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Human Physiology > thermoregulation > Flashcards

thermoregulation Flashcards

1
Q

what is thermoregulation?

A

ability of an organism to keep its body temperature within certain boundaries

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2
Q

what happens when body temp rises?

A

blood vessels dilate resulting in heat loss to enviro

increase blood flow to specific areas to increase heat lost

sweat glands secrete fluid and when evaporates, heat lost from body

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3
Q

what happens when body temp falls?

A

blood vessels constrict so heat is conserved

reduce blood flow to certain areas where heat would be lost

sweat glands don’t secrete fluid

shivering (involuntary contraction of muscles) generates heat, warming body

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4
Q

what are homeotherms?

A

ability to maintain constant internal body temp regardless of external stimuli
(humans have ability to do this)

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5
Q

what do endotherms do?

A

generate heat internally
maintain high basal heat production

e.g mouse

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6
Q

what do ectotherms do?

A

depend on external heat sources
body temp changes with the enviro

e.g snake

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7
Q

what is a human’s internal core body temp?

when does it change?

at what temp is the optimal function?

A

36.5-37.5 *C

changes based on time of day

optimal function between 36.5-40*C

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8
Q

what is defined as a low internal core body temp?

A

<35*C

hypothermia sets in

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9
Q

what is the lowest survivable internal core temperature?

A

14.4*C

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10
Q

what occurs during hypothermia?

A

loss of motor skills
shivering
decrease in blood circulation and skin temp

severe:
confusion
loss of consciousness

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11
Q

when does hyperthermia occur and what happens?

A

when body temp above 38*C

results in either heat exhaustion: e.g sweating and cold skin and weak pulse

or heat stroke: e.g no sweating and hot skin and strong pulse

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12
Q

at what temp does damage to cells occur and what is the highest survivable internal core body temp?

A

> 42*C

highest survivable: 46.5*C

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13
Q

what are some of the factors which influence core body temp?

A
  1. body mass and composition (morphology)
    e. g better at adapting to temp if taller as more skin surface area
  2. enviro
  3. skin
  4. metabolic heat production
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14
Q

what is body temp a balancing act between?

A

heat gain and loss

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15
Q

which part of the brain activates blood vessel dilation/contstriction?

A

hypothalamus

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16
Q

how to measure core body temp?

A

thermometer probe at accessible site

hypothalamus, oesophagus, rectum, intestinal, under tongue and ear drum

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17
Q

what should be considered when measuring skin temp?

A

ambient temp
distance from core
skin blood flow

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18
Q

what is the definition of specific heat capacity?

A

amount of energy required to raise the temperature of a given substance by 1*C

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19
Q

which part of the body has the lowest skin temp when it is less than 15*C and in room temp?

A

feet

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20
Q

what is the specific heat capacity of water and human body tissue?

A

water = 4.186

human body tissue = 3.48

21
Q

how to calculate specific heat capacity?

A

change in thermal energy / mass x change in temp

22
Q

how much heat does 1 litre of O2 consumed produce?

A

20kJ of heat

23
Q

how is heat produced?

A

chemical energy in food
resynthesise ATP
inefficient as energy released doesn’t = ATP resynthesis
releasing energy in form of heat

during exercise

24
Q

voluntary and involuntary heat production?

A

voluntary - exercise - 70-80% EE appears as heat

involuntary - shivering, action of hormones (catecholamine and thyroxin)

25
Q

which factors are in external heat gain?

A

sky thermal radiation

solar radiation

ground thermal radiation

26
Q

what are the 4 factors of heat loss?

A
  1. conduction
  2. convection
  3. radiation
  4. sweat evaporation
27
Q

what is the thermal gradient?

A

heat transfer is always from higher to lower temps

28
Q

what is radiation?

in terms of heat loss

A

transfer of heat in the form of electromagnetic waves

body loses 60% of heat through radiation when at rest (biggest factor)

29
Q

what is evaporation?

in terms of heat loss

A

vaporisation of sweat from water to vapour

1g of sweat = 2.41kJ of heat

(biggest factor for heat loss in exercise)

30
Q

what is conduction?

in terms of heat loss

A

heat transfer from the body to an object with direct contact

31
Q

what is convection?

in terms of heat loss

A

conduction of heat to or from air or water

from one place to another by the movement of fluids

more accountable for heat loss at room temp than conduction

32
Q

describe sweating?

released
activated
increased

A

sweat is released from sweat glands

stimulated by SNS

increased SNS and therefore sweating when exercising, in anticipation or nervous

33
Q

what are the 3 factors influencing evaporation?

A

air temp (high humidity = evaporation decreases as high conc of water)

convective currents (high wind = increased evaporation)

skin exposure (larger surface = increased evaporation)

34
Q

how to calculate sweat loss?

A

change in mass + fluid intake - urine

units are kg or L

35
Q

how to calculate sweat rate?

A

sweat loss/time in h

units are L/h

36
Q

what does sweat loss depend on?

A 
body size
absolute VO2
aerobic fitness
heat acclimatisation
enviro

rugby is highest due to being large size and surface

37
Q

what explains why those with tattoos have a lower sweat rate?

A

changes skin sensors

delayed signal to hypothalamus

can’t sweat as efficiently from tattoed areas

38
Q

which areas of the body has the greatest heat loss?

A

the groin and armpits (not head)

39
Q

how does hyperthermia improve sprint/power performane?

A

decreased resistance in muscles/joints

faster nerve conduction velocity

faster metabolic rate (Q10 effect) so muscles activated quicker

increased SNS activity

40
Q

what does hyperthermia impair?

A

endurance performance and repeated sprint ability

41
Q

what is the Q10 effect?

A

measure of the rate of change of a biological or chemical system as a consequence of increasing the temp by 10*C

42
Q

what may reverse the effects of hyperthermia?

A

hydration

43
Q

why is performance impaired when core temp increases?

A

increased swet rate

decrease in plasma volume, blood volume, venous return and end diastolic volume

44
Q

what are some of the cognitive consequences of high core temp?

A

fatigue perception increase
decreased reaction time and attention
decreased scanning

45
Q

what are the levels of warning signs of hyperthermia?

A

heat cramps

to heat exhaustion (fatigue, nausea)

to heatstroke (most dangerous due to loss of consciousness and stopping of sweating)

46
Q

what are the effects of heat acclimation?

A

body temp lower at certain heat

sweat rate increases

skin blood flow reduced, more blood to muscles

blood volume increases

stroke volume maintained

47
Q

what is heat acclimation?

A

complex series of changes or adaptations that occur in response to heat stress between 7-14 days

48
Q

what is the impotance of hydration?

A

cool drinks can help lower temp and are absorbed in the GI tract faster

49
Q

what is homeostasis?

and what is the process of correcting an imbalance?

A

ability or tendency to maintain internal stability in a human organism to compensate for environmental changes

detect change - received by receptors - send signal through afferent pathway to control centre - signal sent via efferent pathway to receptor - effector responds to change

Human Physiology (9 decks)

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