HOMEOSTASIS (2) - thermoregulation of temperature, control of blood sugar level, water control

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Suitable for GCSE/IGCSE/O level Biology/Science courses or equivalent

This page will answer many questions e.g.

How does the body regulate temperature?

How does the body control blood sugar level

How does the body control its water content?

What is insulin? What does it do?

Homeostasis control in the human body

  • Know that internal conditions that are controlled in the body include:

    • The water content of the body water leaves the body via the lungs when we breathe out and via the skin when we sweat to cool us down, and excess water is lost via the kidneys in the urine.

      • We need to, and are continually taking in water via drinks and food.

      • Any loss needs to be replaced, more so in the summer when we sweat more than in the winter.

    • The ion content of the body ions are lost via the skin when we sweat and excess ions are lost via the kidneys in the urine.

      • For example, the kidney controls the sodium ion (Na+) concentration from digested food containing salt.

      • Any excess of any ion needs to be removed eg by the kidneys and subsequent excretion of urine.

    • The temperature is controlled by the brain to maintain the temperature at which enzymes work best (37oC).

      • Somewhere in the complexity of the brain some kind of 'biochemical thermostat' is at work.

      • This 'thermostat' is sensitive to the blood temperature of the brain.

      •  It also receives nerve signals from the skin about its temperature and so is involved a reflex arc action (discussed in previous section).

    • The blood sugar levels to provide the cells with a constant supply of energy.

      • When sugary or carbohydrate foods are digested the blood sugar levels rise as the sugar is absorbed from the gut into the bloodstream.

      • Your cell metabolism uses and hence removes the sugar in your normal energy releasing chemistry.

      • If you are not doing much physical work your blood sugar level will tend to rise.

      • If you are doing some demanding physical exercise your blood sugar level tend to fall.

      • It can be dangerous if your blood sugar levels become too high or too low, so your blood sugar level is regulated by the hormone insulin, which enables your body to have a regular supply of sugar for a secure supply of energy.

        • Note that details of the action of the skin and kidneys and the control of blood sugar are not required here.

        • Homeostasis is a word that is sometimes used to describe your bodily functions that try to maintain a stable constant internal environment including the factors listed above.


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