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Ex Phys > Thermoregulation > Flashcards

Thermoregulation Flashcards

1
Q

Humans are homeotherms meaning:

A

they maintain a constant core body temp

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2
Q

What is normal core temp?

A

37C or 98.6F

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3
Q

Temperatures above 45C or 113F can:

A

damage proteins and enzymes and lead to death

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4
Q

Temperatures below 34C or 93.2F can:

A

result in decreased metabolism and cardiac arrhythmias

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5
Q

Ideal thermal gradient from body core to skin surface is:

A

4C or 7.2F; best to keep it close together

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6
Q

Hypothalamus increases the body’s temp set point and creates a fever due to:

A

pyrogens like proteins or toxins from bacteria or virus

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7
Q

What indicates the onset of a fever?

A

shivering

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8
Q

What indicates the end of a fever?

A

sweating

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9
Q

During exercise, heat moves from:

A

body core to body shell via blood

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10
Q

What are three ways to measure deep-body (core) temp?

A

rectum, ear, or esophagus

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11
Q

What is the gold standard way to measure core body temp?

A

rectum

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12
Q

What can be used to measure an athlete’s body temp during exercise?

A

ingestible temp sensory telemetry system

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13
Q

What is the issue with ingestible temp sensory system?

A

never know where it’s at in the body which can change internal core temp readings

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14
Q

What is the best way to accurately take skin temp?

A

calculate mean skin temp, take seven readings of temp around the body

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15
Q

During rest, metabolic heat production is:

A

small

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16
Q

An example of voluntary heat production is:

A

exercise; 70-80% energy expenditure released as heat

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17
Q

What is an example of involuntary heat production?

A

shivering, increases heat production by approx 5x

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18
Q

What hormones are involved in non-shivering thermogenesis?

A

thyroxine and catecholamines

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19
Q

What structure is considered the body’s thermostat?

A

hypothalamus

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20
Q

In the absence of Ca2+, this structure covers actin-binding sites

A

tropomyosin

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21
Q

Describe the difference between systolic time and diastolic time at rest. What happens to these phases of the cardiac cycle during exercise?

A

at rest: diastolic time is longer than systolic time
during exercise: the duration of both will decrease but systolic time is longer overall

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22
Q

Radiation

A

transfer of heat via infrared rays

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23
Q

Conduction

A

body heat loss due to contact with another surface

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24
Q

Convection

A

heat transferred from body to air or water

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25
Q

evaporation

A

heat loss due to phase change from liquid to gas

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26
Q

What are the three things that evaporation rate depends on?

A
  • temperature and relative humidity
  • convective currents around the body
  • amount of skin surface exposed to the environment
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27
Q

What is the primary heat loss method during exericse?

A

evaporation (sweat)

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28
Q

What is something in the environment that can impact evaporation during exercise?

A

humidity

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29
Q

Which nervous system acts on skin arterioles during both cold and hot exposure?

A

Sympathetic Nervous System

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30
Q

What does the SNS do for heat loss when it is cold/hot?

A

cold: vasoconstriction minimizes heat loss (think of constriction>holding your arms tight to yourself because its cold)
hot: vasodilation enhances heat loss (think of dilation>opening up>spreading out bc its hot)

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31
Q

What is the primary type of sweat gland?

A

eccrine sweat gland

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32
Q

Explain how the eccrine sweat gland affects heat loss

A

SNS releases acetylcholine on the gland causing sweat to be released which leads to heat loss via evaporation

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33
Q

The eccrine sweat gland is more responsive to changes in:

A

core temperature

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34
Q

Hypothalamic Response to Heat Stress

A
  1. Heat stress increases body temp
  2. Thermal receptors in the body core and skin send signals to the hypothalamus
  3. Hypothalamus initiates signal causing SNS to increase sympathetic activity
  4. Skin vasodilation and sweating
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35
Q

When exercising in the heat, skin arterioles ___ to increase heat loss.

A

dilate

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36
Q

When skin arterioles dilate for long periods of time, blood can start to ___ causing:

A

pool; SV and venous return to decrease

37
Q

When exercising in the heat, blood volume ___

A

decreases

38
Q

What is cardiovascular drift?

A

HR progressively increases during steady state exercise in the heat to compensate for blood volume loss via sweat

39
Q

Heat production that is not lost is stored:

A

in body tissues

40
Q

As exercise intensity increases:

A
  • heat production increases
  • linear increase in body temp
  • core temp increases proportional to active muscle mass
  • increased reliance on evaporative heat loss
41
Q

As ambient temp increases:

A
  • exercise-induced heat production remains constant
  • lower convective and radiant heat loss
  • higher evaporative heat loss
42
Q

Energy output increases as:

A

workload increases

43
Q

When exercising in heat, convective and radiative heat loss becomes:

A

less and less effective

44
Q

Heat index is the measurement of:

A

body’s perception of how hot it feels

45
Q

What is the best way to measure heat index?

