Principles of Human Physiology Chapter 19 PDF

PowerPoint® Lecture Presentation CHAPTER 19 The Urinary System: Fluid and Electrolyte Balance © 2017 Pearson Education, Inc.  19.1 The Concept of Balance To maintain homeostasis, what comes in the body must eventually be used or excreted To be in balan...

PowerPoint® Lecture Presentation CHAPTER 19 The Urinary System: Fluid and Electrolyte Balance © 2017 Pearson Education, Inc.  19.1 The Concept of Balance To maintain homeostasis, what comes in the body must eventually be used or excreted To be in balance Input + production = utilization + output © 2017 Pearson Education, Inc.  Factors Affecting the Plasma Composition Kidneys regulate solute and water content, which also determines volume Regulate acid-base balance Composition is also affected by exchange between different compartments of body Cells Connective tissue Gastrointestinal tract Sweating Respiration © 2017 Pearson Education, Inc.  Figure 19.1 Material exchanges affecting plasma content. Extracellular connective tissue Ingestion Cells (including bone) Absorption Filtration Lumen of Plasma and Lumen of digestive interstitial fluid Secretion renal tract (extracellular fluid) tubules Secretion Reabsorption Excretion (Minimal) Other losses Excretion Feces Sweating, Urine hemorrhage, respiration © 2017 Pearson Education, Inc.  Water Balance Normovolemia = normal blood volume Hypervolemia = high blood volume due to positive water balance Hypovolemia = low blood volume due to negative water balance © 2017 Pearson Education, Inc.  Figure 19.3 Factors affecting water balance. Cellular Water inputs = Ingestion metabolism 2.2 L/day 0.3 L/day 2.2 L/day + 0.3 L/day = 2.5 L/day Filtration Absorption Digestive Total body water Renal Secretion tract 42 L/day tubules Secretion Reabsorption Excretion Other losses Excretion Water outputs = 0.1 L/day 0.9 L/day 1.5 L/day 0.1 L/day + 0.9 L/day + 1.5 L/day Feces Insensible loss, sweating Urine = 2.5 L/day © 2017 Pearson Education, Inc.  Establishment of the Medullary Osmotic Gradient Role of urea in the medullary osmotic gradient Urea Generated by liver Nitrogen elimination Extremely water soluble Requires urea transporters: UTA, UTB, and UTC Transport of urea through UTA from filtrate to peritubular fluid contributes approximately 40% of the osmolarity of the gradient © 2017 Pearson Education, Inc.  Figure 19.8 Contribution of urea to the medullary osmotic gradient. Bowman's capsule UT-C Proximal tubule Glomerulus Afferent Peritubular arteriole capillaries Efferent Distal arteriole tubule Branch of renal vein Cortex Medulla Descending Collecting limb Loop of duct Henle Ascending limb Urea UT-A Vasa recta UT-B © 2017 Pearson Education, Inc.  Establishment of the Medullary Osmotic Gradient Role of the vasa recta Anatomical arrangement of vasa recta capillaries prevents the diffusion of water and solutes from dissipating the medullary osmotic gradient Descending limb of vasa recta (300 mOsm) As it descends, water leaves capillaries by osmosis and solutes enter by diffusion Ascending limb of vasa recta (325 mOsm) Water moves into plasma and solutes move into interstitial fluid Osmolarity is higher due to the lack of urea transporters © 2017 Pearson Education, Inc.  Figure 19.9 How the vasa recta prevents the dissipation of the medullary osmotic gradient. Peritubular fluid Blood Vasa recta Blood flow 300 325 flow 300 Cortex Medulla 300 300 400 425 400 375 600 600 575 625 Osmotic gradient 775 800 825 800 in vasa recta (mOsm) 975 1000 1025 1000 1175 1200 1225 1200 1375 1375 1400 Water movement Solute flow © 2017 Pearson Education, Inc.  Role of the Medullary Osmotic Gradient in Water Reabsorption in the Distal Tubule and Collecting Duct Obligatory water loss Minimum volume of water that must be excreted in the urine per day Maximum osmolarity urine = 1400 mOsm Some solute must be excreted Minimum water loss = 440 mL Necessary to eliminate nonreabsorbed solutes © 2017 Pearson Education, Inc.  Role of the Medullary Osmotic Gradient in Water Reabsorption in the Distal Tubule and Collecting Duct Effects of ADH on water reabsorption ADH regulates permeability of late distal tubules and collecting ducts Urine osmolarity range: 100–1400 mOsm Aquaporin-2 varied by ADH Antidiuretic © 2017 Pearson Education, Inc.  