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44 excretion text

  1. 1. Chapter 44 Osmoregulation and Excretion
  2. 2. <ul><li>Overview: A balancing act </li></ul><ul><li>The physiological systems of animals </li></ul><ul><ul><li>Operate in a fluid environment </li></ul></ul><ul><li>The relative concentrations of water and solutes in this environment </li></ul><ul><ul><li>Must be maintained within fairly narrow limits </li></ul></ul>
  3. 3. <ul><li>Freshwater animals </li></ul><ul><ul><li>Show adaptations that reduce water uptake and conserve solutes </li></ul></ul><ul><li>Desert and marine animals face desiccating environments </li></ul><ul><ul><li>With the potential to quickly deplete the body water </li></ul></ul>Figure 44.1
  4. 4. <ul><li>Osmoregulation </li></ul><ul><ul><li>Regulates solute concentrations and balances the gain and loss of water </li></ul></ul><ul><li>Excretion </li></ul><ul><ul><li>Gets rid of metabolic wastes </li></ul></ul>
  5. 5. <ul><li>Concept 44.1: Osmoregulation balances the uptake and loss of water and solutes </li></ul><ul><li>Osmoregulation is based largely on controlled movement of solutes </li></ul><ul><ul><li>Between internal fluids and the external environment </li></ul></ul>
  6. 6. Osmosis <ul><li>Cells require a balance </li></ul><ul><ul><li>Between osmotic gain and loss of water </li></ul></ul><ul><li>Water uptake and loss </li></ul><ul><ul><li>Are balanced by various mechanisms of osmoregulation in different environments </li></ul></ul>
  7. 7. Osmotic Challenges <ul><li>Osmoconformers, which are only marine animals </li></ul><ul><ul><li>Are isoosmotic with their surroundings and do not regulate their osmolarity </li></ul></ul><ul><li>Osmoregulators expend energy to control water uptake and loss </li></ul><ul><ul><li>In a hyperosmotic or hypoosmotic environment </li></ul></ul>
  8. 8. <ul><li>Most animals are said to be stenohaline </li></ul><ul><ul><li>And cannot tolerate substantial changes in external osmolarity </li></ul></ul><ul><li>Euryhaline animals </li></ul><ul><ul><li>Can survive large fluctuations in external osmolarity </li></ul></ul>Figure 44.2
  9. 9. Marine Animals <ul><li>Most marine invertebrates are osmoconformers </li></ul><ul><li>Most marine vertebrates and some invertebrates are osmoregulators </li></ul>
  10. 10. <ul><li>Marine bony fishes are hypoosmotic to sea water </li></ul><ul><ul><li>And lose water by osmosis and gain salt by both diffusion and from food they eat </li></ul></ul><ul><li>These fishes balance water loss </li></ul><ul><ul><li>By drinking seawater </li></ul></ul>Figure 44.3a (a) Osmoregulation in a saltwater fish Gain of water and salt ions from food and by drinking seawater Osmotic water loss through gills and other parts of body surface Excretion of salt ions from gills Excretion of salt ions and small amounts of water in scanty urine from kidneys
  11. 11. Freshwater Animals <ul><li>Freshwater animals </li></ul><ul><ul><li>Constantly take in water from their hypoosmotic environment </li></ul></ul><ul><ul><li>Lose salts by diffusion </li></ul></ul>
  12. 12. <ul><li>Freshwater animals maintain water balance </li></ul><ul><ul><li>By excreting large amounts of dilute urine </li></ul></ul><ul><li>Salts lost by diffusion </li></ul><ul><ul><li>Are replaced by foods and uptake across the gills </li></ul></ul>Figure 44.3b (b) Osmoregulation in a freshwater fish Uptake of water and some ions in food Osmotic water gain through gills and other parts of body surface Uptake of salt ions by gills Excretion of large amounts of water in dilute urine from kidneys
  13. 13. Animals That Live in Temporary Waters <ul><li>Some aquatic invertebrates living in temporary ponds </li></ul><ul><ul><li>Can lose almost all their body water and survive in a dormant state </li></ul></ul><ul><li>This adaptation is called anhydrobiosis </li></ul>Figure 44.4a, b (a) Hydrated tardigrade (b) Dehydrated tardigrade 100 µm 100 µm
  14. 14. Land Animals <ul><li>Land animals manage their water budgets </li></ul><ul><ul><li>By drinking and eating moist foods and by using metabolic water </li></ul></ul>Figure 44.5 Water balance in a human (2,500 mL/day = 100%) Water balance in a kangaroo rat (2 mL/day = 100%) Ingested in food (0.2) Ingested in food (750) Ingested in liquid (1,500) Derived from metabolism (250) Derived from metabolism (1.8) Water gain Feces (0.9) Urine (0.45) Evaporation (1.46) Feces (100) Urine (1,500) Evaporation (900) Water loss
  15. 15. <ul><li>Desert animals </li></ul><ul><ul><li>Get major water savings from simple anatomical features </li></ul></ul>Figure 44.6 Control group (Unclipped fur) Experimental group (Clipped fur) 4 3 2 1 0 Water lost per day (L/100 kg body mass) Knut and Bodil Schmidt-Nielsen and their colleagues from Duke University observed that the fur of camels exposed to full sun in the Sahara Desert could reach temperatures of over 70°C, while the animals’ skin remained more than 30°C cooler. The Schmidt-Nielsens reasoned that insulation of the skin by fur may substantially reduce the need for evaporative cooling by sweating. To test this hypothesis, they compared the water loss rates of unclipped and clipped camels. EXPERIMENT RESULTS Removing the fur of a camel increased the rate of water loss through sweating by up to 50%. The fur of camels plays a critical role in their conserving water in the hot desert environments where they live. CONCLUSION
  16. 16. Transport Epithelia <ul><li>Transport epithelia </li></ul><ul><ul><li>Are specialized cells that regulate solute movement </li></ul></ul><ul><ul><li>Are essential components of osmotic regulation and metabolic waste disposal </li></ul></ul><ul><ul><li>Are arranged into complex tubular networks </li></ul></ul>
  17. 17. <ul><li>An example of transport epithelia is found in the salt glands of marine birds </li></ul><ul><ul><li>Which remove excess sodium chloride from the blood </li></ul></ul>Figure 44.7a, b Nasal salt gland Nostril with salt secretions Lumen of secretory tubule NaCl Blood flow Secretory cell of transport epithelium Central duct Direction of salt movement Transport epithelium Secretory tubule Capillary Vein Artery (a) An albatross’s salt glands empty via a duct into the nostrils, and the salty solution either drips off the tip of the beak or is exhaled in a fine mist. (b) One of several thousand secretory tubules in a salt- excreting gland. Each tubule is lined by a transport epithelium surrounded by capillaries, and drains into a central duct. (c) The secretory cells actively transport salt from the blood into the tubules. Blood flows counter to the flow of salt secretion. By maintaining a concentration gradient of salt in the tubule (aqua), this countercurrent system enhances salt transfer from the blood to the lumen of the tubule.
