Nerve supply Primarily from sympathetic portion of autonomic NS Sympathetic

Nerve supply primarily from sympathetic portion of

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Nerve supply Primarily from sympathetic portion of autonomic NS Sympathetic stimulation causes vasoconstriction of renal vessels, temporarily decreasing urine formation Controls blood flow thru glomerular capillaries but is not essential for kidney to function; e.g. transplanted kidney Urine Volume Regulation Urine volume is determined by amount of water contained in tubular filtrate when it reaches the renal pelvis 2 hormones, ADH from posterior pituitary gland, and aldosterone secreted by adrenal cortex are responsible for majority of this regulation ADH most important in regulating urine volume o Acts on DCT and collecting ducts to promote water reabsorption o If absent, water will not be reabsorbed and lost in urine, resulting in increased urine volume= polyuria Aldosterone increases reabsorption of sodium into bloodstream in DCT and collecting duct o Causes osmotic imbalance that encourages water to follow Na+ out of tubular filtrate and into blood o But, water cannot move out of DCT and collecting ducts unless sufficient ADH is present Glomerular filtrate moves thru tubules and eventually into renal pelvis bc of difference in pressure that exists btwn fluid in Bowma n’s capsule and fluid in renal pelvis o Bowman’s capsule pressure is higher than almost non -existent pressure in renal pelvis o This forces fluid to move along thru the tubules of nephrons Regulation of BP Kidneys help maintain homeostasis by regulating BP When BP falls, the renin-angiotensin-aldosterone system responds to bring it back to normal Specialized juxtaglomerular cells in AGA constantly monitor BP within arterioles Densely packed cells called macula densa in ascending loop of Henle monitor NaCl conc of tubular filtrate If juxtaglomerular cells detect decrease in BP or if macula densa come in contact w less NaCl (lower amount of slower movement) juxtaglomerular cells release renin Renin: enzyme that facilitates splitting of angiotensin 1 from angiotensin, which is then converted to angiotensin 2 by ACE (angiotensin converting enzyme) Angiotensin 2 causes arteriole constriction and stimulates release of aldosterone from adrenal glands Increasing sodium and water reabsorption into bloodstream increases blood volume, which better fills vascular space and increases BP
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  • Winter '12
  • IraMandell
  • peritubular capillaries, renal pelvis, glomerular filtrate, glomerular capillaries

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