Osmoregulation 5.2.8 Flashcards
What is osmoregulation?
The control of the water potential of body fluids
What is osmoregulation a key part of?
Homeostasis
What are osmoreceptors
Specialised sensory neurones
What do osmoreceptors do?
They monitor the water potential of the blood
Where are osmoreceptors found?
In the hypothalamus
What happens if osmoreceptors detect a decrease in the water potential of the blood?
- Nerve impulses are sent to posterior pituitary gland
- Posterior pituitary gland releases ADH
Where is ADH produced?
Hypothalamus
Where is ADH released?
Posterior pituitary gland
What does ADH stand for?
Anti diuretic hormone
What happens to ADH after being released from the PPG?
They enter the blood and travel throughout the body, causing the kidneys to reabsorb more water by increasing the permeability of the nephron walls
What is the effect of ADH?
Increases the permeability of the nephron walls and reduces the loss of water in the urine
Where does water reabsorption mainly occur in the kidney?
Collecting duct
What does ADH do to the collecting duct walls?
They increase the number of aquaporins in the luminal membranes of the collecting ducts
Describe the process of the release of aquaporins
- Collecting duct cells contain aquaporin contained vesicles
- ADH molecules bind to receptor proteins which activates a signalling cascade - leading to phosphorylation of aquaporin molecules
- This activates the aquaporins, causing the vesicles to fuse with the luminal membranes of collecting duct cells
- This increases the permeability to water
Where does water move from and to in the collecting duct
Moves from the collecting duct (high water potential) through the aquaporins, and into the tissue fluid and blood plasma in the medulla (low water potential)