  18. 18. <ul><li>Concept 44.2: An animal’s nitrogenous wastes reflect its phylogeny and habitat </li></ul><ul><li>The type and quantity of an animal’s waste products </li></ul><ul><ul><li>May have a large impact on its water balance </li></ul></ul>
  19. 19. <ul><li>Among the most important wastes </li></ul><ul><ul><li>Are the nitrogenous breakdown products of proteins and nucleic acids </li></ul></ul>Figure 44.8 Proteins Nucleic acids Amino acids Nitrogenous bases – N H 2 Amino groups Most aquatic animals, including most bony fishes Mammals, most amphibians, sharks, some bony fishes Many reptiles (including birds), insects, land snails Ammonia Urea Uric acid N H 3 N H 2 N H 2 O C C C N C O N H H C O N C H N O H
  20. 20. Forms of Nitrogenous Wastes <ul><li>Different animals </li></ul><ul><ul><li>Excrete nitrogenous wastes in different forms </li></ul></ul>
  21. 21. Ammonia <ul><li>Animals that excrete nitrogenous wastes as ammonia </li></ul><ul><ul><li>Need access to lots of water </li></ul></ul><ul><ul><li>Release it across the whole body surface or through the gills </li></ul></ul>
  22. 22. Urea <ul><li>The liver of mammals and most adult amphibians </li></ul><ul><ul><li>Converts ammonia to less toxic urea </li></ul></ul><ul><li>Urea is carried to the kidneys, concentrated </li></ul><ul><ul><li>And excreted with a minimal loss of water </li></ul></ul>
  23. 23. Uric Acid <ul><li>Insects, land snails, and many reptiles, including birds </li></ul><ul><ul><li>Excrete uric acid as their major nitrogenous waste </li></ul></ul><ul><li>Uric acid is largely insoluble in water </li></ul><ul><ul><li>And can be secreted as a paste with little water loss </li></ul></ul>
  24. 24. The Influence of Evolution and Environment on Nitrogenous Wastes <ul><li>The kinds of nitrogenous wastes excreted </li></ul><ul><ul><li>Depend on an animal’s evolutionary history and habitat </li></ul></ul><ul><li>The amount of nitrogenous waste produced </li></ul><ul><ul><li>Is coupled to the animal’s energy budget </li></ul></ul>
  25. 25. <ul><li>Concept 44.3: Diverse excretory systems are variations on a tubular theme </li></ul><ul><li>Excretory systems </li></ul><ul><ul><li>Regulate solute movement between internal fluids and the external environment </li></ul></ul>
  26. 26. Excretory Processes <ul><li>Most excretory systems </li></ul><ul><ul><li>Produce urine by refining a filtrate derived from body fluids </li></ul></ul>Figure 44.9 Filtration. The excretory tubule collects a filtrate from the blood. Water and solutes are forced by blood pressure across the selectively permeable membranes of a cluster of capillaries and into the excretory tubule. Reabsorption. The transport epithelium reclaims valuable substances from the filtrate and returns them to the body fluids. Secretion. Other substances, such as toxins and excess ions, are extracted from body fluids and added to the contents of the excretory tubule. Excretion. The filtrate leaves the system and the body. Capillary Excretory tubule Filtrate Urine 1 2 3 4
  27. 27. <ul><li>Key functions of most excretory systems are </li></ul><ul><ul><li>Filtration, pressure-filtering of body fluids producing a filtrate </li></ul></ul><ul><ul><li>Reabsorption, reclaiming valuable solutes from the filtrate </li></ul></ul><ul><ul><li>Secretion, addition of toxins and other solutes from the body fluids to the filtrate </li></ul></ul><ul><ul><li>Excretion, the filtrate leaves the system </li></ul></ul>
  28. 28. Survey of Excretory Systems <ul><li>The systems that perform basic excretory functions </li></ul><ul><ul><li>Vary widely among animal groups </li></ul></ul><ul><ul><li>Are generally built on a complex network of tubules </li></ul></ul>
  29. 29. Protonephridia: Flame-Bulb Systems <ul><li>A protonephridium </li></ul><ul><ul><li>Is a network of dead-end tubules lacking internal openings </li></ul></ul>Figure 44.10 Nucleus of cap cell Cilia Interstitial fluid filters through membrane where cap cell and tubule cell interdigitate (interlock) Tubule cell Flame bulb Nephridiopore in body wall Tubule Protonephridia (tubules)
  30. 30. <ul><li>The tubules branch throughout the body </li></ul><ul><ul><li>And the smallest branches are capped by a cellular unit called a flame bulb </li></ul></ul><ul><li>These tubules excrete a dilute fluid </li></ul><ul><ul><li>And function in osmoregulation </li></ul></ul>
  31. 31. Metanephridia <ul><li>Each segment of an earthworm </li></ul><ul><ul><li>Has a pair of open-ended metanephridia </li></ul></ul>Figure 44.11 Nephrostome Metanephridia Nephridio- pore Collecting tubule Bladder Capillary network Coelom
  32. 32. <ul><li>Metanephridia consist of tubules </li></ul><ul><ul><li>That collect coelomic fluid and produce dilute urine for excretion </li></ul></ul>
  33. 33. Malpighian Tubules <ul><li>In insects and other terrestrial arthropods, malpighian tubules </li></ul><ul><ul><li>Remove nitrogenous wastes from hemolymph and function in osmoregulation </li></ul></ul>Figure 44.12 Digestive tract Midgut (stomach) Malpighian tubules Rectum Intestine Hindgut Salt, water, and nitrogenous wastes Feces and urine Anus Malpighian tubule Rectum Reabsorption of H 2 O, ions, and valuable organic molecules HEMOLYMPH
