Transcript Metabolism - College of the Canyons

CH. 17
Energy Balance and
Temperature Regulation
Do We Have Enough Energy?
• Understand what energy is and what it is used for
• Know how much energy is actually used and how much we
lose as heat
• Understand what metabolic rate and basal metabolic rate
are a measure of
• Know the types of energy balances that exsist
• Understand what nutrients are and how we regulate
nutrient intake
Energy
• Input – energy stored in the bonds of ingested
food
• Output – the use of that energy
– External work
• Energy expended during skeletal voluntary skeletal muscle
contractions
– Internal work
• All forms of biological expenditure that do not perform work
outside of the body
– Involuntary skeletal muscle contractions
– All life sustaining activities that are always occurring
Energy Consumption
• How much energy do we actually use?
• Lose about 75% as heat
• Metabolic rate
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Rate of energy use
Energy used/unit time
Expressed in calories, and kilocalories (Calories)
BMR – Basal metabolic rate
• Minimum waking rate of internal energy expenditure
• Influenced by thyroid hormone
Neutral Energy Balance
• Energy input = energy output
• Three states of energy balance
– Neutral energy balance
• Amount of intake = to output
– Body weight remains constant
– Positive energy balance
• Amount of intake > output
– Excess stored s adipose, weight increases
– Negative energy balance
• Amount of intake < output
– Body must use stored energy, weight decreases
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Nutritious and Delicious
• Nutrient
– An ingested chemical that is used for growth, repair, and
maintenance of the body
– Two categories
• Macronutrients
– Must consume in large quantities
– Water, carbohydrates, lipids , and proteins
• Micronutrients
– Small quantities needed
– Minerals and vitamins
• Calories
– Kcal
– Measure of the capacity to do work
Metabolic States
• Absorptive state
– Nutrients are being absorbed and my be used
immediately to meet needs
• Postabsorptive state
– Stomach and small intestines empty, energy needs
met from stored fuel
Regulation of Appetite
• Short-term regulators
– Ghrelin – produces sensation of hunger
– Peptide YY (PYY) – sensation of satisfaction
– CCK – sensory stimulus of vagus nerve (suppressor)
• Long-term regulators (adiposity signals)
– Leptin
– Insulin
• Arcuate nucleus of hypothalamus
– NPY - stimulator
– Melanocortin - suppressor
Psychosocial and Environmental
Influences
• Eat out of habit
• Social custom
• Familial customs
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