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Chapter 22

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

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Chapter 22

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

  2. 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.

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

  4. Brain Controls Food Intake

  5. 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).

  6. 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)

  7. Energy Storage • Glycogen in liver and muscle • Fat

  8. 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

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

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

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

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

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

  14. Metabolism Summary of biochemical pathways for energy production Glycogen Glucose Glucose 6–phosphate Liver only Cytoplasm G L Y C O L Y S I S 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 Some amino acids NH3 ATP + H2O O2 Figure 22-3

  15. Metabolism Push-pull control of metabolism Figure 22-4

  16. Metabolism

  17. Transport and Fate of Dietary Fats Figure 22-5

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

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

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

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

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

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

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

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

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

  27. Homeostatic Control Figure 22-9b

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

  29. Homeostatic Control

  30. 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

  31. Homeostatic Control

  32. 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

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

  34. Homeostatic Control

  35. Endocrine Response to Hypoglycemia Figure 22-15

  36. 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

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

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

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

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

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

  42. 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

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

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

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

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