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PRINCIPLES OF HUMAN PHYSIOLOGY 21 THIRD EDITION Cindy L. Stanfield | William J. Germann The Endocrine System: Regulation of Energy Metabolism and Growth Part A PowerPoint® Lecture Slides prepared by W.H. Preston, College of the Sequoias Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Anabolism • Molecules used in generating energy also used in synthesis of large molecules • Whether used for energy or synthesis depends on body needs • Mechanisms exist to regulate pathways Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Energy Intake, Utilization, and Storage • Following intake, nutrients can be • Catabolized for energy • Substrates for new molecules • Stored for energy (glycogen and fat) Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Uptake, Utilization, and Storage of Energy in Carbohydrates • Absorbed carbohydrates • Monosaccharides • Circulating in blood • Glucose • Usable carbohydrates Copyright • Glucose energy • Glycogen stores energy • Polysaccharides membranes © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Uptake, Utilization, and Storage of Energy in Proteins • Absorbed forms • Tripeptides • Dipeptides • Amino acids • Circulating in blood • Amino acids • Usable form Copyright • Amino acids proteins • Amino acids energy © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Uptake, Utilization, and Storage of Energy in Lipids • Absorbed lipids • Triglycerides • Circulating in blood in lipoproteins • Fatty acids • Monoglycerides • Usable lipids Copyright • Fatty acids energy • Triglycerides store energy • Steroids and phospholipids © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Biomolecules Liver 2 NH3 Glucose Amino acids Urea Lipoproteins Monoglyceride Fatty acids + 1 NH3 1 LPL 1 6 2 2 5 4 4 CO2 + H2O + energy 3 2 Glycogen Protein 3 3 CO2 + H2O + energy 4 + Fatty Glycerol acids 5 Other metabolism (a) Carbohydrates CO2 + H2O + NH3 + energy (b) Proteins Triglyceride (c) Lipids Figure 21.1 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Delivery of Lipids to Cells • Lipids transported in blood • From GI to liver, adipose tissue and other cells in chylomicrons • From liver to body cells in VLDLs • Lipoprotein lipase located on inner surface of capillaries Copyright • Triglycerides monoglyceride + 2 Fatty Acids • Fatty acids diffuse into cells • Monoglycerides go to liver for further metabolism © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Summary of Biomolecules Table 21.1 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Forms of Energy Figure 21.2 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Basal Metabolic Rate • Basal metabolic rate (BMR) = rate of energy expenditure of a person awake, resting, lying down, and fasted for 12 hours • Represents minimum energy expenditure necessary to maintain body functions • Metabolic rate increases with increases in activity Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Energy Balance Varies During Absorptive and Postabsorptive States • Energy balance not continuous • Energy input intermittent • Absorptive state • 3–4 hours following meal • Nutrients in bloodstream plentiful from absorption • Postabsorptive Copyright • Between meals • Energy stores must be mobilized © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Absorptive State • Energy input > output as nutrients absorbed • Glucose = primary energy source for cell • Excess nutrients taken up will be stored Copyright • Liver and muscle store glycogen • Adipose tissue stores triglycerides © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Postabsorptive State • Energy input < output • Glucose spared for nervous system • Other tissues use fatty acids or other sources for energy • Stored nutrients broken down and mobilized Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Absorptive State Reactions Absorption of small nutrients Blood Glucose Fatty acids Amino acids Most body cells Liver and muscle Liver and adipose tissue Liver Muscle and other cells CO2 + H2O + energy Glycogen Fatty acids Protein Glycerol Fatty acids Triglycerides Figure 21.3 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Energy Stores • Note: Glycogen stores in liver and muscle = 500 grams • Note: Triglyceride stores in adipose tissue is unlimited Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Table 21.2 Postabsorptive State Reactions Stored macromolecules Muscle and other cells Adipose tissue Triglycerides Liver Muscle Glycogen Glycogen Proteins Amino acids Fatty acids Glycerol Lactate, pyruvate Liver Glucose Ketones Blood Amino acids Fatty acids Ketones Non-nervous tissue CO2 + NH3 + H2O + energy Glucose Nervous tissue CO2 + H2O + energy Figure 21.4 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Regulation of Absorptive and Postabsorptive Metabolism • Hormonal regulation • Insulin = hormone of absorptive state • Glucagon = hormone of postabsorptive state • Other less important regulators Copyright • Epinephrine • Sympathetic nervous system © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Insulin • Peptide hormone secreted from beta cells of pancreas islets of Langerhans • Promotes synthesis of energy storage molecules (anabolic reactions) • Promotes glucose uptake by body cells Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Insulin Secretion • Secretion increased during absorptive state • Increase glucose in plasma • Increase [amino acids] in plasma • Parasympathetic nervous system • Glucose-dependent insulinotropic peptide (GIP) • Secretion decreased during postabsorptive state Copyright • Sympathetic nervous system activity • Epinephrine © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Actions of Insulin Figure 21.5 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Glucagon • Peptide hormone secreted from alpha cells of pancreas islets of Langerhans • Promotes breakdown of energy storage molecules (catabolic reactions) • Promotes glucose sparing for nervous system by diverting body cells to utilizing other sources of energy Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Glucagon Secretion • Secretion increased during postabsorptive state • Sympathetic nervous system • Epinephrine • Secretion decreased during absorptive state • Copyright Increase glucose in plasma © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Actions of Glucagon Figure 21.6 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Insulin and Glucagon Release Table 21.3 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Regulation of Blood Glucose Levels • Normal blood glucose = 70–100 mg/dL • Hyperglycemia = glucose > 140 mg/dL • Hypoglycemia = glucose < 60 mg/dL • Blood glucose levels maintained primarily by actions of insulin and glucagon Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Glucose Regulation Via Insulin Plasma glucose Beta cells in pancreas Negative feedback Insulin secretion Most tissues Glucose uptake into cells Liver and muscle Glycogen synthesis Liver Gluconeogenesis Glycogenolysis Plasma glucose (a) Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 21.7a Glucose Regulation Via Glucagon Plasma glucose Negative feedback Alpha cells in pancreas Glucagon secretion Liver Gluconeogenesis Adipose tissue Lipolysis Glycogenolysis Plasma fatty acids Plasma glucose (b) Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Glucose spared Figure 21.7b Glucose Regulation Via Glucagon Plasma glucose Alpha cells in pancreas Glucagon secretion Liver Gluconeogenesis Adipose tissue Lipolysis Glycogenolysis Plasma fatty acids Plasma glucose (b) Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Glucose spared Figure 21.7b, step 10