Thermoregulation

Question 1

What is the normal range for body temperature?

Answer 1

36ºC-37.5ºC

Question 2

What is thermoregulation?

Answer 2

The processes involved in maintaining balance between heat production and heat loss

Question 3

What is a temperature “Set Point”

Answer 3

The body temperature that the hypothalamus sets as “normal” and attempts to regulate body temperature around

Question 4

Where are core body temperatures typically measured?

Answer 4

Tympanic (Ear drum) or Rectal sites

Question 5

Where are surface body temperatures typically measured?

Answer 5

Oral or sublingual sites

Question 6

What are four mechanisms of heat transfer?

Answer 6

Conduction, Convection, Radiation, Evaporation

Question 7

How does conduction heat transfer work? What is a practical example of this?

Answer 7

Molecules in a substance or molecules in two objects in contact with each other transmit their kinetic energy to neighbouring molecules by colliding with them. The mediums themselves don’t move. A practical example of this would be hot and cold packs.

Question 8

How does convection heat transfer work? What is a practical example of this?

Answer 8

The heated molecules of a medium move to other areas. When a hot medium flows into a cold medium, the hot medium will heat the cold and vice versa. A practical example of this would be blood becoming heated as it passes through our internal organs and taking that heat towards our skin to be cooled.

Question 9

How does radiation heat transfer work? What are some practical examples of this?

Answer 9

Electromagnetic waves carrying energy from one place to another. Examples of this are the sun and light bulbs.

Question 10

How does evaporation/vaporisation heat transfer work?

Answer 10

The change in state of water from liquid to vapour results in the loss of heat from the surrounding environment.

Question 11

What are some behavioural processes of heat loss?

Answer 11

Staying still
Staying/moving into the shade
Turning on air conditioning if available
Wearing less clothing

Question 12

What are some behavioural processes of heat retention/gaining?

Answer 12

Huddling
Curling into a ball (minimises surface area for heat loss)
Putting on more clothes
Using a heating device if available

Question 13

What are the physiological responses to cause heat loss?

Answer 13

Vasodilation near skin, Decreased metabolic rate and Sweating

Question 14

Is vasodilation controlled by the sympathetic or parasympathetic branch of the autonomic nervous system?

Answer 14

Parasympathetic autonomic nervous system

Question 15

How does vasodilation in the skin promote heat loss?

Answer 15

Heated blood is carried to the skin, then the heat is lost through the skin, cooling the blood at the same time

Question 16

What causes metabolic rate to decrease?

Answer 16

Reduced secretion of thyroxine

Question 17

How does a decreased metabolic rate promote heat loss?

Answer 17

Less energy being used for metabolism produces less heat energy

Question 18

Is sweating caused by the sympathetic or parasympathetic branch of the autonomic nervous system?

Answer 18

Sympathetic autonomic nervous system

Question 19

What electrolytes and body byproducts are found in sweat?

Answer 19

Sodium chloride, urea, lactic acid and potassium ions

Question 20

What are the physiological responses to cause heat retention and gain?

Answer 20

Vasoconstriction near skin, Increase in metabolic rate and Shivering

Question 21

Is vasoconstriction controlled by the sympathetic or parasympathetic branch of the autonomic nervous system?

Answer 21

Sympathetic autonomic nervous system

Question 22

How does vasoconstriction in the skin promote heat retention?

Answer 22

It prevents heat loss through the skin and keeps internal organs warm

Question 23

What causes metabolic rate to increase?

Answer 23

1. The hypothalamus stimulating the adrenal glands to secrete adrenaline and noradrenaline
2. The hypothalamus stimulating the anterior pituitary to secrete thyroid stimulating hormone, acting on the thyroid gland to release thyroxine
   Both of these cause metabolic rate to increase

Question 24

How does an increased metabolic rate promote heat gain?

Answer 24

More energy being used for metabolism produces more heat energy

Question 25

What triggers shivering?

Answer 25

Hypothalamus stimulates regions in brain involved in skeletal muscle toning

Question 26

How does shivering promote heat gain?

Answer 26

Muscles contracting 10-20 times per second generates friction within the muscles and therefore heat

Question 27

What is piloerection?

Answer 27

A vestigial bodily function which raises the hairs on our skin to make goosebumps to trap an insulating layer of still, warm air next to the skin (more useful in animals with long fur than in humans)

Question 28

What is the control centre for thermoregulation?

Answer 28

The anterior hypothalamus

Question 29

Where does the anterior hypothalamus receive thermoregulatory information?

Answer 29

Thermoreceptors in the hypothalamus monitoring blood temperature of blood going to the brain and thermoreceptors in the skin

Question 30

What is a fever?

Answer 30

A bodily defence mechanism against invading microorganisms where body temperature may increase by 2-3ºC.

Question 31

What are the 3 stages of a fever?

Answer 31

The chill phase, plateau phase and defervescence (breaking) phase

Question 32

What occurs in the chill phase of a fever?

Answer 32

The hypothalamus sets a high temperature set point, so the body begins to feel cold and commences physiological heat production and retention responses

Question 33

What occurs in the plateau phase of a fever?

Answer 33

Core body temperature reaches the new high temperature set point and the individual may fluctuate between feeling really hot and really cold

Question 34

What occurs in the defervescence (breaking) phase of a fever?

Answer 34

The hypothalamus resets the temperature set point to a normal temperature, so the body commences physiological heat loss mechanisms. The individual may look red, flushed and sweaty at this time

Question 35

What is the difference between pyrexia (fever) and hyperthermia (heat exhaustion/stroke)?

Answer 35

In pyrexia (fever), the body increases and decreases its temperature set point and its physiological thermoregulatory mechanisms are able to bring the body to the changing set point 
In hyperthermia, the set point doesn't change and it's the inability of the body's physiological thermoregulatory mechanisms to reduce the body's temperature to the set point.

Question 36

What can result from an elevated body temperature?

Answer 36

Fluid loss and dehydration
Electrolyte imbalances
Decreased urine output
Increased physiological demands
Tachycardia and tachypnea
Cellular/tissue damage (if temp to high or high for too long)
- neurological damage
Confusion/delirium
- febrile convulsions (especially in children)

Question 37

What is hypothermia?

Answer 37

When body temperature is less than or equal to 35ºC due to thermoregulatory mechanisms being insufficient to raise body temperature or impaired hypothalamic regulation, causing bodily chemical reaction rates to slow.
Can also be induced during surgery while being closely monitored

Question 38

What is frostbite?

Answer 38

The formation of ice crystals inside cells at temperatures below 0ºC, causing permanent circulatory damage

Question 39

What is the treatment for fever?

Answer 39

To support the physiological mechanisms for each stage of the fever (warm or cool the patient depending on the stage)
Promote comfort (e.g. antipyretic medications)
Monitor fluid, nutrition and electrolytes
- Hydration and electrolyte therapy
Remove the cause of infection

Question 40

What is the treatment for heat exhaustion/stroke?

Answer 40

Facilitate cooling mechanisms
Rehydration
Monitor for further complications

Question 41

What is the treatment for hypothermia?

Answer 41

Rewarming methods

Close monitoring of body temperature

Question 42

What is the treatment for frostbite?

Answer 42

Gradual rewarming
Analgesia (pain management)
Protection of injured tissue

Question 43

How does Panadol and other antipyretics reduce fever?

Answer 43

Acetaminophen inhibits prostaglandins, returning the temperature set point to a normal level