Niyogi Lecture 12 Flashcards
Match the values to the function (20%, 70%, 10%)
For a normal human, daily energy is spent on:
Physical activity
Basic organ function
Thermoregulation
20% Physical activity
70% Basic organ function
10% Thermoregulation
Define metabolism
body processes that use or produce energy occurring at multiple scales
Define metabolic rate
the rate at which body energy is used in metabolism
In what ways is metabolic rate regulated by the CNS and various hormones in mammals?
- motor NS increases skeletal muscle activity
- autonomic NS switches between PNS and SNS
- epinephrine increases metabolism
- T3 directly stimulates cellular ATP and heat production indirectly through various other chemical signals (cortisol, leptin, etc)
How is metabolic rate usually indirectly measured?
through the rate of oxygen consumption
Why are whole-animal metabolic rates and mass-specific metabolic rates inversely related?
Larger animals have more tissues and therefore have a greater metabolic rate.
But small animals with less mass and thus a greater mass to surface area ratio. This causes greater heat loss and so compensate, smaller animals tend to have higher metabolic rates per unit of mass to accommodate for this heat loss.
Endotherms generate heat internally and ectotherms rely on external sources of body heat.
Compare homeotherms and poikilotherms.
Homeotherms: maintain a near constant body temperature
Poikilotherms: do not maintain a steady body temperature
Not all endotherms are homeotherms and not all ectotherms are poikilotherms
Endothermic heterotherm means they regulate their own body temperature but it does not remain constant
Some bats are endothermic heterotherms; during the day time they set their body temperature to a lower level than the night.
Bears hibernate in the winter and during this time their body temperature is maintained much lower.
Compare hibernation and torpor
Hibernation is a state of minimal activity and metabolic depression undergone by some animal species. Hibernation is a seasonal heterothermy characterized by low body-temperature, slow breathing and heart-rate, and low metabolic rate. It most commonly occurs during winter months.
Torpor is the daily changes in body temperature. Essentially it is the same thing with a different time frame.
How are the digestive systems of ectotherms adapted to changes in temperature?
Different forms of body enzymes may have different activities depending on temperature
What are the advantages, disadvantages and consequences of being an ectotherm?
Advantages: less food needed, lower body energy expenditures
Disadvantages: optimal temperature range is limited, need to cope with fluctuation body temperatures
Consequences: limited body complexity, limited environmental range, periods of inactivity
What are the advantages and disadvantages of being an endotherm?
Advantages: always an optimal temperature for body biochemistry
Disadvantages: need a constant supply of high quality food and complex homeostasis to cool and warm body
Describe the physiology of body temperature regulation in endotherms.
Hypothalamus releases Corticotropin-releasing hormone (CRH):
This is a hormone that helps regulate metabolism and immune response by working with the pituitary gland and adrenal gland to release certain steroids, particularly in response to stress.
A negative/positive feedback loop maintains a balance between heat loss and heat gain in endotherms.
negative
Thyroid hormones (especially T3) are important cellular regulators of metabolism in endotherms. Explain in greater detail.