  34. 34. <ul><li>Insects produce a relatively dry waste matter </li></ul><ul><ul><li>An important adaptation to terrestrial life </li></ul></ul>
  35. 35. Vertebrate Kidneys <ul><li>Kidneys, the excretory organs of vertebrates </li></ul><ul><ul><li>Function in both excretion and osmoregulation </li></ul></ul>
  36. 36. <ul><li>Concept 44.4: Nephrons and associated blood vessels are the functional unit of the mammalian kidney </li></ul><ul><li>The mammalian excretory system centers on paired kidneys </li></ul><ul><ul><li>Which are also the principal site of water balance and salt regulation </li></ul></ul>
  37. 37. <ul><li>Each kidney </li></ul><ul><ul><li>Is supplied with blood by a renal artery and drained by a renal vein </li></ul></ul>Figure 44.13a Posterior vena cava Renal artery and vein Aorta Ureter Urinary bladder Urethra (a) Excretory organs and major associated blood vessels Kidney
  38. 38. <ul><li>Urine exits each kidney </li></ul><ul><ul><li>Through a duct called the ureter </li></ul></ul><ul><li>Both ureters </li></ul><ul><ul><li>Drain into a common urinary bladder </li></ul></ul>
  39. 39. Structure and Function of the Nephron and Associated Structures <ul><li>The mammalian kidney has two distinct regions </li></ul><ul><ul><li>An outer renal cortex and an inner renal medulla </li></ul></ul>(b) Kidney structure Ureter Section of kidney from a rat Renal medulla Renal cortex Renal pelvis Figure 44.13b
  40. 40. <ul><li>The nephron, the functional unit of the vertebrate kidney </li></ul><ul><ul><li>Consists of a single long tubule and a ball of capillaries called the glomerulus </li></ul></ul>Figure 44.13c, d Juxta- medullary nephron Cortical nephron Collecting duct To renal pelvis Renal cortex Renal medulla 20 µm Afferent arteriole from renal artery Glomerulus Bowman’s capsule Proximal tubule Peritubular capillaries SEM Efferent arteriole from glomerulus Branch of renal vein Descending limb Ascending limb Loop of Henle Distal tubule Collecting duct (c) Nephron Vasa recta (d) Filtrate and blood flow
  41. 41. Filtration of the Blood <ul><li>Filtration occurs as blood pressure </li></ul><ul><ul><li>Forces fluid from the blood in the glomerulus into the lumen of Bowman’s capsule </li></ul></ul>
  42. 42. <ul><li>Filtration of small molecules is nonselective </li></ul><ul><ul><li>And the filtrate in Bowman’s capsule is a mixture that mirrors the concentration of various solutes in the blood plasma </li></ul></ul>
  43. 43. Pathway of the Filtrate <ul><li>From Bowman’s capsule, the filtrate passes through three regions of the nephron </li></ul><ul><ul><li>The proximal tubule, the loop of Henle, and the distal tubule </li></ul></ul><ul><li>Fluid from several nephrons </li></ul><ul><ul><li>Flows into a collecting duct </li></ul></ul>
  44. 44. Blood Vessels Associated with the Nephrons <ul><li>Each nephron is supplied with blood by an afferent arteriole </li></ul><ul><ul><li>A branch of the renal artery that subdivides into the capillaries </li></ul></ul><ul><li>The capillaries converge as they leave the glomerulus </li></ul><ul><ul><li>Forming an efferent arteriole </li></ul></ul><ul><li>The vessels subdivide again </li></ul><ul><ul><li>Forming the peritubular capillaries, which surround the proximal and distal tubules </li></ul></ul>
  45. 45. From Blood Filtrate to Urine: A Closer Look <ul><li>Filtrate becomes urine </li></ul><ul><ul><li>As it flows through the mammalian nephron and collecting duct </li></ul></ul>Figure 44.14 Proximal tubule Filtrate H 2 O Salts (NaCl and others) HCO 3 – H + Urea Glucose; amino acids Some drugs Key Active transport Passive transport CORTEX OUTER MEDULLA INNER MEDULLA Descending limb of loop of Henle Thick segment of ascending limb Thin segment of ascending limb Collecting duct NaCl NaCl NaCl Distal tubule NaCl Nutrients Urea H 2 O NaCl H 2 O H 2 O HCO 3  K + H + NH 3 HCO 3  K + H + H 2 O 1 4 3 2 3 5
  46. 46. <ul><li>Secretion and reabsorption in the proximal tubule </li></ul><ul><ul><li>Substantially alter the volume and composition of filtrate </li></ul></ul><ul><li>Reabsorption of water continues </li></ul><ul><ul><li>As the filtrate moves into the descending limb of the loop of Henle </li></ul></ul>
  47. 47. <ul><li>As filtrate travels through the ascending limb of the loop of Henle </li></ul><ul><ul><li>Salt diffuses out of the permeable tubule into the interstitial fluid </li></ul></ul><ul><li>The distal tubule </li></ul><ul><ul><li>Plays a key role in regulating the K + and NaCl concentration of body fluids </li></ul></ul><ul><li>The collecting duct </li></ul><ul><ul><li>Carries the filtrate through the medulla to the renal pelvis and reabsorbs NaCl </li></ul></ul>
  48. 48. <ul><li>Concept 44.5: The mammalian kidney’s ability to conserve water is a key terrestrial adaptation </li></ul><ul><li>The mammalian kidney </li></ul><ul><ul><li>Can produce urine much more concentrated than body fluids, thus conserving water </li></ul></ul>
