Roles of the kidney Flashcards
what happens if vasoconstriction or vasodilation occurs in the afferent arteriole?
vasoconstriction- decreases net filtration pressure and GFR
vasodilation - increases net filtration pressure and gfr
what happens if there is vasoconstriction of the efferent arteriole
increases net filtration pressure and gfr
what is the myogenic response to control GFR
- smooth muscle cells act as stretch receptors
- increased bp causes stretch and smooth muscle cells to contract using vasoconstriction of afferent arterioles
- when bp decreases smooth muscle cells relax and cause vasodilation of afferent arterioles
what is tubuloglomerular feedback?
when cells of macular densa detect an increase in flow rate, signal to juxtaglomerular cells to contract and this causes vasoconstriction of afferent arterioles
what is the extrinsic mechanism of the sympathetic ns controlling gfr?
-increase activation of the sympathetic ns
-NA causes constriction of small arteries and afferent arterioles
- can lower renal blood flow to the extent that is inadequate for normal kidney metabolism
what is the extrinsic mechanism of hormone control of GFR
when bp is low, juxtaglomerular cells will release renin, which is required for the production of the vasoconstriction angiotensin II
where does move tubular reabsorption occur?
~70% in the proximal conflated tubule
what is paracellular pathway?
diffusion occurs between adjacent cells of epithelium (substances move through the tight junctions - small lipophillic)
what is the trans cellular pathway?
a substance moved into an epithelial cell (either the apical or basolateral membrane), diffuses through the cytosol, and exits across the opposite membrane (eg, charged molecules)
where is the concentration of sodium higher and where does it move?
in the tubular lumen the sodium concentration is higher so it moves out into the peritubular capillaries
where does the filtrate enter after the bowman’s capsule?
the proximal convoluted tubule
where do larger proteins remain?
in the glomerulus and are not filtered out
how does glucose absorption in the PCT occur?
- inside the epithelial cells the glucose concentration is a lot higher than the tubular fluid
-uses a glucose sodium co-transporter - brings glucose up its concentration gradient (secondary active transport)
- as glucose increases in the epithelial cells it moves out into the interstitial fluid and into the peritubular capillaries
- if glucose is too high it can’t be reabsorbed so this why it may be present in the urine
how does AA reabsorption in pct occur?
using a sodium/amino acid cot-transporter
how does para cellular reabsorption in PCT occur?
- as other solutes are reabsorbed, through the proximal convoluted tubules into the interstitial fluid, water follows by osmosis
- causes conc of solutes that remain in the tubular lumen to increase
- those solutes diffuse when the concentration in the lumen is higher than in the interstitial fluid
how does bicarbonate reabsorption and hydrogen secretion occur?
- sodium hydrogen exchanger causes the hydrogen to move from the epithelial cell into the tubular fluid
- bicarbonate ions in the tubular fluid bind with the hydrogen to form carbonic anhydrase
- then separated into carbon dioxide and water which moves back into the epithelial cells
what nephrons dip down into the medulla?
juxtaglomerular
where does filtrate go as it leaves the proximal convoluted tubules?
loop of henle
what is the descending limb permeable to?
water
- so water moves by osmosis into interstitial fluid and can be reabsorbed by the peritubular capillaries
what occurs in the ascending limb?
active transport of NaCl in the thick section of the ascending limb
- the thick section is impermeable to water
- this increase NaCl concentration in interstitial fluid
how does the sodium potassium-chloride co-transporter work in the loop of henle?
brings 2 chloride ions, one sodium and one potassium into the epithelial
what is countercurrent multiplication?
concentration is graded moving down the medulla (increases)
what is the distal convoluted tubules?
- regulation of the excretion of solutes and waste
- reabsorption is controlled by hormones
- higher the aldosterone, the more Na reabsorbed and the more K secreted
- Ca reabsorption is stimulated by parathyroid hormone
what substances move by tubular secretion?
eg. K+, H+, organic anions move from peritubular capillaries into tubular lumen
