B3.3 Homeostasis Flashcards
Where is urea produced?
in the LIVER
What happens if the water or ion content of the body is wrong?
too much water may move into or out of the cells and damage them
Then do water and ions enter the body?
When we eat and drink
Describe how a healthy kidney produces urine
- filters the blood
- reabsorbs all the sugar
- reabsorbs dissolved ions needed by the body
- reabsorbs as much water as the body needs
- releases urea, excess ions and water as urine
What are the 2 ways that people who suffer from kidney failure can be treated?
dialysis
kidney transplant
Describe how kidney dialysis works
in a dialysis machine, a person’s blood flows between partially permeable membranes.
The dialysis fluid contains the same concentration of the useful substances as the blood.
This ensures that glucose and useful mineral ions are not lost. Urea passes out from the blood into the dialysis fluid
What are some disadvantages and advantages of kidney dialysis?
it restores the concentrations of dissolved substances in the blood to normal levels
readily available, no waiting list
it has to be carried out at regular intervals
may cause blood clots or infection
Describe a kidney transplant
a diseased kidney is replaced with a healthy one from a donor
What are some disadvantages of kidney transplants
- lack of donor organs
- kidney may be rejected by the immune system unless precautions are taken
Describe why a kidney may be rejected
immune system produces antibodies
which attack the antigens on the transplanted kidney
How can you prevent rejection of a transplanted kidney?
- A donor kidney with a ‘tissue-type’ similar to that of the recipient is used
- The recipient is treated with drugs that suppress the immune system
What monitors and controls body temperature?
the thermoregulatory centre in the brain
Describe the thermoregulatory centre in the brain
it monitors and controls body temperature
It has receptors sensitive to the temperature of blood flowing through the brain
temperature receptors in the skin send impulses to the thermoregulatory centre, giving information about skin temperature
What happens if the core body temperature is too high?
blood vessels supplying the skin capillaries dilate so that more blood flows through the capillaries and more heat is lost (easier for heat to be transferred from the blood to the environment) - This is why the skin looks red when we are hot
Sweat glands release more sweat which cools the body down as it evaporates
Describe what happens if the core body temperature is too low?
- Blood vessels supplying the skin capillaries constrict to reduce the flow of blood through the capillaries
- Muscles may ‘shiver’- their contraction needs respiration, which releases some energy to warm the body
What controls the blood sugar concentration of the body?
the PANCREAS
Describe how the pancreas controls blood sugar levels
- produces a hormone called INSULIN which allows the glucose to move from the blood into the cells
- produces GLUCAGON when blood glucose levels fall. This causes GLYCOGEN to be converted into GLUCOSE and be released into the blood