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Title: Control of Water Content ( Homeostasis)
Description: These are detailed notes about a subtopic in Homeostasis. They give you all the knowledge you need to know about control of Water during Homeostasis Mechanisms. This is good for mainly A'Level students but if you find them useful for your level then why not.
Description: These are detailed notes about a subtopic in Homeostasis. They give you all the knowledge you need to know about control of Water during Homeostasis Mechanisms. This is good for mainly A'Level students but if you find them useful for your level then why not.
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Control of Water Content
Thursday, 15 February 2024
06:46
Osmoreceptors, the hypothalamus and ADH
Osmoregulation is the control of the water potential of body fluids
...
The water potential of the blood is constantly monitored by specialised sensory neurones in the hypothalamus, known as
osmoreceptors
...
These impulses stimulate the release of antidiuretic
hormone (ADH), which is a peptide hormone made of nine amino acids
...
The effect of ADH is to reduce the loss of water in the urine by making the kidneys reabsorb as much water as possible
...
The pituitary gland is just below the hypothalamus
...
The cells of the collecting duct are the target cells for ADH
...
Homeostatis Page 13
ADH is produced by neurones in the hypothalamus and is released into the blood where the neurones terminate in the posterior pituitary gland
...
The cells contain ready-made vesicles that have many
aquaporins in their membranes
...
Cyclic AMP activates a signalling cascade leading to the phosphorylation of the aquaporin molecules
...
As the fluid flows through the collecting duct, water molecules move through the aquaporins, out of the tubule and into the
tissue fluid
...
The fluid in the collecting duct loses water and becomes more concentrated
...
A small volume of concentrated urine will flow from the kidneys through the ureters
into the bladder
...
The effects of ADH on the reabsorption of water from urine in the collecting ducts
...
With no stimulus from ADH, the aquaporins are moved out of the cell surface membrane of the collecting duct cells, back
into the cytoplasm as part of the vesicles
...
The fluid flows down the collecting duct without losing any water,
so a dilute urine collects in the renal pelvis and flows down the ureter to the bladder
...
Collecting duct cells do not respond immediately to the reduction in ADH secretion by the posterior pituitary gland
...
However, once ADH stops arriving at the collecting duct cells, it takes only 10–15 minutes for aquaporins to be removed
from the cell surface membrane and taken back into the cytoplasm until they are needed again
Title: Control of Water Content ( Homeostasis)
Description: These are detailed notes about a subtopic in Homeostasis. They give you all the knowledge you need to know about control of Water during Homeostasis Mechanisms. This is good for mainly A'Level students but if you find them useful for your level then why not.
Description: These are detailed notes about a subtopic in Homeostasis. They give you all the knowledge you need to know about control of Water during Homeostasis Mechanisms. This is good for mainly A'Level students but if you find them useful for your level then why not.