Download ppt_E1ch02_regulation of body temperature

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Think about…
2.1 Importance of regulating
body temperature
2.2 The role of skin
2.3 Other mechanisms of body
temperature regulation
2.4 The thermoregulatory centre
Recall ‘Think about…’
Summary concept map
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Heatstroke (中暑) often occurs among
marathon runners, especially on hot and
humid days.
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They fail to lose heat efficiently and the
body temperature may rise to as high as
43℃.
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They feel dizzy and may become
unconscious.
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Heatstroke can be deadly
if not treated immediately.
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Why is heatstroke
more likely to occur
under hot and humid
conditions
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Why may death
result when the body
temperature is too
high
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What are the
treatments and
precautions for
heatstroke
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2.1 Importance of regulating
body temperature
How does the environmental
temperature affect our body
temperature?
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human body
temperature (oC)
2.1 Importance of regulating body temperature
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30
20
body temperature
kept at about 37oC
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0
30
40
10
20
environmental temperature (oC)
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2.1 Importance of regulating body temperature
• metabolic activities are controlled by
enzymes
only work efficiently within a
narrow range of temperature
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2.1 Importance of regulating body temperature
• metabolic activities are controlled by
enzymes
• stable body temperature
 keeps enzyme activity and metabolic
rate steady
 we stay active at all times
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2.1 Importance of regulating body temperature
Heat gain
radiation from
the sun
liver metabolism
respiration in cells
muscle contraction
conduction
from hot sand
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2.1 Importance of regulating body temperature
Heat loss
Radiation?
exhalation
evaporation of
sweat
convection
due to air
current
urination and
defaecation
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2.1 Importance of regulating body temperature
Heat gain = Heat loss
stable body
temperature
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2.1 Importance of regulating body temperature
• skin is the major organ involved in
regulating body temperature
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2.1 Importance of regulating body temperature
1 A stable body temperature allows
enzymes in cells to function
properly, so that the metabolic rate
can be kept steady and we can
stay active at all times.
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2.1 Importance of regulating body temperature
2 Heat is transferred between the
body and the environment by
radiation , conduction ,
convection and evaporation.
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2.2 The role of skin
Structure and functions of skin
• two layers:
epidermis
(表皮)
dermis
(真皮)
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2.2 The role of skin
Structure and functions of skin
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Skin on different parts of the
body
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Skin
• two layers:
epidermis
dermis
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Scanning electron
microscope (SEM) picture
of normal skin
E. coli on the surface of
human skin.
Human hair and skin layers. scanning electron micrograph (SEM) of a section through human skin with a hair
(upper centre) emerging from the surface. The skin layers, from top to bottom, are the stratum corneum (flaky,
brown), composed of flattened, dead skin cells that form the surface of the skin. The dead cells from this layer
are continuously being shed and replaced by cells from the living epidermal layer below (red, extending
downwards around hair follicle). The lowest layer seen here is the dermis (grey-brown, lower centre). This is a
thick layer of fibrous connective tissue that supports and nourishes the epidermis. Magnification: x100
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2.2 The role of skin
1 Epidermis
• three layers:
epidermis
dermis
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2.2 The role of skin
1 Epidermis
• three layers:
i) Innermost layer
• produces new cells
by mitotic cell division
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2.2 The role of skin
1 Epidermis
• three layers:
i) Innermost layer
• contains melanin (黑素)
absorbs UV light
protects the body
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2.2 The role of skin
1 Epidermis
• three layers:
i) Innermost layer
• contains melanin (黑素)
