lecture 33 - renal / urinary physiology Flashcards
what are the three places where water is reabsorbed in the nephron
- proximal convoluted tubule ( bulk reabsorption 67%)
- descending limb of nephron (25%)
- collecting duct (2-8%
is bulk reabsorption of water para or transcellular
both
is regulated reabsorption of water para or transcellular
only transcellular
is bulk reabsorption of water regulated
no = automatic
How is regulated reabsorption of water regulated
regulated by antidiuretic hormone, more ADH less urine
what are the four important places where sodium is reabsorbed
- proximal convoluted tubule (67%)
- ascending limb of the nephron loop (25%)
- distal convoluted tubule (5%)
- collecting duct (2-3%)
what is water reabsorption in the proximal tubule driven by
Na+ reabsorption
what follows glucose and sodium being transported through the proximal tubule
- chloride follows via the paracellular pathway
- water follows by the paracellular and transcellular pathway
what is the descending loop of the nephron permeable to
water (has aquaporins)
what is the ascending loop of the nephron permeable to
ions (sodium)
how is water reabsorbed from the nephron into the peritubular fluid
- via the transcellular pathway = aquaporins
- via the paracellular pathway = across junctions between cells
how do the juxtamedullary nephrons generate of hyper-osmotic medullary gradient
the different permeabilities of the descending (water) and ascending (sodium) parts of the juxtamedullary nephron loop
what regulated the absorption of sodium in the distal convoluted tubule and the collecting duct
aldosterone
what detects change in body osmolarity
osmoreceptors in the hypothalamus
how does ADH balance TBW
ADH alters the permeability of the collecting duct, so water is retained/excreted to balance the initial change in TBW
what will the hypothalamus do in the posterior pituitary if there is a decrease in TBW
increase in ECF osmolarity so posterior pituitary will increase release of ADH
what will increase in ADH secretion do
insertion of aquaporins in apical membrane of CD cells : increase in water permeability
so therefore increase in water reabsorption, decrease in urine
what does an increase in ECF volume mean in terms of released hormone
release of ANP into the kidney
what does the release of ANP cause
increase of Na+ loss in urine
increased water loss in urine
what happens when there is decreased ECF volume (receptors in the kidneys)
baroreceptors in the kidneys will activate release of aldosterone (RAAS)
what does increased release of aldosterone to
increased sodium channels in apical membrane of DCT and CD
- so decreased Na+ in urine
- decreased water loss in urine
how does aldosterone increase sodium and water reabsorption
increase sodium channels in apical membrane of DCT or CD
what is pH of someones normal urine following an average diet
6-7.5
what are things that are found in pathological urine
- glucose
- protein
- blood
- bacteria
- white blood cells
- haemolgobin
