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Flashcards in B12 Homeostasis Deck (22):

where is the thermoregulatory centre and how does it work

it is in the hypothalamus in the brain and contains receptors that sense changes in the temperature of the blood flowing through the brain


what happens when the internal body temperature needs to cool down

vasodilation- blood vessels that supply your surface skin capillaries open wider and let more blood flow through causing your skin to flush so you transfer more energy by radiation which cools you down

produce more sweat which evaporates and cools you down


what happens when your internal body temperature needs to warm up

vasoconstriction- blood vessels that supply skin capillaries constrict to reduce blood flow to skin to reduce energy being transferred by radiation

sweat production is reduced or stopped

shivering- skeletal muscles contract and relax rapidly which needs a lot of respiration (exothermic process). Energy transferred warms the body up


why does carbon dioxide need to be removed from the body

dissolved co2 produces an acidic solution which affects how enzymes work


how is carbon monoxide removed from the body

diffuses out of the cells into the blood down a concentration gradient. diffuses from the blood into the air in the alveoli of the lungs which is then removed when you exhale


how is urea removed from the body

passes from the liver cells into the blood. filtered out of the blood into the kidneys and then passes out in the urine


what is urea made up of

ammonia which forms from the amino group from the amino acids when the liver removes it (deamination). The amino acids come from excess protein from eating or cells being worn out which can't be stored


what are 2 ways of uncontrollable water loss

water is lost each time you exhale
lost through the skin in sweat


what is selective reabsorption

the amount of water and dissolved mineral ions reabsorbed depends on what is needed by your body


what is the role of ADH

a hormone that maintains water balance in the blood by changing the amount of water reabsorbed by the kidney tubules


what are the 2 methods of treating kidney failure

kidney transplant


what does dialysis do

restores the concentrations of urea and mineral ions in the blood that have built up


what are disadvantages of dialysis

have to follow a strict diet
have to spend regular, long sessions connected to it
feel tired and unwell in between sessions
eventually causes serious damage to the body
much more expensive than the transplant


what is the role of dialysis fluid

contains the same levels of glucose and mineral ions as that of a person without kidney disease which ensures there is no net movement of glucose out of the blood


why is diffusion down a concentration gradient so important in dialysis

excess ions move out of the blood into the dialysis fluid by diffusion leaving blood plasma concentration of mineral ions at a normal level


why does a person on dialysis have to reduce the amount of protein they eat between sessions

to limit the amount of urea low as dialysis fluid contains no urea


what is the rejection problem with kidney transplants

there is a risk that the antibodies of the immune system of the recipient will attack the antigens of the donor organ


what are 2 ways to reduce the risk of an organ being rejected

immunosuppressant drugs which suppress the immune response
using a donor kidney with a tissue type similar to the recipient


what are 2 disadvantages of kidney transplants

transplanted kidneys only last about 9 years
immunosuppressant drugs prevent the person from dealing effectively with illness
regular check ups for signs of rejection


what are advantages of dialysis

more readily available than kidneys


what are advantages of kidney transplants

allow you to live a relatively normal life
eat and drink what you want


why is concentration of urea in the urine so much greater than in the blood

reabsorption of water by the kidney