think about… 2.1 importance of regulating body temperature 2.2 the role of skin
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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. Deadly enemy of marathon. runners. - PowerPoint PPT PresentationTRANSCRIPT
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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 heatstrokemore likely to occur under hot and humid conditions
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Why may deathresult when the body temperature is too high
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What are thetreatments 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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hum
an b
ody
tem
pera
ture
(o C
)
environmental temperature (oC)10
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20
20
30
30
40
400
2.1 Importance of regulating body temperature
body temperature kept at about 37oC
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• metabolic activities are controlled by enzymes
only work efficiently within a narrow range of temperatureonly work efficiently within a narrow range of temperature
2.1 Importance of regulating body temperature
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• metabolic activities are controlled by enzymes
keeps enzyme activity and metabolic rate steady
• stable body temperature
we stay active at all times
2.1 Importance of regulating body temperature
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2.1 Importance of regulating body temperature
Heat gainradiation from the sun
liver metabolismrespiration in cells
muscle contraction
conduction from hot sand
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2.1 Importance of regulating body temperature
Heat loss
exhalation
evaporation of sweat
convection due to air current
urination and defaecation
Radiation?
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2.1 Importance of regulating body temperature
Heat lossHeat gain =
stable body temperature
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• skin is the major organ involved in regulating body temperature
2.1 Importance of regulating body temperature
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1 A stable body temperature allowsenzymes
2.1 Importance of regulating body temperature
properly, so that the metabolic rate can be kept and we can stay active at all times.
in cells to function
steady
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, ,
2 Heat is transferred between the body and the environment by
radiation
2.1 Importance of regulating body temperature
conduction
convection and evaporation.
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2.2 The role of skin
epidermis(表皮 )
dermis(真皮 )
• two layers:
Structure and functions of skin
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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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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
Scanning electron microscope (SEM) picture
of normal skin
E. coli on the surface of human skin.
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epidermis
dermis
2.2 The role of skin
1 Epidermis• three
layers:
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2.2 The role of skin
1 Epidermis• three
layers:i) Innermost layer• produces new cells
by mitotic cell divisionby mitotic cell division
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• contains melanin (黑素 )
2.2 The role of skin
1 Epidermis• three
layers:i) Innermost layer
absorbs UV lightabsorbs UV light
protects the bodyprotects the body
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• contains melanin (黑素 )
2.2 The role of skin
1 Epidermis• three
layers:i) Innermost layer
determines skin colourdetermines skin colour
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• produces vitamin D when exposed to sunlight
2.2 The role of skin
1 Epidermis• three
layers:i) Innermost layer
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• consists of living cells
2.2 The role of skin
1 Epidermis• three
layers:ii) Middle layer:
pushed towards surfacepushed towards surface
die and flattendie and flatten
outermost layeroutermost layer
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• consists of dead cells
2.2 The role of skin
1 Epidermis• three
layers:iii) Outermost layer
constantly worn away and replaced by new 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
reduce water lossreduce water loss
• consists of dead cells
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2.2 The role of skin
1 Epidermis• three
layers:iii) Outermost layer
protect from mechanical injury
protect from mechanical injury
• consists of dead cells
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2.2 The role of skin
1 Epidermis• three
layers:iii) Outermost layer
prevent entry of pathogens
prevent entry of pathogens
• consists of dead cells
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i) Sensory receptors
2.2 The role of skin
2 Dermis
pain receptor
touch receptor
thermoreceptor
pressure receptor
• detect stimuli
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ii) Hair follicles (毛囊 )
2.2 The role of skin
2 Dermis
• new hair cells produced from the base
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2.2 The role of skin
2 Dermis
root of hair
• new hair cells produced from the base
ii) Hair follicles (毛囊 )
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iii) Erector muscles (豎毛肌 )
2.2 The role of skin
2 Dermis
and hairs
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2.2 The role of skin
