The role of ADH Flashcards
What does ADH stand for and what does it control?
antidiuretic hormone
amount of water reabsorbed from the nephrons
osmoregulation
What happens when there is too little water in the blood?
brain senses there is not enough water in blood
pituitary gland secretes more ADH
more ADH makes the collecting ducts more permeable
more water is reabsorbed from the kidney tubule back into the blood
a small volume of concentrated urine is produced
What happens when there is too much water in the blood?
the brain senses there is too much water in the blood
the pituitary gland secretes less ADH
less ADH makes the collecting duct less permeable
less water is reabsorbed from the tubule back into the blood
a large volume of dilute urine is produced
What does ADH do?
increases the permeability of the cell membranes in the collecting duct of the nephron so that more water is reabsorbed from the urine by osmosis
Explain what is meant by a neagtive feedback mechanism, using ADH production as an example
increase in blood water content causes pituitary gland to secrete less ADH
less water is reabsorbed by the collecting duct in the kidneys due to less permeability
more water is excreted by the kidneys
decrease in blood water content causes pituitary gland to secrete more ADH
less water is excreted by kidneys
negative feedback mechanism because a change in blood water content causes an opposite change that restores the normal blood water content
State where ADH is produced and its target organ
State what is meant by a target organ
pituitary gland, acts on the kidneys
the organ whose function is changed by the hormone
Blood samples were taken from a person half an hour after they had been exercising and again after they had drunk a large glass of water
explain which sample contained the most ADH
after exercise
water will have been lost from the body in sweat during exercise
more ADH is secreted from the pituitary gland when blood water content is low
this is so more water is absorbed into the blood
alcohol inhibits the production of ADH
a middle aged man is in his garden mowing the lawn on a hot sunny day
he is feeling thirsty so he drinks a glass of beer
explain why this is not the best choice of drink
beer is alcoholic
production of ADH is then inhibited
less water is reabsorbed by the kidneys
more water is lost from the body/he becomes dehydrated/less water for sweat production
