1. 30-1 CHAPTER 30 HomeostasisHomeostasis

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4. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-4 Water and Osmotic Regulation How Marine Invertebrates Meet Problems of Salt and Water Balance How Marine Invertebrates Meet Problems of Salt and Water Balance Most marine invertebrates are in osmotic equilibrium with their seawater environment Most marine invertebrates are in osmotic equilibrium with their seawater environment With body surfaces permeable to water and salts, the internal and external concentrations are equal With body surfaces permeable to water and salts, the internal and external concentrations are equal Such animals cannot regulate osmotic pressure of their body fluids Such animals cannot regulate osmotic pressure of their body fluids Osmotic conformers Osmotic conformers Functions well for open ocean organisms because the open ocean is highly stable environment Functions well for open ocean organisms because the open ocean is highly stable environment

5. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-5 Animals that must live within a narrow salinity range are stenohaline Animals that must live within a narrow salinity range are stenohaline Organisms that tolerate wide variations found in estuaries are euryhaline Organisms that tolerate wide variations found in estuaries are euryhaline A hyperosmotic regulator maintains body fluids in higher concentration than surrounding water A hyperosmotic regulator maintains body fluids in higher concentration than surrounding water Kidneys, or antennal glands in a crab Kidneys, or antennal glands in a crab Maintain a higher concentration by excreting excess water Maintain a higher concentration by excreting excess water Salt-secreting cells in the gills Salt-secreting cells in the gills Remove ions from seawater to counter loss of salt ions Remove ions from seawater to counter loss of salt ions Water and Osmotic Regulation

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7. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-7 Any process that requires an expenditure of energy is an active transport process Any process that requires an expenditure of energy is an active transport process Any process that works against the diffusion gradient will require active transport Any process that works against the diffusion gradient will require active transport Systems within an organism function in an integrated way to maintain a constant internal environment around a setpoint Systems within an organism function in an integrated way to maintain a constant internal environment around a setpoint Water and Osmotic Regulation

8. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-8 Invasion of Fresh Water Invasion of Fresh Water During Silurian and Devonian periods During Silurian and Devonian periods Jawed fishes began to penetrate brackish and freshwater rivers Jawed fishes began to penetrate brackish and freshwater rivers unexploited habitat with abundant food presented a physiological evolutionary challenge unexploited habitat with abundant food presented a physiological evolutionary challenge Freshwater fishes must prevent salt loss and unload excess water Freshwater fishes must prevent salt loss and unload excess water The scaled and mucus-covered surface of a fish is nearly waterproof The scaled and mucus-covered surface of a fish is nearly waterproof Water that enters by osmosis across the gills is pumped out by the kidney as very dilute urine Water that enters by osmosis across the gills is pumped out by the kidney as very dilute urine Water and Osmotic Regulation

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10. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-10 Salt-absorbing cells in the gills move sodium and chloride ions from water to blood Salt-absorbing cells in the gills move sodium and chloride ions from water to blood Salt present in the fish’s food also replaces any salt that is lost by diffusion Salt present in the fish’s food also replaces any salt that is lost by diffusion Clams, crayfishes and aquatic insect larvae are also hyperosmotic regulators with similar mechanisms Clams, crayfishes and aquatic insect larvae are also hyperosmotic regulators with similar mechanisms Amphibians that live in water use their skin to transport sodium and chloride Amphibians that live in water use their skin to transport sodium and chloride Water and Osmotic Regulation

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12. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-12 Return of Fishes to the Sea Return of Fishes to the Sea Modern oceanic bony fishes are descendants of freshwater fishes, returning during the Triassic period Modern oceanic bony fishes are descendants of freshwater fishes, returning during the Triassic period Their ionic body concentration of about one-third that of seawater is related to their marine heritage Their ionic body concentration of about one-third that of seawater is related to their marine heritage Freshwater fish returning to the sea in the Triassic period lost water and gained salt Freshwater fish returning to the sea in the Triassic period lost water and gained salt Marine fish drink seawater Marine fish drink seawater Salt is absorbed in the intestine Salt is absorbed in the intestine It is carried by blood to gills It is carried by blood to gills Special salt-secreting cells in the gills transport the salt back to the sea Special salt-secreting cells in the gills transport the salt back to the sea Water and Osmotic Regulation

13. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-13 Ions that remain in the intestine as residue (e.g. magnesium, sulfate, calcium) are voided with feces Ions that remain in the intestine as residue (e.g. magnesium, sulfate, calcium) are voided with feces Marine bony fishes maintain salt concentration of body fluids at about one-third that of seawater Marine bony fishes maintain salt concentration of body fluids at about one-third that of seawater They are therefore hypoosmotic regulators They are therefore hypoosmotic regulators Marine fish consume only enough water to replace water loss Marine fish consume only enough water to replace water loss Elasmobranchs achieve the same osmotic balance by a different mechanism Elasmobranchs achieve the same osmotic balance by a different mechanism Urea compounds accumulate in the blood until there is no osmotic difference with seawater Urea compounds accumulate in the blood until there is no osmotic difference with seawater Water and Osmotic Regulation

14. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-14 How Terrestrial Animals Maintain Salt and Water Balance How Terrestrial Animals Maintain Salt and Water Balance Animals carried their watery composition with them as they invaded land Animals carried their watery composition with them as they invaded land They continued to adapt to the threats of desiccation and became abundant in arid areas They continued to adapt to the threats of desiccation and became abundant in arid areas Animals lose water across respiratory and body surfaces, excretion of urine and elimination of feces Animals lose water across respiratory and body surfaces, excretion of urine and elimination of feces Water is gained from water in food, drinking water, and metabolic water Water is gained from water in food, drinking water, and metabolic water Some desert arthropods can absorb water vapor from the air Some desert arthropods can absorb water vapor from the air Water and Osmotic Regulation

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16. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-16 In desert rodents, metabolic water constitutes most of the animal’s water uptake In desert rodents, metabolic water constitutes most of the animal’s water uptake Dilution of Wastes Dilution of Wastes Primary end product of protein breakdown is highly toxic urea Primary end product of protein breakdown is highly toxic urea Fishes excrete urea across the gills and the abundance of water keeps it dilute Fishes excrete urea across the gills and the abundance of water keeps it dilute Terrestrial insects, nonavian reptiles and birds convert urea to nontoxic uric acid Terrestrial insects, nonavian reptiles and birds convert urea to nontoxic uric acid Uric acid is insoluble and is excreted with little water loss Uric acid is insoluble and is excreted with little water loss Uric acid can be stored in harmless crystalline form within an egg until hatching Uric acid can be stored in harmless crystalline form within an egg until hatching Marine birds and turtles have a salt gland Marine birds and turtles have a salt gland Secretes concentrated sodium chloride Secretes concentrated sodium chloride Important accessory glands to kidneys that only produce very dilute urine Important accessory glands to kidneys that only produce very dilute urine Water and Osmotic Regulation

17. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-17 Invertebrate Excretory Structures Contractile Vacuole Contractile Vacuole Small, spherical, intracellular vacuoles of freshwater sponges, and radiate animals Small, spherical, intracellular vacuoles of freshwater sponges, and radiate animals Not truly excretory Not truly excretory Ammonia and other nitrogenous wastes diffuse across the cell membrane Ammonia and other nitrogenous wastes diffuse across the cell membrane Contractile vacuole is an organ of water balance Contractile vacuole is an organ of water balance Expels excess water that enters by osmosis Expels excess water that enters by osmosis Contractile vacuoles are absent in marine forms that are isosmotic with seawater Contractile vacuoles are absent in marine forms that are isosmotic with seawater

18. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-18 Nephridium Nephridium Most common design to maintain osmotic balance Most common design to maintain osmotic balance Flame cells system or protonephridium is the simplest arrangement Flame cells system or protonephridium is the simplest arrangement Planaria and other flatworms Planaria and other flatworms Highly branched duct system to all parts of the body Highly branched duct system to all parts of the body Fluid enters the system through specialized “flame cells” and passes through tubules to exit the body Fluid enters the system through specialized “flame cells” and passes through tubules to exit the body Rhythmical beating of a flagellar tuft creates a negative pressure that draws fluid into the tubes Rhythmical beating of a flagellar tuft creates a negative pressure that draws fluid into the tubes Invertebrate Excretory Structures