  49. 49. Solute Gradients and Water Conservation <ul><li>In a mammalian kidney, the cooperative action and precise arrangement of the loops of Henle and the collecting ducts </li></ul><ul><ul><li>Are largely responsible for the osmotic gradient that concentrates the urine </li></ul></ul>
  50. 50. <ul><li>Two solutes, NaCl and urea, contribute to the osmolarity of the interstitial fluid </li></ul><ul><ul><li>Which causes the reabsorption of water in the kidney and concentrates the urine </li></ul></ul>Figure 44.15 H 2 O H 2 O H 2 O H 2 O H 2 O H 2 O H 2 O NaCl NaCl NaCl NaCl NaCl NaCl NaCl 300 300 100 400 600 900 1200 700 400 200 100 Active transport Passive transport OUTER MEDULLA INNER MEDULLA CORTEX H 2 O Urea H 2 O Urea H 2 O Urea H 2 O H 2 O H 2 O H 2 O 1200 1200 900 600 400 300 600 400 300 Osmolarity of interstitial fluid (mosm/L) 300
  51. 51. <ul><li>The countercurrent multiplier system involving the loop of Henle </li></ul><ul><ul><li>Maintains a high salt concentration in the interior of the kidney, which enables the kidney to form concentrated urine </li></ul></ul>
  52. 52. <ul><li>The collecting duct, permeable to water but not salt </li></ul><ul><ul><li>Conducts the filtrate through the kidney’s osmolarity gradient, and more water exits the filtrate by osmosis </li></ul></ul>
  53. 53. <ul><li>Urea diffuses out of the collecting duct </li></ul><ul><ul><li>As it traverses the inner medulla </li></ul></ul><ul><li>Urea and NaCl </li></ul><ul><ul><li>Form the osmotic gradient that enables the kidney to produce urine that is hyperosmotic to the blood </li></ul></ul>
  54. 54. Regulation of Kidney Function <ul><li>The osmolarity of the urine </li></ul><ul><ul><li>Is regulated by nervous and hormonal control of water and salt reabsorption in the kidneys </li></ul></ul>
  55. 55. <ul><li>Antidiuretic hormone (ADH) </li></ul><ul><ul><li>Increases water reabsorption in the distal tubules and collecting ducts of the kidney </li></ul></ul>Figure 44.16a (a) Antidiuretic hormone (ADH) enhances fluid retention by making the kidneys reclaim more water. Osmoreceptors in hypothalamus Drinking reduces blood osmolarity to set point H 2 O reab- sorption helps prevent further osmolarity increase STIMULUS: The release of ADH is triggered when osmo- receptor cells in the hypothalamus detect an increase in the osmolarity of the blood Homeostasis: Blood osmolarity Hypothalamus ADH Pituitary gland Increased permeability Thirst Collecting duct Distal tubule
  56. 56. <ul><li>The renin-angiotensin-aldosterone system (RAAS) </li></ul><ul><ul><li>Is part of a complex feedback circuit that functions in homeostasis </li></ul></ul>Figure 44.16b (b) The renin-angiotensin-aldosterone system (RAAS) leads to an increase in blood volume and pressure. Increased Na + and H 2 O reab- sorption in distal tubules Homeostasis: Blood pressure, volume STIMULUS: The juxtaglomerular apparatus (JGA) responds to low blood volume or blood pressure (such as due to dehydration or loss of blood) Aldosterone Adrenal gland Angiotensin II Angiotensinogen Renin production Renin Arteriole constriction Distal tubule JGA
  57. 57. <ul><li>Another hormone, atrial natriuretic factor (ANF) </li></ul><ul><ul><li>Opposes the RAAS </li></ul></ul>
  58. 58. <ul><li>The South American vampire bat, which feeds on blood </li></ul><ul><ul><li>Has a unique excretory system in which its kidneys offload much of the water absorbed from a meal by excreting large amounts of dilute urine </li></ul></ul>Figure 44.17
  59. 59. <ul><li>Concept 44.6: Diverse adaptations of the vertebrate kidney have evolved in different environments </li></ul><ul><li>The form and function of nephrons in various vertebrate classes </li></ul><ul><ul><li>Are related primarily to the requirements for osmoregulation in the animal’s habitat </li></ul></ul>
  60. 60. <ul><li>Exploring environmental adaptations of the vertebrate kidney </li></ul>Figure 44.18 MAMMALS Bannertail Kangaroo rat ( Dipodomys spectabilis ) Beaver ( Castor canadensis ) FRESHWATER FISHES AND AMPHIBIANS Rainbow trout ( Oncorrhynchus mykiss ) Frog ( Rana temporaria ) BIRDS AND OTHER REPTILES Roadrunner ( Geococcyx californianus ) Desert iguana ( Dipsosaurus dorsalis ) MARINE BONY FISHES Northern bluefin tuna ( Thunnus thynnus )
  61. 61. Chapter 45 Hormones and the Endocrine System
  62. 62. <ul><li>Overview: The Body’s Long-Distance Regulators </li></ul><ul><li>An animal hormone </li></ul><ul><ul><li>Is a chemical signal that is secreted into the circulatory system and communicates regulatory messages within the body </li></ul></ul><ul><li>Hormones may reach all parts of the body </li></ul><ul><ul><li>But only certain types of cells, target cells, are equipped to respond </li></ul></ul>
  63. 63. <ul><li>Insect metamorphosis </li></ul><ul><ul><li>Is regulated by hormones </li></ul></ul>Figure 45.1
  64. 64. <ul><li>Concept 45.1: The endocrine system and the nervous system act individually and together in regulating an animal’s physiology </li></ul><ul><li>Animals have two systems of internal communication and regulation </li></ul><ul><ul><li>The nervous system and the endocrine system </li></ul></ul>
