Respiration Lecture 14:Thermoregulation Flashcards
Thermoregulation
regulation of body temperature
2 main types of thermoregulation
1) homeotherms
2) poiliotherms
Homeotherm
animal whose central temp is independent of a wide range of ambient temps (mode of thermoreg. where animal maintains a relatively stable temp. with little fluctuation)
Endoderm
control body temp through internal means such as shivering, fat burning, and panting
How does temp affect metabolic rxns?
Increased temp = increased metabolic rate due to increased enzyme reaction rates. Small changes in env. temp may enhance or depress metabolism
Poikilotherm
animal whose central temp differs little from ambient temp (internal temp dependent on the external conditions)
ectotherm
exchange heat with surroundings through activities such as basking in the sun and swimming. Use primarily BEHAVIORAL rather than METABOLIC means to regulate body temp
Main difference between homeotherms/poikilotherms and endotherms/ectotherms
H/P are classified by how they respond to environmental temps, wheras E/E are classified by the source of heat determining the body temp
Under what temp. conditions is metabolic rate the highest in most animals?
At very low temperatures, and (to a lesser extent) very high temperatures. Metabolic rate production increases on either end outside of thermoneutral zone
Thermoneutral zone
range of ambient temps without regulatory changes in metabolic heat production. Core temp of an animal is maintained constant while metabolic rate for heat prod. is minimal
Energy Budget Equation***
Heat stored = Energy production - heat loss
S = M - W - [E - (R+C+D)]
where M = total metabolic rate, W=useful physical work, E= evaporative heat loss, and R+C+D= sum of radiant, convective, and conductive heat
Radiation (R)
flow of energy b/w objects in space that depends only on the absolute temp. and the nature of the radiating surface. Energy passes from hot to cool object
Conduction(D)
flow of heat from one object to another with which it is contact
What is the inverse of conduction?
Insulation
Convection (C)
transfer of heat dependent upon a liquid or gas medium b/w hot and cool objects. Heat loss is due to streams of air or fluid moving heat away from surface of the objects
What are the main components of SENSIBLE heat transfer?
Radiation, conduction, and convection
Evaporative heat exchange (E)
removal of heat from the surface of a liquid that is losing some of its molecules as gas. Les effective when surrounding air is humid
What does INSENSIBLE heat transfer include?
Evaporative heat exchange
What happens to evaporative heat loss as ambient temp increases?
Increases
What kind of heat loss occurs when external temp is higher than internal core temp?
Evaporative heat loss
2 main sources of evaporative heat loss
skin + respiratory tract
Panting
rapid, shallow breathing; a characteristic heat-losing rxn. Represents an increase in dead-space ventilation resulting in heat loss without necessarily increasing O2 uptake or CO2 loss.
What anatomical changes occur to increase panting related heat loss?
vascular engorgement of resp. tract and oral mucosa
Sweating and panting
use of sweating usually increases as use of panting decreases in animals. Sweating not effective enough to reg. temp at very high temps
vasodilation
increasing diameter of superficial blood vessels allows for warming of the skin, thus increasing heat loss (opposite of vasoconstriction)
fx and mech. of countercurrent exchange
helps trap body heat in the core and reduce heat loss. Mech = arteries carrying warm blood to extremities pass by vdein returning with cooler blood traveling back to the core, heating it to prevent a drop in core temp
Behavioral patterns during high ambient temp for mammals/birds
Anorexia, body extension, extra drinking, cold-seeking, decreased locomotion, etc.
Behavioral patterns for low ambient temp for mammals/birds
Body flexing, huddling, heat-seeking, nest-building, increased locomotion, etc.
3 factors decreasing heat loss
1) shift in blood distribution
2) decrease in tissue conductance
3) counter-current heat exchange
What is the main control center for thermoreg?
Hypothalamus. Regulates “set point” for body temp
How is heat release triggered?
Activation of warm receptors increases activity in ANTERIOR hypothalamus resulting in peripheral vasodilation, sweating, panting
How is heat storage triggered?
Activation of cold receptors increases activity of the POSTERIOR hypothalamus resulting in heat production, shivering, and non-shivering thermogenesis
Effector mechanisms
try to get temperature back to set point. Include vasomotor, metabolic, and sudomotor (activates sweat glands) mechanisms
Reciprocal inhibition
Warm and cold hypothalamic regulator centers inhibit one another. (negative feedback loop)
Where are thermoreceptors located?
In skin and hypothalamus
Fever
a change in set point (the body temp is regulated at a higher set point). Different than acclimatization
How do mammals and birds acclimatize?
increase insulation, cells produce heat-shock proteins
How do poiliotherms acclimatize?
respond at cellular lvl: increase/alter enzyme production, change membrane lipid arrangement to maintain fluidity,produce cryoproteins or stress-induced heat-shock proteins
Cryoprotein
prevents ice formation in cells
Temporal heterothermy
body temp and metabolic rate are elevated only during activity.
Regional heterothermy
animals maintain different temp. zones in body
Kleptothermy
sharing or stealing of each other’s body heat
