Chapter PowerLecture: 42 The Internal Environment Section 42.0: Weblinks and InfoTrac See the latest Weblinks and InfoTrac articles for this chapter online Impacts, Issues: Truth in a Test Tube Physicians routinely test: sugar level, pH, protein content Urine tests give information about: kidneys hydration pregnancy certain cancers Impacts, Issues: Truth in a Test Tube Athletes take urine tests to screen for prohibited drugs Urine tells potential employers if youve been taking street drugs such as marijuana, cocaine, and Ecstasy Impacts, Issues: Truth in a Test Tube 2 fist-sized kidneys filter all blood in your body more than 30 times each day Filtration allows body to dispose of excess water, wastes and harmful solutes
Impacts, Issues Video Section 42.1: Weblinks and InfoTrac See the latest Weblinks and InfoTrac articles for this chapter online Animal Fluids Interstitial fluid lies between cells and other tissue components Blood transports substances by way of the circulatory system Interstitial fluid and blood make up the extracellular fluid Urinary System Interactions Maintaining Extracellular Fluid Urinary system keeps volume and composition of extracellular fluid within tolerable ranges It interacts with the digestive, respiratory, and circulatory systems to fulfill this task Water Gains and Losses Water Gains Absorption from gut
Metabolism Solute Gains and Losses Solute Gains Absorption from gut Cell secretions Respiration Metabolism Controlling Water Gain & Loss Urinary excretion provides the most control over water loss Concentration of urine can be varied Controlling Water Gain & Loss Water and solute balance Section 42.2: Weblinks and InfoTrac See the latest Weblinks and InfoTrac articles for this chapter online Components of Urinary System Pair of kidneys Pair of ureters Urinary bladder Urethra Components of Urinary System Human urinary system Function of Kidneys Filter water, mineral ions, wastes from the blood Adjust filtrate concentration and return most to blood Remaining water and solutes in filtrate constitute urine Structure of Kidney Renal capsule surrounds kidney Two regions Outer renal cortex Inner renal medulla Renal pelvis collects urine and funnels it to ureter Structure of Kidney Human kidney Urinary Excretion Urine flows from each kidney to a ureter Ureters deliver urine to bladder Contraction of the smooth muscle of the bladder forces urine out of the body into the urethra Skeletal muscle surrounds urethra; allows voluntary control of urination Nephron Functional unit of the kidney Each consists of a renal tubule and associated capillaries Nephron
Urine formation Section 42.3: Weblinks and InfoTrac See the latest Weblinks and InfoTrac articles for this chapter online Urine Formation Urine Formation Structure of the glomerulus Leaky Glomerular Capillaries Glomerular capillaries have large pores Fluid leaks from glomerular capillaries into kidney tubules Filtration Rate Varies Increased blood pressure increases glomerular filtration Flow volume to kidneys changes in response to neural, endocrine, and local changes Most Filtrate Is Reabsorbed Each day, about 180 liters of filtrate flows out of glomerulus into tubules 1 to 2 liters excreted Most filtrate is reabsorbed into blood Tubular Reabsorption Ions move from the filtrate in tubule lumen into the interstitial fluid Sodium ions are actively pumped out of the proximal tubule into the interstitial fluid Chloride ions follow; they are passively transported Tubular Reabsorption Ion flow creates an osmotic gradient; it is saltier outside the tubule than inside Water flows down the osmotic gradient, from the tubule lumen into the interstitial fluid Peritubular capillaries pick up the water and ions from the interstitial fluid Tubular Reabsorption Tubular Reabsorption Tubular reabsorption Reabsorption Reabsorption and secretion Tubular Secretion The opposite of reabsorption Molecules are transported out of the peritubular capillaries, through tubule cells, and into the filtrate Eliminates H+ ions, metabolites, and toxins Section 42.4: Weblinks and InfoTrac See the latest Weblinks and InfoTrac articles for this chapter online Hormone Effects ADH Acts on collecting ducts; makes walls more permeable to water Urine more concentrated Aldosterone Stimulates reabsorption of sodium
Thirst Osmoreceptors detect changes Activate thirst center in hypothalamus and ADH-secreting cells Angiotensin II acts on brain to promote thirst and ADH secretion
Hormone Effects Hormone-induced adjustments Section 42.5: Weblinks and InfoTrac See the latest Weblinks and InfoTrac articles for this chapter online Acid-Base Balance Kidneys work in concert with buffering systems to keep pH in normal range Normal range is 7.37 to 7.43 Normal metabolism produces an excess of H+ Buffer Systems Weak acid and weak base that can reversibly bind and release ions Bicarbonate-carbon dioxide buffer system can neutralize excess H+ Regulating Blood pH (1) Involves secretion of H+ and reabsorption of HCO3- (bicarbonate) HCO3- in filtrate combines with H+ to form carbonic acid (H2CO3) H2CO3 becomes CO2 and H2O, which are reabsorbed into blood from filtrate Regulating Blood pH (2) In blood, HCO3 dissociates to form HCO3- and H+ The H+ can be secreted into proximal tubule, while the HCO3- remains in blood, thus increasing blood pH H+ can also combine with K+ or ammonia and leave body in urine Variation in Urinary Systems Structure of vertebrate urinary systems varies in details Adapted to particular habitats Freshwater sh must deal with continuous inux of water by osmosis Marine sh must deal with continuous loss of water Length of Loop of Henle Longer loop of Henle allows an organism to produce a very steep osmotic gradient Allows reabsorption of more water than a shorter loop Section 42.6: Weblinks and InfoTrac See the latest Weblinks and InfoTrac articles for this chapter online Renal Failure Both kidneys are damaged to the point where they are nonfunctional Fatal if not treated Dialysis is used to restore normal solute balances temporarily Transplant is only way to fully restore function Renal Failure Kidney dialysis
Kidney Disorders Glomerulonephritis Infection of glomeruli leads to chronic inflammation that damages kidney Kidney stones Uric acid and calcium salts settle out of urine, form hard deposits that can lodge in ureter or urethra Section 42.7: Weblinks and InfoTrac See the latest Weblinks and InfoTrac articles for this chapter online Core Temperature Internal temperature of an animals body Must be maintained within a narrow range for normal enzyme function Heat gains and losses must be kept in balance Heat Gains and Losses Metabolic reactions generate heat Radiation, conduction, and convection can move heat to or from body to surroundings Evaporation causes cooling Thermal Strategies Ectotherms Endotherms Heterotherms Thermal Strategies Endotherms and ectotherms Section 42.8: Weblinks and InfoTrac Maintaining Temperature Peripheral thermoreceptors in skin Thermoreceptors deeper in body Feed input to hypothalamus Hypothalamus sends messages to effectors by way of nervous system Response to Heat Stress Peripheral vasodilation Sweating Panting Mammalian Responses to Core Temperature Shifts Mammalian Responses to Core Temperature Shifts Human thermoregulation Fever Part of response to tissue damage Hypothalamus resets body thermostat at higher temperature Moderate fever can promote healing and need not be suppressed Response to Cold Peripheral vasoconstriction Pilomotor response
Shivering response Nonshivering heat response Mammalian Physiological Responses to Cold Stress