15.6 The Kidney And Osmoregulation Flashcards
What is osmoregulation
Controlling the water potential of blood within very narrow boundaries
What is the role of ADH
It increases the permeability of the distal convoluted tubule and the collecting duct to water to control the amount of water lost in the urine
Where is ADH produced
Hypothalamus
Where is permeability stored and abs released from
The pituitary gland
What is the action of ADH to get to the collecting duct
It is carried in the blood and binds to receptors on the cell membrane of the tubule cells and triggers the formation of cyclic AMP as a second messenger
What cascade of events does the cyclic AMP cause when triggered by ADH
Vesicles in the cell lining of collecting duct fuse with cell surface membrane on the side of the cell in contact with the tissue fluid of the medulla
What is the vesicles that fuse with the cell lining by the medulla contain
And what does this mean in the action of ADH
Protein based water channels so the cell lining becomes permeable to water and a route is provided for water to move out of tubule into medulla
What system brings about the permeability of the collecting ducts controlled to match water requirements of the body
And what does this system involve
Complex negative feedback system
Involves osmoreceptors in the hypothalamus of the brain
What does the negative feedback system do when water is in short supply what is happening in the body
The concentration of inorganic ions in the blood rises, this is detected by osmoreceptors and they send an impulse to the posterior pituitary gland which releases ADH to produce concentrated ADH
What happens when the body has an excess of water
Blood is more dilute abs water potential becomes less negative so it’s detected by osmoreceptors and the impulses being sent to the pituitary gland are reduced
