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Chapter Nine

Chapter Nine. Temperature Regulation, Thirst, and Hunger. CHAPTER 9 TEMPERATURE REGULATION, THIRST, AND HUNGER. Homeostasis. Homeostasis: Physiological equilibrium Motivation: Activating and directing behavior Regulation of Body Temperature Set point Mechanisms for detecting deviation

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Chapter Nine

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  1. Chapter Nine Temperature Regulation, Thirst, and Hunger

  2. CHAPTER 9TEMPERATURE REGULATION, THIRST, AND HUNGER

  3. Homeostasis • Homeostasis: Physiological equilibrium • Motivation: Activating and directing behavior • Regulation of Body Temperature • Set point • Mechanisms for detecting deviation • Internal and behavioral elements to regain set point • Adaptations to Temperature • Endotherms • Ectotherms

  4. Figure 9.2 Surface-to-Volume Ratios Affect Temperature Regulation

  5. Homeostasis • Behavioral Responses to Heat and Cold • Ectotherms more dependent on behavioral devices • Changes in position, weight, color and composition of fur • Endothermic Responses to Heat and Cold • Automatic internal response to deviations in temperature • Responses to lower temperatures • Shiver • Blood vessels constrict • Thyroid hormone increase • Responses to lower temperatures • Perspiration, licking • Blood vessels dilate

  6. Homeostasis • Deviations in Human Core Temperature • Fever • Heat stroke (hyperthermia) • Hypothermia • Brain Mechanisms for Temperature Regulation • POA of the hypothalamus, anterior hypothalamus and septum • Temperature Regulation in Infancy • Relatively helpless in adapting to temperature

  7. Figure 9.7 The Hypothalamus Controls Temperature Regulation

  8. Thirst: Regulation of the Body’s Fluid • Intracellular and Extracellular Fluids • Extracellular fluid (33%) • Intracellular fluid (67%) • Osmosis Causes Water to Move • Water moves from an area with lower concentration of solutes to an area with higher concentration • Hypotonic versus hypertonic • The Role of the Kidneys • Excretes excess fluids and sodium

  9. Figure 9.8 The Body’s Fluids Are Held in Three Compartments

  10. Figure 9.9 Osmosis Causes Water to Move

  11. Thirst: Regulation of the Body’s Fluid • The Sensation of Thirst • Occurs as a result of osmotic (drops in the intracellular fluid volume) and hypovolemic (drops in blood volume) thirst • Mechanisms of Osmotic Thirst • Osmoreceptors located in the brain • Organum vasculosum of the lamina terminalis (OVLT) • Mechanisms of Hypovolemic Thirst • Baroreceptors measure blood pressure • Receptors in the heart and kidneys

  12. Table 9.1 Sources of Typical Daily Fluid Loss and Intake in Humans

  13. Figure 9.10 Detecting Osmotic Thirst

  14. Thirst: Regulation of the Body’s Fluid • Hormones, Sodium, and Thirst • Antidiuretic hormone (ADH) or vasopressin • Low blood volume stimulates hunger for sodium • Initiation of Drinking • Begins when angiotensin II acts on subfornical organ (SFO) • Cessation of Drinking • Fluid receptors in mouth, throat, digestive system • Hyponatremia

  15. Figure 9.11 Antidiuretic Hormone Begins a Sequence of Events Leading to Fluid Conservation

  16. Thirst: Regulation of the Body’s Fluid • Thirst and Sports Drinks • Provides more sodium than other beverages, which helps athletes retain fluids and may prevent hyponatremia

  17. Hunger • The Influence of Culture on Food Choices • Learned food preferences begin early in life • The Process of Digestion • Foods are broken down into usable chemicals by the digestive tract • During digestion fats, proteins, and carbohydrates are absorbed into the blood supply and circulated to waiting tissues • The brain uses glucose for energy

  18. Figure 9.13 Lactose Tolerance Correlates with Use of Dairy Products

  19. Figure 9.14 The Major Structures of the Digestive Tract

  20. Hunger • The Pancreatic Hormones • 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 • Type 1 diabetes mellitus • Type 2 diabetes mellitus

  21. Figure 9.15 Insulin Release is Reduced in Type 2 Diabetes

  22. Hunger • The Initiation of Eating • Affected by blood glucose levels and low fat levels • Receptors and Hunger • Glucoreceptors in nucleus of the solitary tract (NST) • Brain Mechanisms for Hunger • Lateral hypothalamus (LH) • Neurochemicals and Hunger • Leptin communicates with neurons in the arcuate nucleus of the hypothalamus (NPY and AgRP) • Ghrelin • Orexins

  23. Figure 9.17 Hypothalamic Nuclei Participate in the Control of Hunger

  24. Hunger • Satiety • Assessing Satiety • Stomach fullness, intestines, CCK • Brain Mechanisms for Satiety • Ventromedial hypothalamus (VMH) • Paraventricular nucleus (PVN) • Nucleus of the solitary tract (NST) • Neurochemicals and Satiety • Leptin found in blood when body fat levels high • αMSH and CART

  25. Figure 9.18 Weight Gain in VMH Syndrome

  26. Figure 9.19 Neurochemical Correlates of Hunger and Satiety

  27. Obesity and Eating Disorders • Defining Normal Weight • Body mass index (BMI) • Body fat measurement • Obesity • Stress and high fat diet increase release of NPY and appetite • Defending the Obese Weight • Diet reduces size of individual fat cells but not the number of fat cells • Interventions for obesity • Weight loss diets reduce calories consumed

  28. Figure 9.20 Body Mass Index Provides a Measure of Ideal Weight

  29. Figure 9.21 The Submersion Test of Body Composition

  30. Obesity and Eating Disorders • Anorexia Nervosa • Maintain 85% or less of normal weight • Bulimia Nervosa • Cyclical pattern of binge eating and purging • Causes for Anorexia and Bulimia • Media images • Biological factors • Addictive processes • Treatment for Eating Disorders • Antidepressants, cognitive behavioral therapy

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