GCSE Biology Unit 2 - Homeostasis

Homeostasis, Kidneys, Insulin & Diabetes, Discovering Insulin

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"Homeostasis is the maintenance of a constant internal environment"

Homeostasis controls: body temperature; water content; ion content; blood sugar levels; carbon dioxide removal and urea removal.

Body temperature;
- Enzymes work best at 37º
- The thermoregulatory centre in the brain monitors body temperature, and recieves info. about surface temperature form receptors in the skin.

When too hot; hairs lie flat; sweat is produced; bood vessels dilate - all these make heat transfer easier.

When too cold; hairs stand up (trap air); no sweat; blood vessels constrict; muscles contract - shivering - all these make it heat transfer harder, or make more heat.

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The kidneys do three main jobs: removing urea from the blood; adjusting ion content in blood; adjusting water content in the blood.

Removing urea
- the body can't store proteins, so amino acids are converted into fats and carbohydrates in the liver, ammonia is produced, then converted into urea - a waste product
- urea is poisonous, (but less poisonous than ammonia) so after it is released into the blood the kidneys filter it back out, turn it into urine, which is stored in the bladder before leaving the body

Ion adjustment
- wrong ion content can change amount of water in cells through osmosis
- the kidneys remove excess ions from the blood stream

Water content
- water is taken in as liquids and food
- it is lost in urine, sweat, and the air breathed out 

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Insulin & Diabetes

Blood sugar has to be controlled. It is controlled by the pancreas, using the hormone insulin.

High blood sugar:
- insulin is released by the pancreas
- insulin turns glucose into glycogen which is stored in the liver

Low blood sugar:
- glucagon is released by pancreas (no insulin)
- glucagon turns glycogen into glucose and releases it into the blood

Type 1 Diabetes is caused by the pancreas not producing insulin. This means that blood sugar could rise to a level that can kill a person. There are several ways to control the blood sugar; carefully controlling diet and exercise; and injecting insulin

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Discovering Insulin

Banting and Best discovered insulin in the 1920's

1920 - Banting theorised that tying off the tube (duct) from the pancreas to the intestine would kill cells making enzymes, but not those making hormones
1921 - Banting & Best start working together
         - They start by working on dogs, tieing off the pancreatic duct from some dogs, and removing pancreases of others to make them diabetic. 
         - After 6 weeks, they removed the damaged pancreases, ground them and injected them into the diabetic dogs. The blood glucose concentrateion was reduced.
         - They repeated this, and found the same results each time.
         - They then used extracts from calf pancreases, but these caused reactions as they were impure.

They later went on to isolate the substance in the pancreatic extract - insulin. After more experiments, Banting & Best tried the insulin out on a person and found it worked. After this, insulin went into mass production.  

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Reece Day


good info, thanks for taking the time to make this(:

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