Respiration Lecture 14:Thermoregulation Flashcards Preview

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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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Kleptothermy

sharing or stealing of each other's body heat

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