L7

Question 1

Temperature vs Heat

Answer 1

temperature - a measure of the speed of the random motions of the atoms or molecules in a substance (degrees)

heat - the total energy that a substance possess by virtue of the sum of random motions of its atoms or molecules (calories)

Question 2

body temperature regulation

Answer 2

At temperatures much higher than optima, proteins denature, losing the structure
necessary for function

even a few degrees deviation from optima can be lethal

Question 3

sources of body heat

Answer 3

Internal to the body - Biochemical reactions.
* The sum of our biochemical reactions lead to heat gains.
* External to the body - Environmental.
* Gains or losses.

Question 4

metabolic heat is always…

Answer 4

positive

Due to the inefficiency of biochemical reactions.

• 35% of the energy to generate ATP from glucose is lost in heat, if we are active or at rest.
• 70% of muscle use of ATP is lost in heat, when we are active

Question 5

heat exchange equation: sums each gain and loss of heat

Answer 5

Tbody = f(T ambient + H metabolism +/- H radiation +/- H conduction +/- H convection -H evaporation)

H metabolism is highly variable

Question 6

heat can be measured by…

Answer 6

direct calorimetry

Put someone in an insulated water bath,
known starting temperature and volume.

Measure the water temperature increase over time

indirect calorimetry

Breathe into a device that measures air flow, CO2 levels, O2 levels.

• Calculate calories from this reaction, based on CO2 produced and O2 consumed

Question 7

endotherms

Answer 7

Consistent high metabolic rates are a major source of energy that contributes to body temperature.

• Endo – internal to
• Therm – heat sources
• Examples: Most mammal

Question 8

Heterotherms

Answer 8

Endotherms with variable metabolic rates that are a major source of energy that contributes to body temperature.

• Hetero – Other, different
• Often change metabolic rates in response to food or temperature stresses

Question 9

ectotherms

Answer 9

Lower metabolic rates provide much less energy contributing to body temperature. Environment more significant.
* Ecto – external to

Question 10

regulators

Answer 10

Use physiology or behavior to adjust temperature

Question 10

non-regulators

Answer 10

No temperature adjusting processes

Question 11

categories of organisms: their Hmetabolism behavior & physiology

Answer 11

Question 12

other heat quation terms: heat exchange occurs across surfaces

Answer 12

slide 17 - explain

Question 13

radiation

Answer 13

heat can be gained or lost

energy is lost/gained as infrared electromagnetic waves

depends on: surface area, emissivity of the surfaces, does not require contact between source

Question 14

conduction

Answer 14

can be gained/lost

requires physical contact of the object w/ a s/l/g

depends on diff in temp of 2 surfaces, area of contact, how well surfaces conduct heat

Question 15

convection

Answer 15

heat can be gained/lost

mass flow within a fluid medium

deoends on surface area, temp diff, rate of flow of medium

Question 16

evaporation

Answer 16

always takes heat away from the body

depends on ambient temp, wolume of h20 evaporated, humidity of ambient air

Question 17

importance of organism size on thermoregulation

Answer 17

smaller animals have higher metabolic rates per gram than larger animals

Question 18

anatomic features that limit heat loss

Answer 18

insulation

animals may evolutionaruly modify conductivity and/or distance to vital organs

Question 19

counter current exchange

Answer 19

regional heterothermy: different regions of the body have diff temp; allows to keep core temp more stable

arrangement of blood vessels in some mammals and birds allows for countercurrent exchange, generating regional heterothermy

Question 20

physiologic responses that regulate body temperature

Answer 20

heat gain from increased metabolic rates (BMR, exercise)

heat loss from evaporative cooling and radiation

insulation (hairs at an angle of upright)

Question 21

uncoupling oxidative phosphorylation (BAT)

Answer 21

Question 22

control of blood flow regulates…

Answer 22

heat exchange

Question 23

vasodilation

Answer 23

increased flow in distal loop exposes blood to exterior
-> increases heat exchange with environment

Question 24

vasoconstriction

Answer 24

Decreased blood flow can shunt flow inside insulating subcutaneous fat
-> reduces heat exchange

Question 25

cooling feedback loop

Answer 25

Question 26

heating feedback loop

Answer 26

Question 27

heterothermy

Answer 27

conserves energy

Heterotherms:
* Reduce metabolic rate, food and water intake, activity
* Do not maintain constant body temperature like homeotherms
* Are tolerant of lower body temperatures

• Hibernation – Seasonal, voluntary, lasts weeks to months
  (Bears, bats, several rodent species. Some non-heterotherms hibernate, e.g. several insect, amphibia, reptiles)
• Torpor – Seasonal, involuntary, lasts hours
  (Bats, hummingbirds, reindeer)

Question 28

benefits of being a homeothermic endotherm

Answer 28

Activity levels can be kept higher

Greater independence from external thermal conditions

More flexibility in exploiting different habitat

Question 29

costs being a homeothermic endotherm

Answer 29

Energetically expensive, especially in colder habitats where Ta < Tb

Regulatory machinery, e.g., sensors, receptors, hormones, effector

Question 30

benefits of being a poikilothermic ectotherm

Answer 30

Energetically cheap

No regulatory mechanisms, which cost energy to build and operate

Question 31

costs of being a poikilothermic ectotherm

Answer 31

No independence from external thermal conditions
Limited flexibility in exploiting different habitat
activity levels are subject to environment
smaller metabolic rate
rely on behavioral responses to thermoregulate