5.1.4- Temperature control in endotherms

Question 1

What is the hypothalamus?

Answer 1

The part of the brain that coordinates homeostatic responses

Question 2

What is a useful physiological mechanism do endotherms have?

Answer 2

Directing blood towards or away from the skin to alter the amount of heat lost to the environment

Question 3

What is the response if the body gets too hot or cold for the organ: Skin? (6 points - 3 Each)

Answer 3

1a) Hot: Sweat glands secrete fluid onto the skin surface -> Latent heat of vaporisation (uses heat from blood).
1b) Cold: less sweat is secreted, so less evaporation means less heat lost

2a) Hot: hairs and feathers lie flat to reduce insulation and allow greater heat loss
2b) Cold: Hairs and feathers stand erect to trap air, which insulates the body

3a) Hot: Vasodilation of arterioles and precapillary sphincters directs blood to the skin surface so more heat can be radiated away from the body
3b) Cold: Vasoconstriction of arterioles and precapillary sphincters leading to the skin surface. Blood is diverted away from the surface of the skin and less heat is lost.

Question 4

What is the response if the body gets too hot or cold for the organ: Gaseous exchange system? (2 points - 1 Each)

Answer 4

Hot: Some animals pant -> increasing evaporation of water from the surface of the lungs and airways.
Cold: Less panting, so less heat is lost

Question 5

What is the response if the body gets too hot or cold for the organ: Liver? (2 points - 1 Each)

Answer 5

Hot: Less respiration takes place, so less heat is released.
Cold: Increased respiration in the liver cells means that more energy from food is converted to heat

Question 6

What is the response if the body gets too hot or cold for the organ: Skeletal muscles? (2 points - 1 Each)

Answer 6

Hot: Fewer contractions means that less heat is released
Cold: Spontaneous muscle contractions (shivering) release heat

Question 7

What is the response if the body gets too hot or cold for the organ: Blood vessels? (2 points - 1 Each)

Answer 7

Hot: Dilation to direct blood to the extremities so that more heat can be lost
Cold: Constriction to limit blood flow to the extremities, so that blood is not cooled too much. This can lead to frostbite in extreme conditions

Question 8

4 behaviours that endotherms do to maintain their constant temperature. (4 Points)

Answer 8

Hot: Hide away from sun in shade or burrow
Cold: lie in sun

Hot: Orientate body to reduce surface area exposed to sun
Cold: Orientate body towards sun to increase surface area exposed

Hot: Remain inactive and spread limbs out to enable greater heat loss
Cold: Move about to generate heat in the muscles or, in extreme conditions, roll into a ball shape to reduce surface area and heat loss.

Hot: Wet skin to use evaporation to help cool the body. Cats lick themselves and elephants spray water over their body
Cold: Remain dry

Question 9

What are the advantages of endothermy? (3 Points)

Answer 9

1) Maintain a fairly constant body temperature whatever the temperature externally
2) Remain active even when external temperatures are low, which means they can take advantage of pretty that may be available or escape from potential predators
3) Inhabit colder parts of the planet

Question 10

What are the disadvantages of endothermy?

Answer 10

1) Use a significant part of their energy intake to maintain body temperature in the cold
2) Need more food
3) Use for growth a lower proportion of the energy and nutrients gained from
4) May overheat in hot weather

Question 11

Where are the temperature receptors found?

Answer 11

Hypothalamus

Question 12

What is the role of the hypothalamus in terms of temperature control? (5 Points)

Answer 12

1) Temp receptors detect change in temperature
2) Hypothalamus sends out impulses causes different responses that will reverse the change
3) Some changes need to be quick to prevent further changes in body temperature
4) Neuronal system transmits the output from the hypothalamus in order to make these responses rapid.
5) Hormonal system transmits the output to cause long term responses.

Question 13

If the core temperature is too low what changes will the hypothalamus bring about?

Answer 13

1) Changes in the skin to reduce heat loss
2) Release of heat through extra muscular contraction
3) Increased metabolism in order to release more heat from exergonic reactions

Question 14

What is the thermoregulatory centre and where is it found?

Answer 14

Found in the hypothalamus, it monitors blood temperatures and detects changes in the core body temperature.

Question 15

What happens if the extremities start to cool down or warm up

Answer 15

It’ll eventually affect the core body temperature.

Question 16

What do the peripheral temperature receptors in the skin monitor?

Answer 16

The temperature in the extremities. Information is fed to the thermoregulatory centre in the hypothalamus. If the thermoregulatory centre signals to the brain that the external environment is very cold or very hot, the brain can initiate behavioural mechanisms for maintaining the body temperature such as moving moving into shade.