determines skin colour
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2.2 The role of skin
1 Epidermis
• three layers:
i) Innermost layer
• produces vitamin D when
exposed to sunlight
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2.2 The role of skin
1 Epidermis
• three layers:
ii) Middle layer:
• consists of living cells
pushed towards surface
die and flatten
outermost layer
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2.2 The role of skin
1 Epidermis
• three layers:
iii) Outermost layer
• consists of dead cells
constantly worn away and
replaced by new cells
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2.2 The role of skin
1 Epidermis
• three layers:
iii) Outermost layer
• consists of dead cells
reduce water loss
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2.2 The role of skin
1 Epidermis
• three layers:
iii) Outermost layer
• consists of dead cells
protect from
mechanical injury
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2.2 The role of skin
1 Epidermis
• three layers:
iii) Outermost layer
• consists of dead cells
prevent entry of
pathogens
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2.2 The role of skin
2 Dermis
i) Sensory receptors
• detect stimuli
pain receptor
touch receptor
thermoreceptor
pressure receptor
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2.2 The role of skin
2 Dermis
ii) Hair follicles (毛囊)
• new hair cells produced
from the base
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2.2 The role of skin
2 Dermis
ii) Hair follicles (毛囊)
• new hair cells produced
from the base
root of hair
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2.2 The role of skin
2 Dermis
iii) Erector muscles (豎毛肌)
and hairs
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2.2 The role of skin
2 Dermis
iii) Erector muscles (豎毛肌)
and hairs
• erector muscle contracts
 hair pulled upright
• erector muscle relaxes
 hair lies flat
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Goose bumps
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Goose bumps
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2.2 The role of skin
2 Dermis
iv) Sweat glands (汗腺)
• form sweat
contains mainly
water, salts, urea
and other
metabolic waste
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2.2 The role of skin
2 Dermis
iv) Sweat glands (汗腺)
sweat pore (汗孔)
sweat duct (汗管)
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2.2 The role of skin
2 Dermis
iv) Sweat glands (汗腺)
• sweat coming out to
the skin surface
 sweating
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2.2 The role of skin
2 Dermis
iv) Sweat glands (汗腺)
• sweat coming out to
the skin surface
 sweating
for regulating
body temperature
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2.2 The role of skin
2 Dermis
iv) Sweat glands (汗腺)
• sweat coming out to
the skin surface
 sweating
for excretion
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Male Sweat Boosts Women’s Hormone Levels
..Sweat has been the main focus of research on human pheromones,
and in fact, male underarm sweat has been shown to improve
women’s moods and affect their secretion of luteinizing hormone,
which is normally involved in stimulating ovulation…
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2.2 The role of skin
2 Dermis
v) Blood vessels
• circulation of blood
supplies oxygen
and nutrients
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2.2 The role of skin
2 Dermis
v) Blood vessels
• circulation of blood
removes waste
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2.2 The role of skin
2 Dermis
v) Blood vessels
• circulation of blood
distributes heat
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2.2 The role of skin
2 Dermis
v) Blood vessels
• vasoconstriction and vasodilation
‘vessel’
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2.2 The role of skin
2 Dermis
v) Blood vessels
• vasoconstriction and vasodilation
regulate heat loss by
controlling the amount of blood
flowing to the body surface
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2.2 The role of skin
2 Dermis
v) Blood vessels
• vasoconstriction and vasodilation
capillary
arteriole
venule
shunt vessel (分流血管)
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2.2 The role of skin
2 Dermis
v) Blood vessels
• vasoconstriction and vasodilation
2 less
blood to
capillary
1 arteriole
constricts
less heat is lost
Under cold
conditions
3 more blood through shunt vessel
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2.2 The role of skin
2 Dermis
v) Blood vessels
• vasoconstriction and vasodilation
2 more
blood to
capillary
1 arteriole
dilates
more heat is lost
Under hot
conditions
3 less blood through shunt vessel
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2.2 The role of skin
Vasoconstriction and
vasodilation occur in
the capillaries.
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2.2 The role of skin
Capillaries cannot
constrict or dilate
because they have
no muscle walls.
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2.2 The role of skin
It is the arterioles in the deeper
part of the dermis that constrict
or dilate.
