Renal Physl 12 Flashcards
What accounts for intake of water?
- Food/beverages 2100/ml/day
* Metabolism 200-300ml/day
What is insensible water loss?
Loss of water through diffusion
Why is maintaining water balance critical?
Because if excessive water is retained or lost, this alters blood volume which impacts blood pressure
What happens once fluid leaves the kidneys?
We can’t get it back
How are the kidneys able to control how concentrated the urine is?
By adjusting the amount of sodium and water
What happens if excess fluid is ingested and must be excreted as a dilute urine?
The kidneys reabsorb solutes without permitting water to be reabsorbed
How do the kidneys produces a concentrated urine and conserve water?
The tubules reabsorb water in excess of the solute so at the tubules, solute and water reabsorption can be varied
What is regulation of water balance subject to?
Hormonal controls
What is another name for vasopressin?
Antidiuretic hormone or ADH
When is Vasopressin typically released?
In conditions of low volume or low pressure or when plasma osmolarity is increased
What is does Vasopressin drive?
Water reabsorption
Which part of the kidneys does vasopressin effect?
The distal tubule and the collecting duct
How does vasopressin affect the distal tubules and collecting duct?
It induces the expression and insertion of water channels making them permeable to water which facilitates the movement of water from the tubule lumen into the interstitium by osmosis
What happens to vasopressin release if there is a lot of water?
Vasopressin release is suppressed and the distal tubule and collecting duct are basically impermeable to water
What does high vasopressin mean?
High permeability and reabsorption water
What are aquaporins?
The specialized water channels induced by vasopressin
Where are the aquaporins inserted in?
In both the apical and the basolateral membrane
What happens to the aquaporins in the absence of vasopressin?
They are removed by endocytosis from the membranes and stored in vesicles within the epithelial cells
What does Vasopressin do when released?
Binds to V2 receptors on epithelial cells of the distal tubule and collecting duct on the basolateral membrane. Activating G proteins the results in exocytosis of storage vesicles
What is the strongest stimulus for vasopressin secretion?
An increase in plasma osmolarity
What is plasma osmolarity monitored by?
Hypothalamic Osmoreceptors
What happens to osmoreceptors when osmolarity increases?
They increase their firing rate
What happens to osmoreceptors when osmolarity decreases?
The neurons have decreased firing
Aside from osmolarity, what also stimulates vasopressin to be released?
Decreased blood volume/pressure
What is different about vasopressin release caused by osmolarity versus decreased blood volume/pressure?
A larger change in BP/volume is required to stimulate vasopressin release
How do hypothalamic osmoreceptors change behavior?
They stimulate thirst when plasma osmolarity rises and stop the signal when when fluid is absorbed by the body
