Chapter 7 - Homeostasis Of Body Temperature

Question 1

What is thermoregulation?

Answer 1

Maintaining the balance between heat production and heat loss

Question 2

What is the optimum body temperature?

Answer 2

37 degrees Celsius

Question 3

What causes heat input?

Answer 3

• heat from body processes (metabolism), especially respiration of muscle and liver cells
• heat gained from surroundings by conduction and radiation

Question 4

What causes heat output?

Answer 4

• radiation, convection and conduction to surroundings

- evaporation of water from skin and lungs, warm air breathed out, warm urine and faeces

Question 5

What does a high temperature above normal cause?

Answer 5

Enzymes denature, change shape, disrupts cellular activity

Question 6

What is higher, internal or external temperature?

Answer 6

Internal due to metabolism

Question 7

Cold conditions: to decrease heat loss

Answer 7

• vasoconstriction
• reduction in sweating
• conscious behaviour such as putting on a jumper
• reduction of surface area by curling into a ball

Question 8

Cold conditions: to increase heat production

Answer 8

• shivering
• increase in voluntary activity
• increased metabolic rate

Question 9

Hot conditions: to increase heat loss

Answer 9

• vasodilation
• increase in sweating
• conscious behaviour
• increase surface area by spreading out

Question 10

Hot conditions: to decrease heat production

Answer 10

• decrease in voluntary activity

- decreased metabolic rate

Question 11

Where are peripheral thermoreceptors found?

Answer 11

Skin and mucous membranes

Question 12

Where are central thermoreceptors found?

Answer 12

Hypothalamus

Question 13

What are the two types of peripheral thermoreceptors?

Answer 13

• cold receptors: stimulated by temperatures lower than normal
• heat receptors: stimulated by temperatures higher than normal

Question 14

Where are other central thermoreceptors located?

Answer 14

Spinal cord and abdominal organs, connected to hypothalamus

Question 15

What is the body’s main temperature regulation centre?

Answer 15

Hypothalamus

Question 16

What would peripheral receptors alone not be efficient in temperature regulation?

Answer 16

Because it is the core body temperature that needs to be controlled

Question 17

What controls vasoconstriction and vasodilation?

Answer 17

Autonomic nerves

Question 18

What is sweating?

Answer 18

The active secretion of fluid by the sweat glands and the periodic contraction of cells surrounding the ducts to pump sweat to the skin surface

Question 19

What is sweat made of?

Answer 19

Water, sodium chloride, urea, lactic acid and potassium ions

Question 20

How does sweat work to increase heat loss?

Answer 20

Evaporation of sweat from the body has a cooling effect: heat is removed from the skin when liquid sweat changes into vapour

Question 21

What stimulates secretion of sweat?

Answer 21

Sympathetic nerves

Question 22

What is shivering?

Answer 22

Rhythmic muscle tremors that occur at a rate of 10-20 per second

Question 23

At what temperature does death occur?

Answer 23

Above 45 degrees

Question 24

What causes heat exhaustion?

Answer 24

When extreme sweating and vasodilation occurs to lose heat

Question 25

What happens when the body is heat exhausted?

Answer 25

- the loss of water in sweating reduces the volume of blood plasma and vasodilation reduces resistance to blood flow - blood pressure is decreased and the output of blood from the heart is reduced

Question 26

What is hypothermia?

Answer 26

When a persons core temperature falls below 33 degrees, the metabolic rate is so low that heat production is unable to replace heat lost and body temperatures continue to fall

Question 27

What is heat stroke?

Answer 27

When humidity is high and it is difficult for the body to lose heat by radiation or evaporation