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Chapter 22
 Energy balance
 Metabolism
 Homeostatic control of metabolism
 Regulation of body temperature
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
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.
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Brain Controls Food Intake
Role of peptides in regulation of food intake
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 22-1
Brain Controls Food Intake
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
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).
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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)
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Energy Storage
 Glycogen in liver and muscle
 Fat
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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
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Summary of Metabolism
DIET
Carbohydrates
Fats
Proteins
Lipogenesis
Free fatty acids + glycerol
Fat
stores
Glucose
Glycogenesis
Lipogenesis
Excess glucose
Glycogen
stores
Lipolysis Urine
Protein
synthesis
Body
protein
Glycogenolysis
Glucose pool
Free fatty
acid pool
Excess nutrients
Amino
acids
Metabolism in
most tissues
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Gluconeogenesis
Range of normal
plasma glucose
Amino acid
pool
Brain
metabolism
Figure 22-2
Summary of Metabolism
DIET
Carbohydrates
Fat
stores
Glucose
Glycogenesis
Lipogenesis
Excess glucose
Glycogen
stores
Urine
Glycogenolysis
Glucose pool
Range of normal
plasma glucose
Metabolism in
most tissues
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Brain
metabolism
Figure 22-2 (1 of 4)
Summary of Metabolism
DIET
Fats
Lipogenesis
Free fatty acids + glycerol
Fat
stores
Lipolysis
Free fatty
acid pool
Excess nutrients
Metabolism in
most tissues
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 22-2 (2 of 4)
Summary of Metabolism
DIET
Proteins
Amino
acids
Protein
synthesis
Body
protein
Glucose pool
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Gluconeogenesis
Range of normal
plasma glucose
Amino acid
pool
Figure 22-2 (3 of 4)
Summary of Metabolism
DIET
Carbohydrates
Fats
Proteins
Lipogenesis
Free fatty acids + glycerol
Fat
stores
Glucose
Glycogenesis
Lipogenesis
Excess glucose
Glycogen
stores
Lipolysis Urine
Protein
synthesis
Body
protein
Glycogenolysis
Glucose pool
Free fatty
acid pool
Excess nutrients
Amino
acids
Metabolism in
most tissues
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Gluconeogenesis
Range of normal
plasma glucose
Amino acid
pool
Brain
metabolism
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
L
Y
S
I
S
Glycerol
Some
amino
acids
NH3
Cytoplasm
2 ATP
Anaerobic conditions
Pyruvate
Lactate
Aerobic conditions
Pyruvate
CoA
Electron transport
system
O2
Acetyl CoA
Citric
acid
cycle
NH3
ATP + H2O
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Mitochondria
Fatty
acids
Ketone
bodies
CO2
(in liver)
2 ATP
Some
amino
acids
Figure 22-3
Metabolism
Push-pull control of metabolism
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Figure 22-4
Metabolism
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Transport and Fate of Dietary Fats
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Figure 22-5
Metabolism
The relationship between LDL-C and risk of developing
coronary heart disease
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 22-6
Fasted-State Metabolism
Adipose lipids
become free
fatty acids and
glycerol that
enter blood.
FASTED-STATE METABOLISM
Liver glycogen becomes glucose.
Liver
glycogen
stores
Free fatty
acids
Glycogenolysis
b-oxidation
Triglyceride stores
Free fatty
acids
Glycerol
Gluconeogenesis
Energy
production
Glucose
Ketone
bodies
Energy production
Glycogen
Gluconeogenesis
Proteins
Pyruvate
or
Lactate
Glucose
Ketone
bodies
Energy production
Brain can
use only glucose
and ketones for energy.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Amino
acids
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
Fasted-State Metabolism
FASTED-STATE METABOLISM
Liver glycogen becomes glucose.
Liver
glycogen
stores
Glycogenolysis
Energy
production
Glucose
Glucose
Energy production
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 22-7 (1 of 5)
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
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 22-7 (2 of 5)
Fasted-State Metabolism
FASTED-STATE METABOLISM
Liver glycogen becomes glucose.
Liver
glycogen
stores
Glycogenolysis
Energy
production
Energy production
Glucose
Glycogen
Gluconeogenesis
Proteins
Pyruvate
or
Lactate
Glucose
Amino
acids
Energy production
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 22-7 (3 of 5)
Fasted-State Metabolism
Adipose lipids
become free
fatty acids and
glycerol that
enter blood.
FASTED-STATE METABOLISM
Liver glycogen becomes glucose.
Liver
glycogen
stores
Triglyceride stores
Free fatty
acids
Free fatty
acids
Glycerol
Glycogenolysis
Gluconeogenesis
Energy
production
Energy production
Glucose
Glycogen
Gluconeogenesis
Proteins
Pyruvate
or
Lactate
Glucose
Energy production
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Amino
acids
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)
Fasted-State Metabolism
Adipose lipids
become free
fatty acids and
glycerol that
enter blood.
FASTED-STATE METABOLISM
Liver glycogen becomes glucose.
Liver
glycogen
stores
Free fatty
acids
Glycogenolysis
b-oxidation
Triglyceride stores
Free fatty
acids
Glycerol
Gluconeogenesis
Energy
production
Glucose
Ketone
bodies
Energy production
Glycogen
Gluconeogenesis
Proteins
Pyruvate
or
Lactate
Glucose
Ketone
bodies
Energy production
Brain can
use only glucose
and ketones for energy.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Amino
acids
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 (5 of 5)
Homeostatic Control
Anatomy of the pancreas
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Figure 22-8b–c
Homeostatic Control
Mechanism is controlled by insulin and glucagon, both
of which are secreted by the pancreas
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 22-9a
Homeostatic Control
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Figure 22-9b
Homeostatic Control
Glucose, glucagon, and insulin levels over a 24-hour
period
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Figure 22-10
Homeostatic Control
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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
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Homeostatic Control
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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
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Homeostatic Control
Fed-state metabolism under the influence of insulin
promotes glucose metabolism by cells
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Figure 22-14
Homeostatic Control
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Endocrine Response to Hypoglycemia
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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
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Normal and Abnormal Results
of Glucose Tolerance Tests
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Figure 22-17
Regulation of Body Temperature:
Energy Balance in the Body
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Figure 22-18
Regulation of Body Temperature:
Heat Balance in the Body
Body temperature is a balance between heat production,
gain, and loss
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Figure 22-19
Regulation of Body Temperature:
Thermoregulatory Reflexes
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Figure 22-20 (1 of 2)
Regulation of Body Temperature:
Thermoregulatory Reflexes
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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
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Regulation of Body Temperature
Homeostatic responses to environmental extremes
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Figure 22-21 (1 of 2)
Regulation of Body Temperature
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
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
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings