Homeostasis

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internal enviroment

homeostasis: keeping your internal enviroment CONSTANT.

  • what needs controlling? body temperature, waste, water and ion content and glucose levels.

waste products from the body:

 CO2(by respiration) through lungs when we breathe out)

 Urea in the liver produce by AMINO ACIDS and removed by the kidneys (stored in the bladder)

THER-MORE-GULATORY CENTRE (in your brain)

  •  controls body temp
  •  has receptors which monitor temp of blood flow through brain
  •  recieves info from your receptors in your skin.
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Hot and cold conditions

Sweating helps you to cool your body. When it is hot more water is lost so you need to drink more to balance this loss. Skin may appear flushed when it's hot (due to increased blood flow beneath the surface)

HOT CONDITIONS: (if core body temp is too high)

blood vessels supplying skin capillaries dilate to increase blood flow and heat loss

Sweat glands release more sweat which cools the skin as it evaporates

COLD CONDITIONS: (if core body temp is too low)

blood vessels supplying skin cappilaries constrict to reduce blood flow and heat loss

muscles start to shiver causing heat energy to be released by respiration in cells

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The Kidneys

they maintain the concentration of dissolved substances in the blood (amount of water, ions and remove urea in urine) 2 kidneys on the back wall of the abdomen

Water and Ions enter the body when you drink and eat. The levels need to be maintained because too much water moving into or out of cells may damage them.

Blood vessels carry blood through kidneys where 3 processes occur:

ULTRA FILTRATION- lots of water and small molecules are squeezed out the blood (under pressure) into tubules in the kidney.

SELECTIVE REABSORPTION- all the sugar, plus any ions and water needed by the body are reabsorbed back into the blood from the tubules.

EXCRETION OF WASTE- excess water, ions and all of the urea now pass into the bladder as urine and is stored there before it's released from the body.

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DIALYSIS

As the blood flows through a dialysis machine:

1. blood is SEPARATED from the DIALYSIS FLUID by PARTIALLY PERMEABLE MEMBRANES.

2. the membranes allow urea, and any excess substances to PASS from the blood to the dialysis fluid.

3.concentrations of dissolved substances in the blood are RESTORED to their normal levels

Dialysis fluid contains the same concentration of useful substances as blood.(glucose and essiential mineral ios aren't lost through diffusion)

Dialysis is carried out regularly to maintain patient's health

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Kidney Transplants

Diseased kidney replaced with healthy one from donor. BUT may be rejected by the recipient's IMMUNE system unless precautions taken:

A donor kidney with a 'tissue type' similar to the recipients. (best achieved when close relative)

The recipient has drugs which SUPRESS the immune system.

ANTIGENS(proteins) on the SURFACE OF CELLS.

The recipients ANTIBODIES may ATTACK the ANTIGENS on the donor organ because they don't recognise them as being part of their own body.

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Blood Sugar Concentration

the PANCREAS controls blood sugar levels and SECRETES the hormone INSULIN. (insulin allows glucose to move from blood into the cells)

Level of insulin in the pancreas affects what happens in the LIVER. If the pancreas doesn't produce enough insulin a person's blood glucose concentration may rise to a HIGH LEVEL.

TYPE 1 DIABETES (controlled by exercise and diet or injecting insulin into the blood)

Instead of using animal insulin, human insulin is now made by genetic engineering (quick and cheap made using bacteria)

insulin CONVERTS glucose into glyCOGEN (which is stored in the liver) A 2nd hormone called gluCAGON is made in the pancres when blood glucose levels fall TOO LOW.

This causes gylCOGEN to be converted into glucose and be realeased into the blood

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