ADH

What is blood conc monitored by?

Osmoreceptors in the hypothalamus

What happens if the blood conc is too high?

It means more negative water potential, osmoreceptors shrink

What happens if blood conc is too low?

Less negative water potential, osmoreceptors swell. Less ADH is released, fewer aquaporins inserted into collecting duct CSM. Collecting duct is less permeable to water, less water is reabsorbed - lots of urine

What does a more negative water potential trigger?

Neurosecretory cells to release ADH by exocytosis y posterior pituitary

Where is ADH made?

ADH is manufactured in the cell body of these cells in the hypothalamus, but flows down their axon to the posterior pituitary gland

What happens when neurosecretory cells are stimulated?

ADH is released from the posterior pituitary gland

What does ADH do?

Causes the collecting duct to become more permeable to water

What is the action of ADH the same as?

Adrenaline

What happens with adenylyl cyclase?

Triggers ATP to cAMP (causes cascade reaction)

What is ADH detected by?

Cell surface receptors on the collecting duct, binds to them

What does ADH trigger?

Release of second messenger

What reactions occur?

Enzyme controlled reactions, vesicles containing water permeable channels (aquaporins) fuse to membrane and become embedded in collecting duct walls

What then happens to the water?

Moves out of the collecting duct into the salty medulla by osmosis, more water enters the blood

What is diabetes insipidus?

Rare condition where not enough ADH is produced

What symptoms are displayed?

Urine being passed in excess, extreme thirst, irritability and fatigue

Explain how the action of ADH on the cells of the collecting duct brings about changes in conc of urine

ADH binds to receptors on cell surface membrane, increase in conc of cAMP, cAMP causes vesicles containing aquaporins to move, aquaporins increase in CSM lining the lumen, more water is reabsorbed and conc increases, cAMP activates protein kinase which increases transcription of aquaporin genes