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62 Cards in this Set
- Front
- Back
Leptin
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Appetite controlling hormone. Lowers food intake and raises metabolic rate when size of fat cells increases. Increases food intake and metabolic rate when fat cells shrink.
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Neuropeptide Y
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Appetite signal in hypothalamus
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Melanocortin
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Satiety signal in hypothalamus
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Ghrelin
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"Hunger hormone" - released in blood before meals; causes production of Neuropeptide Y
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PYY 3-36
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Produced by small and large intestine; satiety signal
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Cholecystokinin
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Released by small intestine; acts as satiety signal
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4 Physiological factors contributing to obesity
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1) increase in circulating glucocorticoids
2) Insulin resistance 3 mutation of leptin receptor 4) production of neuropeptide Y |
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Energy in food consumed =
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external work + internal work + heat produced + stored energy
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Hypothalamus
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Large degree of control over food intake. Arcuate nucleus (containing neuropeptide Y and melanocortin) releases appetite and satiety signals.
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Appetite vs. hunger
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Hunger is physiological need for food, appetite is desire for food.
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Obesity threshold
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Body weight 20% or more higher than desirable weight suggested by USDA OR when BMI greater than or equal to 30
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Definition of overweight
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Body weight 11-19% higher than desirable
BMI of 25-29 |
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Pears vs. apples?
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Visceral fat is more dangerous than other types
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The three metabolic pathways
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Glycolysis = carbs --> ATP
Krebs Cycle = carbs or intermediates --> ATP Oxidative Phosphyrylation = intermediates --> ATP |
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Glycolysis
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Only carbs.
Occurs in cytoplasm. With or without oxygen. Produces ATP quickly, but limited amount produced. Yields 2 ATP per glucose. |
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Krebs cycle
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Uses carbs or intermediates.
Occurs in mitochondria. Oxidative (requires oxygen). Yields 1 ATP (also CO2, NADH + H+, FADH) |
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Oxidative Phosphorylation
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*Coupled with Krebs Cycle*
Uses intermediates. Occurs in cristae of inner membrane of mitochondria. Takes electrons down electron transport chain. Requires oxygen. Full oxidation of glucose molecule yields 38 molecules of ATP. |
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Beta oxidation
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Converts energy in chemical bonds of free fatty acids to ATP.
Yields 146 molecules ATP from one 18 carbon fatty acid. |
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Most efficient way to store energy?
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Triglycerides in adipocytes. To store equivalent energy as glycogen, body would weigh 30% more.
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Proteins as energy substrate?
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only 5% of body's ATP production comes from proteins.
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How does body use proteins for ATP production?
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Breaks down proteins into individual amino acids by proteases.
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Branched-chain amino acids
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Good proteins for use as energy
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Components of protein
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carbon, hydrogen, oxygen and nitrogen
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Where does the body store energy?
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78% Triglycerides
21% proteins 1% carbohydrates (important: brain only uses carbs) |
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How do humans stay at the top of the food chain?
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Our ability to metabolize different types of energy!
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Ideal internal temperature for humans
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37 degrees Celsius
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Normal fluctuation of temperature in humans
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~1 degree Celsius
Body temperature highest at 5-7pm, lowest at 6-7am |
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Temperature at which humans die
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43.3 degrees Celsius
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Temperature at which convulsions begin
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41degrees Celsius
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Lowest tolerable temperature
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35 degrees Celsius
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How does body maintain homeostasis under moderate ambient temperatures?
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Blood flow to skin decreases when cold, increases when hot.
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Thermoneutral zone
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Only changes in blood flow to skin needed to regulate body temperature. 25-30 degrees Celsius (75-86 degrees F)
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Thermoregulatory disorders
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1) Heat cramps
2) Heat exhaustion 3) Heat stroke |
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Heat cramps
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Least dangerous thermoregulatory disorder. Cramping of large muscles during exercise in hot conditions. Treated with hydration.
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Heat exhaustion
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State of collapse. Fainting results from decrease in blood pressure. Only mild increase in body temp.
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Heat stroke
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Very dangerous. Results from breakdown in thermoregulatory systems. Sharp increase in body temperature, no sweating. Heat loss mechanisms are shut down.
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Frostbite
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Tissue damage in extremity by formation of ice crystals.
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Hypothermia
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Cooling whole body exceeds capacity of heat producing/conserving mechanisms. If temperature drop continues, affects mind.
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Acclimatization to heat
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a) earlier onset of sweat
b) greater volume of sweat c) sweat more dilute Takes 14 days for full acclimatization |
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Acclimatization to cold
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Body "shell" increases while "core" decreases. Lowering of hypothalamus's set point to allow toleration of lower temperatures.
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Largest causes of death in world today
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CV disease, cancer, chronic respiratory disease (COPD) and diabetes account for >30 million deaths/year
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Leading causes of death in America
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1) Tobacco - 435,000 deaths annually (18.1% of deaths)
2) poor diet and low physical activity - 400,000 deaths (16.6%) 3) Alcohol consumption - 85,000 deaths (3.5%) 4) Microbial agents - 75,000 deaths |
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Body core
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Abdominal, thoracic cavities, nervous system, skeletal muscle. Cannot tolerate variations in temp.
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Body shell
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Skin and subcutaneous fat. Tolerates temperature variation.
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Radiation
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Transfer of heat by electromagnetic waves.
Body emits and absorbs radiant energy. Mostly emits (50% of produced heat), but absorbs when ambient temp > 37 C |
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Conduction
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Transfer of heat from physical contact. Rate of transfer depends on a) temp gradient, b) surface contact area, c) thermal conductivity of object (solid>liquid>gas)
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Convection
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Transfer of heat via air or water currents.
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Evaporation
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Transfer of heat when water on skin evaporates. Heat required to convert liquid to gas absorbed from skin, cooling body. Can only lead to heat loss when ambient air warmer than body temp.
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Hypothalamus
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Integrating center sensitive to input from thermoreceptors found in CNS and skin. Adjusts heat output to maintain body temp at 37 C.
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Ways hypothalamus increases temperature
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Increases muscle tone, stimulates muscle shivering.
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Brown fat
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Allows for non-shivering heat production in animals and babies
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Ways of spreading infectious diseases
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1) physical contact
2) indirect transmission (contact with object containing pathogens) |
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3 chronic diseases that account for 62% of deaths in developed world
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Cancer, heart disease, stroke
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Re-emergent diseases
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Diseases thought to be under control re-surfacing with adapted microbes resistant to antibiotics
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Amount of nutrient energy converted to ATP (as opposed to being released as heat)
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50%
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Metabolism
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Sum total of all chemical reactions in body
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Metabolic rate
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Rate at which energy is expended during work (internal and external combined)
= energy expenditure/unit of time (kcal/hour) |
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Basal metabolic rate (BMR)
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Metabolic activity needed to maintain basic body functions under resting conditions
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MR accurately measured when:
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a) person is at rest
b) mentally calm c) comfortable room temperature |
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Factors affecting metabolic rate
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1) Thyroid hormone (direct)
2) Physical activity |
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Negative energy balance
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Energy input is less than energy output
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Positive energy balance
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Energy input greater than energy output
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