Figure 19.12 Pathway for extracellular fluid osmolarity and ADH secretion to interact. Slide 1 Osmolarity of extracellular fluid Hypothalamus Osmoreceptors detect and respond Activity of neurosecretory cells in hypothalamus Posterior pituitary Negative feedback ADH secretion Kidneys Water reabsorption Water excretion Conservation of body water Initial stimulus Physiological response Result © 2017 Pearson Education, Inc.  Figure 19.13 Effects of arterial and cardiac baroreceptors on ADH. Slide 1 MAP Blood volume Baroreceptors detect and respond Hypothalamus Activity of neurosecretory cells in hypothalamus Negative Posterior pituitary feedback ADH secretion Kidneys Water reabsorption Water excretion Conservation of blood volume Initial stimulus Physiological response © 2017 Pearson Education, Inc. Result  Role of the Medullary Osmotic Gradient in Water Reabsorption in the Distal Tubule and Collecting Duct Regulating water excretion by changing GFR GFR is normally autoregulated If blood pressure drops to less than 80 mm Hg Decrease in GFR Decrease in water filtered Decrease in water excretion If blood pressure increases to more than 180 mm Hg Increase in GFR Increase in water filtered Increase in water excretion Occurs only in pathological circumstances © 2017 Pearson Education, Inc.  19.3 Sodium Balance Hypernatremia: high plasma sodium Hyponatremia: low plasma sodium Sodium: primary solute in ECF Critical for normal osmotic pressure Critical to function of excitable cells © 2017 Pearson Education, Inc.  The Effects of Aldosterone Increases sodium reabsorption Steroid hormone secreted from adrenal cortex Acts on principal cells of distal tubules and collecting ducts Increases number of Na+/K+ pumps on basolateral membrane Increases number of open Na+ and K+ channels on apical membrane © 2017 Pearson Education, Inc.  Figure 19.15 Effects of aldosterone on principal cells of the distal tubules and collecting ducts. Lumen of late distal Basolateral Peritubular Peritubular tubule or collecting duct membrane fluid capillary Principal cell Apical membrane Na+ Cytosolic receptor Aldosterone K+ K+ Na+ K+ Na + Na+ Na+ K+ Na+ K + K + Na+ K+ K + Na+ Tubular fluid Plasma © 2017 Pearson Education, Inc.  The Effects of Aldosterone Renin-angiotensin-aldosterone system (RAAS) Granular cells of juxtaglomerular apparatus secrete renin Capillary walls contain angiotensin-converting enzyme (ACE), especially in lungs Liver secretes angiotensinogen Angiotensinogen is converted by renin into angiotensin I Angiotensin I is converted by ACE into angiotensin II Angiotensin II stimulates aldosterone production © 2017 Pearson Education, Inc.  The Effects of Aldosterone Stimuli for renin release Decreased pressure in afferent arteriole Renal sympathetic nerve activity Decreases in Na+ and Cl– in distal tubule filtrate © 2017 Pearson Education, Inc.  Renal Handling of Potassium Ions Glomerulus: freely filtered Proximal tubules: reabsorbed Distal tubules and collecting ducts: reabsorbed and secreted K+ secretion in distal tubules and collecting ducts is regulated Aldosterone regulates principal cells K+ in plasma directly stimulates aldosterone release As K+ increases, more aldosterone is released © 2017 Pearson Education, Inc.  19.4 Potassium Balance Hyperkalemia: high plasma potassium Hypokalemia: low plasma potassium Potassium is crucial to function of excitable cells © 2017 Pearson Education, Inc.  Renal Handling of Calcium Blood calcium Bound to carrier proteins Free in plasma Ca2+ + protein Ca-protein Free calcium: freely filtered at glomerulus © 2017 Pearson Education, Inc.  19.5 Calcium Balance Hypercalcemia: high plasma calcium Hypocalcemia: low plasma calcium Calcium balance is critical Triggers exocytosis Triggers secretion Triggers muscle contraction Increases contractility of cardiac and smooth muscle © 2017 Pearson Education, Inc.  Hormonal Control of Plasma Calcium Concentrations Calcitonin Secreted from C cells of thyroid gland Release triggered by high plasma [Ca2+] Actions at target cells Increases bone formation Decreases calcium reabsorption by kidneys © 2017 Pearson Education, Inc.