15.3 Thermoregulation in endotherms

Question 1

how are temperature changes detected in endotherms

Answer 1

• peripheral temperature receptors in skins detect changes in surface temperature
• temperature receptors in the hypothalamus detect blood temperature change (acts as a thermostat to maintain core temperature in dynamic equilibrium)

Question 2

what are the principles of thermoregulation in endotherms

Answer 2

• internal exothermic metabolic activities to keep warm
• energy-requiring physiological responses to cool down
• behavioural responses (basking in the sun, warm surfaces, wallowing in hate and mud, digging burrows, hibernation, aestivation)

Question 3

how do endotherms cool down

Answer 3

• vasodilation
• increased sweating
• reducing the insulating effect of hair/feathers

Question 4

describe vasodilation

Answer 4

• arterioles near the surface of the skin dilate when temperature increases
• arteriovenous vessels constrict
• blood is forced through capillary networks near the skin surface
• skin flushes and cools down due to increased radiation

Question 5

how does increased sweating help cool down

Answer 5

• an increase in core temperature causes an increase in sweating
• sweat spread out across the skin surface and as it evaporates, heat is lost which cools blood down
• some animals open their mouth and pant

Question 6

how does reducing the insulating effect of feathers/ hair help cool down

Answer 6

• body temperature increases
• erector pili muscles relax
• hair/feathers lie flat
• avoids trapping insulating layer of air
• little effect in humans

Question 7

what anatomical adaptations do endotherms that live in hot climates have

Answer 7

• large SA:V ratio to maximise cooling

- pale fur/ feathers to reflect radiation

Question 8

how do endotherms warm up

Answer 8

• vasoconstriction
• decreased sweating
• raising the body hair/feathers
• shivering

Question 9

describe vasoconstriction

Answer 9

• arterioles near the skin surface constrict
• arteriovenous shunt vessels dilate
• little blood flows through capillaries near the skin surface
• pale skin so little radiation occurs
• warm blood kept well below the surface

Question 10

how does decreased sweating help warm up

Answer 10

• decrease in core temperature decreases the rate of sweating
• reduced=s cooling by evaporation of water from the skin
• some evaporation still continues in the lungs

Question 11

how does raising feathers/ hair help warm up

Answer 11

• body temperature decreases
• erector pili muscles contract
• hair and feather erect
• traps layer of insulating air

Question 12

how does shivering help warm up

Answer 12

• rapid, involuntary contracting and relaxing of large voluntary muscles in the body
• metabolic heat from the exothermic reactions warm up the body

Question 13

what anatomical adaptations do endotherms that live in cold climates have

Answer 13

• minimise SA:V ratio
• thick layer of insulating fat
• some hibernate (build up fat stores and build a well-insulted shelter)

Question 14

what does the heat loss centre do

Answer 14

• activates when blood flowing through the hypothalamus increases in temperature
• sends impulses via motor neurones to the effectors
• responses triggered to lower core temperature

Question 15

what does the heat gain centre do

Answer 15

• activates when blood flowing through the hypothalamus decreases in temperature
• sends impulses through the autonomic nervous system to the effectors
• responses triggered to raise core temperature