Exercise & Thermal Stress Flashcards
What are 2 ways the body’s heat-regulating mechanism activates?
-Thermal receptors in the skin provide input to the central control center
-Changes in blood temperature that perfuses the hypothalamus
What portion of the hypothalamus detects changes in blood temperature in addition to receiving peripheral input?
Anterior
What monitoring system assesses body warmth? Detect cold?
-Temperature of the blood assesses body warmth
-Peripheral receptors detect cold
What is heat conduction?
Direct heat transfer from one molecule to another through solid, liquid, or gas
What provides the major defense against overheating?
Evaporation
Excessive sweating leads to two things.
Serious fluid loss and reduced plasma volume
What happens to stroke volume during hot-weather activity?
-Stroke volume decreases due to fluid deficit and lower blood volume. The arterial blood is fighting between sending oxygen (blood) to the working muscles and to the periphery to transport heat for cooling to the skin’s surface.
What happens to heart rate during hot-weather activity?
Heart rate increases.
What happens to cardiac output during hot-weather exercise?
Cardiac output decreases.
What is cutaneous blood flow?
The amount of heat that is lost to the environment.
What takes precedence during physical activity in the heat: muscle/circulatory regulation or heat regulation?
Circulatory/muscle regulation
Describe why a 100-104 degree body temperature impairs muscle activation?
High brain temperature decreases the central drive to exercise.
What determines the change in core temperature with exercise?
Relative intensity
How much sweat loss occurs during a moderate workout of about an hour?
.5-1 L
How do acclimatized humans sustain their exceptional potential for evaporative cooling?
Adequate fluid replacement.
Fluid loss coincides with the following five factors.
-Decreased plasma volume
-Reduced stroke volume
-Reduced skin blood flow for a given core temperature
-Increased heart rate
-General deterioration in thermoregulation efficiency
What indicates water loss and adequacy of rehydration during and following participation in physical activity?
Changes in body weight
What are three ways the aging delays the onset of sweating?
-Modified sensitivity of thermoreceptors
-Limited sweat glad output
-Dehydration-limited sweat output with insufficient fluid replacement
What are the three stages of exercise hyperthermia?
Compensation, crisis, failure.
What causes heat cramps?
An imbalance between electrolyte concentrations and body’s fluid level.
What is the gold standard for treating exertional heat stroke?
Ice bath submersion
What two mechanisms do children rely on in less stressful, cold-air environment?
-Augmented energy metabolism
-More effective peripheral vasoconstruction in the limbs