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20. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-20 Water and metabolites are recovered by reabsorption Water and metabolites are recovered by reabsorption Wastes are left to be expelled Wastes are left to be expelled Nitrogenous wastes, mainly ammonia, diffuse across the surface of the body Nitrogenous wastes, mainly ammonia, diffuse across the surface of the body Flatworms have no circulatory system so the flame cell system must branch throughout the animal Flatworms have no circulatory system so the flame cell system must branch throughout the animal Closed system since fluid must pass across flame cells Closed system since fluid must pass across flame cells Invertebrate Excretory Structures

21. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-21 Metanephridium Metanephridium Open system found in molluscs and annelids Open system found in molluscs and annelids Tubule is open at both ends Tubule is open at both ends Fluid is swept into the tubule through a ciliated funnel-like opening Fluid is swept into the tubule through a ciliated funnel-like opening Network of blood vessels to reclaim water and valuable solutes surrounds a metanephridium Network of blood vessels to reclaim water and valuable solutes surrounds a metanephridium The basic process of urine formation in the tubule remains the same The basic process of urine formation in the tubule remains the same Withdraw useful solutes and add waste solutes Withdraw useful solutes and add waste solutes Invertebrate Excretory Structures

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23. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-23 Arthropod Kidneys Arthropod Kidneys Paired Antennal Glands of Crustaceans Paired Antennal Glands of Crustaceans Located in the ventral part of the head Located in the ventral part of the head Advanced design of nephridia Advanced design of nephridia Lack open nephrostomes Lack open nephrostomes Hydrostatic pressure of the blood forms a protein-free filtrate in the end sac Hydrostatic pressure of the blood forms a protein-free filtrate in the end sac In tubular portion, certain salts are selectively reabsorbed or actively secreted In tubular portion, certain salts are selectively reabsorbed or actively secreted This system is similar to the vertebrate system in sequence of urine formation This system is similar to the vertebrate system in sequence of urine formation Invertebrate Excretory Structures

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25. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-25 Malpighian Tubules Malpighian Tubules Insects and spiders use this system in conjunction with rectal glands Insects and spiders use this system in conjunction with rectal glands Thin, elastic, blind Malpighian tubules are closed and lack arterial supply Thin, elastic, blind Malpighian tubules are closed and lack arterial supply Urine is produced by tubular secretion mechanisms by the cells lining the tubular lumen Urine is produced by tubular secretion mechanisms by the cells lining the tubular lumen Process is initiated by active transport of hydrogen ions into the tubule lumen Process is initiated by active transport of hydrogen ions into the tubule lumen Ions are then transported via protein carriers back into cells and exchanged for sodium or potassium ions Ions are then transported via protein carriers back into cells and exchanged for sodium or potassium ions Invertebrate Excretory Structures

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27. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-27 Chloride ions follow passively Chloride ions follow passively Secretion of ions creates osmotic pressure that draws out water, solutes, and nitrogenous wastes (uric acid) into the tubule Secretion of ions creates osmotic pressure that draws out water, solutes, and nitrogenous wastes (uric acid) into the tubule Once the urine drains into the rectum, water and salts may be reabsorbed by specialized rectal glands Once the urine drains into the rectum, water and salts may be reabsorbed by specialized rectal glands Leaves behind uric acid, excess water, salts, and other wastes Leaves behind uric acid, excess water, salts, and other wastes Especially efficient system for dry environments Especially efficient system for dry environments Invertebrate Excretory Structures

28. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-28 Vertebrate Kidney Function Ancestry and Embryology Ancestry and Embryology Earliest vertebrate kidney had segmentally arranged tubules similar to an invertebrate nephridium Earliest vertebrate kidney had segmentally arranged tubules similar to an invertebrate nephridium Each tubule opened into the coelom at a nephrostome Each tubule opened into the coelom at a nephrostome Other end led into a common archinephric duct Other end led into a common archinephric duct This ancient kidney is called an archinephros This ancient kidney is called an archinephros Similar segmented kidney is found in embryos of hagfishes Similar segmented kidney is found in embryos of hagfishes From the earliest time, the reproductive system utilized the nephric ducts From the earliest time, the reproductive system utilized the nephric ducts

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30. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-30 3 developmental stages occur in the embryonic development of vertebrate kidneys 3 developmental stages occur in the embryonic development of vertebrate kidneys Pronephros Pronephros Observed in vertebrate embryos Observed in vertebrate embryos Usually degenerates except in hagfish and a few bony fish species Usually degenerates except in hagfish and a few bony fish species Mesonephros and Metanephros Mesonephros and Metanephros Together called the opisthonephros Together called the opisthonephros Replace the pronephros and forms the adult kidney of most fishes and amphibians Replace the pronephros and forms the adult kidney of most fishes and amphibians Vertebrate Kidney Function

31. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-31 Metanephros Metanephros Found in adult amniotes Found in adult amniotes More caudally located More caudally located Much larger and compact Much larger and compact Contains a large number of nephric tubules Contains a large number of nephric tubules Ureter Ureter Duct that drains the system Duct that drains the system Archinephric duct has shifted to sperm transport Archinephric duct has shifted to sperm transport The three stages succeed each other embryologically and phylogenetically in amniotes The three stages succeed each other embryologically and phylogenetically in amniotes Vertebrate Kidney Function

32. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-32 Vertebrate Kidney Function Vertebrate Kidney Function Vertebrate kidney Vertebrate kidney Principal organ that regulates volume and composition of internal fluids Principal organ that regulates volume and composition of internal fluids The removal of metabolic wastes is incidental to its regulatory function The removal of metabolic wastes is incidental to its regulatory function Urine is formed in the nephron by filtration, reabsorption and secretion Urine is formed in the nephron by filtration, reabsorption and secretion Vertebrate Kidney Function

33. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-33 Structure of Human Kidney Structure of Human Kidney Kidneys comprise less than one percent of body weight but receive 20–25% of cardiac output Kidneys comprise less than one percent of body weight but receive 20–25% of cardiac output Blood flows through nearly a million nephrons in each kidney Blood flows through nearly a million nephrons in each kidney The nephron begins with a tuft of capillaries called the glomerulus The nephron begins with a tuft of capillaries called the glomerulus Blood pressure in glomerular capillaries forces protein-free filtrate into Bowman’s capsule Blood pressure in glomerular capillaries forces protein-free filtrate into Bowman’s capsule Filtrate passes into a proximal convoluted tubule, the loop of Henle and the distal convoluted tubule Filtrate passes into a proximal convoluted tubule, the loop of Henle and the distal convoluted tubule Collecting ducts join to form the renal pelvis and carry urine through a ureter to the urinary bladder Collecting ducts join to form the renal pelvis and carry urine through a ureter to the urinary bladder Vertebrate Kidney Function

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35. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-35 Throughout the passage, some solutes are reabsorbed and some are concentrated Throughout the passage, some solutes are reabsorbed and some are concentrated The blood from the aorta enters each kidney through a renal artery The blood from the aorta enters each kidney through a renal artery Renal artery branches Renal artery branches Afferent arteriole supplies blood to the glomerulus Afferent arteriole supplies blood to the glomerulus Efferent arterioles conduct blood away Efferent arterioles conduct blood away Efferent arterioles travel through extensive capillary networks around the proximal and distal convoluted tubules and the loop of Henle Efferent arterioles travel through extensive capillary networks around the proximal and distal convoluted tubules and the loop of Henle The capillary network collects to form the renal vein that returns blood to the vena cava The capillary network collects to form the renal vein that returns blood to the vena cava Vertebrate Kidney Function

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37. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-37 Glomerular Filtration Glomerular Filtration The glomerulus is a specialized mechanical filter The glomerulus is a specialized mechanical filter Blood pressure drives a protein-free filtrate (glomerular filtrate) across capillary walls into Bowman's capsule Blood pressure drives a protein-free filtrate (glomerular filtrate) across capillary walls into Bowman's capsule Red blood cells and plasma proteins are too large to through pores Red blood cells and plasma proteins are too large to through pores Filtrate will undergo extensive modification before becoming urine Filtrate will undergo extensive modification before becoming urine About 180 liters (50 gallons) of filtrate form each day About 180 liters (50 gallons) of filtrate form each day Most is reabsorbed and 1.2 liters of urine are voided Most is reabsorbed and 1.2 liters of urine are voided Vertebrate Kidney Function

