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 Tubuloglomerular Feedback Animation: Urinary System: Glomerular Filtration PLAY Afferent arteriole Macula densa Efferent arteriole Bowman’s capsule GlomerulusDistal tubule Proximal tubule Collecting duct Loop of Henle Granular cells GFR increases. Flow through tubule increases. Flow past macula densa increases. Paracrine diffuses from macula densa to afferent arteriole. Afferent arteriole constricts. Resistance in afferent arteriole increases. Hydrostatic pressure in glomerulus decreases. GFR decreases

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-10, steps 1–5 (2 of 4) Tubuloglomerular Feedback Afferent arteriole Macula densa Efferent arteriole Bowman’s capsule GlomerulusDistal tubule Proximal tubule Collecting duct Loop of Henle Granular cells GFR increases. Flow through tubule increases. Flow past macula densa increases. Paracrine diffuses from macula densa to afferent arteriole. Afferent arteriole constricts. Resistance in afferent arteriole increases

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Reabsorption  Transepithelial transport  Substances cross both apical and basolateral membrane  Paracellular pathway  Substances pass through the junction between two adjacent cells

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure Reabsorption Sodium reabsorption in the proximal tubule

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure Reabsorption Sodium-linked glucose reabsorption in the proximal tubule

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Animation: Urinary System: Early Filtrate Processing PLAY Reabsorption  Urea  Passive reabsorption  Plasma proteins  Transcytosis

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure Reabsorption Saturation of mediated transport

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-15a Reabsorption Glucose handling by the nephron

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-15b Reabsorption

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-15c Reabsorption

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings 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

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings 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

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-17a Excretion The relationship between clearance and excretion

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-17b Excretion

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-17c Excretion

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-18a Micturition The storage of urine and the micturition reflex

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-18b 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 Internal sphincter External sphincter Tonic discharge inhibited Sensory neuron Parasympathetic neuron Motor neuron – + Higher CNS input may facilitate or inhibit reflex