Temperature control in endotherms

Question 1

role of hypothalamus

Answer 1

the part of the brain that coordinates homeostatic responses.

Question 2

Endotherms

Answer 2

do not rely on external sources of heat they use physiological adaptations and behavioural means to control their body temperature.

Question 3

What does temperature regulation rely on?

Answer 3

The skin as it is the organ in contact with the external environment. So many of the physiological adaptations to control body temperature involve the skin.

Question 4

Skin- response if body too hot….

Answer 4

• sweat glands secrete fluid into the skin surface; as this evaporates it uses heat from the blood as the latent heat of vaporisation.
• hairs and feathers lie flat to reduce insulation and allow greater heat loss
• vasodilation of arteriole and pre capillary sphincters directs blood to the skin surface so more heat can be radiated away from the body.

Question 5

Skin- response if body too cold

Answer 5

• less sweat is secreted, so less evaporation means less heat lost.
• hairs and feathers stand erect to trap air, which insulates the body.
• Vasoconstriction of arterioles and pre capillary sphincters leading to skin surface. Blood is diverted away from the surface of the skin and less heat is lost.

Question 6

Gaseous exchange- response if body too hot

Answer 6

Some animals pant, increasing evaporation of water from the surface of the lungs and airways. Evaporation uses heat from the blood as the latent heat of vaporisation.

Question 7

Gaseous exchange- response if body too cold

Answer 7

less panting, so less heat is lost.

Question 8

Liver- response if body too hot

Answer 8

less respiration takes place, so less heat is released.

Question 9

Liver- response if body too cold

Answer 9

Increased respiration in the liver cells means that more energy from food is converted to heat.

Question 10

Skeletal muscles- response if body too hot

Answer 10

Fewer contractions- mean that less heat is released

Question 11

Skeletal muscles- response if body too cold

Answer 11

Spontaneous muscle contractions (shivering) releases heat.

Question 12

Blood vessels- response if body too hot

Answer 12

Dilation to direct blood to the extremities so that more heat can be lost.

Question 13

Blood vessels- response if body too cold

Answer 13

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 14

Behaviour if too hot

Answer 14

• Hide away from sun
• reduce surface area exposed to sun
• remain inactive and spread limbs out to enable greater heat loss.
• wet skin to use evaporation to help cool the body. Cats lick themselves

Question 15

Behaviour if too cold

Answer 15

• lie in the sun
• increase surface area exposed to sun
• move to generate heat in muscles.
• remain dry

Question 16

Advantages of endothermy

Answer 16

• can maintain a fairly constant body temp whatever the temperature externally.
• remain active which means can take advantage of prey and escape potential predators.
• inhabit colder parts of the planet.

Question 17

Disadvantages of endothermy?

Answer 17

• use a significant amount of energy intake to maintain body temperature in the blood.
• need more food
• use for growth a lower proportion of the energy and nutrients gained from food.
• my overheat in hot weather

Question 18

What happens if core temperatures are too low?

Answer 18

The hypothalamus will bring about
- changes in the skin to reduce heat loss
- release of heat through extra contraction
- increased metabolism in order to release more heat from exergonic reactions.

Question 19

If the core temperature rises above optimum the hypothalamus will bring about the opposite changes.

Answer 19

an example of negative feedback.