses the glucose in your blood to power your muscles. Your pancreas senses that you're using up your glucose supply.

  • As your blood glucose level drops, your pancreas stops making insulin and your pancreas makes glucagon

  • Glucagon activates an enzyme in your liver which catalyses the following reaction

    Glycogen Glucose

  • These activities push up the amount of glucose in your blood.

Mrs Smith Ch24 regulating Mechanisms


Control of blood sugar

Control of blood sugar

Insulin

Glucose

Glycogen

Glucagon

Mrs Smith Ch24 regulating Mechanisms


Task can you place the boxes into the appropriate places in the table below

Task, can you place the boxes into the appropriate places in the table below!

Mrs Smith Ch24 regulating Mechanisms


Watch this

Watch this

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

Adrenaline – Stress Response

The adrenal glands produce the hormone adrenaline in an emergency when the body needs a quick supply of glucose (for ‘fight or flight’)

Adrenaline is secreted by the adrenal gland and inhibits the secretion of insulin and promotes the breakdown of glycogen to glucose, overriding the normal homeostatic control.

When the crisis is over the normal homeostatic control then returns the blood sugar level to its norm.

Mrs Smith Ch24 regulating Mechanisms

Image source: www.rch.org.au


Unit 2 the continuation of life

Alternative Homeostasis

All factors controlled by homeostasis can be represented by a standard diagram.

When a factor deviates from the norm and is returned to normal it often overshoots the mark, which triggers the reverse set of corrective mechanisms.

So factors in a state of dynamic equilibrium are constantly wavering on either side of the norm. This is usually represented by 2 linked circuits.

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

Diabetes

Diabetics suffering from Diabetes mellitus can not produce enough (if any) insulin which causes their blood sugar level to get too high.

Because of this the kidneys can not reabsorb all of the glucose from the glomerular filtrate and so glucose is excreted in the urine.

Diabetes used to be fatal but can now be treated with a carefully controlled diet or insulin injections.

Mrs Smith Ch24 regulating Mechanisms

Image source:


Unit 2 the continuation of life

Glucose Tolerance Test

Glucose tolerance is the capacity of the blood to deal with the glucose we eat. It depends on the body’s ability to produce enough insulin.

A known mass of glucose is drunk. Then the level of glucose in the blood is monitored & graphed to give a glucose tolerance curve.

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

Glucose Tolerance Curves

Glucose level remains high

Severe diabetic – insulin injections and carefully controlled diet needed

Mild diabetic – condition controlled by diet

Delayed response

Glucose level returns to normal quickly

Not diabetic - Insulin production normal

Mrs Smith Ch24 regulating Mechanisms


Watch this1

Watch this!!!

Mrs Smith Ch24 regulating Mechanisms

http://www.bbc.co.uk/learningzone/clips/the-effect-of-high-sugar-intake-on-blood-sugar-levels/5371.html


Unit 2 the continuation of life

Learning Intentions

Success Criteria

Mrs Smith Ch24 regulating Mechanisms

To know how the heart rate is regulated and the effects of exercise on the cardiovascular and respiratory systems.

To know how blood sugar levels and body temperature are regulated.

  • Explain how temperature is controlled with reference to;

    • The role of the hypothalamus

    • Nerve communication between the hypothalamus and effectors

    • Involuntary and voluntary responses

    • Changes in ability to control body temperature with age


Control of body temperature

Control of Body Temperature

  • Core body temperature must remain at 37oC

  • Careful control of the blood supply to the skin can do this by reducing blood flow to the colder extremities in cool conditions.

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

Regulation of Body Temperature

  • Another example of homeostasis is the body’s regulation of body temperature.

  • The hypothalamus (the body’s temp-monitoring centre)monitors body temperature in two ways:

It contains central thermoreceptors which are sensitive to temperature changes in the blood, allowing detection of the body’s core temperature.

