Biology Homeostasis

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  • Created by: James
  • Created on: 05-03-13 11:38

Ectotherms

Ectotherms cant control their body temperature internally - they control their temperature by changing their behaviour. (reptiles gain temperature by basking in the sun)

Their internal temperature depends on the external temperature of there surroundings.

Their activity level depends on the external temperature - they are more active at higher temperatures and less active at lower temperatures.

They have a variable metabolic rate and they generate very little heat themselves

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Endotherms

Endotherms control their body temperature internally by homeostasis. they can also control their temperature by behavioural changes. (finding shade).

Their internal temperature is less affected by the external temperature (within certain limits).

Their activity level is largely independent of the external temperature - they can be active at any temperature (within certain limits).

They have a constantly high metabolic rate and they generate a lot of heat from metabolic reactions.

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Heat Loss

SWEATING -  More sweat is secreted from the sweat glands when the body's too hot. The water in sweat evaporates from the surface of the skin and takes heat from the body. Therefore cooling the skin.

HAIRS LIE FLAT - Mammals have a layer of hair that provides insulation by trapping air (air is a poor conductor of heat). When it is hot, erector pili muscles relax so the hairs lie flat. Less air is trapped, so the skin is less insulated and heat can be lost more easily.

VASODILATION - When it's hot, arterioles near the surface of the skin dilate (vasodilation). More blood flows through the capillaries in the surface layers of the dermis. This means more heat is lost from the skin by radiation and the temperature is lowered.

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Heat Production

SHIVERING - When its cold muscles contract in spasms. This makes the body shiver and more heat is produced from increased respiration.

HORMONES - The body releases adrenaline and thyroxine. These increase metabolism and consequently more heat is produced.

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Heat Conservation

MUCH LESS SWEAT - Less sweat is secreted from sweat glands when it is cold. reducing the amount of heat loss.

HAIRS STAND UP - Erector pili muscles contract when it is cold, which makes the hairs stand up. This traps more air and therefore prevents heat loss.

VASOCONSTRICTION - When its cold, arterioles near the surface of the skin constrict (vasoconstriction). so less blood flows through the capillaries in the surface layers of the dermis. This consequently reduces heat loss.

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