Download Memmler’s The Human Body in Health and Disease 11th edition

Memmler’s
The Human Body in Health and Disease
11th edition
Chapter 20
Metabolism, Nutrition and Body
Temperature
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Metabolism
Two categories
• Catabolism
– Breakdown complex compounds into simpler
compounds
• Anabolism
– Building simple compounds into needed substances
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Cellular Respiration
• Energy released from nutrients in a series of reactions
• Early studies done with glucose as starting compound
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Cellular respiration. This
diagram shows the
catabolism of glucose
without oxygen (anaerobic)
and with oxygen (aerobic).
(C = carbon atoms in one
molecule of a substance.) In
cellular respiration, glucose
first yields two molecules of
pyruvic acid, which will
convert to lactic acid under
anaerobic conditions, as
during intense exercise.
(Lactic acid must eventually
be converted back to
pyruvic acid.) Typically,
however, pyruvic acid is
broken down aerobically
(using oxygen) to CO2 and
H2O (aerobically).
Zooming In: What does
pyruvic acid produce in
cellular respiration under
anaerobic conditions? Under
aerobic conditions?
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The Anaerobic Phase
• Occurs in cytoplasm
• Yields 2 ATP molecules per glucose molecule
• Product is pyruvic acid
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The Aerobic Phase
• Occurs in mitochondria
• Yields 34-36 ATP molecules per glucose molecule
• Product is carbon dioxide and water
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Metabolic Rate
• Rate at which energy is released from nutrients in cells
• Decreases with age
• Measured in kilocalories (kcal)
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The Use of Nutrients for Energy
• Glucose is main source of energy
– Reserves stored in liver and muscle cells as glycogen
• Other energy sources
– Glycerol
– Fatty acids
– Amino acids
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Anabolism
• Essential nutrients
– Cannot be made by body
– Must be taken in diet
• Essential amino acids
– Nine of 22 must be eaten
• Essential fatty acids
– Linoleic acid and linolenic acid
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Minerals and Vitamins
• Minerals are chemical elements
– Body structure
– Fluid balance
– Muscle contraction
– Nerve impulse conduction
– Blood clotting
• Vitamins are complex substances
– Water soluble
– Fat soluble
• Antioxidants
– Stabilize free radicals
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Nutritional Guidelines
• Percentage of calories in daily diet
• Carbohydrate: 55 – 50%
• Fat: 30% or less
• Protein: 15 – 20%
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Carbohydrates
Diet should be mainly complex, naturally occurring
carbohydrates
• Normal blood glucose range 85 to 125 mg/dL
• Glycemic effect measures how rapidly food raises blood
glucose level, stimulates release of insulin
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Fats
• Saturated
– Most are from animal sources
– Solid at room temperature
• Unsaturated
– Derived from plants
– Liquid at room temperature
• Hydrogenated
– Artificially saturated
– Trans-fatty acids
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Proteins
• Not stored in body
• Most animal proteins supply all essential amino acids
• Most vegetable proteins lack one or more essential amino
acids
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Vitamin and Mineral Supplements
• Supplements are controversial
• Some populations may benefit
• Some vitamins cause toxic effects when taken in excess
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The Food Guide Pyramid
• United States Department of Agriculture publishing guidelines since
1916
• Newest version is 2005 Food Guide Pyramid
• Represents quantities of food recommended each day for good health
• 2006 is first version to include physical exercise as a component of a
healthy diet.
• Other updates in 2006:
–
Stresses variety in the diet
–
Stresses moderation
–
Stresses eating fruits and vegetables
–
Includes choices of “nutrient-dense” foods
–
Does not include sugar, solid fats, or alcohol; termed
“discretionary calories”
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The 2006 Food Guide Pyramid
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Alcohol
• Not a nutrient
• Interferes with metabolism
• Should be consumed in moderation
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Nutritional Disorders
• Excess of nutrients
• Shortage of nutrients
• Weight control
• Food allergies
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Food Allergies
• Allergens can be food or food additives
• Allergic reactions involve
– Skin
– Respiratory tract
– Gastrointestinal tract
• Reactions can be fatal
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Malnutrition
Can occur from missing nutrients or too much of wrong
foods
• Protein and energy malnutrition (PEM)
• Marasmus
• Kwashiorkor
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Overweight and Obesity
• Causes are complex
• Incidence is increasing
• Shortens life span
• Measured by body mass index (BMI)
– Overweight is BMI of 25 – 30
– Obese is BMI greater than 30
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Underweight
• Low reserves of energy
• Reproductive disturbances
• Nutritional deficiencies
• BMI less than 18.5
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Nutrition and Aging
• Nutritional deficiencies may develop
• Medications may interfere with appetite and absorption
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Body Temperature
• Heat is byproduct of chemical activities in body tissues
• Regulatory devices keep body temperature constant
within narrow limits
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Heat Production
Amount of heat produced by organs affected by
• Exercise
• Hormone production
• Food intake
• Age
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Heat Loss
• More than 80% of heat loss occurs through skin
– Conduction
– Radiation
– Convection
– Evaporation
• 15-20% heat loss through respiration and elimination
• Heat loss prevention
– Clothing
– Fat layer under skin
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Temperature Regulation
Body has internal mechanisms for regulating temperature
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The Role of the Hypothalamus
Regulation of
• Heat loss
– Constrict skin blood vessels
– Shiver
– Increase cell metabolism
• Overheating
– Stimulate sweat glands
– Dilate skin blood vessels
– Muscle relaxation
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Age Factors
• Newborns and elderly
• Reduced ability to produce heat
• Reduced ability to regulate overheating
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Normal Body Temperature
• Normal range is 36.3ºC to 37.6ºC (97.8ºF to 100.8ºF)
• Varies with time of day
• Varies by body part
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Fever
• Higher than normal body temperature
• Causes
–
Infection
–
Malignancies
–
Brain injuries
–
Toxic reactions
–
Vaccine reactions
–
Central nervous system diseases
• Crisis
• Lysis
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Responses to Excessive Heat
• Heat cramps
– Localized muscle cramping
• Heat exhaustion
– Heat retention and fluid loss
• Heat stroke
– Medical emergency that can be fatal
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Responses to Excessive Cold
• Hypothermia
– Excessively low body temperature
– Used in some types of surgery
• Frostbite
– Can cause permanent local tissue damage
– Likely areas are face, ears, extremities
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End of Presentation
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