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62 Cards in this Set

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Leptin
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.
Neuropeptide Y
Appetite signal in hypothalamus
Melanocortin
Satiety signal in hypothalamus
Ghrelin
"Hunger hormone" - released in blood before meals; causes production of Neuropeptide Y
PYY 3-36
Produced by small and large intestine; satiety signal
Cholecystokinin
Released by small intestine; acts as satiety signal
4 Physiological factors contributing to obesity
1) increase in circulating glucocorticoids
2) Insulin resistance
3 mutation of leptin receptor
4) production of neuropeptide Y
Energy in food consumed =
external work + internal work + heat produced + stored energy
Hypothalamus
Large degree of control over food intake. Arcuate nucleus (containing neuropeptide Y and melanocortin) releases appetite and satiety signals.
Appetite vs. hunger
Hunger is physiological need for food, appetite is desire for food.
Obesity threshold
Body weight 20% or more higher than desirable weight suggested by USDA OR when BMI greater than or equal to 30
Definition of overweight
Body weight 11-19% higher than desirable

BMI of 25-29
Pears vs. apples?
Visceral fat is more dangerous than other types
The three metabolic pathways
Glycolysis = carbs --> ATP

Krebs Cycle = carbs or intermediates --> ATP

Oxidative Phosphyrylation = intermediates --> ATP
Glycolysis
Only carbs.
Occurs in cytoplasm.
With or without oxygen.
Produces ATP quickly, but limited amount produced.
Yields 2 ATP per glucose.
Krebs cycle
Uses carbs or intermediates.
Occurs in mitochondria.
Oxidative (requires oxygen).
Yields 1 ATP (also CO2, NADH + H+, FADH)
Oxidative Phosphorylation
*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.
Beta oxidation
Converts energy in chemical bonds of free fatty acids to ATP.
Yields 146 molecules ATP from one 18 carbon fatty acid.
Most efficient way to store energy?
Triglycerides in adipocytes. To store equivalent energy as glycogen, body would weigh 30% more.
Proteins as energy substrate?
only 5% of body's ATP production comes from proteins.
How does body use proteins for ATP production?
Breaks down proteins into individual amino acids by proteases.
Branched-chain amino acids
Good proteins for use as energy
Components of protein
carbon, hydrogen, oxygen and nitrogen
Where does the body store energy?
78% Triglycerides
21% proteins
1% carbohydrates (important: brain only uses carbs)
How do humans stay at the top of the food chain?
Our ability to metabolize different types of energy!
Ideal internal temperature for humans
37 degrees Celsius
Normal fluctuation of temperature in humans
~1 degree Celsius
Body temperature highest at 5-7pm, lowest at 6-7am
Temperature at which humans die
43.3 degrees Celsius
Temperature at which convulsions begin
41degrees Celsius
Lowest tolerable temperature
35 degrees Celsius
How does body maintain homeostasis under moderate ambient temperatures?
Blood flow to skin decreases when cold, increases when hot.
Thermoneutral zone
Only changes in blood flow to skin needed to regulate body temperature. 25-30 degrees Celsius (75-86 degrees F)
Thermoregulatory disorders
1) Heat cramps
2) Heat exhaustion
3) Heat stroke
Heat cramps
Least dangerous thermoregulatory disorder. Cramping of large muscles during exercise in hot conditions. Treated with hydration.
Heat exhaustion
State of collapse. Fainting results from decrease in blood pressure. Only mild increase in body temp.
Heat stroke
Very dangerous. Results from breakdown in thermoregulatory systems. Sharp increase in body temperature, no sweating. Heat loss mechanisms are shut down.
Frostbite
Tissue damage in extremity by formation of ice crystals.
Hypothermia
Cooling whole body exceeds capacity of heat producing/conserving mechanisms. If temperature drop continues, affects mind.
Acclimatization to heat
a) earlier onset of sweat
b) greater volume of sweat
c) sweat more dilute
Takes 14 days for full acclimatization
Acclimatization to cold
Body "shell" increases while "core" decreases. Lowering of hypothalamus's set point to allow toleration of lower temperatures.
Largest causes of death in world today
CV disease, cancer, chronic respiratory disease (COPD) and diabetes account for >30 million deaths/year
Leading causes of death in America
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
Body core
Abdominal, thoracic cavities, nervous system, skeletal muscle. Cannot tolerate variations in temp.
Body shell
Skin and subcutaneous fat. Tolerates temperature variation.
Radiation
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
Conduction
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)
Convection
Transfer of heat via air or water currents.
Evaporation
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.
Hypothalamus
Integrating center sensitive to input from thermoreceptors found in CNS and skin. Adjusts heat output to maintain body temp at 37 C.
Ways hypothalamus increases temperature
Increases muscle tone, stimulates muscle shivering.
Brown fat
Allows for non-shivering heat production in animals and babies
Ways of spreading infectious diseases
1) physical contact
2) indirect transmission (contact with object containing pathogens)
3 chronic diseases that account for 62% of deaths in developed world
Cancer, heart disease, stroke
Re-emergent diseases
Diseases thought to be under control re-surfacing with adapted microbes resistant to antibiotics
Amount of nutrient energy converted to ATP (as opposed to being released as heat)
50%
Metabolism
Sum total of all chemical reactions in body
Metabolic rate
Rate at which energy is expended during work (internal and external combined)
= energy expenditure/unit of time (kcal/hour)
Basal metabolic rate (BMR)
Metabolic activity needed to maintain basic body functions under resting conditions
MR accurately measured when:
a) person is at rest
b) mentally calm
c) comfortable room temperature
Factors affecting metabolic rate
1) Thyroid hormone (direct)
2) Physical activity
Negative energy balance
Energy input is less than energy output
Positive energy balance
Energy input greater than energy output