Topic 7 (III): Thermal Energy and Bioenergetics

What is thermoregulation based on?

based on negative feedback pathways in which thermoreceptors detect changes from a set point 

What do signals from thermoreceptors trigger?

physiological and behavioral responses that return the temperature to the set point

What do all responses triggered by negative feedback mechanisms involve?

they involve adjustments in rate of heat-generating oxidative reactions within the body coupled with adjustments in rate of heat gain or loss at the body surface

What happens between 0 C and 45 C?

an animal’s organismal performance varies greatly

organismal performance

biochemical, physiological, and whole-body process

animals gain and lose heat through a combination of…

conduction, convection, radiation, and evaporation

conduction

the flow of heat between atoms or molecules in direct contact 

convection 

the transfer of heat from a body to a fluid (air or water), that passes over its surface 

radiation 

the transfer of heat energy as electromagnetic radiation 

evaporation

heat transfer to the energy required to change a liquid to a gas

What do organisms do to maintain a constant body temperature?

the heat gained or lost through these pathways must be balanced

ectotherms

“cold-blooded” animals; obtain heat primarily from the external environment 

endotherms 

“warm-blooded” animals; obtain heat from internal physiological sources 

How to ectotherms regulate body temperature?

by controlling the rate of heat exchange with the environment through behavioral and physiological mechanisms 

How do endotherms regulate optimal body temperatures?

by regulating:

• the amount of heat generated by internal oxidative reactions

• the amount of heat exchanged with the environment

How does colder weather affect endotherms?

doesn’t prevent normal activities, but it does increase their energy and food needs

How does colder weather affect ectotherms?

more sluggishly, but food needs are reduced

thermal acclimatization 

physiological changes that ectotherms undergo in response to seasonal shifts in environmental temperatures 

What do some ectotherms do when temperatures drop below 0 C?

some add molecules to their body fluids that act as antifreeze to depress their freezing point and retard ice crystal formation 

What are the constant body temperatures of active birds?

39 C - 42 C (102 F to 108 F)

What are the constant body temperatures of active mammals?

36 C - 39 C (97 F - 102 F)

core temperature

the temperature within the central core of the body consisting of the abdominal and thoracic organs, the CNS, and the skeletal muscles