Thermoregulations In Endotherms

Question 1

what detects the change in surface temperatures of endotherms?

Answer 1

peripheral temperature receptors in the skin.

Question 2

what detects the temperature of blood deep in the body?

Answer 2

temperature receptors in the hypothalamus.

Question 3

what temperature is core body temperature?

Answer 3

37 degrees celsius.

Question 4

how do endotherms regulate their core body temperature?

Answer 4

using internal exothermic metabolic activities and energy-requiring physiological responses.

Question 5

what is the opposite of hibernation?

Answer 5

aestivation

Question 6

what additional behaviroual responses do humans have?

Answer 6

• clothes to stay warm
• houses built and then heated or cooled.

Question 7

what responses do endotherms have to cool down?

Answer 7

• vasodilation
• increased sweating
• reducing the insulating effect of hair or feathers.

Question 8

how does vasodilation cool animals down?

Answer 8

1. arterioles near the surface of the skin dilate when the temperature rises.
2. the arteriovenous shunt vessels constrict.
3. this forces blood through the capillary networks close to the surface of the skin.
4. the skin flushes and cools as a result of increased radiation. if the skin is pressed against a cold surface, the cooling results from conduction.

Question 9

how does sweating cool animals down?

Answer 9

1. sweat spreads out across the surface of the skin.
2. sweat evaporates from the surface of the skin.
3. heat is lost and cools the blood below the surface.

Question 10

how much sweat is lost from humans by evaporation on a normal day?

Answer 10

1 dm^3

Question 11

why might animals pant?

Answer 11

loses heat through evaporation as the water evaporates.

Question 12

how does reducing the effects of hairs on the body cool animals down?

Answer 12

1. erector pili muscles in the skin relax when the temperature is high.
2. hair or feathers lie flat to the skin. this avoids trapping air.
   (little effect on humans)

Question 13

what responses do endotherms have to warm up?

Answer 13

• vasoconstiction
• decreased sweating
• raising hairs
• shivering

Question 14

how does vasoconstriction heat animals up?

Answer 14

1. arterioles near the surface of the skin constrict.
2. arteriovenous shunt vessels dilate, so little blood flows through the capillary networks close to the surface of the skin.
3. warm blood is kept away from the surface of skin.

Question 15

how does decreased sweating heat animals up?

Answer 15

1. sweat production may stop entirely if temperatures are too hot.
2. this reduces cooling by the evaporation of water from the surface of the skin.

Question 16

how does raising hairs heat animals up?

Answer 16

1. as body temp falls, erector pili muscles in the skin contract
2. this pulls the hairs or feathers erect.
3. this traps an insulating layer of air and reduces cooling through the skin.

Question 17

how does shivering heat animals up?

Answer 17

1. as body temperature falls, an animal may start to shiver.
2. shivering is the rapid involuntary contracting and relaxing of the large voluntary muscles in the body.
3. metabolic heat from exothermic reactions warm up the body.

Question 18

how do polar bears demonstrate thermoregulation in extreme cold conditions?

Answer 18

• small ears and fur on their feet to insulate them from ice.
• hairs are hollow so permanently trap insulating layer of air.
• skin underneath is black so absorbs warming radiation
• thick layer of fat under the skin

Question 19

what are the physiological responses of endotherms to changes in the core temperature a result of?

Answer 19

complex homeostatic mechanisms involving negative fedback control from the hypothalamus.

Question 20

what are the two control centres for thermoregulation?

Answer 20

• the heat loss centre
• the heat gain centre

Question 21

when is the heat loss centre activated?

Answer 21

when the temperature of the blood flowing through the hypothamalus increases.

Question 22

how does the heat loss centre coordinate a response?

Answer 22

it sends impulses through autonomic motor neurones to effectors in the skin and muscles, triggering responses that act to lower the core temperature.

Question 23

when is the heat gain centre activated?

Answer 23

when the temperature of the blood flowing through the hypothalamus decreases.

Question 24

how does the heat gain centre coordinate a response?

Answer 24

it sends impulses through the autonomic nervous system to effectors in the skin and the muscles, triggering responses that raise the core temperature.