Homeostasis

Humans need to remove waste products from their bodies to keep their internal envirnments relatively constant.

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  • Created by: Jess
  • Created on: 17-05-12 09:12

controlling internal conditions- removing CARBON D

All of the time your body is constantly producing waste products as a result of the chemical reactions which are taking place. The more extreme the contitions you put yourself in the more waste products your cells will make.

There are two main poisonous waste products which would cause major problems for your body if the levels built up:

  • CARBON DIOXIDE: every cell respires and therefore produces CO2.
    • If the CO2 was not removed and instead allowed to dissolve in the cytoplasm of your cells it would affect the pH. Dissolved CO2 produces an acidic solution and a lower pH would affect the working of all the enzymes in your cells.
  • HOW DO YOU REMOVE IT?
    • CO2 moves out of the cells into your blood.
    • Your bloodstream carries it back to your lungs.
    • Almost all of the CO2 you produce is removed from your body via your lungs when you breathe out. The air you breathe in contains only 0.04% CO2, but the air you breathe out contains about 4% CO2.
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controlling internal conditions- removing UREA

  • UREA:
    • Urea is produced in your LIVER when AMINO ACIDS are broken down. 
    • Amino acids cannot be used as fuel for your body. But in your liver the amino group is removed and converted into UREA.
    • The urea passes from the liver cells into your blood.

    Urea is poisonous and if the levels build up in your blood then it will cause alot of damage.

    • fortunately the urea is filtered out of your blood by your kidneys.
    • It is then removed in your urine, along with any excess water and salt.

Urine is produced all the time by your kidneys. it leaves your kidneys and is stored in your bladder which you then empty from time to time.   

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maintaining body balance

WATER & IONS enter your body when you eat or  drink.                                                 

the water and ion content are carfully controlled to prevent damage to your cells.

  • water loss:
    • through breathing
    • through sweating
    • in the urine
  • ion loss:
    • through sweating
    • in the urine.

If the water or ion content of your body is wrong, too much water may move into or out of your cells. Therefore control is vital.

 

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Controlling body temperature

Your core body temperature is maintained at around 37(degrees. C)-the temperature at which your enzymes work best.

various things can affect your internal body temperature. including:

  • heat produced in your muscles during excercise
  • fevers caused by disease
  • the external temperature rising or falling.

control of the temperature relies on the THERMOREGULATORY CENTRE in the BRAIN.

  • this contains receptors which are sensitive to temperature changes.
    • they monitor the temperature of the blood flowing through the brain itself.

Extra information comes from the temperature receptors in the skin. These send impulses to the THERMOREGULATORY CENTRE giving information about the skin temperature. (they can detect a difference of as little as 0.5 (degrees.C).

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Controlling body temperature- cooling down

If you get too hot, your enzymes denature and no longer catalyse the reactions in your cells.

  • If your core temperature begins to rise, impulses are sent from the thermoregulatory centre and your body:
    • The blood vessels, which supply your skinn capillaries, dilate -open wider- THIS LETS MORE BLOOD THROUGH THE CAPILLARIES. your skin flushed so you lose more heat by radiation. 
    •  Your rate of sweating goes up.
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Controlling body temperature- Reducing heat loss

It is just as dangerous for your core temperature to drop as it is to rise. If you get very cold then the rate of the enzyme-controlled reactions in your cells fall too low. Meaning you don't make enough energy and your cells begin to die.

If your core temperature starts to get too low, impulses are sent from your thermoregulatory centre to the body to conserve and even generate more heat.

  • The blood vessels which supply your skin capillaries constrict (close up) to reduce the flow of blood through the capillaries. This reduces the heat lost through the surface of the skin, and makes you look pale.
  • Shivering begins- your muscles contract and relax rapidly which involves lots of cellular respiration. This releases some energy as heat.
  • Sweat production is reduced
  • Hairs pulled erect to trap insulating layer of air.
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Controlling blood sugar

It is is very important that your cells have a constant supply of the glucose they need for cellular respiation.

Glucose is transported around your body to all of the cells by your blood.

Your blood glucose concentrtion is constantly monitored and controlled by two hormones known as Insulin and Glucagon, produced in your pancreas.

  • when your blood glucose concentration rises above the ideal range after you have eaten a meal, insulin is released.
    • Insulin causes your liver to remove any glucose which is not needed at the time from your blood. The soluble glucose is converted to an insoluble carbohydrate called Glycogen which is stored in your liver.
  • When your blood glucose concentration falls below the ideal range, the Pancrease secreates Glucagon.
    • Glucagon makes your liver break down glycogen converting it back into glucose. In this way the stored sugar is released back into the blood.

A normal concentration is usually about 90mg glucose per 100cm3 of blood.

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