Homeostasis biology unit 1a

About the homeostasis of the body

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Homeostasis


Homeostasis means keeping the conditions inside the body constant. Conditions include temperature, blood suagar, water and carbon dioxide. Having a 'constant internal environment'.

The body temperature is normally 37 degrees Celcius if the temperature drops or rises by 3 degrees you will become ill.

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Homeostasis is maintaining a constant internal env


Conditions in your body need to be kept steady so that cells can function properly. This involves balancing imputs with outputs.

  • levels of CO2 - respiration in cells constantly produces CO2, which you need to get rid of
  • Levels of oxygen - you need to replace the oxygen that your cells use up in respiration
  • Water content - you need to keep a balance between the water you gain in drink, food and from respiration and the water you lose by pee, sweat and when breathing out.
  • Body Temperature - you need to get rid of excess body heat when you are hot but retain heat when the environment is cold.
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Water is Lost from the Body in Various Ways

Water is taken into the body as food and drink and is lost from the body:
-- through the skin and sweat
-- via the lungs in breath
-- via the kidneys in urine

On  a cold day or when you are not exercising, you don't exercise as much so you'll produce more urine, which will be pale.
On a hot day or when you are exercising you are sweating a lot so you will produce less urine but this will be concerntrated ( a deeper colour). You will also lose more water through breathing when you exercise becuase you breathe faster.

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Negative Feedback Helps things Steady

Water is taken into the body as food and drink and is lost from the body:
-- through the skin and sweat
-- via the lungs in breath
-- via the kidneys in urine

On  a cold day or when you are not exercising, you don't exercise as much so you'll produce more urine, which will be pale.
On a hot day or when you are exercising you are sweating a lot so you will produce less urine but this will be concerntrated ( a deeper colour). You will also lose more water through breathing when you exercise becuase you breathe faster.

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Body Temperature

All enzymes work best at certain temperatures. The enzymes in the human body work at best around 37 degrees celcius and so this is the temperature that the body tries to mantain.

A part of the brain acts as your own personal thermostat. It's sensitive to the blood temperature in the brain and it recieves messages from the skin that provide information about skin temperature.

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Ion content is Regulated by the Kidneys

  • Ions are taken into the body in food then absorbed into the blood.
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  • If the food contains too much of any kind of ion then the excess ions need to be removed
  • some ions are lost in sweat
  • The kidneys will remove the excess from the blood - this is then got rid of in urine
  • Sports drinks can help contain your body keep things in order. The electrolytes replace those lost in sweat, while the carbohydrates can give a bit of energy boost. But the claims need to be looked at very carefully.
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When You're Too Hot

  • Hairs lie flat 
  • Lots of sweat is produced - when it evaporates it transfers heat from you to the environment, cooling you down.
  • Blood vessels become close to the surface of the skin. This allows more blood to flow nearer the surface, so it can radiate heat into the surroundings.
  • You can take off layers of clothing to help you cool down
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When You're Too Cold

  •  Hairs stand on end to trap an insulating layer of air which helps you keep warm
  • Very little sweat is produced
  • Blood vessels near the surface constrict so that less heat can be transferred from the blood to the surroundings
  • You shiver and the movement generates heat in muscles - exercise does the same
  • You can put on more clothes to trap the heat in
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Key Words:

Homeostasis - keeping the conditions inside the body constant
Thermogulation - constant body temperature
Vasodilation - blood vessels near the surface of the skin dilate so more blood goes to the surface and more heat is lost by radiation.
Shivering - repeated contractions of muscle which generates heat
Constriction - blood vessel's near the surface of the skin constrict so less blood goe to the surface and less heat lost by radiation.

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