Hemeothermy

Question 1

Homeothermy

Answer 1

o Thermoregulation and endothermy
o Regulate Tb by physiological means
o Beneficial to operate in any environment, costly metabolically

Question 2

Thermoneutral zone (TNZ)

Answer 2

Range of Ta over which an animal’s metabolic rate is constant; basal metabolic rate is measured within TNA under resting and fasted conditions

Question 3

Lower-critical temperature

Answer 3

o Ta below which animal’s metabolic rate increases with further decrease in Ta
o Thermal gradient for dry heat transfer keeps increasing
o Insulation already at max, thermal conductance can no longer be minimized
o Heat generation much increase

Question 4

Upper-critical temperature

Answer 4

o Ta above which animal’s metabolic rate increases with further increases in Ta
o Thermal gradients for dry heat transfer reversed
o Challenge is to dump excess metabolic heat fast enough, and prevent heat gain from environment
o Evaporative cooling becomes critical

Question 5

Basal metabolic rate

Answer 5

the amount of energy expressed in calories that a person needs to keep body functioning at rest

Question 6

Dry heat transfer

Answer 6

Sum total of HCond, HConvec, and HRad in uniform thermal environment

Question 7

Linear heat-transfer equation

Answer 7

M=C(Tb-Ta), Linear equation, x-intercept is Tb

Question 8

Insulation

Answer 8

o Animal can vary value of C within the TNZ
o Insulation or I = 1/C
o The inverse of conductance, means dry heat transfer is less likely

Question 9

Hyperthermia

Answer 9

Tb greatly higher than normal

Question 10

Pilomotor response

Answer 10

Small smooth muscle bundles at base of individual hair or feature can make it stand up or lie flat. Insulation increases when up.

Question 11

Bergmann’s rule

Answer 11

Animals from higher latitudes/colder environmental temps tend to have larger body masses

Question 12

Vasomotor responses

Answer 12

Constrict arterioles supplying blood to superficial veins; less warm blood comes into proximity with skin surface

Question 13

Postural responses

Answer 13

Curling into fetal potion, reduces surface area, thus minimizing available area for heat transfer

Question 14

Shivering thermogenesis

Answer 14

o Skeletal muscle contraction converts chemical energy in ATP to mechanical energy in the form of myosin movement
o Randomly activate motor units
o No useful movement but a boat-load of heat is liberated

Question 15

Non-shivering thermogenesis

Answer 15

o Electron transport chain. As electrons move down chain, H+ ions pumped into intermembrane space. H+ ion gradient then produces ATP as H+ ion flow back into mitochondrial matrix

Question 16

Brown adipose tissue (BAT):

Answer 16

major site for non-shivering thermogenesis and UCP1

Question 17

Uncoupling protein 1 (UCP1)

Answer 17

o There are positioned in the inner mitochondrial membrane and allow H+ ions to flow down concentration gradient without producing ATP but generating a lot of heat

Question 18

Sweating:

Answer 18

Dilute fluid with some Na+ secreted by sweat glands onto skin surface, increases evaporative H2O loss by 50X

Question 19

Panting

Answer 19

o Increase breaking rate, water evaporates from respiratory tract into inhaled air, then exhaled.
o Minimizes Na+ loss but can potentially cause respiratory alkalosis and requires higher increase in metabolic rate

Question 20

Gular fluttering

Answer 20

o Rapidly vibrate floor of mouth, increase air flow across upper respiratory tract
o Minimizes risk of respiratory alkalosis

Question 21

Rete mirabile

Answer 21

o Specialized circulation cools arterial blood before entering brain.
o By cooling the brain (thermoreceptors) suppress AND activity that would otherwise lead to evaporative cooling

Question 22

Allen’s rule

Answer 22

Animals from high latitude/colder environmental temps tend to have smaller appendages