(2) K\' secretion-not reabsorption -90% of total reabsorption in PCT-unregulated
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(2) K' secretion-not reabsorption -90% of total reabsorption in PCT-unregulated Fig 17.28 _ remaining 10% reabsorbed in DCT if no aldosterone Increased K secretion due to aldosterone ( "undoes" -0.10% reabsoption "undone" depending upon con the 10% normal reabsorption in c. of K' in body fluids DCT) -increased secretion of K /H coupled to increased reabsorption of (3) Water -Unregulated reabsorption in PCT, DLOH CD main site of regulated reabsorption Causes insertion of aquaporins (water channels); increases rate of osmosis --caused by malfunctioning ; reduced reabsorption of water; up to 5-10 L large urine volume plus increased thirst mimics symptoms of diabetes mellitus (but no elevated glucose conc. in urine) (4) Blood flow to of afferent arteriole --regulates amt. of blood entering glomerulus -sympathetic NS (fight or flight syndrome) -constriction of blood flow (1) diversion of blood to muscles and heart (2) also conserves blood volume to important organs (e.g. during cardiovascular shock) Integration of nervous, renal and cardiovascular systemsExplanation / Answer
2. Increased K+ secretion due to Aldostreone.
(Along the distal tubule and collecting ducts, there is net secretion of K which is stimulated by aldosterone and when there is dietary K excess. : Assuming the Fig. 17.28 site this )
3. Cortex : Site were unregulated water reabsorption happens. Water is reabsorbed with solutes.
Medulla : The osmotic gradient allows the kidneys to produce urine that can be roughly 5 times as concentrated as the ECF. Urine concentration can be varied through the regulation of water permeability in the collecting duct.
The permeability of cell membranes to water depends upon the presence of water channels known as aquaporins (AQP3 & AQP2)
AQP3 : is constitutively expressed on the basolateral surface of cells in the collecting duct.
AQP2 : is found on the apical surface of these cells, but the number of AQP2 channels on the membrane is regulated by the hormone vasopressin, also known as antidiuretic hormone.
Which in case of DM gets impaired causing increased urine secretion.
4. Sympathetic stimulation regulates the amount of blood flowing to the afferent arterioles. When stimulation is controlled/reduced vasodilation occurs causing increased blood flow through the kidneys (usually during resting conditions).
When the frequency of action potentials increases, the arteriolar smooth muscle constricts causing vasoconstriction , resulting in diminished glomerular flow, so less filtration occurs.
This process regulates the blood volume to vital organ during emergency.
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