Homeostasis & Thermoregulation

Question 1

What is homeostasis?

Answer 1

The process of keeping the environment inside the body constant

Question 2

What does homeostasis maintain?

Answer 2

• Core body temperature
• pH concentration
• Concentration of glucose
• Concentration of oxygen and CO2
• Blood pressure
• Concentration of metabolic wastes

Question 3

What is it meant by a dynamic equilibrium?

Answer 3

When there are fluctuations around a normal level

Question 4

What does positive feedback refer to?

Answer 4

Response is reinforced or intensified which results in a greater response eg child birth - oxytocin

Question 5

What does negative feedback refer to?

Answer 5

Negative feedback has the effect of reducing or eliminating the stimulus caused eg air conditioning

Question 6

What is the difference between negative and positive feedback?

Answer 6

Negative feedback has the effect of reducing or eliminating the stimulus that caused where as positive feedback reinforces and intensifies the stimulus eg oxytocin in childbirth

Question 7

What does the term thermoregulation refer to?

Answer 7

The maintaining the balance between heat production and heat loss

Question 8

List the body’s heat inputs?

Answer 8

• Heat from body processes such as respiration of liver and muscle cells
• Heat gained from surroundings by conduction and radiation

Question 9

Lost the body’s heat outputs?

Answer 9

• Radiation , conduction and convection to surroundings

- Evaporation of water from skin and lungs, warm air breathed out

Question 10

What ways are there to loss some but retain heat during hot conditions?

Answer 10

• Sweating
• Dilation of blood vessels in the skin
• Conscious behaviour such as removing clothes
• Increase surface area of body by spreading out

Question 11

What are the ways to reduce heat in hot conditions?

Answer 11

• Decrease in voluntary activity

- Decreased metabolic rate (long term response)

Question 12

What are the ways to retain heat in cold conditions?

Answer 12

• Constriction of blood vessels in the skin
• Reduction in sweating
• Conscious behaviour such as putting on a jumper
• Reduction in surface area by curling up in a ball

Question 13

What are the ways to increase heat production in cold conditions?

Answer 13

• Shivering
• Increase in voluntary activity
• Increases metabolic rate (long term response)

Question 14

What are the three ways metabolic rate is affected?

Answer 14

1. Exercise
2. Stress
3. Rising body temperature

Question 15

How does exercise affect metabolic rate?

Answer 15

During exercise muscular activity increases metabolic rate by up to 40 times which leads to an increase in heat production

Question 16

How does stress affect metabolic rate ?

Answer 16

Stress also increases metabolic rate as the activities of the autonomic division of the nervous system. Stimulation of sympathetic nerves release noradrenaline which increases metabolic activity of the cells

Question 17

How does rising body temperatures affect metabolic rate ?

Answer 17

For each 1 degrees rise in temperature, the rate of biochemical reactions increased by 10% therefore Increasing metabolic rate

Question 18

What are the body’s thermoreceptors?

Answer 18

1. Peripheral thermoreceptors - those in the skin and mucous membranes, cold and hot receptors
2. Central thermoreceptors - located in the hypothalamus
3. Other internal receptors - located in the spinal cord

Question 19

What role does the skin play in regulating temperature?

Answer 19

• Changes in the skin can speed up or slow down the rate at which heat is lost from the body
• Blood vessels carry heat to the skin from the core of the body
• Heat can be lost from the skin by conduction, convection, radiation, evaporation
• When large amounts of body heat must be lost by the skin and blood vessels are already at maximum dilation, sweating must occur

Question 20

What is sweating?

Answer 20

The active secretion of fluid by sweat glands periodic contraction of cells surrounding the ducts to pump sweat to the skin surface is stimulated by sympathetic nerves

Question 21

How does evaporation work?

Answer 21

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

Question 22

What is conduction?

Answer 22

When heat is transferred to another object by direct contact , heat is transferred from a hot object to a cold object

Question 23

What is convection?

Answer 23

Heat leaves the body and moves away as air currents (convection currents) the faster the flow of the air, the faster the rate heat is transferred

Question 24

What is evaporation?

Answer 24

The conversion of a liquid to a vapour the surface is cooled when evaporation takes place eg sweating leads to heat loss

Question 25

What is radiation?

Answer 25

The transfer of heat from one object to another without physical contact, heat leaves the body in the form of electromagnetic radiation

Question 26

What are the ways the body can maintain heat?

Answer 26

1. Vasoconstriction (Increases blood pressure) - decreases the heat transfer from internal organs to skin
2. Stimulation of adrenal medulla - secrete adrenaline and noradrenaline to increase metabolic rate and heat production
3. Shivering - under control of hypothalamus
4. Increase in thyroxine - causes AN love to secede TSH which causes the thyroid to release thyroxine and thus increase metabolic rate increasing heat
5. Behavioural response - putting on a jumper or curling up in a ball

Question 27

How does the body prevent body temperature from rising?

Answer 27

1. Vasodilation - Increases blood flow through the skin, heat is lost through radiation and convection
2. Sweating - needed to increase heat loss from the body, has a cooling affect
3. Decrease in metabolic rate - reduction in the secretion of thyroxine to reduce heat production
4. Behavioural response - turning on air conditioner, removing clothing

Question 28

What does temperature tolerance refer to?

Answer 28

Extreme changes in body temperate:

1. Hypothermia - extreme cold conditions
2. Hyperthermia - extreme heat conditions, death can occur when body temperature reaches 44-46 degrees