Flashcards in Respiration Lecture 14:Thermoregulation Deck (42):
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Thermoregulation
regulation of body temperature
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2 main types of thermoregulation
1) homeotherms
2) poiliotherms
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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)
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Endoderm
control body temp through internal means such as shivering, fat burning, and panting
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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
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Poikilotherm
animal whose central temp differs little from ambient temp (internal temp dependent on the external conditions)
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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
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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
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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
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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
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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
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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
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Conduction(D)
flow of heat from one object to another with which it is contact
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What is the inverse of conduction?
Insulation
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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
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What are the main components of SENSIBLE heat transfer?
Radiation, conduction, and convection
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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
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What does INSENSIBLE heat transfer include?
Evaporative heat exchange
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What happens to evaporative heat loss as ambient temp increases?
Increases
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What kind of heat loss occurs when external temp is higher than internal core temp?
Evaporative heat loss
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2 main sources of evaporative heat loss
skin + respiratory tract
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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.
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What anatomical changes occur to increase panting related heat loss?
vascular engorgement of resp. tract and oral mucosa
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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
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vasodilation
increasing diameter of superficial blood vessels allows for warming of the skin, thus increasing heat loss (opposite of vasoconstriction)
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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
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Behavioral patterns during high ambient temp for mammals/birds
Anorexia, body extension, extra drinking, cold-seeking, decreased locomotion, etc.
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Behavioral patterns for low ambient temp for mammals/birds
Body flexing, huddling, heat-seeking, nest-building, increased locomotion, etc.
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3 factors decreasing heat loss
1) shift in blood distribution
2) decrease in tissue conductance
3) counter-current heat exchange
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What is the main control center for thermoreg?
Hypothalamus. Regulates "set point" for body temp
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How is heat release triggered?
Activation of warm receptors increases activity in ANTERIOR hypothalamus resulting in peripheral vasodilation, sweating, panting
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How is heat storage triggered?
Activation of cold receptors increases activity of the POSTERIOR hypothalamus resulting in heat production, shivering, and non-shivering thermogenesis
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Effector mechanisms
try to get temperature back to set point. Include vasomotor, metabolic, and sudomotor (activates sweat glands) mechanisms
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Reciprocal inhibition
Warm and cold hypothalamic regulator centers inhibit one another. (negative feedback loop)
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Where are thermoreceptors located?
In skin and hypothalamus
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Fever
a change in set point (the body temp is regulated at a higher set point). Different than acclimatization
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How do mammals and birds acclimatize?
increase insulation, cells produce heat-shock proteins
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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
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Cryoprotein
prevents ice formation in cells
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Temporal heterothermy
body temp and metabolic rate are elevated only during activity.
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Regional heterothermy
animals maintain different temp. zones in body
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