2 Dermis
• erector muscle contracts
hair pulled upright• erector muscle relaxes
hair lies flat
and hairsiii) Erector muscles (豎毛
肌 )
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Goose bumps
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Goose bumps
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iv) Sweat glands (汗腺 )
2.2 The role of skin
2 Dermis
• form sweat
contains mainly water, salts, urea
and other metabolic waste
contains mainly water, salts, urea
and other metabolic waste
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2.2 The role of skin
2 Dermis
sweat duct (汗管 )
iv) Sweat glands (汗腺 )sweat pore (汗
孔 )
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2.2 The role of skin
2 Dermis
• sweat coming out to the skin surface sweating
iv) Sweat glands (汗腺 )
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2.2 The role of skin
2 Dermis
• sweat coming out to the skin surface sweating
for regulating body temperature
for regulating body temperature
iv) Sweat glands (汗腺 )
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2.2 The role of skin
2 Dermis
• sweat coming out to the skin surface sweating
for excretionfor excretion
iv) Sweat glands (汗腺 )
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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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v) Blood vessels
2.2 The role of skin
2 Dermis
• circulation of blood
supplies oxygen and nutrients
supplies oxygen and nutrients
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v) Blood vessels
2.2 The role of skin
2 Dermis
• circulation of blood
removes wasteremoves waste
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v) Blood vessels
2.2 The role of skin
2 Dermis
• circulation of blood
distributes heatdistributes heat
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v) Blood vessels
2.2 The role of skin
2 Dermis
• vasoconstriction and vasodilation
‘vessel’
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v) Blood vessels
2.2 The role of skin
2 Dermis
• vasoconstriction and vasodilation
regulate heat loss by controlling the amount of blood
flowing to the body surface
regulate heat loss by controlling the amount of blood
flowing to the body surface
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v) Blood vessels
2.2 The role of skin
2 Dermis
• vasoconstriction and vasodilation
arteriole
capillary
venule
shunt vessel (分流血管 )
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v) Blood vessels
2.2 The role of skin
2 Dermis
• vasoconstriction and vasodilation
1 arteriole constricts
2 less blood to capillary
3 more blood through shunt vessel
less heat is lost
Under cold conditionsUnder cold conditions
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v) Blood vessels
2.2 The role of skin
2 Dermis
• vasoconstriction and vasodilation
1 arteriole dilates
2 more blood to capillary
3 less blood through shunt vessel
more heat is lost
Under hot conditionsUnder hot conditions
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Vasoconstriction and vasodilation occur in the capillaries.
2.2 The role of skin
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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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vi) Sebaceous glands
2.2 The role of skin
2 Dermis
• secrete sebum (皮脂 )
keeps hairs and skin supple and
waterproof
keeps hairs and skin supple and
waterproof
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vi) Sebaceous glands
2.2 The role of skin
2 Dermis
• secrete sebum (皮脂 )
a natural antiseptica natural antiseptic
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2.2 The role of skin
hair follicle
epidermissweat duct
sebaceous gland
mammalian skin (L.S)
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Pimples – inflamed
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• insulates the body to reduce heat loss
2.2 The role of skin
Subcutaneous fat
• as energy reserve
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2.1
Examination of the mammalian skin
1 Examine a prepared slide of mammalian skin or a skin model.
2.2 The role of skin
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 by mitotic
cell divisionnew cells
• contains which protects the body against ultraviolet light
melanin
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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 formthe outermost layer
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2.2 The role of skin
Functions of structures of the skin:Epidermis:
3 Outermost layer• reduces by
evaporationwater loss
• protects the body frommechanical 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 for excretion and
body temperature regulationsweat
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2.2 The role of skin
Functions of structures of the skin:Dermis:
5 Blood vessels• supply and to
skin cells and remove waste from them
nutrientsoxygen
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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 andvasodilation
vasoconstriction
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2.2 The role of skin
Functions of structures of the skin:Dermis:
6 Sebaceous glands• secrete that keeps the
hairs and skin supple and waterproof, and reduces the growth of harmful microorganisms
sebum
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2.2 The role of skin
Functions of structures of the skin:Subcutaneous fat:• acts as a layerheat insulating
• acts as reserveenergy
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How does skin regulate body temperature?
