Thermoregulation Flashcards
Heat gain factors
BMR Muscular Activity Hormones Thermic effect of food Postural changes of the environment
Heat loss factors (4)
Radiation
Conduction
Convection
Evaporation
Hypothalamic Temperature Regulation: What is it and how is it activated (2)
Acts as thermostat set and regulated at 37°C ±1°C
initiates responses to protect from gain or loss of heat
CANNOT TURN OFF HEAT, initiates responses to protect from gain or loss of heat
Activation of heat-regulating mechanisms:
- Thermal receptors in skin =input to central control center
- Changes in Tblood perfusing hypothalamus directly stimulate central control centre
Heat Gain Factors (6)
BMR Muscular Activity Hormones Thermic effect of food Postural changes Environment
Increased Body temperature during exercise
Increase in body temperature with work rate
Linear across wide range of temperatures
Linear for both arm and leg exercises
Temperature proportional to active muscle mass
Effects of Clothing on thermoregulation (6)
- Wind Speed: Higher speed disturbs zone of insulation
- Body movements: Moving disturbs zone of insulation
- Chimney Effect: Loosely hanging clothing ventilates trapped air layers away from body
- Bellows Effect: vigorous body movements increase ventilation of air layers that conserve body heat
- Water vapor transfer: clothes resist water vapor exit
- Permeation efficiency factor: how well clothing absorbs liquid by capillary action
Football uniforms
Football equipment and clothing seal off 50% of body from evaporative cooling benefits
-Football gear exacerbates increase in rectal and skin temp with exercise
Is ear temp a good measurement of core temp
Ear temp generally measures lower than actual core temperature.
Effect of Ambient Temperature (3)
- Heat production remains constant
- Lower convective and radiant heat loss
- Higher evaporative loss
Evaporation
In order for heat to be lost by sweat it MUST evaporate
Wiping sweat is wastful and innefective
Three Factors influence total amount of sweat vaporized from skin and/or pulmonary surfaces
- Surface exposed to environment
- Temperature and relative humidity of ambient air
- Convective air currents about the body
Most important factor determining effectiveness of evaporative heat loss
Ratio of water in ambient air (at a given temperature) to total quantity of moisture that air could contain.
Sweat Production & Electrolyte Loss
- Sodium (Dominant): Loss will be noticed in kidneys, which will affect nerve transmission, muscle activation and blood volumes
- Potassium (Limited)
- Magnesium
Pathway Heat takes to escape
Tissues -> Skin -> Blood -> Environment
Fatigue and Core Temperature
Generally coincides with core temperatures between 38 to 40 C
Impairs muscle activation from high brain temperature
Decreases central drive to exercise