thermoregulatory system Flashcards

1
Q

thermoregulatory system

A

the ability of an organism to keep its body temperature within certain boundaries
homeotherms
- constant internal body temp regardless of external stimuli
endotherms
- generate heat internally
- maintain high basal heat production
ectotherms
- depend on external heat sources
- temp changes with environment

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2
Q

internal (core) body temp

A

36.5 - 37.5 degrees celsius
optimal function 36.5 -40

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3
Q

hypothermia

A

low body temp
< 35 degrees c
lowest survivable =~ 14.4 degrees c
symptoms:
- loss of motor skills
- shivering
- decrease in blood circulation and skin temperature
moderate or severe symptoms:
- confusion/ fatigue
- loss of consciousness

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4
Q

hyperthermia

A

high body temp
> 38 degrees c
damage to cells > 42 degrees c
highest survivable =~46.5 degrees c
heat exhaustion
- faint or dizzy
- excessive sweating
- cool,clammy skin
- nausea or vomiting
- rapid, weak pulse
- muscle cramps
heat stroke
- throbbing headache
- no sweating
- red, hot, dry skin
- nausea or vomiting
- rapid, strong pulse
- may lose consciousness

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5
Q

measuring core body temp

A

thermometer probe at an accessible site
- hypothalamus
- oesophagus
- rectum
- intestinal
- oral under tongue
- ear drum

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6
Q

measuring skin temp

A

depends on:
- ambient temp
- distance from core
- skin blood flow

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7
Q

law of conservation of energy

A

energy neither created nor destroyed
only transformed from one state to another
heat production
- liberate chemical energy in food we eat
- use it to resynthesize ATP
- but process is inefficient as the energy release not equal to ATP resynthesis
- release energy in form of heat
voluntary heat production
-exercise
- 70-80% EE app
involuntary heat production
- shivering
- action of hormones
-> thyroxine
-> catecholamines

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8
Q

heat production during dynamic exercise

A

to contract the muscles
- chemical energy as ATP
- exothermic reaction convert to mechanical energy
- 25-30% converted to mechanical work (rest is heat)

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9
Q

oxygen consumption

A

VO2 as an indicator of energy expenditure (heat production)
- 1 litre of 02 consumed produces ~ 20kJ heat
- resting vo2
-~0.25 L/min
- 0.25 x 20 = 5 kJ/ min of heat

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10
Q

external heat gain

A

sky thermal radiation
solar radiation
- reflected
- air temperature and humidity
ground thermal raditaion

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11
Q

specific heat capacity

A

amount of energy required to raise the temperature of a given substance by 1 degrees c
water = 4.186 kJ/kg/c
human body tissue = 3.48 kJ/ kg/c
change in thermal energy = mass x specific heat capacity x change in temp

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12
Q

radiation

A

transfer of heat in the form of electromagnetic waves
~ 60% heat loss at rest at room temp

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13
Q

conduction

A

heat transfer from the body to an object with direct contact
~3% heat loss at rest at room temp

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14
Q

convection

A

heat transfer from one place to another by movement of fluids (air or water)
~12% heat loss at rest at room temp

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15
Q

skin blood flow

A

conduction of heat to or from air or water
dependant on skin blood flow
during exercise heat dissipation by convection is reduced

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16
Q

thermal gradient

A

heat transfer is always from higher to lower temps

17
Q

evaporation

A

vaporisation of sweat from water to vapour
~25% heat loss at rest and ~85% during exercise
sweat evaporation
- water to vapour
-> 1g sweat = 2.41 kJ of heat
factors effecting evaporation
- air temp (humidity) = decrease
- convection currents (wind) = increase
-skin exposure (surface) = increase

18
Q

sweating

A

sweat released from sweat glands
stimulated by sympathetic nervous system
increased SNS activity when exercising, anticipation or nervous

19
Q

quantifying sweat loss and rate

A

sweat loss (L) = change in mass + fluid intake - urine
sweat rate (L/h) = sweat loss/ time (h)
sweat rate depends on:
- body size
- absolute VO2
- aerobic fitness
- heat acclimatisation
- environment

20
Q

cold exposure: ways body loses heat

A

heat loss
- evaporation
-radiation
-conduction
-convection
evaporation (sweating) when core temperature >37 degrees c at rest ~25% and ~85% during exercise
radiation: ~60% heat loss
conduction (cold ground) : ~2% through sir conduction
- water causes more heat loss than air
convection (wind) : body loses ~12% of its heat

21
Q

methods to reduce hyperthermia during exercise

A

heat acclimation
- body temp lower at given heat
- sweat rate increases and sweat more dilute
- skin blood flow reduced more blood to muscles
- blood vol increases/ not decrease
- stroke vol maintained

22
Q

areas of body with greater heat loss

A

skull
groin
armpits
extermities

23
Q

heat exhaustion treatment

A

cooler environment
elevate feet
saline
-oral
- intravenous

24
Q

heat stroke treatment

A

rapidly cool body
-cold water
- ice bath
- wet towel
medical attention

25
hyperthermia improves sprint/ power performance
- faster nerve conduction velocity - improvement in muscle contractile elements - faster metabolic rate -> Q10 effect - increased SNS activity impairs endurance performance impairs repeated sprint ability
26
Q10
temperature coefficient measure of the rate of change of a biological/ chemical system as a consequence of increasing the temp by 10 degrees c
27
hyperthermia: how performance impaired
increase core temp = increase sweat rate decrease plasma vol decrease blood vol decrease venous return decrease end diastolic vol
28
hyperthermia: cardiovascular consequences
decrease stroke vol increase heart rate decrease cardiac output decrease blood pressure increase peripheral resistance decrease muscle blood flow
29
hyperthermia: cognitive consequences
impairment in - fatigue perception increases - scanning vigilance -reaction time - attention - visual motor tracking
30
hyperthermia: metabolic consequences
decrease VO2 MAX increase anaerobic metabolism increase muscle lactate
31
central fatigue
brain stops sending out neural impulses to contract muscles
32
sodium cations
90% of extracellular cations pivotal role in fluid and electrolyte balance as accounts for half of osmolality of ECF main electrolyte lost in sweat 40-50 mmol/L replace Na+ with fluid intake
33
sodium ion and body water regulation
sodium ion only cation to exert significant osmotic pressure sodium ion leak into cells and pumped out against electrochemical gradient conc Na in ECF stable Na+ loss through urine and presipitation
34
ADH
antidiuretic hormone released from posterior pituitary secretion stimulated by - haemoconcentration - increase plasma osmolarity - decrease plasma volume promotes water retention in kidney to dilute plasma
35
aldosterone
mineralocorticoid hormone released from adrenal cortex secretion stimulated by: - decrease plasma sodium - decrease blood vol - decrease pressure - increase plasma potassium conc
36
alcohol when dehydrated after exercise
increased rate of urination lower fluid retention reduced plasma vol
37
post exercise
drink to replace fluid lost in sweat include glucose for glycogen resynthesis inclusion of Na+ aids fluid absorption in kidneys and water retention