It acts as a thermostat by detecting nerve impulses from thermoreceptors in the skin (this conveys info about the surface temp of the body).

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

Regulation of Body Temperature

The hypothalamus sends nerve impulses to the effectors allowing the body to correct overcooling or overheating by:

Production of sweat.

Control of body hairs.

Vasodilation or Vasoconstriction of blood flow in the skin

Mrs Smith Ch24 regulating Mechanisms

Image source: www.pg.com


Unit 2 the continuation of life

Role of the Skin

The skin plays a leading role in temperature regulation. In response to nerve impulses from the hypothalamus the skin can act as both a receptorand an effector.

Image source:images.encarta.msn.com


Unit 2 the continuation of life

Role of the Skin

The skin helps to correct overheating of the body by

Increasing the rate of sweating.

Vasodilation

The skin help to correct overcooling of the body by

Decreasing the sweat of sweating.

Vasoconstriction

Contraction of erector muscles


Unit 2 the continuation of life

Correcting and heat loss and gain

1 & 3 . Sweating - Why sweat?

Sweat glands dampen the skin. This loses heat by causing evaporation of the sweat

1. When we sweat, heat energy from the body causes water from sweat to evaporate which cools the body.

3. When we are cold sweating in inhibited to conserve heat.


Sweating under pressure

Sweating under pressure!

Sweating caused by heat

Sweating caused by muscular contraction

Mrs Smith Ch24 regulating Mechanisms


Fyi nine sweaty facts

FYI: Nine Sweaty Facts

  • Humans are the most prolific sweaters in the entire animal kingdom

  • Sweating is accomplished through specialized sweat glands

  • These glands are found in the dermis and epidermis, distributed all over the body, except for the margins of the limbs, sex organs, and ear drums

  • They average between 150 and 340 glands/cm2 of skin for a total of between 2,000,000 and 5,000,000

  • Add them all together and you get a hole the size of your mouth

  • The sweat glands are innervated by the sympathetic nervous system

  • When a rise in core temperature is detected by the hypothalamus, impulses to the sympathetic system cause an increase in sweat output

  • The sweat gland consists of a deep coiled portion and a duct that opens on the skin

  • The duct aids in the re-absorption of electrolytes, mainly sodium and chloride, in the sweat so that the fluid discharged onto the skin has had the electrolyte concentration reduced by a factor of about 20

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

2. Correct overheating: Vasodilatation

When we get too hot arterioles leading to the skin become dilated, which allows lots of blood to flow near the skins surface and a loss of heat from the blood by radiation.

FYI: Red skin indicates vasodilatation, Alcohol increases this hence rosy cheeks after a few tipples!

View the animation: Scholar Unit 2, Figure 6.10: Vasodilation and vasoconstriction http://courses.scholar.hw.ac.uk/vle/scholar/session.controller?action=viewContent&back=search&contentGUID=8062401e-bfa9-4231-9508-4b6df971a8b6


Unit 2 the continuation of life

4. Correct overcooling: Vasoconstriction

When we are cold arterioles leading to the skin become constricted, which reduces the flow of blood to the skins surface so only a little heat is lost from the blood by radiation.


Unit 2 the continuation of life

Insulating layer of air

5: Preventing overcooling: Contraction of erector muscles

In a cold environment we need to reduce heat loss. This system is more efficient in furry animals than in humans.

Nerve impulses from the hypothalamus cause the erector muscles in our skin contract causing the hair (or feathers in birds) to rise up. This increases the layer of insulating air trapped by them so keeps the body warm.

hairs erect

erector muscles relaxed

erector muscles contracted


Unit 2 the continuation of life

hair

Surface of skin

Hair muscle

Contraction of this muscle makes the hair stand on end, trapping more insulating air.

