1. © Cengage Learning 2016 Homeostasis and Motivation Chapter 9

2. © Cengage Learning 2016 Homeostasis: steady internal balance or equilibrium Regulatory systems actively defend certain values, or set points –Temperature –Fluid levels –Body weight Motivation: activates and directs behavior toward a goal Homeostasis and Motivation

3. © Cengage Learning 2016 Involves all of the major features of a homeostatic system –A precisely defined set point –Mechanisms for detecting deviations away from the set point –Internal and behavioral elements designed to regain the set point. Regulating Body Temperature

4. © Cengage Learning 2016 Set Points

5. © Cengage Learning 2016 Two solutions for maintaining internal temperature in animals –Endotherms: internal metabolic activity –Ectotherms: external factors, such as sunlight or warm surfaces Adaptations Maintain Temperature

6. © Cengage Learning 2016 Influenced by surface-to-volume ratio –The larger the volume the more heat is produced –Heat is lost as a function of surface area –Smaller animals have more surface area relative to volume and thus lose heat more easily Adaptations Maintain Temperature (cont’d.)

7. © Cengage Learning 2016 Surface-to-Volume Ratios Affect Temperature Regulation

8. © Cengage Learning 2016 Adaptations to Climate Occur within Species

9. © Cengage Learning 2016 Ectotherms are more dependent on behavioral devices Endotherms and ectotherms change in body position, colors, fur/clothing, and use shelter Social animals huddle to maintain body heat Behavioral Responses to Heat and Cold

10. © Cengage Learning 2016 Automatic internal response to deviations in temperature –Responses to lower temperatures Shiver; blood vessels constrict Thyroid hormone increases to boost metabolic rate Newborn animals increase activity of brown fat cells –Responses to higher temperatures Perspiration, licking, panting Blood vessels dilate near skin surface Endothermic Responses to Heat and Cold

11. © Cengage Learning 2016 Raynaud’s Disease Produces an Extreme Reaction to Cold

12. © Cengage Learning 2016 Hot flashes during menopause are a result of decreasing estrogen Fever is effective in fighting disease Heat stroke (hyperthermia) occurs when compensating mechanisms fail Serotonin syndrome Hypothermia Deviations in Human Core Temperature

13. © Cengage Learning 2016 Heat Stroke

14. © Cengage Learning 2016 Structural hierarchy from spinal cord, through the brainstem to the hypothalamus Preoptic area (POA) of hypothalamus coordinates thermoreceptors with responses (panting, sweating) Brain Mechanisms for Temperature Regulation

15. © Cengage Learning 2016 The Hypothalamus Controls Temperature Regulation

16. © Cengage Learning 2016 Pyrogens Reset the Temperature Set Point in Fever

17. © Cengage Learning 2016 Maintaining appropriate fluid levels is essential to survival Solutes are molecules that have been dissolved in a fluid A solution is the fluid that contains the solutes An electrolyte is when solutes break into ions when dissolved Thirst: Regulating the Body’s Fluid Levels

18. © Cengage Learning 2016 Three major compartments –Extracellular fluid: higher concentrations of Na and Cl Blood Supply Cerebrospinal –Intracellular fluid: higher concentrations of K –Interstitial fluid Intracellular and Extracellular Fluid Compartments

19. © Cengage Learning 2016 The Body’s Fluids Are Held in Three Compartments

20. © Cengage Learning 2016 Water moves from an area of lower solute concentration to an area of higher solute concentration –Isotonic solutions have equal concentrations of solutes –Hypotonic solutions have a lower concentration of solutes compared to a reference solution –Hypertonic solutions have a higher concentration of solutes compared to a reference solution Osmosis Causes Water to Move

21. © Cengage Learning 2016 Osmosis Causes Water to Move

22. © Cengage Learning 2016 Excrete excess water and sodium Filter blood of purities using nephrons Send impurities to bladder for excretion Return filtered blood to circulation The Kidneys

23. © Cengage Learning 2016 A result of osmotic and hypovolemic thirst Mechanisms of osmotic thirst –Drop in the intracellular fluid volume –Osmoreceptors located in the brain Mechanisms of hypovolemic thirst –Drop in blood volume –Baroreceptors measure blood pressure –Receptors in the heart and kidneys The Sensation of Thirst

24. © Cengage Learning 2016 Sources of Typical Daily Fluid Loss and Intake in Humans

25. © Cengage Learning 2016 Detecting Osmotic Thirst

26. © Cengage Learning 2016 Antidiuretic hormone (ADH) or vasopressin –Urine production decreased –Kidneys secrete renin, which leads to increased angiotensis II production; aids in maintaining blood pressure –Adrenal glands secrete aldosterone, which signals the kidneys to retain sodium Responding to Thirst

27. © Cengage Learning 2016 Antidiuretic Hormone Begins a Sequence of Events Leading to Fluid Conservation

28. © Cengage Learning 2016 Angiotensin II acts on subfornical organ (SFO) The SFO communicates with the median preoptic nucleus, which receives input from the nucleus of the solitary tract (NST) The NST receives input from baroreceptors and osmoreceptors Stimulation of the zona incerta stimulates drinking Initiation of Drinking

29. © Cengage Learning 2016 Initiation of Drinking

30. © Cengage Learning 2016 Fluid receptors in mouth, throat, digestive system Hyponatremia is a dangerous condition in which sodium levels drop to 10% or more below normal Cessation of Drinking

