The fluid which enters the Loop of Henle has a ___ osmolarity.
The fluid which leaves the Loop of Henle has a ___ osmolarity.
entering - low osmolarity
leaving - still a low osmolarity, but ADH sorts that in distal tubules and collecting duct
Tubular fluid becomes highly concentrated in the Loop of Henle to set up the cortico-medullary concentration gradient and then becomes less concentrated again as it leaves
What is the osmolarity of the interstitium of the renal cortex?
same as most of the body
What is the concentration gradient going from the renal cortex to medulla?
(300 - 1200 mosmol/L)
As fluid goes down the collecting ducts, the osmolarity of the interstitium around it (increases / decreases).
So the water from the fluid moves to the interstitium, increasing fluid osmolarity
Leading to the production of a low volume of hypertonic urine
Where do the distal tubules drain?
What occurs in the distal tubules and collecting ducts?
What regulates the absorption of ions and water in the distal tubules and collecting ducts?
What hormones regulate water and ion reabsorption in the distal tubules and collecting ducts?
What does ADH cause?
Increased water reabsorption
What does aldosterone cause?
Increased SODIUM REABSORPTION
Increased K+ and H+ secretion
What does ANP cause?
Decreased sodium reabsorption
opposite of aldosterone
What affects the permeability of the distal tubules to water?
In the absence of ADH, the permeability of the distal tubules to water is ___.
How does the early distal tubule absorb ions?
How does the late distal tubule reabsorb ions?
Action of ALDOSTERONE (Na+) and PTH (Ca2+)
In the basal state, how permeable is the early collecting duct to ions?
Which gland produces ADH?
stored and secreted by posterior pituitary
Which ion triggers __cytosis of peptide hormones from cells?
Ca2+ dependent exocytosis
What is the half life of ADH?
10 - 15 minutes
When is ADH released by the posterior pituitary?
Reduced blood volume e.g dehydration, haemorrhage, sepsis
Which vessels have ADH receptors?
Which type of receptor are they?
Late collecting ducts
G-protein coupled receptors
What is produced by G-protein-coupled ADH receptors when they are activated?
What does this cause in the apical membrane of the distal tubule and late collecting duct?
Opening of aquaporins
Reabsorption of water
What is ADH also known as?
The movement of water through ___ of the distal tubules and late collecting duct creates what between the tubules and capillaries?
High levels of ADH lead to the production of ___ urine.
Low levels of ADH lead to the production of ___ urine.
hypertonic / concentrated
hypotonic / dilute
As water is reabsorbed, the osmolarity of tubular fluid ___.
Is the ascending limb of the Loop of Henle permeable to water?
In high concentrations of ADH, the distal tubules and collecting ducts are ___ to water.
In low concentrations of ADH, the distal tubule and collecting ducts are ___ to water.
Why does fluid leaving the Loop of Henle always have a low osmolarity?
Corticomedullary concentration gradient, loses all its salt as it travels back up, reducing its osmolarity
Remember ascending limb is impermeable to water so osmosis INTO the ascending limb doesn't occur to reduce the osmolarity