Thermoregulation 1 Flashcards
Temperature Concept
- Temperature is a level of thermal energy
- Low energy = low temperature
- High energy = high temperature
- The greater the level of velocity of a particle the high the thermal energy
Temperature Scales
- Human = 37 celsius
- Kelvin 0 = no thermal energy (no movement of particles)
Homeothermy
- Poikilotherms - species where their core temperature changes with the ambient temperature, cannot regulate temperature
- Homeotherms - core body temperature is maintained despite ambient temperature
- Most mammals and birds
Body Temperature
- core and shell
The core is an internal region of the body whereas the shell is outside the core. Both are not fixed. The core is contracted as we get colder and expands when we get warmer
- Mean core temperature for humans = 36.9
- The shell is more variable
Temperature Measurement Sites
- Sublingual & outer ear - not the best place to get temperature for exercise
- Rectal - probe is inserted about 10-12 cm into the rectum. Good way to measure temperature for exercise
- Gastrointestinal tract - pill that has a sensor swallowed. Limitation (moves through regions that vary in temperature and limited for how long you can use it for). Reasonable way to measure temp for exercise
- Esophagus - a probe is inserted through the nose and travels down the throat to the lower esophageal sphincter right behind the heart. Best way to measure core body temperature
Variation and Limits in body temperature
- Females and males
(REFER TO GRAPH IN LECTURE)
- Faint line - average core body temperature for males and females in the luteal phase (36.9)
- Hyperthermia - higher than normal body temperature
- Hypothermia - below than normal temperature
- Range: 1-1.5 degrees(higher in the afternoon and lowest in the morning)
- Females on average - 36.5 (increases when ovulating)
Thermal Balance & Heat Flows
HINT: Anything that increases…
- Anything that increases thermal energy over time will increase the temperature overtime
- Anything that decreases thermal energy overtime will decrease the temperature overtime
- The rate of heat gain and the rate of heat loss determine the behaviour of the level of thermal energy and the variation of temperature overtime.
- Heat gain - metabolism
- Heat loss - skin blood flow (brining more blood to the surface of the skin), radiation, conduction, convection and evaporation
Thermoregulation and Physiological Mechanisms
- Heat flow
- Heat flow - rate at which heat is gained or lost
- Physiological regulation: the body uses three main mechanism to regulate body temperature - metabolism, skin blood flow, sweating
- Sweating and skin blood flow are sensitive to a rise in core temperature (ambient temperature of 28-29 C)
Thermoneutral Zone
When the core temperature is stable. Relates to the ambient temperature that you feel comfortable and can maintain core temperature very easily
Exercise in Thermoneutral conditions: effects of intensity and duration
- Muscle temperature
- Skin temperature
- At rest - core temp is higher than muscle temp
- During exercise - core temp lower than muscle temp
- Core temperature rises roughly proportionate to intensity when exercising
- Muscle temp rises greatly (about 2 degrees) from rest to exercise
- Much greater change in muscle than in core
- Skin temp decreases when exercising (under thermoneutral conditions)
Contracting muscle is source of heat gain
- 80% of energy release = heat
- What is powering muscle contraction?
- The breakdown of ATP to ADP + Pi (inorganic phosphate) with the presence of a fuel
Thermal balance perspective of exercise effect on body temperature
- Heat gain and heat loss
When heat gain and heat loss are equal there is no addition to thermal energy and core temperature is stabilized
- When we exercise, thermal energy rises
- Heat gain is instantaneous as soon as we exercise
- Heat loss also rises when we exercise so that we don’t fall into hyperthermia
Heat loss mechanism & skin
- The eccrine sweat glands releases a watery substance (drawn from blood) up to the surface of the skin. When the sweat vaporises, heat is lost
Skin blood flow during exercise
Resting values = 500 ml/min
Peak exercise values = 1500-2000 ml/min
Skin heating = 7000 ml/min
- Skin blood flow during exercise is higher that it is at rest. However it is the highest at moderate exercise intensities (60% VO2max)
Sweating during exercise
- Sweat rate increases in proportionate to the exercise intensity
- Sweat gland output increase as a function of exercise
