OCR A-Level Biology Thermoregulation Summary

&




Ectotherms surroundings for
Rely on heat from their warmth
:




↳ fish amphibians Reptiles
, .




Endotherms :



Rely on heat from their own metabolic processes ->
stable core temperature


Behavioural Responses Sun
basking Burrowing vibrating
· .
:




·

Orientate or extend their bodies so the maximum surface is
facing towards/away from the sun
area ie
opening wings
↳
wingsie expand
.

open or



Physiological Responses :




Cold climate Darker radiation Hot lighter colours
·
:

colours absorb more
·
Climate
:




Peripheral temperature receptors :
In the skin , detect external
change
Internal temperature receptors In the the temperature of blood
hypothalamus monitor the
:
,




Behavioural Responses :




Basking Burrowing wallowing mud/water Hibernation/aestivation
·
.
in
· .




Physiological Responses :




Cooling Down :
·
Vasodilation :
Shin flushes and cools due to increased radiation
heat is lost
Sweating water evaporates
·
:
->




Reducing Insulation of hair/feathers Erector pili muscles relax and hair lies flat
·
:




Warming up :
vasoconstriction Shin and little radiation
pales
·
occurs
:




Raising hair feathers Erector pili contract ->
insulating air layer forms
·

muscles an
:
or



shivering metabolic heat of the exothermic reaction warms the
·



body
:




Heat loss Centre :

Temperature of the blood increases -> response is coordinated
Heat
gain Centre : Temperature of the blood decreases ->
response is coordinated