Transport of other ions and different functions Flashcards
how much sodium is reabsorbed in the loop of Henle?
20% of filtered load
function of distal tubule
fine regulation of renal electrolytes and water output
important region of the distal tubule
macula densa
what is the macula densa sensitive to?
decreased and increased sodium chloride concentration
what may increase the concentration of sodium and chloride?
increased flow rate, less time for equilibration in ascending limb
increased GFR
percentage absorption in distal tubule
7%
transporters in distal tubule
sodium chloride NCC and basolateral sodium potassium pump
what happens if there is decreased sodium and chloride?
- production of prostaglandins which vasodilate the afferent renal arteriole
- prostaglandins also activate juxtaglomerular cells to release renin
- renin leads to the constriction of the efferent arteriole
explain renin-angiotensin system
- renin secreted into blood stream from afferent arteriole
- renin catalyses the conversion of angiotensinogen to angiotensin I in the liver
- angiotensin I is converted to angiotensin II by ACE within vascular endothelial cells of the lungs
- angiotensin II acts as a vasoconstrictor of the efferent arteriole, increasing glomerular pressure
another function of angiotensin II
stimulates the secretion of the hormone aldosterone from the adrenal cortex
Aldosterone function
- stimulates sodium reabsorption at the principal cells of the collecting duct
- increased ENaC and basolateral sodium potassium pump, so more sodium and water reabsorbed
- this increases the blood volume and therefore blood pressure
what does aldosterone cause as a side effect?
excess potassium excretion into urine
hypokalemia
what happens if there is increased sodium and chloride in macula densa?
- too much chloride, ATP released from cells in macula densa
- ATP forms adenosine which inhibits renin release by binding to granular cells
what else may lead to renin’s release?
baroreceptors in the afferent arteriole which notice a decrease in blood pressure
what else may stimulate aldosterone?
increased plasma potassium
what stimulates thirst?
angiotensin iI
Where is atrial natriuretic peptide released? + when
atria of the heart
atrial distention
atrial natriuretic peptide mechanism of action
- raises cell cGMP by activating guanylyl cyclase
- leads to vasodilation of afferent arteriole which increases GFR but inhibits reabsorption
inhibits ENaC on apical side of collecting duct and Na/K+ exchanger
dilutes body fluid and leads to volume extraction
atrial natriuretic peptide function
decrease of sodium absorption prevents the reabsorption of water
more water and sodium lost in urine
decreases blood pressure
ANP has the opposite affect of what hormone?
angiotensin II which increases renal sodium retention whereas ANP increases renal sodium loss
what is secreted by the kidney in response to cellular hypoxia?
erythropoietin
where is erythropoietin produced?
interstitial fibroblasts in the kidney in close association with peritubular capillaries and proximal convoluted tubules
erythropoietin function
promotes the survival of red blood cell progenitors and precursors from apoptosis
erythropoiesis stimulated, development of stem cells to mature red blood cells
which vitamin is activated in the kidneys?
vitamin D
explain activation of vitamin D
- vitamin D synthesised in the skin and then carried to liver
- converted into prohormone calcifediol
- calcifediol converted into calcitriol (active form of vit D) in the kidneys, specifically the proximal tubule
