Homeostasis - The Kidneys 135-137 Flashcards
how do the kidneys act as filters for the blood
3 points
1) they make urine by taking waste products out of your blood
2) substances are filtered out of the blood as it passes through the kidneys, this is called filtration
3) useful substances like glucose, some ions and the right amount of water are absorbed back into the blood, this is called selective reabsorption
how is urea removed from the body
3 points
1) proteins can’t be stored by the body, so any excess amino acids are converted into fats and carbs which can be stored, this happens in the liver and is called deamination
2) ammonia is produced as a waste product from this process
3) ammonia is toxic to it’s converted into urea in the liver then transported to the kidneys where it’s filtered out of the blood and excreted out in urine
how is water removed from the body
3 points
1) the amount of water in the body needs to be constantly balanced
2) we lose water from the skin in sweat and from the lungs when we breath out
3) in this way we can’t control how much we lose, so it’s balanced by the amount we consume and the amount removed by the kidneys in urine
how are ions removed from the body
5 points
1) ions like sodium are taken into the body in food then absorbed into the blood
2) if the ion or water content of the body is wrong, it could upset the balance between ions and water, meaning too much or too little is drawn into the cells by osmosis
3) having the wrong amount can damage cells
4) some ions are lost in sweat, but this amount is not regulated so keeping the balance is maintained by the kidneys.
5) the right amount of ions is reabsorbed into the blood after filtration and the rest is removed in urine
how is the concentration of urine controlled
3 points
1) it’s controlled by a hormone called anti-diuretic hormone (ADH)
2) it’s released into the bloodstream by the pituitary gland
3) the brain monitors the water content of the blood and instructs the pituitary gland to release ADH into the blood according to how much is needed
how is water content controlled
4 points
1) controlled by negative feedback
2) a receptor in the brain detects the water content is too high/low
3) the coordination centre in the brain receives the information and coordinates a response
4) the pituitary gland releases less ADH so less water is reabsorbed from the kidneys if the water content is too high and the opposite happens if it’s too low
what happens if your kidneys don’t work properly
2 points
1) waste substances build up in the blood and you lose your ability to control levels of ions and water, this eventually leads to death
2) people with kidney failure can be kept alive by having dialysis treatment or a kidney transplant
how frequently does dialysis need to take place
5 points
1) needs to be done regularly to keep concentration of dissolved substances in the blood at normal levels and remove waste substances
2) patients with kidney failure have to have sessions 3 times a week each session takes 3-4 hours
3) dialysis can cause blood clots or infections
4) being on dialysis is not a nice experience and it’s also expensive for the NHS
5) however it can buy the patient time for them to find a donor
how does a dialysis machine work
5 points
1) in the machine the persons blood flows between partially permeable membranes surrounded by dialysis fluid
2) the membranes are permeable to things like ions and waste substances but not big molecules like proteins
3) the dialysis fluid has the same concentration of dissolved ions and glucose as healthy food
4) this means that useful dissolved ions and glucose won’t be lost from blood during dialysis
5) only waste substances and excess ions and water diffuses across the barrier
what is the only cure for kidney failure
kidney transplant
how does someone become a donor
5 points
1) kidneys are often transplanted from people who’ve died suddenly
2) the person who’s died needs to be on the organ donor register or carry a donor card
3) they can be transplanted from people who are still alive but there’s a risk for the donor
4) there’s also a risk the kidney can be rejected by the patients immune system, the patient is treated with drugs to prevent this but it can still happen
5) transplants are cheaper than dialysis but their waiting lists are longer
