Filtration
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Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-8b Filtration
description
Filtration. Figure 19-8b. Filtration. Figure 19-8c. GFR Regulation. Myogenic response Similar to autoregulation in other systemic arterioles - PowerPoint PPT Presentation
Transcript of Filtration
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-8b
Filtration
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-8c
Filtration
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
GFR Regulation
Myogenic response Similar to autoregulation in other systemic arterioles
When smooth muscle in wall of arteriole stretches, stretch-sensitive ion channels open, and the muscle cells contract. Vasoconstiction increases resistance and slows flow. This keeps GFR constant.
Tubuloglomerular feedback
Hormones and autonomic neurons By changing resistance in arterioles (sympathetic
stimulation causes vasoconstriction)
By altering the filtration coefficient
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-9
Juxtaglomerular Apparatus
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-10
Tubuloglomerular Feedback
Animation: Urinary System: Glomerular FiltrationPLAY
Afferentarteriole
Maculadensa
Efferent arteriole Bowman’s capsule GlomerulusDistal tubuleProximal
tubule
Collectingduct
Loopof
Henle
Granularcells
GFR increases.
Flow through tubule increases.
Flow past macula densaincreases.
Paracrine diffuses from macula densa to afferent arteriole.
Afferent arteriole constricts.
Resistance in afferent arteriole increases.
Hydrostatic pressurein glomerulus decreases.
GFR decreases.
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Tubuloglomerular Feedback
Afferentarteriole
Maculadensa
Efferent arteriole Bowman’s capsule GlomerulusDistal tubuleProximal
tubule
Collectingduct
Loopof
Henle
Granularcells
GFR increases.
Flow through tubule increases.
Flow past macula densaincreases.
Paracrine diffuses from macula densa to afferent arteriole.
Afferent arteriole constricts.
Resistance in afferent arteriole increases.
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Reabsorption
Transepithelial transport Substances cross both apical and basolateral
membrane
Paracellular pathway Substances pass through the junction between two
adjacent cells
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Reabsorption
Sodium reabsorption in the proximal tubule
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Reabsorption
Sodium-linked glucose reabsorption in the proximal tubule
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Animation: Urinary System: Early Filtrate ProcessingPLAY
Reabsorption
Urea Passive reabsorption
Plasma proteins Transcytosis
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Reabsorption
Saturation of mediated transport
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Reabsorption
Glucose handling by the nephron
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Reabsorption
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Reabsorption
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Secretion
Transfer of molecules from extracellular fluid into lumen of the nephron Active process
Secretion of K+ and H+ is important in homeostatic regulation
Enables the nephron to enhance excretion of a substance
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Excretion
Excretion = filtration – reabsorption + secretion
Clearance Rate at which a solute disappears from the body by
excretion or by metabolism
Non-invasive way to measure GFR
Inulin and creatinine used to measure GFR
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Excretion
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Excretion
The relationship between clearance and excretion
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Excretion
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Excretion
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Micturition
The storage of urine and the micturition reflex
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Micturition
Stretch receptors fire.
Stretch receptors
Parasympathetic neurons fire.Motor neurons stop firing.
Smooth muscle contracts.Internal sphincter passively pulled open. External sphincter relaxes.
(b) Micturition
Internalsphincter
Externalsphincter
Tonicdischargeinhibited
Sensory neuron
Parasympatheticneuron
Motor neuron
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+
Higher CNSinput may
facilitate orinhibit reflex.
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