7.2

Question 0

Radiation is when heat energy is transferred from one place to another as

Answer 0

Electromagnetic waves

Question 1

3 ways in which the body gains or loses heat:

Answer 1

• radiation
• conduction
• convection

Question 2

Conduction is in which heat energy is transferred by the collisions of

Answer 2

Molecules

Solids and liquids conduct heat better than air

Question 3

Convection is in which heat is transferred by

Answer 3

Currents in air or water

Question 4

The body also loses heat by

Answer 4

Evaporation of sweat

Question 5

(Evaporation) when water in sweat turns from liquid into vapour, it takes heat from the

Answer 5

Body

Question 6

Heat is also lost in substances that leave the body, such as:

Answer 6

Urine
Faeces
Exhaled air

Question 7

Human body temperature is controlled by the

Answer 7

Hypothalamus in the brain

Question 8

Sensory receptors in the brain, called thermoreceptors, monitor the temperature of the blood

Answer 8

Flowing through the hypothalamus (known as core body temperature)

Question 9

Thermoreceptors are also in the skin which monitor skin temperature. These thermoreceptors send nerve impulses to the

Answer 9

Hypothalamus

Question 10

If the thermoreceptors in the hypothalamus detect a change in body temperature away from the normal level, the hypothalamus brings about

Answer 10

Corrective mechanisms

Question 11

Responses are split into:

Answer 11

Heat loss

Heat conservation

Question 12

If the thermoreceptors in the hypothalamus detect an increase in body temperature, the hypothalamus corrects this by bringing about:

Answer 12

Heat loss responses

Question 13

Heat loss responses include:

Answer 13

Vasodilation
Increased rate of sweating
Pilorelaxation

Question 14

(HLR) vasodilation occurs by;

Answer 14

• Hypothalamus sends impulses along the parasympathetic nerves to the skin arterioles
• Smooth muscle in the walls of these arterioles relax
• Shunt vessel constricts, forcing more blood to flow through the surface capillaries

Question 15

(HLR) vasodilation causes an increase in the amount of energy lost by

Answer 15

Radiation

Question 16

(HLR) increased rate of sweating occurs by more sweat being secreted on to the surface of the skin. As the water on the skin evaporates it

Answer 16

Removes heat from the body

Question 17

(HLR) pilorelaxation has little effect in modern humans as we do not have hairy skins. However the parasympathetic nerves going to the wrecker pilli muscles at the base of the skin hairs causes these muscles to relax. This means that the hairs

Answer 17

Lie flat

• less air is trapped next to the skin
• reduces the insulating effect of the body hair

Question 18

Humans also reduce their body temperature by:

Answer 18

Behavioural responses - opening a window

Question 19

Behavioural responses as the thermoreceptors in the skin and hypothalamus send impulses to the cerebral cortex in the brain. This makes the person aware that they are too hot. As a result, they do something to help cool down.

People also become more inactive when they are too hot. This helps to reduce body temperature as the rate of respiration in muscle tissue decreases. This means that

Answer 19

Less heat is produced

Question 20

if a person is exposed to high temperatures for a long period of time, the body produces less

Answer 20

Thyroxine

Question 21

Thyroxine is a hormone that increases metabolic rate. As a result of being less produced in high temperatures the metabolic rate is

Answer 21

Reduced

Question 22

If the thermoreceptors in the hypothalamus detect a decrease in body temperature, the hypothalamus corrects this by bringing about

Answer 22

Heat conservation responses

Question 23

Heat conservation responses include:

Answer 23

• vasoconstriction
• decreased rate of sweating
• piloerection

Question 24

(HCR) vasoconstriction- the hypothalamus sends impulses along the sympathetic nerves to the skin arterioles, causing

Answer 24

• smooth muscles in the walls of arterioles to contract

- the shunt vessel relaxes(forcing less blood to flow through the surface capillaries)

Question 25

(HCR) effect of vasoconstriction is it reduces the amount of

Answer 25

Heat energy lost by radiation

Question 26

(HCR) decreased rate of sweating, less sweet is secreted in to the surface of the skin, so less heat energy from the body is:

Answer 26

Used to evaporate the water in the sweat into vapour

Question 27

(HCR) piloerection - although this has very little effect in humans, the erector pili muscles attached to the hairs in the skin pull the hairs ‘on end’ this traps an

Answer 27

Insulating layer of air, reducing heat loss

Question 28

(HCR) behavioural responses also help to conserve heat, such as

Answer 28

Putting on a jumper

Question 29

(HCR) shivering also generates heat. This is an involuntary response that occurs when:

Answer 29

-skeletal muscle contract and relax rapidly

Question 30

(HCR) shivering increases the rate of respiration in muscles, so more heat is

Answer 30

Generated

Question 31

(HCR) the hormone adrenaline is released, which

Answer 31

Increases the metabolic rate

Question 32

(HCR) if a person is exposed to cold temperatures for long, the body produces more thyroxine - which

Answer 32

Increases metabolic rate