Chapter 22 Energy balance Metabolism Homeostatic control of metabolism Regulation of body temperature

Brain Controls Food Intake Hypothalamus has two centers that regulate food intake: Feeding center: Tonically active Satiety center: Inhibits the feeding center Glucostatic theory: When blood glucose level decreases, the satiety center is suppressed. Lipostatic theory: a signal from the body’s fat stores to the brain modulates eating behavior to maintain certain body weight.

Brain Controls Food Intake Role of peptides in regulation of food intake Figure 22-1

Brain Controls Food Intake

Energy Balance Energy input equals energy output Energy output = work + heat Transport work: moving molecules across cell membrane Mechanical work: movement Chemical work: used for growth, maintenance, and storage of information and energy (ATP bonds, glycogen bonds).

Metabolic Rate: Individual’s Energy Expenditure Age and gender Amount of lean muscle mass Activity level Diet Hormones Genetics Energy intake and level of physical activity Measure of Metabolic Rate: Rate of oxygen consumption and/or carbon dioxide production Basal Metabolic Rate: Lowest metabolic rate (for example: rate during rest)

Energy Storage Glycogen in liver and muscle Fat

Metabolism Extract energy from nutrients Use energy for work and synthesis Store excess energy Anabolic (smaller to larger molecules) versus catabolic Fed (just ate) versus fasted state

Summary of Metabolism Figure 22-2 Carbohydrates Fats Free fatty acids + glycerol Fat stores Glucose Excess glucose Glycogen Amino acids Proteins DIET Lipogenesis Brain metabolism Range of normal plasma glucose Gluconeogenesis Body protein Glycogenolysis Glycogenesis Protein synthesis Metabolism in most tissues Free fatty acid pool Urine Excess nutrients Lipolysis Glucose pool Amino acid pool Figure 22-2

Summary of Metabolism Figure 22-2 (1 of 4) DIET Carbohydrates Fat stores Glucose Excess glucose Glycogen DIET Lipogenesis Brain metabolism Range of normal plasma glucose Glycogenolysis Glycogenesis Metabolism in most tissues Urine Glucose pool Figure 22-2 (1 of 4)

Summary of Metabolism Figure 22-2 (2 of 4) DIET Fats Free fatty acids + glycerol Fat stores DIET Metabolism in most tissues Free fatty acid pool Excess nutrients Lipogenesis Lipolysis Figure 22-2 (2 of 4)

Summary of Metabolism Figure 22-2 (3 of 4) DIET Proteins Protein Amino acids Proteins DIET Range of normal plasma glucose Gluconeogenesis Body protein Protein synthesis Glucose pool Amino acid pool Figure 22-2 (3 of 4)

Summary of Metabolism Figure 22-2 (4 of 4) Carbohydrates Fats Free fatty acids + glycerol Fat stores Glucose Excess glucose Glycogen Amino acids Proteins DIET Lipogenesis Brain metabolism Range of normal plasma glucose Gluconeogenesis Body protein Glycogenolysis Glycogenesis Protein synthesis Metabolism in most tissues Free fatty acid pool Urine Excess nutrients Lipolysis Glucose pool Amino acid pool Figure 22-2 (4 of 4)

Metabolism Summary of biochemical pathways for energy production Glycogen Glucose Glucose 6–phosphate Liver only G L Y C O S I Cytoplasm Glycerol 2 ATP NH3 Anaerobic conditions Some amino acids Pyruvate Lactate Aerobic conditions Pyruvate Mitochondria Fatty acids Acetyl CoA CoA Ketone bodies (in liver) CO2 Citric acid cycle 2 ATP Electron transport system NH3 Some amino acids O2 ATP + H2O Figure 22-3

Metabolism Push-pull control of metabolism Figure 22-4

Metabolism

Transport and Fate of Dietary Fats Figure 22-5

Metabolism The relationship between LDL-C and risk of developing coronary heart disease Figure 22-6

Fasted-State Metabolism Liver glycogen stores Energy production Energy production Free fatty acids Glycerol Amino Ketone bodies Glucose Adipose lipids become free fatty acids and glycerol that enter blood. Muscle glycogen can be used for energy. Muscles also use fatty acids and break down their proteins to amino acids that enter the blood. Liver glycogen becomes glucose. Brain can use only glucose and ketones for energy. or Triglyceride stores Glycogen Pyruvate Lactate Proteins b-oxidation Glycogenolysis Gluconeogenesis Figure 22-7

