TORPOR
DEFINITION:
lowering body temperature (TB) below activity temperature.
CONCEPT:
lowering TB decreases rate of body function (metabolism) due to Van’t
Hoff’s Rule – for every 10 degrees C drop in temperature, rates of
biochemical reactions (metabolism) slow by half.
TYPES:
- SEASONAL
TORPOR: more than one day
-
In response to cold – HIBERNATION
-
Deep: body temperature follows outside temp. to close to freezing.
- Shallow:
body temperature drops only somewhat.
- In
response to heat/dryness – SEASONAL ESTIVATION
- DAILY
TORPOR: less than 24 hours
-
In response to cold – DAILY TORPOR IN
RESPONSE TO COLD
-
In response to heat/dryness – DAILY ESTIVATION
ADAPTIVE
VALUES:
- Saves
Energy
-
By decreasing temperature difference between body and outside, the rate
of heat loss is lowered, thus reducing energy expenditure to replace the
lost heat energy.
-
By slowing metabolism, all tissues use less energy.
- Saves
Water
-
By decreasing cutaneous water loss (lower body temperature means lower
rate of evaporation out external surface).
-
By decreasing excretory water loss (lower metabolism generates less urine
and feces thus less water lost).
-
By decreasing respiratory water loss (fewer breaths per minute and less
water lost per breath). Lower metabolism requires slower breathing rate
and lower TB means exhaled air is cooler, thus contains less
water.
|
outline | thermoregulation |
torpor | water conservation |
size matters |