Biology 3 Unit 3

Homeostasis is the maintenance of the internal body conditions

• Carbon dioxide - produced by respiration and removed via the lungs when we breathe out
• Urea - produced in the liver from the breakdown of amino acids, removed by the kidneys in the urine and temporarily stored in the bladder

If the water or ion content in the body is wrong, too much water may move into it or out of the cells and damage them.

They excrete substances that the body does not want

• First filtering the blood
• Reabsorbing all the sugars
• Reabsorbing the dissolved ions needed by the body
• Reabsorbing as much water as the body needs
• Releasing urea, excess ions and water in the urine

• People who suffer from kidney failure can be kept alive by dialysis
• Dialysis is a treatment that restores the concentration if dissolved substances in the blood to normal levels and has to be carried out in regular intervals

• In a dialysis machine a person's blood flows between partially permeable membranes
• Dialysis fluid contains the same concentration of useful substances as the blood. This ensures that glucose and useful mineral ions are not lost.
• Urea diffuses out if the blood and into the dialysis fluid

In kidney transplants a diseased kidney is replaced with a healthy one from a donor.

• If successful the patient will not need further dialysis
• Diseased kidney is replaced with a healthy one
• Less fluid / diet restrictions

• Treatment involves suppressing the patient's immune system, which leaves them vulnerable to common infections
• Risk of rejection: The new kidney must be a very good 'tissue match'
• Risk associated with surgery

• A donor kidney with a "tissue-type" similar to that of the recipient is used
• The recipient is traded with drugs that suppress the immune system

So that the enzymes will work efficiently

• The body temperature is monitored and controlled by the thermoregulatory centre in the brain
• The centre has receptors sensitive to the temperature of the blood flowing through the brain

Temperature receptors in the skin send impulses to the thermoregulatory centre

The skin goes red when we are hot due to the increased blood flow

• If the core temperature rises:
• Blood vessels supplying the skin capillaries dilate so that more blood flows through the capillaries and more heat is lost
• Swear glands release more sweat which cools the body as it evaporates

• Is the core temperature falls:
• Blood vessels near the surface of the skin constrict and less blood flows through the skin capillaries. Less energy radiated
• We 'shiver'. Muscles contract quickly. This requires respiration and done of the energy released warms the blood

• The pancreas monitors and controls the level of glucose in our blood
• The pancreas produces the hormone insulin, which allows glucose to move from the blood into cells

• If the levels get too low receptors in the pancreas detect the low level
• The pancreas produces the hormone glucagon which causes the glycogen in the liver to change into glucose

Type 1 diabetes is a disease in which a persons blood glucose levels rise to a high level due to the pancreas not producing enough insulin

Type 1 diabetes is controlled by injection of insulin and careful attention to diet and levels of exercise