5.1.4: Temperature control in endotherms

Question 1

Endotherms do not rely on external sources of heat, what do they use to control their body temperature?

Answer 1

They can use physiological adaptations and behavioural means to control body temperature

Question 2

What does temperature regulation rely on?

Answer 2

The skin and muscles.

Question 3

Why do so many physiological adaptations to control body temperature involve the skin?

Answer 3

Because the skin is the organ in contact with the external environment. The changes that take place in the skin alter the amount of heat being lost to the environment.

Question 4

Many chemical reactions in the body are exergonic, what does this mean?

Answer 4

-They release energy in the form of heat.

Question 5

How do endotherms stay warm by using some of their energy intake?

Answer 5

-Endotherms can increase respiration (an exergonic reaction) in the muscles and live simply to release heat.

Question 6

what other useful physiological mechanisms do endotherms have?

Answer 6

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

Question 7

Organ: Skin (sweat glands)

What is the response if the body is too hot or too cold?

Answer 7

Too hot: sweat glands secrete fluid onto the skin surface; as this evaporates it uses heat from blood as the latent heat of vaporisation.

Too cold: less sweat is secreted, so less evaporation means less heat is lost.

Question 8

Organ: Skin (hairs)

What is the response if the body is too hot or too cold?

Answer 8

Too hot: hairs/feathers lie flat to reduce insulation and allow greater heat loss.

Too cold: hairs/feathers stand erect to trap air, which insulates the body.

Question 9

Organ: arterioles and precapillary sphincters

What is the response if the body is too hot or too cold?

Answer 9

Too hot: vasodilation of arterioles and precapillary sphincters directs blood to the skin surface so more heat can be radiated away from the body.

Too cold: vasoconstriction of arterioles and precapillary sphincters leading to skin surface. Blood is diverted away from the surface of the skin and less heat is lost.

Question 10

Organ: gaseous exchange system

What is the response if the body is too hot or too cold?

Answer 10

Too hot: some animals increase evaporation of water from the surface of their lungs and airways. Evaporation uses heat from the blood as the latent heat of vaporisation.

Too cold: less panting so less heat is lost.

Question 11

Organ: liver

What is the response if the body is too hot or too cold?

Answer 11

Too hot: less respiration takes place, so less heat is released.

Too cold: increased respiration in liver cells means more energy from food is converted to heat.

Question 12

Organ: Skeletal muscles

What is the response if the body is too hot or too cold?

Answer 12

Too hot: Fewer contractions means that less heat is released.

Too cold: spontaneous muscle contractions release heat.

Question 13

Organ: Blood vessels

What is the response if the body is too hot or too cold?

Answer 13

Too hot: dilation to direct blood to the extremities so that more heat can be lost.

Too cold: constriction to limit blood flow to extremities, so that blood is not cooled too much - this can lead to frostbite in extreme conditions.

Question 14

What are behavioural adaptations do endotherms use when too hot?

Answer 14

• hide away from the sun in the shade or in a burrow.
• orientate body to reduce surface area exposed to the sun.
• remain inactive and spread limbs out to enable heat loss.
• wet skin to use evaporation to help cool the body. Cats lick themselves and elephants spray water over their bodies.

Question 15

What are behavioural adaptations do endotherms use when too cold?

Answer 15

• lie in the sun.
• orientate body towards the sun to increase surface area exposed.
• move about to generate heat in the muscles or, in extreme conditions, roll into a ball shape to reduce surface area and heat loss.

Question 16

What are the advantages of endothermy?

Answer 16

Endotherms can:

• maintain a fairly constant body temperature whatever the temperature externally.
• remain active even when external temperatures are low, which means that they can take advantage of prey that may be available or escape from predators.
• Inhabit colder parts of the planet.

Question 17

What are the disadvantages of endothermy?

Answer 17

endotherms:

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

Question 18

What detects changes in core body temperature?

Answer 18

temperature receptors in the hypothalamus in the brain.

Question 19

how does the hypothalamus respond once it detects a change in core body temperature?

Answer 19

The hypothalamus sends out impulses that cause different responses that will reverse the change.

Question 20

Some responses to a change in core body temperature need to be quick in order to prevent further change in body temperature. Which system transmits the output if this is the case?

Answer 20

The neuronal system transmits the output from the hypothalamus in order to make these responses rapid.

Question 21

Other responses to a change in core body temperature need to be longer term. Which system transmits the output if this is the case?

Answer 21

The hormonal system transmits the output to cause these responses.

Question 22

if the core temperature is too low, the hypothalamus will bring about…

Answer 22

• changes in the skin to reduce heat loss.
• release of heat through extra muscular contractions.
• increased metabolism in order to release more heat from exergonic reactions.

(if the core temperature is too low, the hypothalamus will bring about the opposite changes, this is an example of negative feedback)

Question 23

What does the thermoregulatory centre in the hypothalamus do?

Answer 23

Monitors blood temperature and detects changes in core body temperature.

Question 24

What could help the hypothalamus to respond more quickly and reduce variation in core body temperature?

Answer 24

An early warning sign that the body temperature may change…

• If the extremities start to cool down or warm up this may eventually affect the core body temperature.
• peripheral temperature receptors in the skin monitor the temperature in the extremities.
• This 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 hot, the brain can initiate behavioural mechanisms of maintaining body temperature such as moving into the shade.

Question 25

what do peripheral temperature receptors in the skin do?

Answer 25

• peripheral temperature receptors in the skin monitor the temperature in the extremities.
• This 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 hot
• The brain can initiate behavioural mechanisms of maintaining body temperature such as moving into the shade.