osmoregulation Flashcards
what is osmoregulation and how is it achieved
control of water potential in the body by controlling levels of both water and salt
-achieved by altering the water permeability of the collecting duct
why is osmoregulation important
essential to prevent damage to cells by osmotic lysis or crenation
what are the different ways by which water is gained and lost
gained from:
-food
-drink
-metabolism (e.g respiration)
lost by:
-urine
-sweat
-water vapour exhaled
-faeces
which cells of the body monitor the water potential of the blood and where are they found
osmoreceptors found in the hypothalamus
what happens to osmoreceptors when the water potential of the blood is too low and what detects this change
they lose water by osmosis if WP of blood is too low resulting in shrinkage which is detected by neurosecretory cells in the hypothalamus
what do the neurosecretory cells produce, where does it act and what is the response
-neurosecretory cells are specialised neurones that produce and release anti-diuretic hormone (ADH) which flows down the axon to the terminal bulb in the POSTERIOR pituitary gland where it is stored in vesicles
what happens after the neurosecretory cells are stimulated by shrinkage of osmoreceptor cells
-send an action potentials down their axons to stimulate release of ADH into the blood circulation
explain the effect of ADH on the collecting duct
1)ADH detected by cell surface receptors (specific to shape of protein) on the plasma membrane
2)triggers enzyme controlled reactions
3)vesicles containing water permeable channels (aquaporins) fuse to membrane
4)more water can be reabsorbed due to more aquaporins on the surface = more water reabsorbed to the blood
what kind of feedback is the effect of ADH on the collecting duct
negative feedback
suggest where ADH is removed from the blood and describe what then happens to the ADH molecule
-in the liver
-hydrolysis of hormone by protease
-deamination
-orinthine cycle/ formation of urea
