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What time of climate are humans better prepared for?
Heat - shivering is our only way of producing heat and isn't very effective whereas with vasodilation, sweating etc, we are much better at cooling our bodies.
What is acclamation?
Using a climate chamber to get used to the temperature
What is acclimatisation?
Visiting the environment in order to get used to it
What are the 2 parallel processes that thermoregulatory control are accomplished through?
- (1) Behavioural temperature regulation (conscious behaviour)
- (2) Physiological temperature regulation (unconscious behaviour)
From where/what is body heat gained?
Metabolic heat and environmental heat
Through what 4 processes do we lose heat?
- (1) Radiation
- (2) Conduction
- (3) Convection
- (4) Evaporation
What is conduction?
The transfer of heat via direct contact with a cooler surface
What is convection?
The transfer of heat via movement of gas or fluid
What is radiation?
The transfer of heat via electromagnetic heat waves (i.e. heat from anything that is warmer than it's surroundings)
What is evaporation?
The transfer of heat via vapourisation of fluids from the skins surface
What percentage of heat is lost through C&C, R and E at rest and during exercise?
- At rest:
- C&C 20%
- R 60%
- E 20%
- During exercise:
- C&C 15%
- R 5% E 80%
What 4 effectors alter body temperature back to normal?
- Sweat glands - open slowly then sweat heavier so that others open up
- Smooth muscle around arterioles - dilate
- Skeletal muscle - shiver in the cold
- Endocrine glands - release hormones that produce heat
Describe the process of controling heat exchange within the body.
Sensory receptors (thermoreceptors) detect changes
Relay information to the hypothalmus (thermal control centre)
At a preset level we start sweating or shivering
What implications does loss of fluids have on the rest of the body?
Fluid sweated out comes from fluid % in blood and therefore heart beats faster because heart is pumping sludge - at this point ADA gets released to increase fluid being reabsorbed from urine.
Describe the major cardiovascular problem from heat loss during exercise through skin blood flow.
Body needs to provide enough blood flow to muscle to support its metabolic requirements and enough blood flow to the skin to dissapate.
Keep the muscles working or cool the body down??
Discuss heat loss during exercise through evaporation.
Evaporation = major heat loss mechanism during exercise.
- Sweating can begin within a few minutes
- Increase in evaporative heat loss = decrease in total body water
- Changes in total body water has consequences for temperature control
What is the major difference between heat loss during rest and exercise?
The contribution from different heat exchange mechanisms.
At rest, skin blood flow can be dramatically increased because of the low physiological demand
During exercise, the competition for blood flow and greater heat load leads to mismatch between heat exchange mechanisms
How does hummidity affect heat exchange?
Humidity plays a major role (particularly evaporation).
When humidity is high, air is highly saturated with water and therefore has decreased capacity to accept more.
During exercise under high humidity conditions and increased temperatures, the body may not be able to lose sufficient heat - leads to critical levels of body temp.
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