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Temperature Regulation, Thirst, and Hunger
Chapter Nine Temperature Regulation, Thirst, and Hunger
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CHAPTER 9 TEMPERATURE REGULATION, THIRST, AND HUNGER
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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
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Figure 9.2 Surface-to-Volume Ratios Affect Temperature Regulation
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Behavioral Responses to Heat and Cold
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 Perspiration, licking Blood vessels dilate
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Deviations in Human Core Temperature
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
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Figure 9.7 The Hypothalamus Controls Temperature Regulation
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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
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Figure 9.8 The Body’s Fluids Are Held in Three Compartments
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Figure 9.9 Osmosis Causes Water to Move
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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
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Table 9.1 Sources of Typical Daily Fluid Loss and Intake in Humans
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Figure 9.10 Detecting Osmotic Thirst
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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
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Figure 9.11 Antidiuretic Hormone Begins a Sequence of Events Leading to Fluid Conservation
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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
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The Influence of Culture on Food Choices The Process of Digestion
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
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Figure 9.13 Lactose Tolerance Correlates with Use of Dairy Products
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Figure 9.14 The Major Structures of the Digestive Tract
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The Pancreatic Hormones
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
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Figure 9.15 Insulin Release is Reduced in Type 2 Diabetes
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The Initiation of Eating
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
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Figure 9.17 Hypothalamic Nuclei Participate in the Control of Hunger
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Hunger Satiety Assessing Satiety Brain Mechanisms for 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
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Figure 9.18 Weight Gain in VMH Syndrome
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Figure 9.19 Neurochemical Correlates of Hunger and Satiety
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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
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Figure 9.20 Body Mass Index Provides a Measure of Ideal Weight
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Figure 9.21 The Submersion Test of Body Composition
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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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