kidneys and homeostasis Flashcards
(36 cards)
describe the three main roles of the kidneys
removal of urea and other waste products from the blood
adjustment of salt levels in the blood
adjustment of water content of the blood
what is osmoregulation
the maintenance of constant water levels in the body fluids of an organism
why is osmoregulation important
it prevents cells bursting or shrinking when water enters or leavers by osmosis
cellular reactions occur in aqueous solution therefore water levels affect concentrations and the rate of reactions in cells
what is a nephron
functional unit of the kidney where filtration and selective reabsorption takes place
what are the three stages involved in the formation of urine
filtration
selective reabsorption
osmoregulation
describe filtration in the kidneys
blood flows through the capillary knot under high pressure small molecules (e.g. urea, glucose), water and slats are filtered out of the blood and into the bowman's capsule
why is there a build-up of pressure in the capillary knot
due to the arteriole leading into the capillary knot being wider than the arteriole taking blood from the capillary knot
why do large molecules (like protein) remain in the blood
they are too large to fit through the pores in the capillary walls
which substances are selectively reabsorbed from the nephron tubule
all sugars
some water
some ions
what happens to the molecules that are not selectively reabsorbed
they travel down the kidney tubule as urine and are transported to the bladder via the ureter. here they are stored and eventually excreted
what is urine
waste solution containing urea, excess water, excess ions
if blood water levels become too high, the kidney produces more _____ urine
dilute
if blood levels become too low the kidney produces more _____ urine
concentrated
how is the concentration and volume of urine controlled
it is controlled by the secretion of anti-diuretic hormone (ADH)
how is the concentration and volume of urine controlled
it is controlled by the secretion of anti-diuretic hormone (ADH)
what produces anti-diuretic hormone (ADH)
the pituitary gland
describe how anti-diuretic hormone (ADH) affects the kidney
ADH causes the kidneys to reabsorb more water into the blood
more concentrated urine is produced
describe the composition of urine
contains:
some water
some salts
urea
what may glucose in the urine indicate
diabetes
what may blood or cells in the urine indicate
kidney disease
why is it important that salt content is regulated in the blood
removing excess salts is important because, if the concentration of salts in the body is wrong, it could mean too much or too little water is drawn into cells by osmosis
what is the process of water content regulation controlled by
negative feedback system
what happens when water content increases
a receptor in the brain detects that the water content is too high
the coordinator centre in the brain receives the information and organises a response
the pituitary glands releases less ADH, so less water is reabsorbed from the kidneys
more dilute urine is produced
what happens when water content decreases
a receptor in the brain detects that the water content is too low
the coordination centre in the brain receives the information and organises a response
the pituitary gland releases more ADH, so more water is reabsorbed for the kidneys
more concentrated urine is produced
