osmoregulation Flashcards
define osmoregualtion
the homeostatic control of water and solute composition in the blood via a negative feedback mechanism
where does osmoregulation occur
1) collecting duct
2) distal convoluted tubule
what is the name of the hormone which is used in osmoregulation
Antidiuretic hormone -ADH
outline the process of osmoregulation if there is a decrease in water potential of the blood
1) Stimulus- decrease in water potential of the blood
2) Detector- osmoreceptors in the hypothalamus of the brain detect the decrease in water potential of the blood as it flows through it
3) Co-ordinator- posterior lobe of the pitatory gland releases ADH
4) Effector- cells of the collecting duct and DCT increase in permeability of water
5) response- more water is absorbed from the collecting duct into the blood
6) results in increase blood water potential and more concentrated urine
outline the process of osmoregulation when there is an increase in the water potential of the blood
1) Stimulus- increased water potential of the blood
2) Detector- osmoreceptors in the hypothalamus detect this increase from the blood passing through it
3) co-ordinator- posterior lobe of the pituitary gland stops releasing ADH
4) effector- cells of the collecting duct and DCT become less permeable to water
5) response- less water is reabsorbed into the blood
6) as a result water potential levels decrease and a large volume of diluted urine is secreted
outline the role of ADH in increasing or decreasing cell permeability in the collecting duct and DCT
1) ADH binds to the membrane receptors
2) vesicles containing aquaporins in the cytoplasm move and fuse to the cell membrane
3) aquaporins become incorporated to the membrane
4) water molecules move in single file through the pores into the cell down the water potential gradient
5) as hormone levels fall the aquaporins are removed from the cell and accumulate in vesicles again