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2.2 The role of skin
2 Dermis
vi) Sebaceous glands
• secrete sebum (皮脂)
keeps hairs and
skin supple and
waterproof
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2.2 The role of skin
2 Dermis
vi) Sebaceous glands
• secrete sebum (皮脂)
a natural
antiseptic
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2.2 The role of skin
epidermis
sweat
duct
hair
follicle
mammalian
skin (L.S)
sebaceous
gland
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Pimples – inflamed
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2.2 The role of skin
Subcutaneous fat
• insulates the body to
reduce heat loss
• as energy reserve
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2.2 The role of skin
2.1
Examination of the mammalian skin
1 Examine a prepared
slide of mammalian
skin or a skin model.
2 Identify the structures.
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2.2 The role of skin
Functions of structures of the skin:
Epidermis:
1 Innermost layer
• produces new cells by mitotic
cell division
• contains melanin which
protects the body against
ultraviolet light
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2.2 The role of skin
Functions of structures of the skin:
Epidermis:
1 Innermost layer
• produces vitamin D
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2.2 The role of skin
Functions of structures of the skin:
Epidermis:
2 Middle layer
• when pushed towards the
surface , cells die and form
the outermost layer
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2.2 The role of skin
Functions of structures of the skin:
Epidermis:
3 Outermost layer
• reduces water loss by
evaporation
• protects the body from
mechanical injury
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2.2 The role of skin
Functions of structures of the skin:
Epidermis:
3 Outermost layer
• prevents the entry of pathogens
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2.2 The role of skin
Functions of structures of the skin:
Dermis:
1 Sensory receptors
• detect stimuli
2 Hair follicles
• produce new hairs
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2.2 The role of skin
Functions of structures of the skin:
Dermis:
3 Erector muscles and hairs
• help regulate body temperature
4 Sweat glands
• secrete sweat for excretion and
body temperature regulation
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2.2 The role of skin
Functions of structures of the skin:
Dermis:
5 Blood vessels
• supply oxygen and nutrients to
skin cells and remove waste from
them
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2.2 The role of skin
Functions of structures of the skin:
Dermis:
5 Blood vessels
• help regulate body temperature
by vasoconstriction and
vasodilation
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2.2 The role of skin
Functions of structures of the skin:
Dermis:
6 Sebaceous glands
• secrete sebum that keeps the
hairs and skin supple and
waterproof, and reduces the
growth of harmful microorganisms
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2.2 The role of skin
Functions of structures of the skin:
Subcutaneous fat:
• acts as a heat insulating layer
• acts as energy reserve
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2.2 The role of skin
How does skin regulate
body temperature?
3D animation
• by controlling heat loss
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2.2 The role of skin
Under cold conditions
1 erector muscles contract
to pull hairs upright
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2.2 The role of skin
Under cold conditions
2 sweating is reduced
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2.2 The role of skin
Under cold conditions
3 vasoconstriction
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2.2 The role of skin
Under cold conditions
less heat
is lost
4 layer of subcutaneous fat becomes
thicker (long-term response)
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2.2 The role of skin
Under hot conditions
1 erector muscles relax and
hairs lie flat
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2.2 The role of skin
Under hot conditions
2 sweating increases
3 vasodilation
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2.2 The role of skin
Under hot conditions
more heat
is lost
4 layer of subcutaneous fat becomes
thinner (long-term response)
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2.2 The role of skin
Sweat is produced
only when the body
temperature increases.
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2.2 The role of skin
Sweat is produced
most of the time to
remove metabolic
waste.
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2.2 The role of skin
Structure
1 Erector
muscles
2 Hairs
3 Sweat glands
Response under
cold conditions
Contract
Pulled upright
Secrete less
sweat
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2.2 The role of skin
Response
under
Structure
cold conditions
Constrict
4 Arterioles
(vasoconstriction)
5 Subcutaneous Becomes thicker
(long-term)
fat
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2.2 The role of skin
Structure
1 Erector
muscles
2 Hairs
3 Sweat glands
Response under
hot conditions
Relax
Lie flat
Secrete more
sweat
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2.2 The role of skin
Structure
4 Arterioles
5 Subcutaneous
fat
Response under
hot conditions
Dilate
(vasodilation)
Becomes thinner
(long-term)
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2.3 Other mechanisms of body
temperature regulation
Muscle contraction
• metabolism in muscle cells generates heat
• shivering (顫抖)
- skeletal muscles contract
involuntarily
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2.3 Other mechanisms of body temperature regulation
Action of hormone
• body temperature is also regulated by
thyroxine (甲狀腺素)
increases metabolic rate
 generates heat to keep the
body warm
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2.3 Other mechanisms of body temperature regulation
Action of hormone
• body temperature is also regulated by
thyroxine (甲狀腺素)
secretes
thyroid gland
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2.3 Other mechanisms of body temperature regulation
Action of hormone
• body temperature is also regulated by
thyroxine (甲狀腺素)
• increased thryoxine secretion is a
long-term response
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2.3 Other mechanisms of body temperature regulation
Under cold conditions
1 A decrease in blood temperature
stimulates the hypothalamus to secrete
TSH-releasing hormone (TRH).