  65. 65. <ul><li>The nervous system </li></ul><ul><ul><li>Conveys high-speed electrical signals along specialized cells called neurons </li></ul></ul><ul><li>The endocrine system, made up of endocrine glands </li></ul><ul><ul><li>Secretes hormones that coordinate slower but longer-acting responses to stimuli </li></ul></ul>
  66. 66. Overlap Between Endocrine and Nervous Regulation <ul><li>The endocrine and nervous systems </li></ul><ul><ul><li>Often function together in maintaining homeostasis, development, and reproduction </li></ul></ul>
  67. 67. <ul><li>Specialized nerve cells known as neurosecretory cells </li></ul><ul><ul><li>Release neurohormones into the blood </li></ul></ul><ul><li>Both endocrine hormones and neurohormones </li></ul><ul><ul><li>Function as long-distance regulators of many physiological processes </li></ul></ul>
  68. 68. Control Pathways and Feedback Loops <ul><li>There are three types of hormonal control pathways </li></ul>Pathway Example Stimulus Low blood glucose Receptor protein Pancreas secretes glucagon ( ) Endocrine cell Blood vessel Liver Target effectors Response Pathway Example Stimulus Suckling Sensory neuron Hypothalamus/ posterior pituitary Neurosecretory cell Blood vessel Posterior pituitary secretes oxytocin ( ) Target effectors Smooth muscle in breast Response Milk release Pathway Example Stimulus Hypothalamic neurohormone released in response to neural and hormonal signals Sensory neuron Hypothalamus secretes prolactin- releasing hormone ( ) Neurosecretory cell Blood vessel Anterior pituitary secretes prolactin ( ) Endocrine cell Blood vessel Target effectors Response Mammary glands Milk production (c) Simple neuroendocrine pathway (b) Simple neurohormone pathway (a) Simple endocrine pathway Hypothalamus Glycogen breakdown, glucose release into blood Figure 45.2a–c
  69. 69. <ul><li>A common feature of control pathways </li></ul><ul><ul><li>Is a feedback loop connecting the response to the initial stimulus </li></ul></ul><ul><li>Negative feedback </li></ul><ul><ul><li>Regulates many hormonal pathways involved in homeostasis </li></ul></ul>
  70. 70. <ul><li>Concept 45.2: Hormones and other chemical signals bind to target cell receptors, initiating pathways that culminate in specific cell responses </li></ul><ul><li>Hormones convey information via the bloodstream </li></ul><ul><ul><li>To target cells throughout the body </li></ul></ul>
  71. 71. <ul><li>Three major classes of molecules function as hormones in vertebrates </li></ul><ul><ul><li>Proteins and peptides </li></ul></ul><ul><ul><li>Amines derived from amino acids </li></ul></ul><ul><ul><li>Steroids </li></ul></ul>
  72. 72. <ul><li>Signaling by any of these molecules involves three key events </li></ul><ul><ul><li>Reception </li></ul></ul><ul><ul><li>Signal transduction </li></ul></ul><ul><ul><li>Response </li></ul></ul>
  73. 73. Cell-Surface Receptors for Water-Soluble Hormones <ul><li>The receptors for most water-soluble hormones </li></ul><ul><ul><li>Are embedded in the plasma membrane, projecting outward from the cell surface </li></ul></ul>Figure 45.3a (a) Receptor in plasma membrane SECRETORY CELL Hormone molecule VIA BLOOD Signal receptor TARGET CELL Signal transduction pathway Cytoplasmic response Nuclear response NUCLEUS DNA OR
  74. 74. <ul><li>Binding of a hormone to its receptor </li></ul><ul><ul><li>Initiates a signal transduction pathway leading to specific responses in the cytoplasm or a change in gene expression </li></ul></ul>
  75. 75. <ul><li>The same hormone may have different effects on target cells that have </li></ul><ul><ul><li>Different receptors for the hormone </li></ul></ul><ul><ul><li>Different signal transduction pathways </li></ul></ul><ul><ul><li>Different proteins for carrying out the response </li></ul></ul>
  76. 76. <ul><li>The hormone epinephrine </li></ul><ul><ul><li>Has multiple effects in mediating the body’s response to short-term stress </li></ul></ul>Figure 45.4a–c Different receptors different cell responses Epinephrine  receptor Epinephrine  receptor Epinephrine  receptor Vessel constricts Vessel dilates Glycogen breaks down and glucose is released from cell (a) Intestinal blood vessel (b) Skeletal muscle blood vessel (c) Liver cell Different intracellular proteins different cell responses Glycogen deposits
  77. 77. Intracellular Receptors for Lipid-Soluble Hormones <ul><li>Steroids, thyroid hormones, and the hormonal form of vitamin D </li></ul><ul><ul><li>Enter target cells and bind to specific protein receptors in the cytoplasm or nucleus </li></ul></ul>
  78. 78. <ul><li>The protein-receptor complexes </li></ul><ul><ul><li>Then act as transcription factors in the nucleus, regulating transcription of specific genes </li></ul></ul>(b) Receptor in cell nucleus Figure 45.3b SECRETORY CELL Hormone molecule VIA BLOOD TARGET CELL Signal receptor Signal transduction and response DNA mRNA NUCLEUS Synthesis of specific proteins
