Homeostasis - mainting the body’s water balance

Question 1

what happens if the blood becomes too concentrated (leaves of water in blood falls)?
what is this known as?

Answer 1

pituitary gland releases ADH into bloodstream which travels to the kidneys causing the kidney tubes to become more permeable to water (more water pass out of tubules) so more water can reabsorb into bloodstream from tubules. Because if this, less urine is produced and amount of water in blood rises back to normal level
- known as negative feedback cycle

Question 2

what happens when water levels in blood are back to normal?

Answer 2

pituitary gland will stop releasing ADH into bloodstream

Question 3

what happens if blood becomes too dilute?

Answer 3

concentration of water rises so pituitary gland stops producing ADH. kidneys then reabsorb less water into the blood so now more urine is produced and concentration of water in blood returns to normal

Question 4

what happens if kidneys fail?

Answer 4

the levels of urea, water and ions need adjusting with a machine - kidney dialysis

Question 5

what happens to the levels in the blood when a person has kidney failure?

Answer 5

they will have a higher concentration of water ions and urea than they should

Question 6

what halogens during kidney dialysis?

Answer 6

• patients blood passes over a semi-permeable membrane
• this allows urea, ions and water though it but larger molecules such as proteins and blood cells are too large
• other side of membrane is dialysis fluid contains normal concentration of water and ions and no urea. this created a concentration for urea from the blood. urea then diffuses from blood into dialysis fluid which is constantly changed to ensure a large concentration gradient for urea
• some water and ions will diffuse from blood into dialysis fluid so concentration of water and ions in patients blood will return to normal

Question 7

why can kidney dialysis be inconvenient?

Answer 7

patient has to visit hospital several times a week and they have a controlled diet to stop too much urea being produced

Question 8

what is a better alternative then kidney dialysis? and why? problem with this.

Answer 8

a kidney transplant as a diseased kidney can be replaced with a healthy kidney from a donor
problem: patients immune system could reject donors kidney

Question 9

comparison between kidney transplant and kidney dialysis

Answer 9

kidney transplant:
- shortage of kidney donors
- patient can lead a normal life
- it is expensive initially
- patient has to take anti-rejection drugs for the rest of their life

kidney dialysis:
- there is no shortage of dialysis machines
- patient had to have frequent treatments and controlled diets
- it is expensive in the long running