Biology-Homeostasis

GCSE Additional Science-Biology 

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  • Created by: Mel
  • Created on: 27-05-12 11:42
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HOMEOSTASIS
The conditions inside the body must be controlled within narrow limits. This is called
homeostasis. These conditions include water content, ion content, body temperature and
blood glucose concentration.
The thermoregulatory centre is the part of the brain that monitors and controls body
temperature. The pancreas meanwhile monitors and controls blood glucose concentration.
It produces a hormone called insulin that reduces blood glucose levels. Diabetes is a
disease which can be caused by insufficient insulin.
Removing waste products
Waste products must be removed from the body. If they are not, they will increase in concentration
and may interfere with chemical reactions or damage cells. Waste products that must be removed
include carbon dioxide and urea.
Production and removal of waste products
Waste Why is it produced? How is it removed?
product
carbon it is a product of aerobic respirationthrough the lungs when we breathe out
dioxide
urea it is produced in the liver when the kidneys remove it from the blood and make
excess amino acids are broken urine, which is stored in the bladder temporarily
down
Water enters the body through food and drink. It is also a product of aerobic respiration in cells. If
the amount of water in the body is wrong, cells can be damaged because too much water enters or
leaves them. The animation shows how the amount of water lost as urine is controlled. Note that you
do not need to know any details of this for the examination.
Controlling blood glucose
You found out in your GCSE Science Biology 1 studies that the blood glucose concentration is
controlled to provide cells with a constant supply of energy. You might want to check your
understanding of this by looking at the section in Bitesize AQA GCSE Science about Hormones.
The pancreas and insulin
The pancreas monitors and controls the concentration of glucose in the blood. It produces a
hormone called insulin. Insulin causes glucose to move from the blood into cells. It lowers the blood
glucose concentration if it has become too high. This can happen after eating a meal that is rich in
carbohydrates (for example, sweets, potatoes, bread, rice or pasta).
Diabetes
Diabetes is a disease where the concentration of glucose in the blood is not controlled properly by
the body. In type 1 diabetes, the pancreas does not produce enough insulin. This can lead to high
levels of glucose in the blood, which can be fatal.

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Banting and Best
You should be able to evaluate experimental data from Banting and Best's experiments which led to
insulin being discovered.
Two doctors, Frederick Banting and Charles Best, made an extract from the pancreas in 1921. The
extract had antidiabetic properties, and they tested it successfully on diabetic dogs. The first tests in
humans were carried out in 1922, and were a success too. Some patients who were in a diabetic
coma even recovered. The extract contained the hormone insulin.…read more

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When we get too cold:
Muscles contract rapidly we shiver. These contractions need energy from respiration, and some of
this is released as heat.
Blood vessels leading to the skin capillaries become narrower they constrict letting less blood
flow through the skin and conserving heat in the body.
The hairs on the skin also help to control body temperature. They lie flat when we are warm, and
rise when we are cold.…read more

Comments

Swallowtail

A well presented set of notes with clear diagrams which covers key topics in homeostasis. Higher students might need additional information on the kidney with some   additional diagrams to help cover the extra knowledge needed.

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