05.1 Osmolarity Control Flashcards
What are the efferent pathways that respond to the hypothalamus detecting an increase in plasma osmolarity?
ADH.
Thirst.
How does ADH increase water and sodium retention?
Puts aquaporin channels in the apical membrane of the collecting duct causing water reabsorption.
This increases Na+ reabsorption in the loop of Henle.
Which is used for larger deficits in water, ADH or Thirst?
Thirst.
When faced with circulatory collapse but normal plasma osmolarity how do the kidneys respond?
Continue to conserve water even if it does decrease the osmolarity of body fluids.
What is diabetes insipidus?
Either the pituitary gland doesn’t sufficiently secrete ADH or the kidney is insensitive to ADH.
This leads to a large quantity of urine produced.
What is SIADH?
Syndrome of inappropriate antidiuretic hormone secretion.
Excessive ADH release.
Dilutional hyponatreamia.
Where is plasma osmolarity detected.
Osmoreceptors in the (OVLT of the) hypothalamus.
What three mechanisms are essential for generating the corticopapillary osmotic gradient?
Active NaCl transport in the thick ascending limb.
Recycling of urea.
Unusual arrangement of blood vessels.
How is the medullary gradient generated?
Thick ascending limb removes only solute hence increases the osmolarity of the interstitium. (This means that the loop of Henle acts as a counter current mechanism).
Urea recycling moves from CD into interstitium and back into the loop.
How does ADH affect urea recycling?
ADH increases urea recycling which increases the medullary gradient and hence reabsorption of water.
How is the medullary gradient maintained?
Vasa recta flowing in the opposite direction.
