thermoregulation Flashcards
what body systems/ processes can be affected by heat stress/ hyperthermia?
-Brain function
-digestive tract
-muscles
-metabolism
-cardiac
-respiratory
-Cardiovascular
What factors contribute to performance?
-strength
-flexibility
-power
-speed
-aerobic endurance
-anaerobic endurance
what is average core temperature for humans?
Between 35-42, average is 37
Why is there a set point for core temperature at 37c and what happens to blood flow in certain conditions in order to maintain core temp?
body functions are optimised at this temperature
-when cold-blood flow increases to core in order to maintain core temp
-when warm-bloow flow increases to skins surface
What are 3 methods to measure body temperature?
-Skin blood flow measurement (can see where blood flow is being redistributed)
-Sweat rate: by body mass loss(measure weight before and after exercise), sweat patches or capacitance hygrometry
-Core temperature measurement (by rectal measurement)
what is the chain of exercise command within the body?
Brain > spinal cord > peripheral nerves > muscle sarcolemma > Ca release > cross-bridge formation > power output
what has happened to the chain of exercise command if maximum power output is reached or if there’s a reduction of power output?
-if maximum power output is achieved then heat must have impacted one of the stages within the chain
- If there is a reduction of power output (usually in endurance exercise) there is a negative effect on one of the stages
what are the reasons for maximal power output being achieved/ limited?
-increased rate of phosphocreatine utilisation
-greater ATP turnover and adenine nucleotide degradation
-accelerated muscle fibre conduction velocity
-increased cross bridge cycling rate
How is core temperature maintained during anaerobic endurance exercise?
-Linear relationship between muscle temp and speed/strength/power (as one increases so does the other)
-Core temperature becomes elevated at some point during exercise
-Strength/power/speed overall continues to increase but at a slower more gradual rate than before
Why does core temp increase during exercise?
-Is maintained until point where environmental increases greatly so we can’t adjust any longer so core temperature starts to rise instead
what are methods of heat loss from the body?
-convection, conduction, radiation & evaporation
what are methods of heat gain to the body?
-posture, resting metabolic rate, thermic effect of food, physical activity, environment
how is body heat balance maintained?
-must be balance between heat loss and heat gain
formula for heat storage?
Heat storage = heat production ± heat loss (± Cv ± Cd ±R ±E)
what is radiation?
the emission of electromagnetic heat waves
what is conduction?
The direct transfer of heat through a liquid, solid or gas down a temperature gradient (ice drinks)
what is convection?
the transfer of heat by the circulation or movement of the heated parts of a liquid or gas
what is evaporation?
the process of turning from liquid into vapour (sweating)
when is sweating not an effective cooling method for the body?
in humid environment sweat can’t evaporate so remains on the body (unable to call body down)
what are thermoreceptors?
free nerve endings that sense temperature and provide information to the brain
Describe the process of neuro thermoregulatory control?
1.Internal temp, skin temp and thermoreceptors send signal to central nervous system
2.CNS sends signal to either speed up or change what’s happening to the sweat glands (by the sudomotor) or the blood vessels (by the vasoconstrictor or vasodilator)
3.This causes can action to occur eg. vasoconstriction of blood vessels in digestive tract as it’s not primary target) allowing us to maintain temperature
how does neuro thermoregulatory control occur?
Occurs by negative feedback loop:
system checks > error signal (difference between input and output controls) > central controller sends message to make corrective action (eg.sweat more, send more blood to skin)
what is fluid balance a result of?
what we intake vs output
describe what intake into the body consists of?
-200ml metabolic water
-700ml food intake
-1600ml fluid intake
describe what output from the body consists of?
-200ml feces
-300ml expired air
-400/500ml sweat
-1500ml urine
what organ plays a role in fluid balance?
-kidneys as they control urine output
which 3 factors can affect fluid balance?
-how much fluid taken on
-state of hydration
-content of the drink itself
Describe the intracellular response to dehydration in the body?
-increased plasma osmotic pressure
-stimulation of osmoreceptors in the hypothalamus (cuases stimulation of brain thirst centres)
-AVP or ADH released from pituitary gland (vasoconstriction & increase in BP)
-Kidney water reabsorption
Describe the extracellular response to dehydration in the body?
-decrease plasma volume and BP
-Stimulation of volume receptors in kidney (stimulates brain thirst centres)
-renin release from liver (causes vasoconstriction and BP increase)
-adrenal glands release aldosterone
-kidney sodium reabsorption
How have humans evolved to transfer heat when exercising?
-we’ve evolved to be able to transfer heat generated from exercise to environment around us -the transfer of heat from core to skin allows to sustain endurance exercise
how is heat generated by the body during exercise?
human muscle contractions generate metabolic heat
what are the 4 ways heat is lost from the body during exercise?
-conduction-through shoes and contact with surface
-convection- air flows past body and picks up heat
-evaporation- of sweat
-respiration-breathing in cool air and breathing out warm air
what factors define body cooler power?
-ambient temperature
-ambient vapour pressure
-solar radiation
-air movement
-clothing heat resistance
-clothing vapour permeability
-clothing ventilation
-skin temperature
-skin vapour pressure
