thermoregulation Flashcards
body temp regulation
- what does - humans are endotherms - mean?
- how do humans generate heat
- what happens to energy generated from this
- why are we homeotherms
- what happens when enviro changes
- generate own internal body heat, not rely on sunlight
- metabolism of food
- 75-80% lost as heat, 20-25% does work
- body temp maintained within narrow range around 37 deg although our enviro fluctuates largely ensuring enzymes optimally function
- body detects and alters core body temp
circadian rhythm
- how much does core body temp fluctuate
- when is temp highest and lowest
- around 1 deg
- lowest at night (low activity), highest in day (active)
seasonal changes
- difference in body temp in night during summer and winter
- winter body temp lower at night than summer
menstrual cycle
- when is core body temp highest
- second half of cycle due to progesterone
4 mechanisms of heat transfer
- conduction- direct contact between objects
- convection- when fluid flows over surface
- radiation- infrared rays
- evaporation- of water at body surface
thermoreg
- how is does the hypothalamus maintain body temp
- receptors and where they send info to
- 2 types of nerves, where they come from and go to with efferent info
- balancing heat gain and loss
- thermoreceptors send aff info to hypothalamus and cerebral cortex
- sympathetic nerves from hypothalamus to adrenal medulla, sweat glands and skin arterioles
- motor nerves from hypothalamus to SM for involuntary motor response
- motor nerves from cerebral cortex to SM for voluntary motor response
responses to heat
- vasodilation
- sweating
- decrease sympathetic stim and also acetylcholine release cause blood vessels dilate nearer skin
- sweat glands innervated by cholinergic nerve fibres via stim of muscarinic receptors. circulating epinephrine from adrenal medulla increase sweat production (hypotonic solution). decrease skin temp when sweat vaporises to enviro
responses to cold
- vasoconstriction (how frostbite prevented)
- shivering
- piloerection
- behavioural responses
- increase sympathetic stim to skin innervated by sympathetic adrenergic fibres
- subcutaneous fat and short periods of vasodilation in extreme cold prevent frostbite
- involuntary muscle contraction which breaks down ATP releasing heat and no movement
- goosebumps but aren’t effective in humans
- eg. voluntary movement, layers, heating
hypothermia
- what is it and what happens at extreme
- when core body temp falls too low, further it gets, worse it gets and becomes life threatening as heart has cardiac arrhythmias, lose responsiveness and fall unconscious
hyperthermia
- what is mild and extreme versions called
- what causes it
- what it leads to
- signs
- heat exhaustion and heat stroke
- caused by over exposure and metabolic heat production
- health risks of heat stroke, decreased physical performance which is dangerous
- dizziness, disorientation, dry skin, too high hr, collapse
impact of exercise and thermoregulation
- what does it do
- impact on muscles
- impact of heat on endurance capacity
- during exercise set point reset and is maintained above 38 deg
- An increase in muscle temperature due to metabolism, improves muscle elasticity and flexibility, decreasing muscle tightness, so ROM increases and risk of injury falls. encourages greater blood flow to meet metabolic needs
- endurance capacity reduced in heat
acclimatisation
- how its done
- what does it allow
- how long does it take to adjust
- what do acclimatised individuals do differently
- repeated exposure to heat by habitation or an environmental chamber
- efficient regulation of body temp in heat
- takes 5-10 days
- sweat more and sooner, increased blood flow to skin, more dilute sweat which conserves electrolytes, maintains blood volume and therefore stroke volume, reduces core body temp, hr, glycogen use and fatigue