hypothalamus
TRH
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2.3 Other mechanisms of body temperature regulation
Under cold conditions
2 TRH stimulates the pituitary gland to
secrete thyroid stimulating hormone
(TSH).
hypothalamus
TRH
pituitary gland
TSH
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2.3 Other mechanisms of body temperature regulation
Under cold conditions
3 TSH stimulates the thyroid gland to
secrete thyroxine.
hypothalamus
TRH
pituitary gland
TSH
thyroxine
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2.3 Other mechanisms of body temperature regulation
Under cold conditions
4 Thyroxine increases the metabolic rate of
body cells and more heat is generated.
hypothalamus
TRH
pituitary gland
TSH
thyroxine
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2.3 Other mechanisms of body temperature regulation
Under cold conditions
thyroxine inhibits secretions of
TRH and TSH (negative feedback)
hypothalamus
TRH
pituitary gland
TSH
thyroxine
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2.3 Other mechanisms of body temperature regulation
Change of behaviour
• voluntary behaviour also plays a
part in regulating body temperature
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2.3 Other mechanisms of body temperature regulation
Under cold conditions
wear more
clothes
turner on
the heater
take in warm
food/drinks
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2.3 Other mechanisms of body temperature regulation
Under hot conditions
wear fewer
clothes
turner on
the fan
take in cold
food/drinks
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2.3 Other mechanisms of body temperature regulation
1
Metabolism in muscle cells
generates heat to maintain the body
temperature. Muscle contraction
also generates heat. Shivering
provides extra amount of heat to
keep us warm under cold conditions.
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2.3 Other mechanisms of body temperature regulation
2
Thyroxine increases the metabolic
rate of most cells, so that more heat
can be generated to keep the body
warm. Increased thyroxine secretion
is a long-term response to a cold
environment.
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2.3 Other mechanisms of body temperature regulation
3 Behavioural mechanisms that help
regulate body temperature:
a Under cold conditions, we can
reduce heat loss and increase
heat gain by means like wearing
more clothes, turning on the
heater and taking in more warm
food and drinks.
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2.3 Other mechanisms of body temperature regulation
3 Behavioural mechanisms that help
regulate body temperature:
b Under hot conditions, we can
promote heat loss and reduce
heat gain by means like wearing
fewer clothes, turning on the fan
and taking in more cold food
and drinks.
