What is Homeostasis?

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Homeostasis is a very important biological function that occurs in all endotherms but not ectotherms. Endotherms have the ability to adjust their body temperature: they are not dependent on the surrounding temperature of the environment. Examples of endotherms are mammals: humans.

Homeostasis works by using a process called negative feedback which works by adjusting a condition in the body so that the internal environment stays, on average, the same. It works using nerves. A receptor detects the change in the surrounding environment and sends nerve impulses to the centres in the brain, such as the medulla, which sends nerve impulses to glands or muscles to bring about an effect which will lower or increase a condition in the internal environment to keep it within certain limits.

Homeostasis is used to control body temperature, blood glucose concentration and the water content of the blood.

The body temperature in endotherms is controlled by dilation and contraction of arterioles, sweat and contraction of the erector pili muscles. This is called thermoregulation. When the temperature of the surrounding environment increases the internal environment must be decreased. To do this the arterioles dilate (vasodilation) so that more blood flows through the capillaries next to the skins surface. This means more heat can be released through the skin as the blood is closer to the upper dermis of the skin and escapes by radiation. The sweat glands secrete sweat which can evaporate from the skin and so takes heat away from the skin and the skin cools down as the water in sweat needs heat energy in order to evaporate. The erector pili muscles also relax so that hair on the skin lies flat which means that air isn’t trapped underneath the hair.

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When the body needs to warm up no sweat is secreted as the body doesn’t need to loose heat by evaporation. Vasoconstriction occurs, which means that arterioles gets thinner so less blood is pumped to the capillaries near the skin’s dermis so less heat is lost from this blood. The erector pili muscles contract and raise the hairs from the skin which means that air currents can be trapped underneath the raised hairs and acts as an insulating layer.

Glucose is used for respiration and so there must always be enough available in the body, especially the ...

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