Thermoregulation Flashcards
What are the 3 ways heat can be transferred?
- Conduction
- Convection
- Radiation
What is conduction?
Transfer of thermal energy in solids caused by vibrating particles. Also occurs in liquids and gases as particles collide.
What is Convection?
Movement of molecules in liquids or gases which can transfer heat.
What is thermal radiation?
Thermal energy emitted from a solid, gas or liquid.
What is the body’s normal core temperature?
36.8 degrees
What is the threshold for hyperthermia and hypothermia?
Hyperthermia = 39 degrees
Hypothermia = 35 degrees
What are the 4 main physiological mechanisms of thermoregulation?
Vasomotor
Sweating
Shivering
Metabolism
What 5 things does your body do to thermoregulate when you are too hot?
Sweating
Vasodilation
Metabolism decreases
Increased respiration
Decreased appetite
What 5 things does your body do to thermoregulate when you are too cold?
Piloerection
Vasoconstriction
Metabolism increases
Shivering
Appetite increases
What generates the most heat within the body?
Major organs such as the brain, heart and liver
What environmental factor can reduce the effectiveness of sweating to cool the body?
Humidity
What is the acceptable range for a body’s core temperature in the Military?
+/- 2 degrees due to the nature of our working environments
Define Homeostasis
The body’s ability to physiologically regulate its inner environment to ensure its stability in response to fluctuations in the outside environment and the weather.
How many days does it take to fully acclimatise to a new environment?
15
What factors affect acclimatisation?
Exposure time
Physical fitness
Medical health
Thermal environment conditions
Food and fluid intake
Task/duty management
Alcohol/drugs/medication
Physical activity / work
Obesity
Age
Complexion
Clothing
Accomodation
Education
What is the definition of thermal comfort?
The absence of any significant strain on the body’s thermoregulatory mechanisms
What are the optimum comfort zones
Air temperature = 18 - 22 degrees
Air movement = 0.1 - 0.5m/sec
Relative humidity = 40 - 70%
Radiant heat temperature = 21 degrees
What is the primary method of heat gain / loss?
Respiration
Cold diuresis is a result of what?
Vasoconstriction leading to increase of blood pressure
What is cold diuresis?
Increased need to urinate due to blood vessel construction. Kidneys need to filter out extra fluid to make room.
The autonomic nervous system regulates what?
The visceral functions it the body e.g
Heart rate
Digestion
Vasodilation
Respiration rate
Salivation
Perspiration
What is natural convection?
In still air the body’s upward flow of warm air
What is forced convection?
Movement of air past the body, e.g. wind
What can account for 70% of the body’s water loss?
Perspiration
What can affect our ability to sweat?
Humidity
Clothing
Lungs can account for what % of body water loss due to warming and wetting of inhaled air?
10%
Which part of the brain regulates body temperature?
Hypothalamus
Which body systems does the hypothalamus control?
Endocrine system
Nervous system
What are the body’s physiological reactions to a hot environment?
Vasodilation
Increased heart rate
Increased sweating
Reduced metabolism
What are the body’s physiological reactions to a cold environment?
Vasoconstriction
Increased metabolism
Shivering
Piloerection
How long does it take for partial acclimatisation?
8 days
What environmental factors affect thermal comfort?
Air temp
Air movement (convection)
Relative humidity (affecting perspiration)
Radiant heat
