chapter22a Metabolism and Energy Balance 1

chapter22a Metabolism and Energy Balance 1 - Chapter 22a...

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Chapter 22a Metabolism and Energy Balance
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About this Chapter Appetite and satiety Energy balance Metabolism Homeostatic control of metabolism Regulation of body temperature
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Appetite and Satiety Food intake is carefully controlled Two competing behavioral states Appetite (or hunger) = desire for food Satiety = sense of fullness (or satisfaction) Hypothalamus contains two key control centers Feeding center Satiety center
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Four Types of Input to the Hypothalamus Neural input from the cerebral cortex Neural input from the limbic system Peptide hormones from the GI tract Adipocytokines from adipose tissue
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Two Theories for Regulation of Food Intake Glucostatic theory Theory proposes that blood glucose levels ultimately control the feeding and satiety centers Lipostatic theory Theory proposes that the level of body fat regulates the feeding and satiety centers Recent discovery of several peptides (especially leptin and neuropeptide Y) seems to support this theory
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Figure 22-1 Peptides Regulate the Feeding Center
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Table 22-1 Many Peptides Alter Food Intake
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Energy Balance - The Key to Weight Control Energy input = energy output Energy output = work  heat Three categories of work done by our cells Membrane transport Mechanical work Chemical work = building molecules, including synthesis of energy storage molecules Short-term energy storage (ATP) Long-term energy storage (glycogen, fat)
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Energy Balance Methods for measuring energy use Direct calorimetry Measures the energy content of food Fat 9 Kcal/g / protein and CHO ~ 4 Kcal/g Indirect calorimetry Estimates metabolic rate as a measure of energy use Oxygen consumption Carbon dioxide production Ratio of CO2 to O2 (RQ or RER)
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Metabolic Rate Basal metabolic rate ( BMR ) is most common measure of metabolic rate Six factors affecting metabolic rate 1 - Age and gender 2 - Amount of lean muscle mass 3 - Activity level 4 - Energy intake (diet) – fat vs protein thermogenesis 5 – Hormones – thyroid hormone thyroxin 6 - Genetics Only energy intake and level of physical activity can be voluntarily changed
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Two Chemical Forms of Energy Storage Glycogen (highly branched polymer of glucose) Stored glycogen binds water Liver glycogen is used to regulate blood glucose Muscle glycogen is used to power muscle contraction Fat (triglycerides) Fats have higher energy content per gram Little water is required for fat storage Energy in fats is harder and slower to access
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This note was uploaded on 01/03/2012 for the course BIO 308 taught by Professor Acbrown during the Spring '10 term at Portland.

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chapter22a Metabolism and Energy Balance 1 - Chapter 22a...

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