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39. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-39 Tubular Reabsorption Tubular Reabsorption About 60% of filtrate volume and nearly all glucose, amino acids, and vitamins are reabsorbed in the proximal convoluted tubule About 60% of filtrate volume and nearly all glucose, amino acids, and vitamins are reabsorbed in the proximal convoluted tubule Most reabsorption is by active transport Most reabsorption is by active transport Unique ion pumps retrieve sodium, calcium, potassium, etc. Unique ion pumps retrieve sodium, calcium, potassium, etc. Water passively follows the osmotic gradient with active reabsorption of solutes Water passively follows the osmotic gradient with active reabsorption of solutes For most substances, there is an upper limit to reabsorption (transport maximum or renal threshold) For most substances, there is an upper limit to reabsorption (transport maximum or renal threshold) Normally no glucose is present in urine because the transport maximum is well above the glucose level Normally no glucose is present in urine because the transport maximum is well above the glucose level Vertebrate Kidney Function

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41. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-41 A kidney filters 600 grams of sodium a day and retrieves 596 grams, excreting 4 grams A kidney filters 600 grams of sodium a day and retrieves 596 grams, excreting 4 grams If human intake of sodium is higher than 4 grams, excess sodium may build in tissues and cause problems If human intake of sodium is higher than 4 grams, excess sodium may build in tissues and cause problems Distal convoluted tubule carries out final adjustment of filtrate composition Distal convoluted tubule carries out final adjustment of filtrate composition About 85% of sodium absorbed by the proximal convoluted tubule is obligatory or set About 85% of sodium absorbed by the proximal convoluted tubule is obligatory or set In the distal convoluted tubule, sodium reabsorption is controlled by aldosterone In the distal convoluted tubule, sodium reabsorption is controlled by aldosterone Vertebrate Kidney Function

42. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-42 Aldosterone increases active reabsorption of sodium in distal tubules and decreases loss of sodium Aldosterone increases active reabsorption of sodium in distal tubules and decreases loss of sodium Secretion of aldosterone Secretion of aldosterone Regulated by the enzyme renin Regulated by the enzyme renin Produced by the juxtaglomerular apparatus Produced by the juxtaglomerular apparatus Complex of cells located in the afferent arteriole at its junction with the glomerulus Complex of cells located in the afferent arteriole at its junction with the glomerulus Vertebrate Kidney Function

43. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-43 Renin is released in response to low blood sodium level or low blood pressure Renin is released in response to low blood sodium level or low blood pressure Initiates a series of enzymes that result in production of angiotensin, a blood protein Initiates a series of enzymes that result in production of angiotensin, a blood protein Angiotensin Angiotensin Stimulates release of aldosterone, which increases sodium reabsorption in the distal tubule Stimulates release of aldosterone, which increases sodium reabsorption in the distal tubule Increases secretion of antidiuretic hormone (vasopressin) promoting water conservation by kidney Increases secretion of antidiuretic hormone (vasopressin) promoting water conservation by kidney Vertebrate Kidney Function

44. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-44 Angiotensin increases blood pressure and stimulates thirst Angiotensin increases blood pressure and stimulates thirst These actions reverse the circumstances that triggered the secretion of renin These actions reverse the circumstances that triggered the secretion of renin Sodium and water are conserved Sodium and water are conserved Blood volume and pressure return to normal Blood volume and pressure return to normal Selective pressure has restricted sodium levels in humans while sodium range is broad in rodents Selective pressure has restricted sodium levels in humans while sodium range is broad in rodents Vertebrate Kidney Function

45. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-45 Tubular Secretion Tubular Secretion The nephron also secretes materials into the filtrate, the reverse of tubular reabsorption The nephron also secretes materials into the filtrate, the reverse of tubular reabsorption Carrier proteins in tubular epithelial cells Carrier proteins in tubular epithelial cells Selectively transport substances from blood to tubule Selectively transport substances from blood to tubule Results in increase in urine concentrations of hydrogen and potassium ions, drugs, etc. Results in increase in urine concentrations of hydrogen and potassium ions, drugs, etc. Primary site of tubular secretion Primary site of tubular secretion Distal convoluted tubule Distal convoluted tubule More complex process in marine fishes, nonavian reptiles, and birds than in mammals More complex process in marine fishes, nonavian reptiles, and birds than in mammals Marine bony fishes actively secrete large amounts of magnesium and sulfate Marine bony fishes actively secrete large amounts of magnesium and sulfate Uric acid is actively secreted by the tubular epithelium Uric acid is actively secreted by the tubular epithelium Vertebrate Kidney Function

46. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-46 Water Excretion Water Excretion The kidney closely regulates the osmotic pressure of the blood The kidney closely regulates the osmotic pressure of the blood When fluid intake is high When fluid intake is high Kidney excretes dilute urine and saves salts Kidney excretes dilute urine and saves salts When fluid intake is low When fluid intake is low Kidney conserves water and forms concentrated urine Kidney conserves water and forms concentrated urine A dehydrated person can concentrate urine to approximately four times blood osmotic concentration A dehydrated person can concentrate urine to approximately four times blood osmotic concentration Vertebrate Kidney Function

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48. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-48 Countercurrent Multiplication Countercurrent Multiplication Mammal and bird kidneys produce concentrated urine by interaction between the loop of Henle and the collecting ducts Mammal and bird kidneys produce concentrated urine by interaction between the loop of Henle and the collecting ducts Forms an osmotic gradient in the kidney Forms an osmotic gradient in the kidney In the cortex In the cortex Interstitial fluid is isosmotic with the blood Interstitial fluid is isosmotic with the blood Deep in the medulla Deep in the medulla Osmotic concentration is four times greater than that of the blood Osmotic concentration is four times greater than that of the blood High osmotic concentrations in the medulla are produced by an exchange of ions in the loop of Henle High osmotic concentrations in the medulla are produced by an exchange of ions in the loop of Henle Vertebrate Kidney Function

49. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-49 “Countercurrent” refers to the opposite directions of the loop of Henle “Countercurrent” refers to the opposite directions of the loop of Henle Down the descending limb and up the ascending limb Down the descending limb and up the ascending limb “Multiplication” describes the increasing osmotic concentration in the medulla “Multiplication” describes the increasing osmotic concentration in the medulla Results from ion exchange between the two limbs Results from ion exchange between the two limbs Descending limb of the loop of Henle Descending limb of the loop of Henle Permeable to water but impermeable to solutes Permeable to water but impermeable to solutes Ascending limb of the loop of Henle Ascending limb of the loop of Henle Impermeable to both water and solutes Impermeable to both water and solutes Sodium chloride is actively transported out of the thick portion of the ascending limb and into surrounding tissue Sodium chloride is actively transported out of the thick portion of the ascending limb and into surrounding tissue Vertebrate Kidney Function

50. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-50 As the interstitial area surrounding the loop becomes concentrated As the interstitial area surrounding the loop becomes concentrated Water is withdrawn from the descending limb by osmosis Water is withdrawn from the descending limb by osmosis Tubular fluid at the base of the loop is more concentrated and moves up the ascending limb where more sodium is pumped out Tubular fluid at the base of the loop is more concentrated and moves up the ascending limb where more sodium is pumped out Effect of active ion transport in the ascending limb is multiplied as more water is withdrawn from the descending limb and more concentrated fluid is presented to the ascending limb ion pump Effect of active ion transport in the ascending limb is multiplied as more water is withdrawn from the descending limb and more concentrated fluid is presented to the ascending limb ion pump Vertebrate Kidney Function

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52. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-52 Because of high concentration of solutes surrounding a collecting duct Because of high concentration of solutes surrounding a collecting duct Water is withdrawn from urine Water is withdrawn from urine As urine becomes concentrated As urine becomes concentrated Urea diffuses out, adding to a high osmotic pressure in the kidney medulla Urea diffuses out, adding to a high osmotic pressure in the kidney medulla Amount of water reabsorbed depends on the permeability of the walls of the distal convoluted tubule Amount of water reabsorbed depends on the permeability of the walls of the distal convoluted tubule Controlled by antidiuretic hormone (ADH, or vasopressin) released by the posterior pituitary Controlled by antidiuretic hormone (ADH, or vasopressin) released by the posterior pituitary ADH increases the permeability of the collecting duct and water diffuses outward ADH increases the permeability of the collecting duct and water diffuses outward If overhydrated, the pituitary decreases ADH secretion and more urine is excreted If overhydrated, the pituitary decreases ADH secretion and more urine is excreted Vertebrate Kidney Function

53. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-53 Temperature Regulation Chemical Environment Chemical Environment Biochemical activities are sensitive to temperature because enzymes have an optimum temperature Biochemical activities are sensitive to temperature because enzymes have an optimum temperature Temperature constraints on animals are due to their need to maintain biochemical stability Temperature constraints on animals are due to their need to maintain biochemical stability At colder temperatures, metabolic reactions may be too slow to maintain activity and reproduction At colder temperatures, metabolic reactions may be too slow to maintain activity and reproduction At high temperatures, enzyme activity is impaired or destroyed At high temperatures, enzyme activity is impaired or destroyed Generally animals function between 0 o and 40 o C Generally animals function between 0 o and 40 o C Animals may locate such habitats or develop means to stabilize their metabolism Animals may locate such habitats or develop means to stabilize their metabolism

54. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-54 Ectothermy and Endothermy Ectothermy and Endothermy “Cold-blooded” and “warm-blooded” “Cold-blooded” and “warm-blooded” Not well-defined terms Not well-defined terms Fish, insects, and reptiles basking in the sun may be warmer than mammals Fish, insects, and reptiles basking in the sun may be warmer than mammals Poikilothermic Poikilothermic Variable body temperature Variable body temperature Homeothermic Homeothermic Maintaining a constant body temperature Maintaining a constant body temperature These terms pose definition problems These terms pose definition problems All animals produce some heat from cellular metabolism All animals produce some heat from cellular metabolism Temperature Regulation

55. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-55 In ectotherms, the heat is conducted away as fast as it is produced In ectotherms, the heat is conducted away as fast as it is produced Many ectotherms may behaviorally select areas of more favorable temperature, such as basking in the sun Many ectotherms may behaviorally select areas of more favorable temperature, such as basking in the sun Endotherms are able to generate enough heat to elevate their own temperature to a high and stable level Endotherms are able to generate enough heat to elevate their own temperature to a high and stable level Birds and mammals Birds and mammals Some reptiles and fast-swimming fishes, and at times certain insects Some reptiles and fast-swimming fishes, and at times certain insects Endothermy allows birds and mammals to stabilize internal biochemical processes and nervous system functions Endothermy allows birds and mammals to stabilize internal biochemical processes and nervous system functions Endotherms can remain active in winter and exploit habitats denied to ectotherms Endotherms can remain active in winter and exploit habitats denied to ectotherms Endotherms that are small tend to decrease activity and hibernate in colder climates due to the high heat loss and/or limited food supply Endotherms that are small tend to decrease activity and hibernate in colder climates due to the high heat loss and/or limited food supply Temperature Regulation

56. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-56 How Ectotherms Achieve Temperature Independence How Ectotherms Achieve Temperature Independence Some ectotherms behaviorally regulate body temperature Some ectotherms behaviorally regulate body temperature Desert lizards exploit hour-to-hour changes in solar radiation Desert lizards exploit hour-to-hour changes in solar radiation In cool mornings, they bask with bodies flattened; in the hottest daytime, they retreat to burrows In cool mornings, they bask with bodies flattened; in the hottest daytime, they retreat to burrows Such lizards hold body temperature between 36 o and 39 o C while the environment varies from 29 o to 44 o C Such lizards hold body temperature between 36 o and 39 o C while the environment varies from 29 o to 44 o C Temperature Regulation

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58. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-58 Metabolic Adjustments Metabolic Adjustments Within limits, most ectotherms can adjust metabolic rate to the prevailing temperature Within limits, most ectotherms can adjust metabolic rate to the prevailing temperature Temperature compensation involves complex biochemical and cellular adjustments Temperature compensation involves complex biochemical and cellular adjustments Allows a fish or salamander to sustain the same level of activity in warm or cold water Allows a fish or salamander to sustain the same level of activity in warm or cold water Temperature Regulation

59. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-59 Temperature Regulation in Endotherms Temperature Regulation in Endotherms Most mammals have body temperatures between 36 o and 38 o C Most mammals have body temperatures between 36 o and 38 o C Most birds range from 40 o to 42 o C Most birds range from 40 o to 42 o C Much of an endotherm’s daily caloric intake goes to generate heat Much of an endotherm’s daily caloric intake goes to generate heat Must eat more than an ectotherm Must eat more than an ectotherm Heat is lost by radiation, conduction and convection to a cooler environment, and by evaporation of water Heat is lost by radiation, conduction and convection to a cooler environment, and by evaporation of water If an animal becomes too cool If an animal becomes too cool Generate heat by exercise or shivering Generate heat by exercise or shivering Decrease heat loss by increasing insulation Decrease heat loss by increasing insulation Temperature Regulation

