Osmoregulation Flashcards
What happens when water levels are low (dehydrated)?
• the water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
• when the water potential is very low, they shrink, and stimulate neurosecretory cells in the hypothalamus
- they produce and release anti douse tic hormone which flows down the axon to the posterior pituitary gland where it is stored until needed
- when the neurosecretory cells are stimulated they send action potentials down their axons which causes the release of ADH
• ADH travels in the blood to the kidney and binds to glycoproteins (receptors) in the membrane of the cells in the wall of the collecting duct
- this causes vesicles containing aquaporins (water channels) to move and fuse with the cell membrane
• this causes the cell membrane to become more permeable to water so more water is reabsorbed by osmosis from the collecting duct into the capillary
• this means that a smaller volume of concentrated urine is produced which increases the water potential of the blood
What happens if the water level in the blood is high? (Hydrated)
• the water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
• when the water potential is high, they do not shrink, and stimulate neurosecretory cells in the hypothalamus
- they produce and release anti diurectictic hormone which flows down the axon to the posterior pituitary gland where it is stored until needed
- when the neurosecretory cells are stimulated they send action potentials down their axons which causes the release of ADH
• however less impulses are sent to the neurosecretory cell so less ADH is released
• so less ADH travels in the blood to the kidney and binds to glycoproteins (receptors) in the membrane of the cells in the wall of the collecting duct
- this causes less vesicles containing aquaporins (water channels) to move and fuse with the cell membrane
• this causes the cell membrane to become less permeable to water so less water is reabsorbed by osmosis from the collecting duct into the capillary
• this means that a larger volume of dilute urine is produced which decreases the water potential of the blood
