- The Loop of Henle is where most water is reabsorbed.
- The longer the loop of Henle the more water is reabsorbed from the filtrate - back in the blood.
E.g. A desert rat would have a longer loop of Henle than a horse or a beaver as it requires more water to be reabsorbed and conserve to help it survive in the heat. A beaver would have a smaller loop of Henle in comparison to the horse as it lives in water.
When you are THIRSTY
- it is detected by osmoreceptors in the hypothalamus
- the osmoreceptors shrink due to a decrease in water potential in the blood
- it then synapses with neurosecretory cell - terminal bulb (which is equivalent to synaptic knobs) and fires off an action potential
- it releases vesicles that contains the hormones Antidiuretic Hormones (ADH) into the blood in the posterior pituitary gland
- ADH in blood targets cells forming walls of collecting duct
- causing a series of enzyme reactions including cyclic AMP
- vesicles with water channels aka aquaporins fuse with the cell membrane makin collecting duct more permeable to water
- the collecting duct passes through medulla (salty tissue fluid) so water pulls out of the filtrae by osmosis to be reabsorbed in blood.
- this produces a small quantity of concentrated urine
- water back in the blood blood water potential is restored back to normal
- this process switches off = negative feedback
No comments:
Post a Comment