LEWIS: Thermoregulation Flashcards
Necessary to lose that heat in order to keep body temperature constant so blood is moved from the core to close to the surface of the skin, from here heat can be lost to surrounding environment by 4 mechanisms:
1) CONDUCTION
2) CONVECTION
3) RADIATION
4) EVAPORATION
During exercise heat is produced as a waste product of
Muscle contraction
Conduction involves the
Transfer of heat through direct contact, from warm skin to clothes and air
Convection involves transfer of heat by
Gases
Air passing over our skin takes away air molecules that have been warmed by the skin
Radiation is the main way we lose heat when we are
resting
Evaporation is the main way we lose heat during exercise
As fluid evaporates from the skin
Heat is lost
Sweating, to work as a cooling system, the sweat must evaporate from the
Skin’s surface
Sweat that stays on the skin’s surface or that drops off provides little or
No
Cooling effect
Humidity of surrounding air is high, sweat evaporation is
Limited
Humidity is low, sweating becomes
Easier
Internal body temp =
37•C
Changes in body temperature are detected by receptors and information is sent to the hypothalamus, which starts mechanisms such as
Sweating
Vasodilation (increases blood flow to skin)
Shivering (when cold)
BLOOD, during exercise has 2 main functions:
1) supply muscles with nutrients and oxygen
2) supply the skin to allow heat to be lost
Blood - when exercising in a warm environment a large proportion of the cardiac output must be shared by the skin and the working muscles, this in turn
Reduces the volume of blood returning to the heart and so reduces the stroke volume
The heart, in order to maintain cardiac output required there has to be a gradual increase in heart rate (cardiovascular drift)
But these changes are limited in their effectiveness in terms of performance
The combination of a high rate of heat production from the exercise and a restricted capacity for heat loss can lead to
Hyperthermia (high body temperature)
Heat exposure combined with exercise results in hypohydration if fluid losses are not
Replaced
Fluid loss can lead to:
Symptoms of dehydration such as lethargy, nausea, loss of appetite, anxiety, inability to concentrate
Dehydration can eventually lead to
Exhaustion
Heat stroke
Dehydration limits performance by:
Decreasing blood plasma volume which results in less oxygen being delivered to the exercising muscles and increase breathing & heart rates
In order to prevent dehydration, attention to fluid intake:
Before
During
After
Drinks containing carbohydrate and electrolytes are useful for
Recovery, providing carbs for glycogen storage and promoting fluid retention
Performance deteriorates in cold environments, the body attempts to gain heat by
Shivering and by vasoconstriction of arteriolar near skin surface
Heat loss is increased by wind, which increases convection
This effect is known as
Wind chill
Cold reduces the strength of muscles - they can
Generate less force
Produce more lactate
During continued exercise in the cold, energy supplies quickly reduce and exercise intensity declines, and the performer becomes increasingly likely to suffer from
Hypothermia
