what is the role of the loop of henle?
creates a low water potential with high solute concentration in the tissue fluid around the nephron in the medulla region of the kidney
describe the urine of mammals due to the loop of henle
more concentrated than their blood (hypertonic to blood)
- water saving
define the counter current system
fluid flows in opposite directions in two vessels close to each other
how do the 2 limbs of the loop of henle act as a countercurrent multiplier
ascending limb uses ATP to create the conc gradient needed for water to be removed from the descending limb which moves it back into blood
what is the advantage of having a counter current flow?
maximises concentration gradient
the ascending limb is ….
permeable to mineral ions but not permeable to water
how is the water potential of the tissue fluid decreased?
Na+ and Cl- move out of ascending limb into tissue fluid
describe the water potential inside the start of the descending limb
high
how is the water potential inside the start of the descending limb decreased?
water moves out into tissue fluid
define osmoregulation
control of water potential to prevent osmotic issues in cells
describe how water is conserved
- low water potential detected by hypothalamus osmoreceptors
- ADH released
- DCT walls and collecting duct become more permeable
- more water is reabsorbed
- less water goes into urine so it is more concentrated
describe how water is removed
- high water potential detected by hypothalamus osmoreceptors
- less ADH released
- DCT walls and collecting duct less permeable
- less water reabsorbed
- more water goes into urine so it is more dilute