2.2 The role of skin
3D animation
• by controlling heat loss
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2.2 The role of skin
1 erector muscles contract to pull hairs upright
Under cold conditionsUnder cold conditions
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2.2 The role of skin
2 sweating is reduced
Under cold conditionsUnder cold conditions
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2.2 The role of skin
3 vasoconstriction
Under cold conditionsUnder cold conditions
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2.2 The role of skin
4 layer of subcutaneous fat becomes
Under cold conditionsUnder cold conditions
less heat is lost
thicker (long-term response)
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2.2 The role of skin
Under hot conditionsUnder hot conditions
1 erector muscles relax and hairs lie flat
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2.2 The role of skin
Under hot conditionsUnder hot conditions
2 sweating increases
3 vasodilation
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2.2 The role of skin
Under hot conditionsUnder hot conditions
4 layer of subcutaneous fat becomesthinner (long-term
response)
more heat is lost
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Sweat is produced only when the body temperature increases.
2.2 The role of skin
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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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StructureResponse under cold conditions
1 Erector muscles
2 Hairs
3 Sweat glands
Contract
Pulled upright
2.2 The role of skin
Secrete less sweat
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StructureResponse under cold conditions
4 Arterioles
5 Subcutaneous fat
Constrict (vasoconstriction
)
2.2 The role of skin
Becomes thicker (long-term)
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StructureResponse under hot conditions
1 Erector muscles
2 Hairs
3 Sweat glands
Relax
Lie flat
2.2 The role of skin
Secrete more sweat
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StructureResponse under hot conditions
4 Arterioles
5 Subcutaneous fat
Dilate (vasodilation)
2.2 The role of skin
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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Action of hormone2.3 Other mechanisms of body temperature regulation
• body temperature is also regulated by thyroxine (甲狀腺素 )
increases metabolic rate
generates heat to keep the body warm
increases metabolic rate
generates heat to keep the body warm
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Action of hormone2.3 Other mechanisms of body temperature regulation
thyroid gland
secretes
• body temperature is also regulated by thyroxine (甲狀腺素 )
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Action of hormone2.3 Other mechanisms of body temperature regulation
• increased thryoxine secretion is a long-term response
• body temperature is also regulated by thyroxine (甲狀腺素 )
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2.3 Other mechanisms of body temperature regulation
Under cold conditionsUnder 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 conditionsUnder 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 conditionsUnder 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 conditionsUnder 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 conditionsUnder cold conditions
thyroxine inhibits secretions of TRH and TSH (negative feedback)
hypothalamus TRH
pituitary gland
TSH thyroxine
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Change of behaviour2.3 Other mechanisms of body temperature regulation
• voluntary behaviour also plays a part in regulating body temperature
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2.3 Other mechanisms of body temperature regulation
Under cold conditionsUnder 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
wear fewer clothes
turner on the fan
take in cold food/drinks
Under hot conditionsUnder hot conditions
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1 in muscle cells generates heat to maintain the bodytemperature.
Metabolism
also generates heat. Shivering provides extra amount of heat to keep us warm under cold conditions.
Muscle contraction
2.3 Other mechanisms of body temperature regulation
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2 increases the metabolic rate of most cells, so that more heat can be generated to keep the body warm. Increased thyroxine secretion is a response to a cold environment.
long-term
Thyroxine
2.3 Other mechanisms of body temperature regulation
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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 food and drinks.
3 Behavioural mechanisms that help regulate body temperature:
2.3 Other mechanisms of body temperature regulation
warm
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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 food and drinks.