31. © Cengage Learning 2016 Extreme Sports and the Risk of Hyponatremia

32. © Cengage Learning 2016 We eat to obtain the energy and specific nutrients needed by our bodies We also eat for pleasure Complex cultural and psychological factors can overwhelm the body’s natural regulatory mechanisms, leading to different patterns of disordered eating Hunger: Regulating the Body’s Supply of Nutrients

33. © Cengage Learning 2016 Cultural differences in food intake can have their roots in biology –Inuit: mostly meat –Asian: lactose intolerance –Scandinavia and Middle East: lactose tolerance –Food preferences learned in utero The Environment and Eating

34. © Cengage Learning 2016 Lactose Tolerance Correlates with Use of Dairy Products

35. © Cengage Learning 2016 Foods are broken down into usable chemicals by the digestive tract During digestion, fats, proteins, and carbohydrates are metabolized Excess glucose is stored as glycogen in the liver Excess fat is stored in adipose tissue The Process of Digestion

36. © Cengage Learning 2016 The Major Structures of the Digestive Tract

37. © Cengage Learning 2016 Energy from glucose is regulated in large part by two pancreatic hormones, glucagon and insulin Glucagon converts stored glycogen back into glucose Insulin helps store glucose as glycogen and assists in moving glucose from the blood supply into body cells The Pancreatic Hormones

38. © Cengage Learning 2016 Disturbances in the activity of the pancreatic hormones have serious health consequences –Type 1 diabetes mellitus Disorder of insulin production Diagnosed in childhood or early adulthood –Type 2 diabetes mellitus Disorder of insulin recognition by cells Adult onset Obesity is a major risk factor The Pancreatic Hormones (cont’d.)

39. © Cengage Learning 2016 Insulin Release is Reduced in Type 2 Diabetes

40. © Cengage Learning 2016 Triggered by low available glucose levels and low fat levels Glucoreceptors assess glucose levels and communicate with areas of the brain that initiate feeding behavior. Receptors for glucose and fatty acids located in the liver influences release of insulin The Initiation of Eating: Receptors

41. © Cengage Learning 2016 Lateral hypothalamus (LH) participates in the initiation of eating Leptin released by adipose cells when fat stores are low Low leptin and insulin stimulates release of neuropeptide Y and agouti-related protein from the arcuate nucleus –Release of TSH and ACTH The Initiation of Eating: Brain Mechanisms

42. © Cengage Learning 2016 Melanin-concentrating hormone (MCH) interacts with leptin to regulate the initiation of feeding Ghrelin and orexins stimulate feeding behavior The Initiation of Eating: Brain Mechanisms (cont’d.)

43. © Cengage Learning 2016 Hypothalamic Nuclei Participate in the Control of Hunger

44. © Cengage Learning 2016 Neurochemical Correlates of Hunger and Satiety

45. © Cengage Learning 2016 Assessing satiety –Stomach fullness, intestines, CCK Brain mechanisms for satiety –Ventromedial hypothalamus (VMH) –Paraventricular nucleus (PVN) –Nucleus of the solitary tract (NST) Satiety

46. © Cengage Learning 2016 Neurochemicals and satiety –Leptin found in blood when body fat levels high –High leptin levels stimulate αMSH and CART to inhibit feeding Satiety (cont’d.)

47. © Cengage Learning 2016 Weight Gain in VMH Syndrome

48. © Cengage Learning 2016 Our bodies evolved to survive with a limited, difficult-to-obtain food supply Maintaining a healthy body weight can be difficult in modern cultures in which food is often amply available Healthy and Disordered Eating

49. © Cengage Learning 2016 Body mass index (BMI) –Medical standard for determining ideal weight –A BMI of between 18.5 and 24.9 is considered healthy Body fat measurement –Submersion test Defining Normal Weight

50. © Cengage Learning 2016 Body Mass Index Provides a Measure of Ideal Weight

51. © Cengage Learning 2016 The Submersion Test of Body Composition

52. © Cengage Learning 2016 Contributions to obesity –Acceptance of large body size –Stress and high fat diet increase release of NPY and appetite –Genetics –Type of bacteria in the gut Obesity

53. © Cengage Learning 2016 Interventions for obesity –Lifestyle changes that can be sustained –Weight loss diets reduce calories consumed –Medications Orlistat Orcaserin Phentermine-topiramate –Surgical interventions Obesity (cont’d.)

54. © Cengage Learning 2016 Anorexia nervosa –Very low body weight –Distorted body image Bulimia nervosa –Cyclical pattern of binge eating and purging Binge-eating disorder –Binge-eating without compensatory purging Disordered Eating

55. © Cengage Learning 2016 Causes for anorexia and bulimia –Media and social perspectives on beauty –Genetic factors may influence personality traits that may increase vulnerability to eating disorders –Once established, biological factors (e.g., CART levels) help to maintain the eating disorder –Addictive processes Causes of Disordered Eating

56. © Cengage Learning 2016 Treatment for eating disorders –No medication effective in alleviating anorexia nervosa –Emergency hospitalization –Antidepressants –Cognitive behavioral therapy Disordered Eating (cont’d.)

57. © Cengage Learning 2016 Anorexia and Fashion Models

58. © Cengage Learning 2016 External Influences Can Change Cultural Ideals of Beauty