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2.4 The thermoregulatory centre
• in hypothalamus
• has thermoreceptors that detect the
temperature of blood passing through it
• receives nerve impulses about changes
in external temperature from the
thermoreceptors in the skin
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2.4 The thermoregulatory centre
thermoreceptors
heat loss
centre
rises
thermoregulatory
centre in
hypothalamus
normal
body temp
heat gain
centre
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2.4 The thermoregulatory centre
thermoreceptors
heat loss
centre
rises
initiates
mechanisms
falls
normal
body temp
normal
body temp
heat gain
centre
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2.4 The thermoregulatory centre
Mechanisms to promote heat loss and
decrease heat gain:
Physiological
• relaxation of erector muscles
• increased sweating
• vasodilation
• decreased secretion of thyroxine
(long-term)
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2.4 The thermoregulatory centre
Mechanisms to promote heat loss and
decrease heat gain:
Structural
• thinner layer of subcutaneous fat
(long-term)
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2.4 The thermoregulatory centre
Mechanisms to promote heat loss and
decrease heat gain:
Behavioural
• wear fewer clothes
• turn on the fan
• take in more cold food
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2.4 The thermoregulatory centre
thermoreceptors
heat loss
centre
rises
falls
normal
body temp
normal
body temp
falls
thermoreceptors
initiates
mechanisms
rises
heat gain
centre
initiates
mechanisms
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2.4 The thermoregulatory centre
Mechanisms to reduce heat loss and
increase heat gain:
Physiological
• contraction of erector muscles
• reduced sweating
• vasoconstriction
• shivering
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2.4 The thermoregulatory centre
Mechanisms to reduce heat loss and
increase heat gain:
Physiological
• increased secretion of thyroxine
(long-term)
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2.4 The thermoregulatory centre
Mechanisms to reduce heat loss and
increase heat gain:
Structural
• thicker layer of subcutaneous fat
(long-term)
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2.4 The thermoregulatory centre
Mechanisms to reduce heat loss and
increase heat gain:
Behavioural
• wear more clothes
• turn on the heater
• take in more warm food
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2.4 The thermoregulatory centre
1a
Thermoreceptors in skin
detect changes in external
temperature and send nerve
impulses to the thermoregulatory
centre in the hypothalamus .
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2.4 The thermoregulatory centre
1b
Thermoreceptors in the
hypothalamus detect changes
in the temperature of blood
passing through it.
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2.4 The thermoregulatory centre
2a
Skin or blood temperature rises
heat loss centre stimulated
mechanisms
• erector muscles relax and hairs lie flat
• sweating increases
• vasodilation occurs
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2.4 The thermoregulatory centre
2a
Skin or blood temperature rises
heat loss centre stimulated
mechanisms
• thyroxine secretion decreases
• subcutaneous fat becomes thinner
• behavioural mechanisms ,
e.g. wear fewer clothes, turn on the fan
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2.4 The thermoregulatory centre
2b
Skin or blood temperature falls
heat gain centre stimulated
mechanisms
• erector muscles contract and hairs are
pulled upright
• sweating decreases
• vasoconstriction and shivering occur
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2.4 The thermoregulatory centre
2b
Skin or blood temperature falls
heat gain centre stimulated
mechanisms
• thyroxine secretion increases
• subcutaneous fat becomes thicker
• behavioural mechanisms, e.g. wear
more clothes, turn on the heater
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1
Why is heatstroke more likely to
occur under hot and humid conditions?
High humidity lowers the rate of
evaporation of sweat, so the body
cannot lose heat effectively and
heatstroke is likely to occur.
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2
Why may death result when the
body temperature is too high?
When the body temperature is too high,
enzymes cannot work properly and
cells fail to function.
126
3
What are the treatments and
precautions for heatstroke?
To treat heatstroke, we should move the
person to shaded areas and wrap the
body with cool wet towels.
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3
What are the treatments and
precautions for heatstroke?
To prevent heatstroke, we should avoid
doing vigorous exercise in a hot
environment.
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A stable body temperature
maintained by
balancing
heat loss
heat gain
controlled by
thermoregulatory centre
in hypothalamus
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thermoregulatory centre
in hypothalamus
through mechanisms
that involve
skin
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skin
structures involved
erector
muscles
and hairs
sweat
glands
blood
vessels
subcutaneous fat
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thermoregulatory centre
in hypothalamus
through mechanisms
that involve
blood circulation
controls
distribution
by
of heat
vasoconstriction
and vasodilation
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thermoregulatory centre
in hypothalamus
through mechanisms
that involve
skeletal muscles
under cold
conditions
shiver
production of
more heat
leads to
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thermoregulatory centre
in hypothalamus
through mechanisms
that involve
thyroid gland
secretes
thyroxine
increases
metabolic rate
134
thermoregulatory centre
in hypothalamus
through mechanisms
that involve
cerebrum
brings about
behavioural
mechanisms
135