Fasted-State Metabolism Liver glycogen stores Energy production Energy production Glucose Liver glycogen becomes glucose. Glycogenolysis Figure 22-7 (1 of 5)

Fasted-State Metabolism Liver glycogen stores Energy production Energy production Glucose Liver glycogen becomes glucose. or Glycogen Pyruvate Lactate Glycogenolysis Gluconeogenesis Figure 22-7 (2 of 5)

Fasted-State Metabolism Liver glycogen stores Energy production Energy production Amino acids Glucose Liver glycogen becomes glucose. or Glycogen Pyruvate Lactate Proteins Glycogenolysis Gluconeogenesis Figure 22-7 (3 of 5)

Fasted-State Metabolism Liver glycogen stores Energy production Energy production Free fatty acids Glycerol Amino Glucose Adipose lipids become free fatty acids and glycerol that enter blood. Muscle glycogen can be used for energy. Muscles also use fatty acids and break down their proteins to amino acids that enter the blood. Liver glycogen becomes glucose. or Triglyceride stores Glycogen Pyruvate Lactate Proteins Glycogenolysis Gluconeogenesis Figure 22-7 (4 of 5)

Fasted-State Metabolism Liver glycogen stores Energy production Energy production Free fatty acids Glycerol Amino Ketone bodies Glucose Adipose lipids become free fatty acids and glycerol that enter blood. Muscle glycogen can be used for energy. Muscles also use fatty acids and break down their proteins to amino acids that enter the blood. Liver glycogen becomes glucose. Brain can use only glucose and ketones for energy. or Triglyceride stores Glycogen Pyruvate Lactate Proteins b-oxidation Glycogenolysis Gluconeogenesis Figure 22-7 (5 of 5)

Homeostatic Control Anatomy of the pancreas Figure 22-8b–c

Homeostatic Control Mechanism is controlled by insulin and glucagon, both of which are secreted by the pancreas Figure 22-9a

Homeostatic Control Figure 22-9b

Homeostatic Control Glucose, glucagon, and insulin levels over a 24-hour period Figure 22-10

Homeostatic Control

Insulin Secretion Increased glucose concentrations Increased amino acids concentrations Feedforward effects of GI hormones: GI hormones stimulate release of insulin in anticipation of increased glucose concentration Parasympathetic activity stimulates secretion of insulin Sympathetic activity inhibits secretion of insulin

Homeostatic Control

Insulin Promotes Anabolism Increases glucose transport into most, but not all, insulin-sensitive cells Enhances cellular utilization and storage of glucose Enhances utilization of amino acids Promotes fat synthesis

Homeostatic Control Fed-state metabolism under the influence of insulin promotes glucose metabolism by cells Figure 22-14

Homeostatic Control

Endocrine Response to Hypoglycemia Figure 22-15

Type 2 Diabetes Accounts for 90% of all diabetics Insulin resistance Complications include atherosclerosis, neurological changes, renal failure, and blindness Therapy Diet and physical exercise Drugs

Normal and Abnormal Results of Glucose Tolerance Tests Figure 22-17

Regulation of Body Temperature: Energy Balance in the Body Figure 22-18

Regulation of Body Temperature: Heat Balance in the Body Body temperature is a balance between heat production, gain, and loss Figure 22-19

Regulation of Body Temperature: Thermoregulatory Reflexes Figure 22-20 (1 of 2)

Regulation of Body Temperature: Thermoregulatory Reflexes Figure 22-20 (2 of 2)

Regulation of Body Temperature Alterations in cutaneous blood flow conserve or release heat Sweat contributes to heat loss Heat production Voluntary muscle contraction and normal, metabolic pathways Regulated heat production Shivering versus nonshivering thermogenesis

Regulation of Body Temperature Homeostatic responses to environmental extremes Figure 22-21 (1 of 2)

Regulation of Body Temperature Figure 22-21 (2 of 2)

Regulation of Body Temperature Body’s thermostat can be reset Pathological conditions Hyperthermia Heat exhaustion Heat stroke Malignant hyperthermia Hypothermia