Chapter 10: Thermoregulation Flashcards
Thermoregulation
Maintenance of fairly constant tissue temperature
5 types of thermoregulation
- Insulation
- Cooling by evaporation
- Circulatory adaptation
- Heat loss
- Regulating Environmental ?
Regional Heterothermia
Body core stays at a regulatory temp while limbs are set closer to ambient temps
Heat
A form of energy that a substance possesses by virtue of the random motions of its atomic and molecular constituents
Temperature
The speed (or intensity) of the random motions of atoms and molecules
Important temperatures (*C):
- Boiling point (H2O)
- Body temp
- Room temp
- Freezing point (H2O)
- Absolute zero
- Boiling point (H2O) = 100 *C
- Body temp = 37 *C
- Room temp = ~20 *C
- Freezing point (H2O) = 0 *C
- Absolute zero = -273 *C or 0 *K
Endothermy
When an animal’s tissues are warmed by its metabolic production of heat
Ectotherms
Body temp is the same as the environment’s temp
Poikilotherms
Variable body temp close to the environment’s temp
Endotherms
Can produce metabolic heat
Homeotherms
Thermoregulated by physiological heat
Heterothermy
A difference in thermal relations from one time to another (temporal) or one body region to another within a single individual (regional)
Eurythermal
Can exist in a high range of temps
Stenothermal
Can only exist in narrow temp ranges
3 tissue processes that are effected by temperature
- Metabolic rates
- Rates of biochemical reactions (enzymes)
- Rates of biophysical processes (diffusion and osmosis)
Hypothalamus
The thermoregulatory control center in the brain
Thermoneutral zone (TNZ)
A range of ambient temperatures which is the resting metabolic rate
2 Modulations of insulation
- Pilomotor response (hair)
- Vasomotor response (blood vessels)
2 types of heat production
- Shivering
- Nonshivering thermogenesis
Shivering
Unsynchronized contraction and relaxation of skeletal muscle motor units in high-frequency rhythms
Nonshivering thermogenesis
- Involves brown adipose tissue
- Receives a rich supply of blood vessels
- Contains great numbers of large mitochondria
- Releases Norepi in the brown adipose tissue
- Tissue increases oxidation of its stored lipids to increase heat production
Uncoupling protein 1 (UCP 1)
Prevents ATP from forming causing the brown adipose tissue to release heat
Countercurrent heat exchange
Arteries are set close together in the appendages so heat short-circuiting from arterial blood into venous blood and is not lost into the environment
Sweating
Fluid secreted by way of sweat gland ducts in skin (activated by the sympathetic nervous system)
Panting
Increase in breathing rate in response to heat stress
Evaporative cooling
The ultimate line of defense for mammals faced with high environmental or metabolic heat loads
