Angiotensin II in Peripheral Capillary Beds Causes brief powerful

Angiotensin ii in peripheral capillary beds causes

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Angiotensin II in Peripheral Capillary Beds Causes brief, powerful vasoconstriction of arterioles and precapillary sphincters Elevating arterial pressures throughout body Angiotensin II in the CNS Stimulate thirst Triggers release of antidiuretic hormone (ADH) stimulates reabsorption of water in distal portion of DCT and collecting system Increases sympathetic motor tone: mobilizing the venous reserve increasing cardiac output stimulating peripheral vasoconstriction Natriuretic Peptides Atrial natriuretic peptide (ANP) is released by atria Brain natriuretic peptide (BNP) is released by ventricles Are released by the heart: in response to stretching walls due to increased blood volume or blood pressure Trigger dilation of afferent arterioles and constriction of efferent arterioles Elevates glomerular pressures and increases GFR Decrease tubular reabsorption of sodium ions: increasing urine production
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Exam 5 decreasing blood volume and blood pressure Autonomic Regulation of GFR Mostly consists of sympathetic postganglionic fibers Sympathetic activation: constricts afferent arterioles decreases GFR slows filtrate production Changes in blood flow to kidneys due to sympathetic stimulation: may be opposed by autoregulation at local level Increased Blood Volume Automatically increases GFR: to promote fluid loss Hormonal factors further increase GFR: accelerating fluid loss Reabsorption and Secretion Reabsorption : recovers useful materials from filtrate Secretion : ejects waste products, toxins, and other undesirable solutes Occur in every segment of nephron: except renal corpuscle 1% of daily filtrate is excreted as urine 400 ml minimum – obligatory water loss Water moves by osmosis – must have concentration gradient 5 Functions of the PCT 1. Reabsorption of organic nutrients 2. Active reabsorption of ions 3. Reabsorption of water 4. Passive reabsorption of ions 5. Secretion
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Exam 5 PCT PCT cells normally reabsorb 60–70% of filtrate produced in renal corpuscle Reabsorbed materials enter peritubular fluid: and diffuse into peritubular capillaries Sodium Ion Reabsorption Is important in every PCT process Ions enter tubular cells by: diffusion through leak channels sodium-linked cotransport of glucose counter-transport for hydrogen ions Na + / K + pump The Loop of Henle Reabsorbs about 1/2 of water, and 2/3 of sodium and chloride ions remaining in tubular fluid by the process of countercurrent multiplication Is exchange that occurs between 2 parallel segments of loop of Henle: the thin, descending limb the thick, ascending limb Are very close together, separated only by peritubular fluid Have very different permeability characteristics The Thin Descending Limb Is permeable to water Osmosis to vasa recta – not in tissue Is relatively impermeable to solutes Thus tubular fluid reaches high osmolality The Thick Ascending Limb
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