Bio 4,5,6


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B4 Homeostasis

Homeostasis, the maintenance of a constant internal environment.

It is achieved baby balancing body inputs and outputs and removing waste products.

Homeostasis aims to keep temperature, hydration, salt and blood oxygen levels constant in everyday environment aswel as; 'vigorous excersise' which can affect hydration and temperature; 'mountain climbing' this can affect blood oxygen levels; 'living in hot climates' can affect the temperature, hydration and salt levels; 'scuba diving' can affect blood oxygen levels. These are a few things which can affect Homeostatis.

An incubator is an artificial system which keeps a new born/ill baby in a constant environment controlling oxygen and temperature levels. It works the same as a body with receptors, processing centre and effectors.

Many systems have effectors which work antagonistically, (opposite to each other), one effector to increase one effector to decrease. This method of control is accurate and sensitive.

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B4 Homeostasis

Enzymes use the lock and key model to conduct a reaction. The molecule fits into the active site on the enzyme perfectly. Each enzyme has a different shape so it is specific to speeding up a particular reaction.

They are protein molecules, and work best in a human at 37 degrees. If the temperature in the body exceeds 40 degrees enzymes begin to denature, (they lose their shape), this is an irreversible reaction. All enzymes have a specific optimum temperature where the denature. If the temperature falls there are few collisions and the reactions are slow.

If the body temperature exceeds 42 degrees Heat Stoke occurs; hot/dry skin, confusion, dizziness, fast pulse rate and fainting are symptoms. Treatment is to sponge with water, put near a fan, put ice under arms, in groin and on the neck and head.

If body temperature drops below 35 degrees hypothermia occurs; shivering, confusion, slurred speech, loss of co ordination, patient enters a coma if body falls below 30 degrees and death if below 28 degrees. Treat the patient by insulating them, warm them gently with hot drinks and warm towels.

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B4 homeostasis

Kidneys help control water balance. They do this by adjusting the amount of urine that is excreted from the body.

If the water level is to low; it is detected by the hypothalamus and a stimulus is sent to the pituitary gland, thirst is stimulated. More ADH is secreted into the blood, the kidneys become more permeable to water, more water is absorbed, a small quantity of concentrated urine is produced.

If the water level is to high; receptors in the hypothalamus detect the change and no stimulus is sent to the pituitary gland. Less ADH is secreted into the blood, so the kidneys become less permeable so less water is absorbed, a large quantity of dilute urine is produced.

Caffeine and Alcohol Are diuretic which means they increase the amount of urine produced. Drugs like Ecstasy can interfere with the brain stopping the body excreting water, there is too much water in the blood, people drink because they are hot increasing the amount of water in the blood this can then cause cells to rupture.

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