Human Physiology8-27-11
REVIEW SESSION THIS THURSDAY, 7:30 AM
MetabolismThe sum of all biochemical reactions going on at the body at a given time.
Metabolic rate = heat production = ATP production = oxygen consumption
Basal metabolic rate = lowest metabolic rate necessary to keep a person alive.
Measured under conditions of rest, non-digesting, non-reproducing, non-emotionally stressed, andnon-temperature stressed conditions.
Time of day also a factor, but ignored by medical science.
Factors that can affect level of BMR
Long-term effects1. Sex 2. Age3. Body Size
Factors that can affect level of BMR
Long-term effects1. Sex 2. Age3. Body Size
Short-term factors that can affect BMR
1. Exercise2. Digestion3. Alcohol4. Trauma5. Changes in hormonal status (norepinephrine or thyroxin)6. Air temperature
Regulation of Body Temperature
Heat vs. temperature
Physical Principles1. Heat always flows from area of greater heat energy to lower heatenergy.
2. The rate of heat flow is dependent on the temperature differential between the warmer area and the cooler area (larger T
causes faster rate of heat flow)
Mechanisms of heat exchange
1. Radiation (heat loss or heat gain)2. Conduction (heat loss or heat gain)3. Convection (heat loss or heat gain)4. Evaporation (heat loss only)
All living things produce heat but..
Depending on the rate of heat production, heat production may or may not affect body temperature.
Metabolic rate of all living organisms increases with increasing temperature
Temperature
log Metabolic rate
Birds and mammals(homeothermic, endothermic)
Tb
Air temperature Air temperature
7872
Met. rate
98F
If heat prod = heat loss, Tb constantIf heat prod > heat loss, Tb risesIf heat prod < heat loss, Tb drops
SweatingShiveringPiloerection
Vasodilationvasoconstriction
Insulation decreases the need for increased heat production in the
cold
Met.rate
Air temperature 72
Temperature Regulation System1. Morphology
a. sensors--located in skin, brain, spinal cord, liver, muscle
Firing rate
Temperature of skin, or brain, etc.
cold warm
hot
2. Integrator (hypothalamus)
cold
warm
hot
output
Hypothalamus compares input from sensors with a “setpoint”, and takes preventative action BEFORE body temp. changes
3. Output 1. Motor
a. shiveringb. posture changesc. behavior
2. Sympathetic nervous system (one branch of the autonomic nervous system) a. vasomotor responses b. piloerection c. sweating