Download The Endocrine System: Regulation of Energy Metabolism and Growth

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
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Forms of Energy
Figure 21.2
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© 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
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© 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
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•
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
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© 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
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•
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
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•
Sympathetic nervous system activity
•
Epinephrine
© 2008 Pearson Education, Inc., publishing as Benjamin Cummings.
Actions of Insulin
Figure 21.5
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© 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