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61. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-61 Adaptations for Hot Environments Adaptations for Hot Environments Small desert animals are often fossorial, living in the ground, or nocturnal, active at night Small desert animals are often fossorial, living in the ground, or nocturnal, active at night Lower temperatures and higher humidity of burrows also reduces water loss from evaporation Lower temperatures and higher humidity of burrows also reduces water loss from evaporation Desert animals may also drink no water Desert animals may also drink no water Derive all water from food and produce dry feces Derive all water from food and produce dry feces The desert eland has many adaptations for desert living The desert eland has many adaptations for desert living Glossy, pallid fur; fur insulation; fat tissue isolated on the back; and dropping body temperature at night Glossy, pallid fur; fur insulation; fat tissue isolated on the back; and dropping body temperature at night When the body temperature reaches 41° C, it uses evaporative cooling by sweating and panting When the body temperature reaches 41° C, it uses evaporative cooling by sweating and panting The desert camel has all of these adaptations perfected for desert living The desert camel has all of these adaptations perfected for desert living Temperature Regulation

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63. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-63 Adaptations for Cold Environments Adaptations for Cold Environments Mammals and birds use decreased conductance and increased heat production to survive the cold Mammals and birds use decreased conductance and increased heat production to survive the cold In winter, fur may increase in thickness by 50% In winter, fur may increase in thickness by 50% Countercurrent Heat Exchange Countercurrent Heat Exchange A well-insulated body can lose substantial heat through blood flowing along exposed limbs A well-insulated body can lose substantial heat through blood flowing along exposed limbs Arterial blood in the leg of an arctic mammal or bird passes in contact with returning cold blood Arterial blood in the leg of an arctic mammal or bird passes in contact with returning cold blood Heat exchange all along the opposite vessels transfers nearly all body heat to returning venous blood that returns to the body core Heat exchange all along the opposite vessels transfers nearly all body heat to returning venous blood that returns to the body core Similar countercurrent exchange systems keep aquatic mammal flippers from losing body heat Similar countercurrent exchange systems keep aquatic mammal flippers from losing body heat Footpads and hooves must be able to operate at near- freezing temperatures Footpads and hooves must be able to operate at near- freezing temperatures Temperature Regulation

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65. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-65 Augmented muscular activity increases heat by exercise or shivering Augmented muscular activity increases heat by exercise or shivering Nonshivering thermogenesis uses increased oxidation of stores of brown fat Nonshivering thermogenesis uses increased oxidation of stores of brown fat Small mammals live in the milder climate under the snow, a subnivean environment Small mammals live in the milder climate under the snow, a subnivean environment Temperature Regulation

66. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-66 Adaptive Hypothermia in Birds and Mammals Adaptive Hypothermia in Birds and Mammals Endotherm must always have an energy supply to support its high metabolic rate Endotherm must always have an energy supply to support its high metabolic rate Small birds and mammals Small birds and mammals Have an intense metabolism that is difficult to support on cold nights Have an intense metabolism that is difficult to support on cold nights Daily torpor is dropping body temperature when asleep or inactive Daily torpor is dropping body temperature when asleep or inactive Prevents energy loss Prevents energy loss Hummingbirds may drop body temperature at night when food supplies are low Hummingbirds may drop body temperature at night when food supplies are low Hibernation Hibernation Prolonged and controlled dormancy Prolonged and controlled dormancy Temperature Regulation

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68. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30-68 True hibernators prepare for winter by storing body fat True hibernators prepare for winter by storing body fat Entry into hibernation is gradual Entry into hibernation is gradual Animal eventually cools to near ambient temperature Animal eventually cools to near ambient temperature Respiration may drop from 200 breaths per minute to 4–5 per minute Respiration may drop from 200 breaths per minute to 4–5 per minute Heart rate from 150 to 5 beats per minute Heart rate from 150 to 5 beats per minute Arousal from hibernation may require shivering and nonshivering thermogenesis Arousal from hibernation may require shivering and nonshivering thermogenesis Bears, badgers, raccoons and opossums enter a prolonged sleep with little or no decrease in body temperature Bears, badgers, raccoons and opossums enter a prolonged sleep with little or no decrease in body temperature This prolonged sleep is not true hibernation the animal can be awakened if disturbed This prolonged sleep is not true hibernation the animal can be awakened if disturbed Some invertebrates and vertebrates Some invertebrates and vertebrates Enter of state of summer dormancy called estivation Enter of state of summer dormancy called estivation Temperature Regulation

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