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 Tcauses 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

warmhot

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