Controlling Internal Conditions:
The internal conditions must be carefully controlled, keeping the conditions within a narrow range is called homeostasis. Temperature, blood glucose, water content, ion content and levels of waste products must all be controlled. Waste products that must be removed from your body include:
- carbon dioxide produced by respiration, removed via the lungs when we breathe out
- urea produced in the liver, removed by the kidneys temporarily stored in the bladder
Water and ions enter the body when we eat and drink. If the ion or water content in the body is wrong, too much water may move in or out of the cells. This could damage or destroy cells.
The Human Kidney:
The body has two kidneys that filter the blood, excreting waste substances and keeping substances your body needs. A healthy kidney produces urine by:
- filtering the blood
- reabsorbing all the sugar
- reabsorbing the dissolved ions needed by the body
- reabsorbing as much water as the body needs
- releasing urea, excess ions and water into the urine
Dialysis and Kidney Transplants:
If a person suffers from kidney failure they can be kept alive by dialysis. Dialysis restores the concentration of substances in the blood back to normal but needs to be carried out at regular intervals. A dialysis machine carries out the same jobs as the kidneys. The dialysis fluid contains the same concentration of useful substances that the patients blood does meaning these substances do not diffuse out of the blood and so don't need to be reabsorbed. Urea diffuses out of the blod into the dialysis fluid.
Kidney transplants are another option to use when kidneys fail by using a donor kidney. They dont need regular treatments like dialysis does, however they are very rare and have to match your tissue type exactly so they will not be rejected by your bodies immune system. Another way to prevent it from rejecting is by taking immunosuppressant drugs.
Controlling Body Temperature:
Human body temperature must be kept at about 37*C so that enzymes can work efficiently. Body temperature is monitored and controlled by the thermoregulatory centre in the brain. This centre has receptors which detect the temperature of the blood flowing through the brain and in the skin. If the core temperature rises:
- blood vessels near the surface of the skin dilate allowing more blood to flow through the skin capillaries. Energy is transferred by radiation and the skin cools.
- sweat glands produce more sweat which evaporates from the skin, cooling skin
If the core temperature falls:
- blood vessels near the surface pf the skin constrict and less blood flows through the skin capillaries so less energy is radiated.
- muscles contract which uses respiration, the energy released warms the blood
Controlling Blood Glucose:
The pancreas monitors and controls the level of glucose in the blood. If there is too much glucose in our blood the pancreas produces insulin. Insulin causes the glucose to move from the blood into the cells. In the liver excess glucose is converted into glycogen for storage. Type 1 diabetes is when you dont have any or very little insulin produced by your pancreas and have to inject insulin yourself.
If there is too little blood glucose, receptors in the pancreas detect this and releases glucagon. Glucagon causes glycogen in the liver to convert back into glucose which is released back into the blood.
Typre 1 diabetes is treated with insulin injection before meals everyday. However doctors and scientists are trying to develop new treatments and possibly cures; pancreas translants, translplanting pancreas cells, using embryonic stem cells to produce insulin secreting cells and genetically engineering pancreas cells.