control of body temperature

Ectotherms

* cant control body temperature internally
* control body temp by changing their behaviour, and depend on external temperature


* have a variable metabolic rate and generate little heat themselves
* e.g reptiles and fish

Endotherms

* control their body temperature internally by homestasis, and by changing their behaviour
* e.g mammals and birds

mechanisms to reduce body temp?

* sweating
* hairs lie flat
* vasodilation

mechanisms to increase body temp?

* shivering
* less sweat
* hairs stand up
* vasoconstriction
* homones

sweating

sweat is secreted from sweat glands when body is too hot, the water evaporates from skin surface and takes heat from body, cooling the skin

hairs/feathers

when too hot, erector pili muscles relax so hairs lie flat, less air is trapped and skin is less insulated so heat can be lost more easily. the opposite occurs when too cold

vasodilation

when too hot arterioles near skin surface dilate, more blood flows through cappiliries near surface so more heat is lost by radiation, temp is lowered

hormones

when too cold the body produces adrenaline and thyroxie which increases metabolism so more heat is produced

vasoconstriction

when too cold, arterioles near skin surface constrict, less blood flows through capillaries near skin reducing heat loss

shivering

when too cold muscles contract in spasms making the body shiver, more heat is produced from increased respiration

what detects temperature internally?

thermoreceptors in hypothalamus

what detects temperature externally?

thermoreceptors in skin called peripheral temperature receptors

what happens in response to a rise in body temp?

1) thermoreceptors detect high temp

2) hypothalamus sends signals to effectors

3) vasodialtion, sweating, hairs lie flat ect

4) more heats lost and less heat is produced by body