1 glomerulus receives feedback on status of its own downstream tubular fluid

1 glomerulus receives feedback on status of its own

This preview shows page 32 - 39 out of 68 pages.

1 glomerulus receives feedback on status of its own downstream tubular fluid and adjusts filtration rate accordingly - This regulates filtrate composition, stabilizes renal function, compensates for fluctuations in blood pressure Macula densa: sense Na, K, Cl secrete ATP Mesangial cells: ATP Adenosine Granular cells : Adenosine contraction of G. cells constricts afferent arteriole * mesangial cells also contract further constricting afferent arteriole Juxtaglomerular Apparatus @ end of nephron loop/start of DCT where folds back into/meshes w/ afferent & efferent arterioles of same nephron
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23-33 Renal Autoregulation - Tubuloglomerular Feedback, continued Juxtaglomerular Apparatus ( JGA ) - components Macula densa, patch of sensory cells in nephron loop If GFR is high filtrate contains more NaCl macula densa absorbs more NaCl secretes ATP nearby mesangial cells convert ATP to Adenosine Adenosine stimulates granular cells to contract Granular (juxtaglomerular) cells: modified smooth muscle cells; wrapped @ arterioles (close to macula densa) Adenosine sm. muscle contracts afferent arteriole constricts  blood flow adjusts GFR Remains relatively constant Mesangial cells also contract, constricting capillaries further limit GFR ALSO When BP , Granular cells secrete Renin JGA is component of Renin-Angiotensin-Aldosterone system’ This system controls blood volume and pressure
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23-35 Tubuloglomerular Feedback = Negative Feedback Control of GFR DCT can absorb Na & Cl, Tubuloglomerular feedback prevents system overwhelming capacity of DCT to absorb Na & Cl and prevent excess loss of Na, Cl and H 2 O in urine
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23-36 How is glomerular filtration rate regulated? Renal Autoregulation Sympathetic Control Hormonal Control Sympathetic nerve fibers richly innervate renal blood vessels Sympathetic input plus adrenal epinephrine constrict afferent arterioles during strenuous exercise OR acute conditions, e.g., circulatory shock Reduces GFR urine output maintains plasma volume Redirects blood from kidneys to heart, brain, & skeletal muscles GFR may be as low as a few milliliters per minute
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23-37 When BP detected by carotid and aorta baroreceptors sympathetic nervous system granular cells release Renin Renin-Angiotensin-Aldosterone System system of hormones that helps regulate blood pressure and GFR Renin converts angiotensinogen angiotensin I
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Renin-Angiotensin-Aldosterone System In lungs and kidneys, angiotensin-converting enzyme (ACE) converts angiotensin I to angiotensin II Angiotensin II (ANG II), hormone that increases BP
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