Loop of Henle Flashcards
How can the loop of Henle be described (shape and function)
As a hairpin (shape), counter current (fluid flows in opposite directions in ascending vs descending limbs) multiplier (increases concentration of solutes)
Overall function of Loop of Henle
concentrate salt in the kidney medulla in preparation for osmoregulation
Describe permeability of ascending vs descending limb to water
A= impermeable
D= permeable
Explain what occurs in the ascending limb
Na+ and Cl- are pumped via Act Trans out
Causes solute potential of medulla tissue fluid to increase
Explain what happens at descending limb
Bc off the high solute pot and low water pot of the medulla tissue fluid, water moves out of the descending limb via osmosis
Has no affect on solute pot bc water moves immediately into Vasa Recta
So fluid in descending limb becomes more concentrated as it falls
Where is the medulla tissue fluid and filtrate most concentrated
At apex of loop
Unit for measuring osmotic concentrations
Milliosmoles: mOs/kg
Higher value= Lowe water potential
Affect of length of loop 2
Longer the loop, the more concentrated the salt in the medulla so more water can be reabsorbed in the collecting duct
Adaptations of LoH to environment
Desert animals have a longer LoH than humans, than aquatic animals
Where does osmoregulation occur and what controls it
Collecting duct and Distal convoluted tubule, permeability of tubes is controlled by hormones
What is osmoregulation
Homeostatic control of water and solute composition of the blood.
Endocrine gland involved in osmoregulation+ hormone
Pituitary gland, Anti Diuretic Hormone
What and where are the receptors that detect decrease in water potential of blood
Osmoreceptors, in hypothalamus
What blood do osmoreceptors test
The blood flowing through them
Coordinator in osmoregulation and response to stimulation
Posterior lobe of pituitary gland, releases ADH
Effectors in osmoregulation and response to stimulation
cells of collecting duct and DCT, become more permeable to water
Overall response upon release of ADH into blood
More water reabsorbed into the blood
Small vol of more concentrated urine produced
Aquaporins
Channel proteins that allow water molecules to pass through
Affect of binding of ADH to receptors of CD/ DCT cells
Vesicles with aquaporins on their surface move towards and fuse with plasma mem at lumen of the CD/DCT
Aquaporins allow entrance of water into the cell via osmosis
Water leaves the cell into the medulla tissue fluid and then enters the capillaries via osmosis
Why does osmosis occur from CD/DCT to cells to tissue fluid to capillaries
Medulla tissue fluid has very low water potential so water moves down water potential grad
When release of ADH is stopped?
ADH in body breaks down after approx 15mins
No longer bound to receptors
Vessicle switch aquaporins are reabsorbed into cells via endocytosis
Membrane at lumen is no longer water permeable
How many molecules of water moving through each aquaporin per sec when open
3 billion
What causes vesicles to move towards and fuse with the membrane
Secondary messengers that travel through the cytoplasm as the ADH cannot pass through the membrane
What is the affect of the body not producing enough ADH
Causes diabetes insipidus
Means the kidney cant produce enough concentrated urine, too much water is passed from the body