3 Behavioural mechanisms that help regulate body temperature:
2.3 Other mechanisms of body temperature regulation
cold
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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
heat loss centre
thermoregulatory centre in hypothalamus
normal body temp
thermo-receptors
rises
heat gain centre
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2.4 The thermoregulatory centre
heat loss centre
normal body temp
thermo-receptors
rises
initiates mechanisms
normal body temp
falls
heat gain centre
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2.4 The thermoregulatory centre
Mechanisms to promote heat loss and decrease heat gain:
• relaxation of erector muscles• increased sweating
• vasodilation• decreased secretion of thyroxine
(long-term)
Physiological
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2.4 The thermoregulatory centre
Mechanisms to promote heat loss and decrease heat gain:
• thinner layer of subcutaneous fat (long-term)
Structural
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2.4 The thermoregulatory centre
Mechanisms to promote heat loss and decrease heat gain:
• wear fewer clothes
Behavioural
• turn on the fan
• take in more cold food
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2.4 The thermoregulatory centre
heat loss centre
heat gain centre
normal body temp
thermo-receptors
rises
initiates mechanisms
normal body temp
falls
falls
thermo-receptors
initiates mechanisms
rises
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2.4 The thermoregulatory centre
Mechanisms to reduce heat loss and increase heat gain:
• contraction of erector muscles• reduced sweating
• vasoconstriction• shivering
Physiological
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2.4 The thermoregulatory centre
Mechanisms to reduce heat loss and increase heat gain:
• increased secretion of thyroxine (long-term)
Physiological
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2.4 The thermoregulatory centre
Mechanisms to reduce heat loss and increase heat gain:
• thicker layer of subcutaneous fat (long-term)
Structural
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2.4 The thermoregulatory centre
Mechanisms to reduce heat loss and increase heat gain:
• wear more clothes
Behavioural
• turn on the heater
• take in more warm food
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in skin detect changes in external temperature and send nerve impulses to the thermoregulatory centre in the .
Thermoreceptors
hypothalamus
2.4 The thermoregulatory centre
1a
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Thermoreceptors in the hypothalamus detect changes in the temperature of passing through it.
blood
2.4 The thermoregulatory centre
1b
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Skin or blood temperature rises
heat loss
2.4 The thermoregulatory centre
2a
centre stimulatedmechanisms
• erector muscles and hairsrelax lie flat• sweating increases• occursvasodilation
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Skin or blood temperature rises
heat loss
2.4 The thermoregulatory centre
2a
centre stimulatedmechanisms
• thyroxine secretion decreases• subcutaneous fat becomes thinner• ,
e.g. wear fewer clothes, turn on the fanbehavioural mechanisms
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Skin or blood temperature falls
heat gain
2.4 The thermoregulatory centre
2b
centre stimulatedmechanisms
• erector muscles and hairs arecontractpulled upright
• sweating decreases• and shivering occurvasoconstriction
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2.4 The thermoregulatory centre
• thyroxine secretion increases• subcutaneous fat becomes thicker• behavioural mechanisms, e.g. wear
more clothes, turn on the heater
Skin or blood temperature falls
heat gain
2b
centre stimulatedmechanisms
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Why is heatstroke more likely tooccur under hot and humid conditions?1High 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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Why may death result when thebody temperature is too high?2When the body temperature is too high, enzymes cannot work properly and cells fail to function.
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What are the treatments andprecautions for heatstroke?3To treat heatstroke, we should move the person to shaded areas and wrap the body with cool wet towels.
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What are the treatments andprecautions for heatstroke?3To prevent heatstroke, we should avoid doing vigorous exercise in a hot environment.
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maintained by balancing
A stable body temperature
heat gain
thermoregulatory centre in hypothalamus
controlled by
heat loss
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thermoregulatory centre in hypothalamus
through mechanisms that involve
skin
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structures involvedskin
subcutaneous fat
erector muscles and hairs
sweat glands
blood vessels
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thermoregulatory centre in hypothalamus
through mechanisms that involve
blood circulation
distribution of heat
controls vasoconstriction and vasodilation
by
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thermoregulatory centre in hypothalamus
through mechanisms that involve
skeletal musclesunder cold conditions
production of more heat
leads toshiver
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thermoregulatory centre in hypothalamus
through mechanisms that involve
thyroid glandsecretes
metabolic rateincreases
thyroxine
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thermoregulatory centre in hypothalamus
through mechanisms that involve
cerebrumbrings about
behavioural mechanisms