U3 Homeostasis: Thermoregulation

Question 1

Define thermoregulation

Answer 1

The balance of heat gain and loss to maintain a constant internal body temperature of around 37°C independent of the environmental temperature

Question 2

Why does the body temperature need to remain constant at around 37°C?

Answer 2

• It is the optimal temperature for cellular reactions and stable cell function
• increased body temperature can cause nerve damage, structural change of proteins and death

Question 3

Why is the human body usually maintained at a higher temperature than the external environment?

Answer 3

Because of heat produced as a result of metabolic activity

Question 4

Why does exercise increase body temperature?

Answer 4

Exercise increases the metabolic rate and generates more heat than the body needs to keep its temperature constant

Question 5

What are the two ways the body responds to deviations in temperature?

Answer 5

Behavioural:
- where we consciously change our behaviour

Physiological:
- where our body automatically changes its functioning without conscious control

Question 6

How does heat gain/input occur?

Answer 6

• Heat from metabolic processes in the body
• Heat gained from surroundings by conduction and radiation

Question 7

How does heat loss/output occur?

Answer 7

• Radiation, conduction and convection to surroundings
• Evaporation of water from skin and lungs
• Warn air breathed out
• Warm urine and feces

Question 8

Define metabolic rate

Answer 8

The rate at which energy is released to the body by the breakdown of food

Question 9

What increases the metabolic rate?

Answer 9

• Exercise (muscular activity)
• Stress (increased activities of autonomic nervous system)
• Body temperature (increases rate of biochemical reactions)

Question 10

Define thermoreceptors

Answer 10

Receptors locate din the skin or hypothalamus that detect changes in temperature

Question 11

What are the two types of thermoreceptors?

Answer 11

Peripheral thermoreceptors
- located in skin and some mucus membranes
- detect temperature changes in external environment
- sends information to hypothalamus

Central thermoreceptors
- located in hypothalamus
- detect the temperature of the internal environment

Question 12

Distinguish between cold receptors and heat receptors

Answer 12

Cold receptors
- thermoreceptors stimulated by temperatures lower than normal
- when stimulated, the hypothalamus receives the information and initiates heat conservation and heat production mechanisms

Heat receptors
- thermoreceptors stimulated by temperatures higher than normal
- when stimulated, the hypothalamus receives the information and initiates heat production and heat loss mechanisms

Question 13

What are the ways that body temperature is regulated?

Answer 13

• Skin
• Blood vessels
• Sweating
• Shivering

Question 14

Why is the skin important in regulating body temperature?

Answer 14

The skin has a large surface area and its located between the internal and external environments

Question 15

How can heat be lost/gained by the skin?

Answer 15

Conduction:
- transfer of heat by direct movement between particles

Convection:
- transfer of heat by movement of liquid or gas

Radiation:
- transfer of heat by infrared radiation emitted by objects

Evaporation:
- process of a liquid forming a gas, which absorbs heat energy

Question 16

How do blood vessels regulate body temperature?

Answer 16

• Blood vessels located in the dermis of the sin carry heat from the core of the body to the skin
• The diameter of the surface arterioles is controlled by autonomic nerves

Vasodilation
- an increase in the diameter of the surface arterioles
- increases the blood flow through surface arterioles
- more blood is transported to the capillaries in the skin
- rate of heat loss increases

Vasoconstriction
- a decrease in the diameter of the surface arterioles
- decreases the blood flow through surface arterioles
- less blood is transported to the capillaries in the skin
- rate of heat loss decreases

Question 17

How does sweating regulate body temperature?

Answer 17

• Occurs when body heat must be lost and surface blood vessels are at maximum dilation
• Sweating: the active secretion of fluid by the sweat glands to the skin surface
• Evaporation of sweat from the skin surface has a cooling effect as the heat is removed from the skin when liquid sweat change into vapour
• Cooling of the skin results in the cooling of the blood flowing through the skin

Question 18

How does shivering regulate body temperature?

Answer 18

• Shivering: rhythmic muscle tremors that increase body heat production
• As no work is being done, heat produced by the muscles is released as heat

Question 19

What occurs to decrease heat loss in cold conditions?

Answer 19

• Vasoconstriction of blood vessels in the skin
• Decreased sweating
• Conscious behaviour: putting on a jumper, curling into a ball

Question 20

What occurs to increase heat production in cold conditions?

Answer 20

• Increased shivering
• Increased metabolic rate
• Increased voluntary physical activity

Question 21

What occurs to increase heat loss in hot conditions?

Answer 21

• Vasodilation of blood vessels in the skin
• Increased sweating
• Conscious behaviour: removing clothes, turning on a fan

Question 22

What occurs to decrease heat production in hot conditions?

Answer 22

• Decreased metabolic rate
• Decreased voluntary physical activity

Question 23

Distinguish between heat exhaustion and heat stroke (4 dot points each)

Answer 23

Heat exhaustion
- Occurs in high temperature and normal humidity
- Involves increased sweating, evaporation and cooling
- There is no change in core body temperature
- Is not fatal

Heat stroke
- Occurs in high temperature and high humidity
- Involves increased sweating, but no evaporation and therefore no cooling
- The core body temperature increases
- Can be fatal

Question 24

Hypothermia

Answer 24

• Occurs when a person’s core body temperature falls below 33°C
• The metabolic rate is decreased
• The amount of heat the body produced is decreased
• There is greater heat loss to the environment than heat gain