Transcript Physiological homeostasis

Higher Human Biology
Unit 2: The Continuation of
Life
Chapter 24:
Regulating Mechanisms
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Mechanisms
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Learning Intentions
To know how
the heart rate
is regulated.
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Success Criteria
1. Outline the principle of
negative feedback
2. Explain how heart rate
is controlled with
reference to the role of
hormonal and nervous
system
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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….
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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).
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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.
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8. Negative Feedback Control
When a factor
affecting the
body’s internal
environment
deviates from its
norm (or setpoint) the body
responds to
correct the
change.
Image
source:
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www.hw.ac.uk
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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
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community
of living cells Mrs
to Smith
function
efficiently and survive.
Mechanisms
9. Control of Heart Rate: Pacemaker
Although the heartbeat is initiated by the pacemaker tissue 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.
Sino-atrial node
(SAN)
= Pacemaker
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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.
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Image source:
www.drstandley.com
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Control of Heart rate.
The Autonomic Nervous System
• 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:
– homeostasis within the body (parasympathetic branch)
– response to stress – the "fight or flight" response (sympathetic
branch)
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Parasympathetic v Sympathetic
homeostasis
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response to stress
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Image source: www.biocomtech.com
The Autonomic Nervous System:
The Vagus Nerve
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.
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People have two
vagus nerves,
one for each
side, running
roughly parallel
from the
medulla in the
brain to the
12
bowels.
A. 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.
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A. 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
The cardio-inhibitor centre sends
Causes a decrease in heart
rate
nerve impulses via the
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parasympathetic
vagusMrsnerve.
Image source: http://courses.scholar.hw.ac.u
Mechanisms
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
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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
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At pacemaker:
adrenaline
causes an
increase in the
rate of cardiac
impulses
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Increase in
heart rate
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Learning Intentions
Success Criteria
To know how the
heart rate is
regulated and the
effects of exercise
on the
cardiovascular and
respiratory
systems.
3. Analyse graphs
showing distribution of
blood to tissues at rest
and during exercise
4. Calculate cardiac output
under different
conditions
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Control of the Heart. C. Exercise
• 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
Breathing rate & depth
increases to increase
• need more glucose
ventilation this promotes O2
• produce more CO2.
uptake and CO2 removal
• 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.
View
the Scholar animation: Mrs Smith Ch24 regulating
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http://courses.scholar.hw.ac.uk/vle/scholar/session.controller?action=viewContent&contentGUID=92be7024-6e80-a2da-455b-e306b499a29a
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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.
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Mechanisms
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.
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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.
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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.
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SUMMARY: The effect of Exercise on the
Respiratory System: Homeostatic control
High CO2
concentration
Chemoreceptors in
cartoid arteries &
aorta detect CO2
concentration
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More nerve impulses
sent to respiratory
control centre in
medulla
An example of
negative
feedback control
Breathing rate &
depth increases
causing a return to
normal CO2
concentration
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More nerve
impulses sent to
intercostal muscles
and diaphragm
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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
All of these increase
with exercise and even
more with strenuous
exercise
The stronger the
contraction the
higher the stroke
volume
ml/min
beats/min
Cardiac output
litres
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Cardiac output =
volume of blood
pumped out of a
ventricle per min
=
Heart rate
X Stroke volume
1000
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To convert ml to litres
Task!!!
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Try this calculation! These figures actually
show the effect of exercise on cardiac output
for the average adult human!
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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.
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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).
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Control of local distribution of blood
During exercise…
Chemoreceptors
detect CO2
concentration
An example
of negative
feedback
control
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Increase in
CO2
concentration
Nerve impulses sent to
cardio-accelerator
centre in medulla
Nerve impulses sent
to arterioles in
working muscles
causing arteriole wall
to relax to increase
blood flow
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Nerve impulses sent
to arterioles in
abdominal organs
cause muscles in
arteriole wall to
contract to restrict
blood flow 29
Distribution of blood to tissues during exercise
During exercise blood flow to various parts of the body changes.
Tissue
Change due to
exercise
Reason
Heart
Increase
to meet its demand for more glucose and oxygen
Brain
None
Basic energy demands of cells not affected
Kidneys
Decrease
kidney processes can be postponed until the
exercise is finished
Skin
Increase
allow the heat produced in muscles to be
radiated from the surface of the skin
Intestines
Decrease
processes of digestion and absorption can be
postponed until the exercise is finished
Increase
to meet their demands for more glucose and
oxygen
& liver
Skeletal
muscles
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Task: Torrance-TYK pg192 Qu 1-3
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Learning Intentions
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.
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.
Success Criteria
5. Explain how blood sugar
level is controlled by the
hormones insulin,
glucagon and adrenalin.
6. Analyse glucose
tolerance curves of
normal and diabetic
subjects
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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!
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DNA replication
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Image source: library.tedankara.k12.tr
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.
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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.
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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.
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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
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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.
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Control of blood sugar
Insulin
Glucose
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Glucagon
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Glycogen
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Task, can you place the boxes into the
appropriate places in the table below!
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Watch this
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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.
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Image source:
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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
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represented by 2 linked
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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.