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

Summary: Body Temperature


Activity complete the table using the given terms

Activity: Complete the table using the given terms

Mrs Smith Ch24 regulating Mechanisms


Answers

ANSWERS:

Mrs Smith Ch24 regulating Mechanisms


Quick quiz

Quick Quiz

Mrs Smith Ch24 regulating Mechanisms


Answers1

Answers

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

Investigating response to sudden heat loss

If one hand is plunged into icy water the temperature of that hand will drop, as will the temperature of the other hand (this is measured with a device called a THERMISTOR this can take a measurement every 30 seconds) . It is therefore concluded when heat is lost from one extremity, there is a compensatory reduction in temperature that occurs in the matching extremity.

This helps to conserve the temperature of the body’s core so that the body’s core temperature will stay the same.

Extremities vary in temperature much more than the body’s core.


Unit 2 the continuation of life

Role of other effectors in temperature regulation

These other effectors help temperature regulation by generating heat when it is needed:

Shivering by skeletal muscles: muscle contractions which generate heat energy, helping return temperature to normal

Liver:

high metabolic activity produces heat and helps to maintain body temperature

  • Hormones: increase metabolic rate

  • release of adrenaline during sudden exposure to cold temperatures

  • release of thyroxin


Unit 2 the continuation of life

turning on the heating

  • putting on a jumper

drinking a warm drink

Voluntary Responses for temperature regulation.

Temperature regulation mechanisms controlled by the hypothalamus are subconscious and involuntary.

However body temperature is also controlled by voluntary responses e.g.

When body temperature drops (or rises) nerve impulses pass the information to the thinking part of the brain (the cerebrum), which makes the person feel cold (or hot) and react.


Coping with heat and cold

Coping with heat and cold

Factors Affecting Thermal Acclimation

Age

Both infants and elderly have lessened ability to acclimatize to heat or cold

Body size and shape

The surface area to weight ratio will affect the level of acclimatization attainable

Body composition

Subcutaneous adipose deposits (fat) insulate the core and make it more difficult to dissipate heat in hot or easier to retain heat in the cold

Mrs Smith Ch24 regulating Mechanisms


Involuntary responses

Involuntary responses

  • The mechanisms of temperature regulation discussed thus far have all been involuntary responses, which are controlled at a subconscious level by the hypothalamus.

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

turning on the heating

  • putting on a jumper

drinking a warm drink

Voluntary Responses

However body temperature is also controlled by voluntary responses e.g.

When body temperature drops (or rises) nerve impulses pass the information to the thinking part of the brain (the cerebrum), which makes the person feel cold (or hot) and react.


Watch this2

Watch this

Mrs Smith Ch24 regulating Mechanisms


Unit 2 the continuation of life

Learning Intentions

Success Criteria

Mrs Smith Ch24 regulating Mechanisms

To know how body temperature is regulated.

  • Discuss Hypothermia in infancy & old age


Unit 2 the continuation of life

Brown fat

Temperature regulation in infants

  • The exposed area of a small animal relative to its volume is greater than that of a larger animal of similar shape.

  • So the relative surface area of a baby is greater than an adults. So a baby would suffer more heat loss than an adult.

  • Baby’s involuntary responses to decrease in temperature:

  • vasoconstriction of skins blood vessels

  • increase in metabolic rate in brown fat (adipose) tissue (more supplied with blood vessels than white fat)

Brown fat deposits are found in newborns and hibernating mammals, and can produce heat to warm the body.


Unit 2 the continuation of life

Uncontrollable shivering and blue lips are early signs of hypothermia

Babies and the elderly are the most susceptible to hypothermia

Hypothermia

Hypothermia is caused when the body’s core temperature drops to a dangerously low temperature.


Unit 2 the continuation of life

Critical Temperature

The lower critical temperature is the external temperature (~27oC) when a naked adult’s body can only just manage to maintain normal body temperature.

Any temperature below this needs heat energy to be generated by metabolism to keep the body at 37oC.

As babies have a larger surface area they are more susceptible to the effects of cold temperature and have a higher critical temperature adults.

