homeostasis and thermoregulation

Question 1

what is homeostasis

Answer 1

the maintenance of constant internal conditions which is vital for biochemical reactions controlled by enzymes.

Question 2

negative feedback

Answer 2

the process in which any departure from a set level causes specific receptors to convey information to effectors which then return the system to its original value

Question 3

positive feedback

Answer 3

where an output enhances the original stimulus, e.g childbirth

Question 4

how do homeostatic mechanisms keep conditions close to normal

Answer 4

1. stimulus produces change in a variable
2. receptors detects change
3. input - information sent along afferent pathway to control centre
4. output - information sent along efferent pathway to effector
5. response of effector feeds back to reduce effect of stimulus and returns value to homeostatic level

Question 5

how is temperature returned to normal after an increase

Answer 5

1. increase in temperature warms the blood and activated heat loss centre by thermoreceptors in the hypothalamus
2. hypothalamus sends impulses to activate sweat glands to secrete precipitation to then be vaporised by body heat and to dilate skin blood vessels so capillaries become flushed with warm blood sp the heat radiated from skin surface
3. behavioural response of taking off clothes
4. body temperature decreases again

Question 6

how is temperature returned to normal after a decrease

Answer 6

1. decrease in temperature cools the blood and activates heat promotion centre by thermoreceptors in hypothalamus
2. hypothalamus sends impulses and skin blood vessels constrict so blood from capillaries is withdrawn to deeper tissues to minimise heat loss from the surface and skeletal muscles activated to cause shivering
3. body temperature increases again

Question 7

how does the skin regulate internal temperature

Answer 7

when too hot:
- vasodilation of arterioles
- sweating
- pilorelaxation ( hairs flatten )
- stretching out to increase surface area
when too cold:
- vasoconstriction of arterioles
- shivering
- piloerection ( hairs stand up)
- curling up

Question 8

how is energy transferred in and out of the body

Answer 8

• infrared radiation from the skin
• evaporation of water from the skin
• conduction to and from solid objects next to the skin
• convection to surrounding