1. State and explain the importance of maintaining a stable body temperature.
Metabolic activities in our body are controlled by enzymes.
Enzymes only work efficiently within a narrow range of temperature.
So a stable body temperature keeps metabolic rate steady.
2. List the different ways how the body loses heat.
(1) Conduction
(2) Convection
(3) Radiation
(4) Evaporation (after sweating)
3. What is the prior criteria 先決條件for the human body to lose heat by conduction, convection and radiation?
The external temperature is lower than the body temperature
4. Where is the location of the thermoregulatory centre in the human body?
Hypothalamus
5. What are the two parts of the thermoregulatory centre in the hypothalamus?
(1) Heat loss centre
(2) Heat gain centre
6. How does the human body carry out thermoregulation when the body temperature rise?
When skin temperature rises, the thermoreceptors on the skin detect the rise and
send nerve impulses to the hypothalamus, stimulating the heat loss centre.
Also when the blood temperature rises, when blood passes through the
hypothalamus, the thermoreceptors at the hypothalamus detect the rise and
stimulate the heat loss centre. The heat loss centre will initiate mechanisms that promote heat less and decrease heat gain. Finally lead to decrease in body temperature until the normal body temperature is restored.
7. List the structures of the skin.
Epidermis: Outermost layer, Middle layer, Innermost layer
Dermis: hair, hair follicle, sebaceous gland, erector muscle, sweat pore,
sweat duct, sweat gland, nerve fibre, superficial capillary, subcutaneous gland.
8. What are the features of the outermost layer of the epidermis? What are the functions of the outermost layer of the epidermis?
Feature:
(1) Consists of dead cells
(2) Constantly shedding off
(3) Replaced by new cells from the inner layer
Function:
(1) Reduce water loss
(2) Protect the body from mechanical injury
(3) Prevent the entry of pathogens
9. What are the features of the innermost layer of the epidermis? What are the functions of the innermost layer of the epidermis?
(1) Constantly carrying out mitotic cell division to produce new cells: forming
epidermal cells or hair
(2) Contains melanin: absorb UV light, protect the body and produce Vitamin D.
10. How many types of sensory receptors are there in the dermis? Name each of them.
Touch, pressure, pain, cold, hot
11. Under cold conditions, how can the erector muscles and hairs help reduce heat loss?
Upon feeling cold, Erector muscles contract and pull hairs upright, a thicker layer of air is trapped, since air is a good insulator, heat loss to the surrounding is reduced.
12. Under hot conditions, how can the sweat gland help dissipate heat (散熱)?
Upon feeling hot, Sweat gland take more tissue fluid from the surrounding blood capillaries and release more sweat by discharging them through the sweat duct and sweat pore. As sweat is evaporated, heat is taken away by the sweat, thus help dissipate heat.
13. What are the 3 functions of the sebum secreted by the sebaceous gland?
1) lubricate the skin
2) waterproofs the hairs and the skin, reduce water loss from the skin by
evaporation
3) inhibit the growth of microorganism
14. What are the 2 functions and the relevant significance of the subcutaneous fat under the dermis?
(1) Insulates the body to reduce heat loss
(2) Serves as energy reserve
15. What are the 3 functions and the relevant significance of the blood vessels in the skin?
(1) supply oxygen and nutrients to the living cells of the skin
(2) remove waste produced by skin cells
(3) assist in thermoregulation
16. Under cold conditions, what are the mechanisms that the skin can use to respond?
Short term:
(1) Erector muscles contract to pull hair upright
(2) vasoconstriction of arterioles in the skin
(3) sweating reduces
Long term:
(1) subcutaneous fat becomes thicker
17. Under cold conditions, how does the blood vessels help reduce heat loss?
Arteriole in the skin constricts. Less blood flows to the capillaries near the skin
surface. More blood flows through the shunt vessels. Less heat is lost to the
surrounding by conduction, convection and radiation.
18. During hot conditions, what is the mechanism carry out by the skin in response?
Short term:
(1) Erector muscles relax and hairs lie flat
(2) The arterioles in the skin dilate (vasodilation)
(3) Sweating increases
Long term:
(1) Layer of subcutaneous fat becomes thinner
19. During cold conditions, apart from the response of the skin, what other responses will also be carried out by the body?
Short term :
Skeletal muscle: Shivers to increase the rate of respiration which generate more heat.
Long term :
Thyroid gland: More thyroxine is released to increase the metabolic rate of body cells.
20. Upon feeling cold, what are the behaviours that the body will do?
Keep warm:
(1) Wear more clothes
(2) Curl up the body, reduce the surface area of the body.
Absorb or produce more heat:
(1) Take in more hot food
(2) Hold hand warmer
(3) do more exercise
(4) expose to sunlight