Homeostasis

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Homeostasis is maintaining a constant internal environment. Conditions in the body need to be kept steady so cells will function properly. This involves balancing input with outputs.

• Levels of co2 - respiration constantly produces co2, which your body needs to get rid of.

• Water content – you need to balance the amount of water gained and the water you release (sweat, pee and exhale).

• Body temperature – you need to get rid of excess body heat when you’re too hot, but retain heat when the environment is too cold.

A mechanism called negative feedback keeps these things steady.

Changes in the environment trigger a response that counteracts the changes, e.g. a rise in body temperature causes a response that lowers body temperature.

This means that the internal environment tends to stay around a norm, the level which the cells work best.

All enzymes have an optimum temperature they work best at. For enzymes it’s about 37oc.

There is a thermoregulatory centre in the brain which acts as your own personal thermostat.

It contains receptors that are sensitive to the blood temperature in the brain. It also receives impulses from the skin that provide information about skin temperature. The brain can respond to the information and bring about changes in the body’s temperature using the nervous and hormonal system to initiate temperature control mechanisms. For example:

When you’re too hot:

1. Hairs lie flat.

2. Lots of swat is produced. This transfers the heat from your skin to the environment.

3. Blood vessels close to the surface of the skin widen. This allows more blood to flow near the surface, so it can radiate more heat into the surroundings. This is called vasodilation.

When we are exposed to high temperatures you can get heat stroke. This is when you’re so dehydrated that your body stops producing sweat. And because there is no sweat being produced, the body temperature rises, killing enzymes (no reaction take place). This can causes you to collapse or even die.

When you’re too hot:

1. Hairs stand on end to trap an insulating layer of air which helps keep you warm.

2. Very little sweat is produced.

3. Blood vessels near the surface constrict, this is so less heat can be transferred to the surroundings. This is called vasoconstriction.

4. You shiver, the movement generates heat in the muscles.

Your body temperature can drop to dangerous levels if you’re exposed to very low temperatures for a long period of time – this is hypothermia. If you don’t get help quickly, you can die.