Controlling body temperature

Question 1

Why is it important to control body temperature?

Answer 1

because enzymes in the main organs are most active at this temperature

Question 2

Describe the structure and function of the skin

Answer 2

• epidermis is the top layer
• dermis is the second layer of skin
• the dermis contains hair follicles, which contain hairs
• when it is cold, the hair muscles contract, which pulls the hairs upright, trapping insulating air
• when it is warm the hairs lie flat
• sweat glands in the dermis release sweat onto the epidermis when it is warm, to lose heat by evaporation
• blood vessels and capillaries change blood flow to the surface of the skin depending on temperature

Question 3

vasoconstriction

Answer 3

• cold
• more blood through deep skin shunt vessel, less blood through surface capillaries
• the shunt vessel dilates
• surface capillaries constrict
• more blood through shunt vessel
• less blood closer to surface
• reduces heat loss through the skin, less heat transferred to air

Question 4

vasodilation

Answer 4

• warm
• more blood through surface capillaries, less through shunt vessel
• shunt vessel constricts
• capillaries dilate
• more blood flows closer to the surface
• more heat loss through the skin
• heat can transfer easier to air through radiation

Question 5

shivering, sweating, and hair follicles

Answer 5

• shivering
• cold
• muscles quickly contract and relax
• requires more energy from respiration
• increased respiration, more heat released as a byproduct
• sweating
• hot
• sweat glands contain water and salt
• sweat secreted onto epidermis
• as water evaporates so does the heat energy it contains
• hair follicles
• cold
• the erector muscles cause the hair follicles to change direction
• hairs stand on end
• traps an insulating warm layer of air close to the skin
• reduces heat loss through skin
• more effective in other animals

Question 6

Describe the role of the dermis and epidermis of the skin in cooling the body

Answer 6

sweat glands in the dermis secrete sweat onto the epidermis
this evaporates along with heat energy, cooling the body down

erector muscles in the dermis relax, allowing hairs in follicles to lie flat
this means there is a thinner layer of insulating air trapped against the epidermis

Question 7

A pale skinned person may look pink after exercise

a) identify what causes this change
b) describe and explain what effect this has on body temperature

Answer 7

a) they look pink because more blood is flowing near the surface of the skin as a result of vasodilation

b) this increases the rate of transfer of heat energy from the body to the environement
and so reduces the body temperature