Hormones And Homeostatis

Front 1

Outline the role of the skin in temperature regulation. (5)

Back 1

heat causes vasodilation of arterioles;
blood closer to surface so heat loss from skin;
heat causes sweating (from sweat glands);
evaporation of sweat leads to cooling;
cold causes vasoconstriction of arterioles;
less blood at surface so less heat loss from skin;
cold leads to less sweating/evaporation of water from skin / hair becomes erect and
traps air/goose bumps appear;
temperature receptors in skin transmit impulses to the hypothalamus;

Front 2

Outline what is meant by homeostasis. (4)

Back 2

a. maintaining (stable) internal environment/conditions;
b. within (narrow) limits;
c. example (e.g. body temperature / blood pH / blood glucose / water / CO2
concentration);
d. levels of these variables are monitored (internally);
e. negative feedback mechanisms / OWTTE; (reject if positive feedback included)
f. involves hormonal / nervous control;

Front 3

Describe how body temperature is maintained in humans (6)

Back 3

a. maintained close to 36.7/37 C/98.6 F ;
b. heat is transferred/distributed in body by blood;
c. hypothalamus contains thermoreceptors;
d. hypothalamus monitors temperature/sends message to effectors/causes
response;
e. (vaso) dilation of skin arterioles warms skin/cools body;
f. (vaso) constriction of skin arterioles retains body heat;
g. skin/sweat glands produce sweat to cool the body when overheated;
h. removal of heat through evaporation of sweat;
i. shivering generates heat / increased metabolism / hair erection to retain heat;
j. example of behavioural change to warm/cool the body to thermoregulate;

Front 4

During a period of physical exercise, the rate of urine production falls, but the ventilation rate and the body temperature rise. Explain the mechanisms that are used to cool the body when it is overheated. (5)

Back 4

sweat/perspiration secreted/produced;
evaporation of sweat causes cooling/heat to be removed from skin;
skin arterioles become wider/vasodilate;
more blood flows through (capillaries in) the skin;
heat carried to the skin / skin becomes warmer / skin reaches core temperature;
more heat lost by skin to the environment;
behavioural responses / reduced activity / other example of behaviour resulting in
cooling;