  79. 79. Paracrine Signaling by Local Regulators <ul><li>In a process called paracrine signaling </li></ul><ul><ul><li>Various types of chemical signals elicit responses in nearby target cells </li></ul></ul>
  80. 80. <ul><li>Local regulators have various functions and include </li></ul><ul><ul><li>Neurotransmitters </li></ul></ul><ul><ul><li>Cytokines and growth factors </li></ul></ul><ul><ul><li>Nitric oxide </li></ul></ul><ul><ul><li>Prostaglandins </li></ul></ul>
  81. 81. <ul><li>Prostaglandins help regulate the aggregation of platelets </li></ul><ul><ul><li>An early step in the formation of blood clots </li></ul></ul>Figure 45.5
  82. 82. <ul><li>Concept 45.3: The hypothalamus and pituitary integrate many functions of the vertebrate endocrine system </li></ul><ul><li>The hypothalamus and the pituitary gland </li></ul><ul><ul><li>Control much of the endocrine system </li></ul></ul>
  83. 83. <ul><li>The major human endocrine glands </li></ul>Figure 45.6 Hypothalamus Pineal gland Pituitary gland Thyroid gland Parathyroid glands Adrenal glands Pancreas Ovary (female) Testis (male)
  84. 84. <ul><li>Major human endocrine glands and some of their hormones </li></ul>Table 45.1
  85. 85. Table 45.1
  86. 86. Relation Between the Hypothalamus and Pituitary Gland <ul><li>The hypothalamus, a region of the lower brain </li></ul><ul><ul><li>Contains different sets of neurosecretory cells </li></ul></ul>
  87. 87. <ul><li>Some of these cells produce direct-acting hormones </li></ul><ul><ul><li>That are stored in and released from the posterior pituitary, or neurohypophysis </li></ul></ul>Figure 45.7 Hypothalamus Neurosecretory cells of the hypothalamus Axon Anterior pituitary Posterior pituitary HORMONE ADH Oxytocin TARGET Kidney tubules Mammary glands, uterine muscles
  88. 88. <ul><li>Other hypothalamic cells produce tropic hormones </li></ul><ul><ul><li>That are secreted into the blood and transported to the anterior pituitary or adenohypophysis </li></ul></ul>Tropic Effects Only FSH, follicle-stimulating hormone LH, luteinizing hormone TSH, thyroid-stimulating hormone ACTH, adrenocorticotropic hormone Nontropic Effects Only Prolactin MSH, melanocyte-stimulating hormone Endorphin Nontropic and Tropic Effects Growth hormone Neurosecretory cells of the hypothalamus Portal vessels Endocrine cells of the anterior pituitary Hypothalamic releasing hormones (red dots) HORMONE FSH and LH TSH ACTH Prolactin MSH Endorphin Growth hormone TARGET Testes or ovaries Thyroid Adrenal cortex Mammary glands Melanocytes Pain receptors in the brain Liver Bones Pituitary hormones (blue dots) Figure 45.8
  89. 89. <ul><li>The anterior pituitary </li></ul><ul><ul><li>Is a true-endocrine gland </li></ul></ul><ul><li>The tropic hormones of the hypothalamus </li></ul><ul><ul><li>Control release of hormones from the anterior pituitary </li></ul></ul>
  90. 90. Posterior Pituitary Hormones <ul><li>The two hormones released from the posterior pituitary </li></ul><ul><ul><li>Act directly on nonendocrine tissues </li></ul></ul>
  91. 91. <ul><li>Oxytocin </li></ul><ul><ul><li>Induces uterine contractions and milk ejection </li></ul></ul><ul><li>Antidiuretic hormone (ADH) </li></ul><ul><ul><li>Enhances water reabsorption in the kidneys </li></ul></ul>
  92. 92. Anterior Pituitary Hormones <ul><li>The anterior pituitary </li></ul><ul><ul><li>Produces both tropic and nontropic hormones </li></ul></ul>
  93. 93. Tropic Hormones <ul><li>The four strictly tropic hormones are </li></ul><ul><ul><li>Follicle-stimulating hormone (FSH) </li></ul></ul><ul><ul><li>Luteinizing hormone (LH) </li></ul></ul><ul><ul><li>Thyroid-stimulating hormone (TSH) </li></ul></ul><ul><ul><li>Adrenocorticotropic hormone (ACTH) </li></ul></ul>
  94. 94. <ul><li>Each tropic hormone acts on its target endocrine tissue </li></ul><ul><ul><li>To stimulate release of hormone(s) with direct metabolic or developmental effects </li></ul></ul>
  95. 95. Nontropic Hormones <ul><li>The nontropic hormones produced by the anterior pituitary include </li></ul><ul><ul><li>Prolactin </li></ul></ul><ul><ul><li>Melanocyte-stimulating hormone (MSH) </li></ul></ul><ul><ul><li> -endorphin </li></ul></ul>
  96. 96. <ul><li>Prolactin stimulates lactation in mammals </li></ul><ul><ul><li>But has diverse effects in different vertebrates </li></ul></ul><ul><li>MSH influences skin pigmentation in some vertebrates </li></ul><ul><ul><li>And fat metabolism in mammals </li></ul></ul><ul><li>Endorphins </li></ul><ul><ul><li>Inhibit the sensation of pain </li></ul></ul>
  97. 97. Growth Hormone <ul><li>Growth hormone (GH) </li></ul><ul><ul><li>Promotes growth directly and has diverse metabolic effects </li></ul></ul><ul><ul><li>Stimulates the production of growth factors by other tissues </li></ul></ul>
  98. 98. <ul><li>Concept 45.4: Nonpituitary hormones help regulate metabolism, homeostasis, development, and behavior </li></ul><ul><li>Many nonpituitary hormones </li></ul><ul><ul><li>Regulate various functions in the body </li></ul></ul>