If a newborn baby is exposed to cold temperatures, it will use up its limited food reserves to keep the body warm and once these are used up its core body temperature will drop.


Unit 2 the continuation of life

Hypothermia in Babies

Temperatures that are uncomfortably cold, but tolerable, for adults can cause hypothermia or even death in babies because their body’s temperature regulation mechanisms are not fully developed.

Pre-term (premature) babies are even more susceptible to hypothermia because:

  • Their temperature regulation

  • mechanisms are even less developed.

  • Small size, so larger relative surface area to loose heat.

  • Higher critical temperature & burn food reserves at higher temperatures than normal.

  • Small food reserves which run out quickly.


Unit 2 the continuation of life

Hypothermia in the Elderly

  • The elderly are more susceptible to hypothermia because:

  • Their temperature regulation mechanisms are less efficient

    • Blood vessels fail to undergo vasoconstriction when exposed to cold temperatures

    • Fail to shiver when cold

  • They have a slower rate of metabolism so don’t generate heat needed to keep body warm

  • They are less active so don’t generate heat through movement

  • Body temperature drops when you sit for long periods in a cold room


Unit 2 the continuation of life

Breakdown of homeostasis

Homeostasis only works in certain limits!!

If exposed to an extreme environmental condition for a long time the negative feedback control breaks down.

For example, the elderly often fail to realise the signs of hypothermia so don’t take corrective action (e.g. turning up the heating). If their homeostatic temperature control has broken down their body can’t recover on its own. They become hypothermic and need urgent medical attention.


Task torrance tyk pg199 qu 1 3

Task: Torrance-TYK pg199 Qu 1-3

Mrs Smith Ch24 regulating Mechanisms


Task torrance ayk pg199 202 qu s 1 6

Task: Torrance AYK pg199/202 Qu’s 1-6

Mrs Smith Ch24 regulating Mechanisms


Essay style questions scholar

Essay style Questions Scholar

Give an account of hormonal control of the regulation of blood sugar levels.

Mrs Smith Ch24 regulating Mechanisms


Answer give an account of hormonal control of the regulation of blood sugar levels 10

ANSWER: Give an account of hormonal control of the regulation of blood sugar levels. (10)

  • Each numbered point is worth 1 mark. The information in brackets is not a required part of the

  • Correct facts (8 marks)

  • Insulin is secreted by the pancreas/islets of Langerhans when blood glucose/sugar levels are high

  • Insulin controls/causes the conversion of blood glucose/sugar into glycogen (not 'converts')

  • Glycogen is stored in the liver

  • When blood glucose/sugar levels return to normal, insulin production decreases

  • Glucagon is secreted by the pancreas/islets of Langerhans when blood glucose/sugar levels are low

  • Glucagon controls/causes the conversion of glycogen to glucose (not 'converts')

  • When blood glucose/sugar levels return to normal, glucagon production decreases

  • This type of control is known as negative feedback control (mark if given for either insulin or glucagon, but not both)

  • In emergency situations, (the hormone) adrenaline is secreted by the adrenal glands

  • Adrenaline overrides the action of insulin

  • Once the emergency is over, adrenaline levels return to normal

  • and the homeostatic control (by insulin and glucagon) is regained

  • Coherence (1 mark)

  • One mark is given if at least 5 relevant points provided.

  • Relevance (1 mark)

  • It causes glycogen to be (rapidly) converted to glucose (not 'converts')

  • One mark is deducted if a detailed explanation of negative feedback control is given.


Sqa past paper 2012

SQA Past Paper 2012

Qu 2b. Describe involuntary mechanisms of temperature control. (10).

Mrs Smith Ch24 regulating Mechanisms


Sqa past paper 2008

SQA Past Paper 2008

  • Give an account of temperature regulation in cold conditions under the

  • following headings:

  • (i) voluntary responses (3)

  • (ii) involuntary responses (5)

  • (iii) hypothermia (2)

Mrs Smith Ch24 regulating Mechanisms


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