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Homeostasis – maintaining body temperature. By the end of the lesson you should know. The ideal range for core body temperature and consequences if this rises or falls. How heat can be gained and lost by the body. How the body tries to maintain a constant body temperature.
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By the end of the lesson you should know... • The ideal range for core body temperature and consequences if this rises or falls. • How heat can be gained and lost by the body. • How the body tries to maintain a constant body temperature.
Metabolism – all the chemical reactions which occur in body generate heat. How do we gain and lose heat? From the skin’s surface. Heat loss is greatest if you are in contact with cold surfaces or in a cold environment. The more skin which is exposed, the more heat will be lost. 1. HEAT GAIN 2. HEAT LOSS This amount increases with activity. Environment – heat can be gained from the sun or warm surfaces. Expired air,. Urine and faeces.
Above 43oC = DEATH. Above 38oC (in absence of a fever) = heat exhaustion or stroke. Above 37.2oC = fever Normal core body temperature is.... 36.8oC. Acceptable range 36.5-37.2oC. 32oC = Hypothermia. Below 25oC = DEATH.
Which cat will lose body heat the quickest in cold temperatures? Give 2 reasons why.
Control of body temperature • Thermoreceptors in the skin detect temperature changes in the surroundings. • Thermoreceptors in the hypothalamus detect temperature changes in the blood. • These send nerve impulses to the hypothalamus in the brain. • The hypothalamus sends impulses to different parts of the body to cause a change.
Shivering starts – this generates heat due to extra respiration happening. Less sweat produced. Erector pili muscles make hairs stand up – the idea is to trap warm air. - Muscle in the arterioles contract, causing blood to be diverted away from the surface of the skin. More sweat produced. Heat is taken from the body to evaporate the sweat – this cools the body down. Erector pili muscles relax. Hairs lie flat and warm air is not trapped. - Muscle in the arterioles relaxes, allowngblood to move towards the surface of the skin.
If body temperature changes seriously it shows a failure in these mechanisms (and a probable health problem). In some cases however, the bodies response to infection is to raise body temperature to aid recovery.