  99. 99. Thyroid Hormones <ul><li>The thyroid gland </li></ul><ul><ul><li>Consists of two lobes located on the ventral surface of the trachea </li></ul></ul><ul><ul><li>Produces two iodine-containing hormones, triiodothyronine (T 3 ) and thyroxine (T 4 ) </li></ul></ul>
  100. 100. <ul><li>The hypothalamus and anterior pituitary </li></ul><ul><ul><li>Control the secretion of thyroid hormones through two negative feedback loops </li></ul></ul>Figure 45.9 Hypothalamus Anterior pituitary TSH Thyroid T 3 T 4 +
  101. 101. <ul><li>The thyroid hormones </li></ul><ul><ul><li>Play crucial roles in stimulating metabolism and influencing development and maturation </li></ul></ul>
  102. 102. <ul><li>Hyperthyroidism, excessive secretion of thyroid hormones </li></ul><ul><ul><li>Can cause Graves’ disease in humans </li></ul></ul>Figure 45.10
  103. 103. <ul><li>The thyroid gland also produces calcitonin </li></ul><ul><ul><li>Which functions in calcium homeostasis </li></ul></ul>
  104. 104. Parathyroid Hormone and Calcitonin: Control of Blood Calcium <ul><li>Two antagonistic hormones, parathyroid hormone (PTH) and calcitonin </li></ul><ul><ul><li>Play the major role in calcium (Ca 2+ ) homeostasis in mammals </li></ul></ul>Calcitonin Thyroid gland releases calcitonin. Stimulates Ca 2+ deposition in bones Reduces Ca 2+ uptake in kidneys STIMULUS: Rising blood Ca 2+ level Blood Ca 2+ level declines to set point Homeostasis: Blood Ca 2+ level (about 10 mg/100 mL) Blood Ca 2+ level rises to set point STIMULUS: Falling blood Ca 2+ level Stimulates Ca 2+ release from bones Parathyroid gland Increases Ca 2+ uptake in intestines Active vitamin D Stimulates Ca 2+ uptake in kidneys PTH Figure 45.11
  105. 105. <ul><li>Calcitonin, secreted by the thyroid gland </li></ul><ul><ul><li>Stimulates Ca 2+ deposition in the bones and secretion by the kidneys, thus lowering blood Ca 2+ levels </li></ul></ul><ul><li>PTH, secreted by the parathyroid glands </li></ul><ul><ul><li>Has the opposite effects on the bones and kidneys, and therefore raises Ca 2+ levels </li></ul></ul><ul><ul><li>Also has an indirect effect, stimulating the kidneys to activate vitamin D, which promotes intestinal uptake of Ca 2+ from food </li></ul></ul>
  106. 106. Insulin and Glucagon: Control of Blood Glucose <ul><li>Two types of cells in the pancreas </li></ul><ul><ul><li>Secrete insulin and glucagon, antagonistic hormones that help maintain glucose homeostasis and are found in clusters in the islets of Langerhans </li></ul></ul>
  107. 107. <ul><li>Glucagon </li></ul><ul><ul><li>Is produced by alpha cells </li></ul></ul><ul><li>Insulin </li></ul><ul><ul><li>Is produced by beta cells </li></ul></ul>
  108. 108. <ul><li>Maintenance of glucose homeostasis </li></ul>Beta cells of pancreas are stimulated to release insulin into the blood. Insulin Liver takes up glucose and stores it as glycogen. Body cells take up more glucose. Blood glucose level declines to set point; stimulus for insulin release diminishes. STIMULUS: Rising blood glucose level (for instance, after eating a carbohydrate- rich meal) Homeostasis: Blood glucose level (about 90 mg/100 mL) Blood glucose level rises to set point; stimulus for glucagon release diminishes. STIMULUS: Dropping blood glucose level (for instance, after skipping a meal) Alpha cells of pancreas are stimulated to release glucagon into the blood. Liver breaks down glycogen and releases glucose into blood. Glucagon Figure 45.12
  109. 109. Target Tissues for Insulin and Glucagon <ul><li>Insulin reduces blood glucose levels by </li></ul><ul><ul><li>Promoting the cellular uptake of glucose </li></ul></ul><ul><ul><li>Slowing glycogen breakdown in the liver </li></ul></ul><ul><ul><li>Promoting fat storage </li></ul></ul>
  110. 110. <ul><li>Glucagon increases blood glucose levels by </li></ul><ul><ul><li>Stimulating the conversion of glycogen to glucose in the liver </li></ul></ul><ul><ul><li>Stimulating the breakdown of fat and protein into glucose </li></ul></ul>
  111. 111. Diabetes Mellitus <ul><li>Diabetes mellitus, perhaps the best-known endocrine disorder </li></ul><ul><ul><li>Is caused by a deficiency of insulin or a decreased response to insulin in target tissues </li></ul></ul><ul><ul><li>Is marked by elevated blood glucose levels </li></ul></ul>
  112. 112. <ul><li>Type I diabetes mellitus (insulin-dependent diabetes) </li></ul><ul><ul><li>Is an autoimmune disorder in which the immune system destroys the beta cells of the pancreas </li></ul></ul><ul><li>Type II diabetes mellitus (non-insulin-dependent diabetes) </li></ul><ul><ul><li>Is characterized either by a deficiency of insulin or, more commonly, by reduced responsiveness of target cells due to some change in insulin receptors </li></ul></ul>
  113. 113. Adrenal Hormones: Response to Stress <ul><li>The adrenal glands </li></ul><ul><ul><li>Are adjacent to the kidneys </li></ul></ul><ul><ul><li>Are actually made up of two glands: the adrenal medulla and the adrenal cortex </li></ul></ul>