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Image source:
Diabetes used to
be fatal but can
now be treated
with a carefully
controlled diet or
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insulin injections.
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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.
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Glucose Tolerance Curves
Glucose level
remains high
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Severe diabetic – insulin
injections and carefully
controlled diet needed
Delayed response
Mild diabetic – condition
controlled by diet
Glucose level
returns to
normal quickly
Not diabetic - Insulin
production normal
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Watch this!!!
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http://www.bbc.co.uk/learningzone/clips/the-effect-of-high-sugar-intake-on-blood-sugarMechanisms
levels/5371.html
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Learning Intentions
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.
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Success Criteria
7. 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
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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.
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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:
1. It contains central thermoreceptors which are
sensitive to temperature changes in the blood,
allowing detection of the body’s core temperature.
2. It acts as a thermostat by detecting nerve impulses
from thermoreceptors in the skin (this conveys info
about the surface temp of the body).
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Regulation of Body Temperature
The hypothalamus sends nerve impulses to the
effectors allowing the body to correct overcooling or
overheating by:
1. Production of sweat.
2. Control of body hairs.
3. Vasodilation or
Vasoconstriction of
blood flow in the skin
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Image source: www.pg.com
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 receptor and an effector.
Image source: images.encarta.msn.co
Role of the Skin
The skin helps to
correct overheating of
the body by
1. Increasing the rate
of sweating.
2. Vasodilation
The skin help to correct
overcooling of the body by
3. Decreasing the sweat of
sweating.
4. Vasoconstriction
5. Contraction of erector muscles
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!
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Sweating
caused by
heat
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Sweating
caused by
muscular
contraction
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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
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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&b
ack=search&contentGUID=8062401e-bfa9-4231-9508-4b6df971a8b6
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.
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
Insulating
layer of air
erector muscles
relaxed
erector muscles
contracted
hair
Surface
of skin
Hair muscle
Contraction of
this muscle
makes the hair
stand on end,
trapping more
insulating air.
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Summary: Body Temperature
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Activity: Complete the table
using the given terms
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ANSWERS:
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Quick Quiz
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Answers
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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.
Role of other effectors in
temperature regulation
These other effectors help temperature regulation by
generating heat when it is needed:
Shivering by skeletal
Liver:
Hormones: increase
muscles: muscle
high metabolic
metabolic rate
contractions which
activity produces
• release of adrenaline
generate heat energy, heat and helps to during sudden exposure to
helping return
maintain body
cold temperatures
temperature to normal
temperature
• release of thyroxin
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.
putting on a
jumper
turning on the heating
drinking a warm
drink
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
• 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
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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.
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Voluntary Responses
However body temperature is also controlled by
voluntary responses e.g.
putting on a jumper
turning on the heating
drinking a warm
drink
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 this
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Learning Intentions
Success Criteria
To know how
body
temperature
is regulated.
8. Discuss Hypothermia in
infancy & old age
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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 Brown fat
heat to warm the body.
Hypothermia
Hypothermia is caused
when the body’s core
temperature drops to a
dangerously low
temperature.
Uncontrollable
shivering and
blue lips are early
signs of
hypothermia
Babies and the elderly are
the most susceptible to
hypothermia
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.
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.
Hypothermia in the Elderly
The elderly are more susceptible to hypothermia because:
1. Their temperature regulation mechanisms are less
efficient
 Blood vessels fail to undergo vasoconstriction when
exposed to cold temperatures
 Fail to shiver when cold
2. They have a slower rate of metabolism so don’t generate
heat needed to keep body warm
3. They are less active so don’t generate heat through
movement
4. Body temperature drops when you sit for long periods in a
cold room
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
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Task: Torrance AYK
pg199/202 Qu’s 1-6
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Essay style Questions Scholar
Give an account of hormonal
control of the regulation of
blood sugar levels.
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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)
1.Insulin is secreted by the pancreas/islets of Langerhans when blood glucose/sugar levels are
high
2.Insulin controls/causes the conversion of blood glucose/sugar into glycogen (not 'converts')
3.Glycogen is stored in the liver
4.When blood glucose/sugar levels return to normal, insulin production decreases
5.Glucagon is secreted by the pancreas/islets of Langerhans when blood glucose/sugar levels are low
6.Glucagon controls/causes the conversion of glycogen to glucose (not 'converts')
7.When blood glucose/sugar levels return to normal, glucagon production decreases
8.This type of control is known as negative feedback control (mark if given for either insulin or
glucagon, but not both)
9.In emergency situations, (the hormone) adrenaline is secreted by the adrenal glands
11.Adrenaline overrides the action of insulin
12.Once the emergency is over, adrenaline levels return to normal
13.and the homeostatic control (by insulin and glucagon) is regained
Coherence (1 mark)
1.One mark is given if at least 5 relevant points provided.
Relevance (1 mark)
10.It causes glycogen to be (rapidly) converted to glucose (not 'converts')
1.One mark is deducted if a detailed explanation of negative feedback control is given.
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SQA Past Paper 2012
Qu 2b. Describe
involuntary mechanisms
of temperature control.
(10).
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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)
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