  114. 114. Catecholamines from the Adrenal Medulla <ul><li>The adrenal medulla secretes epinephrine and norepinephrine </li></ul><ul><ul><li>Hormones which are members of a class of compounds called catecholamines </li></ul></ul>
  115. 115. <ul><li>These hormones </li></ul><ul><ul><li>Are secreted in response to stress-activated impulses from the nervous system </li></ul></ul><ul><ul><li>Mediate various fight-or-flight responses </li></ul></ul>
  116. 116. Stress Hormones from the Adrenal Cortex <ul><li>Hormones from the adrenal cortex </li></ul><ul><ul><li>Also function in the body’s response to stress </li></ul></ul><ul><ul><li>Fall into three classes of steroid hormones </li></ul></ul>
  117. 117. <ul><li>Glucocorticoids, such as cortisol </li></ul><ul><ul><li>Influence glucose metabolism and the immune system </li></ul></ul><ul><li>Mineralocorticoids, such as aldosterone </li></ul><ul><ul><li>Affect salt and water balance </li></ul></ul><ul><li>Sex hormones </li></ul><ul><ul><li>Are produced in small amounts </li></ul></ul>
  118. 118. <ul><li>Stress and the adrenal gland </li></ul>Spinal cord (cross section) Nerve signals Nerve cell Releasing hormone Stress Hypothalamus Anterior pituitary Blood vessel ACTH Adrenal gland Kidney Adrenal medulla secretes epinephrine and norepinephrine. Adrenal cortex secretes mineralocorticoids and glucocorticoids. Effects of epinephrine and norepinephrine: 1. Glycogen broken down to glucose; increased blood glucose 2. Increased blood pressure 3. Increased breathing rate 4. Increased metabolic rate 5. Change in blood flow patterns, leading to increased alertness and decreased digestive and kidney activity Effects of mineralocorticoids: 1. Retention of sodium ions and water by kidneys 2. Increased blood volume and blood pressure Effects of glucocorticoids: 1. Proteins and fats broken down and converted to glucose, leading to increased blood glucose 2. Immune system may be suppressed (b) Long-term stress response (a) Short-term stress response Nerve cell Figure 45.13a,b
  119. 119. Gonadal Sex Hormones <ul><li>The gonads—testes and ovaries </li></ul><ul><ul><li>Produce most of the body’s sex hormones: androgens, estrogens, and progestins </li></ul></ul>
  120. 120. <ul><li>The testes primarily synthesize androgens, the main one being testosterone </li></ul><ul><ul><li>Which stimulate the development and maintenance of the male reproductive system </li></ul></ul>
  121. 121. <ul><li>Testosterone causes an increase in muscle and bone mass </li></ul><ul><ul><li>And is often taken as a supplement to cause muscle growth, which carries many health risks </li></ul></ul>Figure 45.14
  122. 122. <ul><li>Estrogens, the most important of which is estradiol </li></ul><ul><ul><li>Are responsible for the maintenance of the female reproductive system and the development of female secondary sex characteristics </li></ul></ul><ul><li>In mammals, progestins, which include progesterone </li></ul><ul><ul><li>Are primarily involved in preparing and maintaining the uterus </li></ul></ul>
  123. 123. Melatonin and Biorhythms <ul><li>The pineal gland, located within the brain </li></ul><ul><ul><li>Secretes melatonin </li></ul></ul>
  124. 124. <ul><li>Release of melatonin </li></ul><ul><ul><li>Is controlled by light/dark cycles </li></ul></ul><ul><li>The primary functions of melatonin </li></ul><ul><ul><li>Appear to be related to biological rhythms associated with reproduction </li></ul></ul>
  125. 125. <ul><li>Concept 45.5: Invertebrate regulatory systems also involve endocrine and nervous system interactions </li></ul><ul><li>Diverse hormones </li></ul><ul><ul><li>Regulate different aspects of homeostasis in invertebrates </li></ul></ul>
  126. 126. <ul><li>In insects </li></ul><ul><ul><li>Molting and development are controlled by three main hormones </li></ul></ul>Figure 45.15 Brain Neurosecretory cells Corpus cardiacum Corpus allatum EARLY LARVA LATER LARVA PUPA ADULT Prothoracic gland Ecdysone Brain hormone (BH) Juvenile hormone (JH) Low JH Neurosecretory cells in the brain produce brain hormone (BH), which is stored in the corpora cardiaca (singular, corpus cardiacum ) until release. 1 BH signals its main target organ, the prothoracic gland, to produce the hormone ecdysone. 2 Ecdysone secretion from the prothoracic gland is episodic, with each release stimulating a molt. 3 Juvenile hormone (JH), secreted by the corpora allata, determines the result of the molt. At relatively high concen- trations of JH, ecdysone-stimulated molting produces another larval stage. JH suppresses metamorphosis. But when levels of JH fall below a certain concentration, a pupa forms at the next ecdysone-induced molt. The adult insect emerges from the pupa. 4
  127. 127. <ul><li>Brain hormone </li></ul><ul><ul><li>Is produced by neurosecretory cells </li></ul></ul><ul><ul><li>Stimulates the release of ecdysone from the prothoracic glands </li></ul></ul>
  128. 128. <ul><li>Ecdysone </li></ul><ul><ul><li>Promotes molting and the development of adult characteristics </li></ul></ul><ul><li>Juvenile hormone </li></ul><ul><ul><li>Promotes the retention of larval characteristics </li></ul></ul>