A

Wet bulb globe temperature

46
Q

What is a sign of the start of heat illness?

A

heat cramps

47
Q

When someone experiences heat cramps, should you pull them from exercise?

A

yes

48
Q

What are heat cramps?

A
  • least serious of three heat illnesses
  • severe, painful cramping of large muscles
  • triggered by Na+ loss, dehydration
  • most common in heavy sweaters
  • prevented by liberal intake of Na+, water
49
Q

Which heat illness is a sign that things are going downhill quickly?

A

heat exhaustion

50
Q

What is heat exhaustion?

A
  • accompanied by fatigue, dizziness, nausea, vomiting, fainting, weak and rapid pulse
  • caused by severe dehydration from sweating
  • simultaneous blood flow needs of muscle met due to low blood volume
  • thermoregulatory mechanisms are functional but overwhelmed
51
Q

During heat exhaustion, are thermoregulatory mechanisms still working?

A

yes, but they are overwhelmed

52
Q

What would someone’s pulse who is suffering from heat exhaustion look like?

A

rapid and weak

53
Q

What is the most serious heat illness?

A

heat stroke

54
Q

What is best for dealing with heat stroke?

A

putting person in an ice bath with convection

55
Q

Will someone suffering from heat stroke be sweating?

A

no

56
Q

During heat stroke, are thermoregulatory mechanisms working?

A

no

57
Q

What will the pulse of someone suffering heat stroke feel like?

A

strong and rapid

58
Q

What is heat stroke?

A
  • life threatening, most dangerous
  • thermoregulatory mechanisms fail
  • characterized by core temp >40C (104F) and confusion, disorientation, unconsciousness
  • if untreated, results in coma, unconsciousness, and death
  • must cool whole body ASAP
  • recent heat illness compromises the body’s ability to deal with heat making heat stroke more likely
59
Q

What is heat stroke characterized by?

A

core body temp over 40C (104F) and confusion, unconsciousness, and disorientation

60
Q

Ways to prevent heat injuries:

A
  • exercise during cool hours
  • lower exercise intensity and/or duration
  • expose skin
  • frequent rests
  • frequent water breaks
61
Q

To prevent dehydration during exercise:

A
  • hydrate prior
  • consume 150-300 mL fluid every 15-20 mins
  • monitor urine color
62
Q

What are the causes of exercise performance impairment in hot environments?

A
  • accelerated glycogen metabolism
  • increased free radical production
  • reduced muscle blood flow due to increased skin blood flow and sweating
  • high brain temp reduces neuromuscular drive
63
Q

What is the consequence of accelerated glycogen metabolism?

A

increased lactate accumulation

64
Q

What is the consequence of increased free radical production?

A

damage to muscle contractile proteins

65
Q

What is the consequence of high brain temp that reduces neuromuscular drive?

A

reduction in motor unit recruitment (central fatigue)

66
Q

What are the three factors that contribute to impaired exercise performance in the heat?

A
  • central nervous system dysfunction
  • cardiovascular dysfunction
  • accelerated muscle fatigue
67
Q

What is heat acclimation?

A
  • rapid adaptation to environmental change
  • elevation of core temp promotes adaptation
68
Q

What is a heat acclimation training plan?

A
  • exercise in heat for 10-14 days
  • low intensity and long duration for 80-100 mins per day
  • moderate intensity, short duration for 30-35 mins per day
69
Q

Acclimation is lost within:

A

a few days of inactivity or no heat exposure, significant after 7 days, complete loss after 28 days

70
Q

What are some adaptations during heat acclimation?

A
  • increased plasma volume
  • earlier onset of sweating and higher sweat rate
  • reduced sodium chloride loss in sweat
  • reduced skin blood flow
  • increased cellular heat shock proteins
71
Q

Hypothermia is determined by a body temp below:

A

35 degrees celcius or 95 degrees F

72
Q

During cold stress, heat loss is ___ than heat production

A

greater

73
Q

Hypothalamic response to cold stress

A
  1. cold stress decreased body temp
  2. body core and skin neural thermal receptors send signal to the brain (hypothalamus)
  3. hypothalamus initiates signal causing sympathetic nervous system (SNS) to increase sympathetic activity
  4. effects act (shivering, decreased blood flow, increased thyroxin and sympathetic catecholamine release
74
Q

What is cold stress?

A

environmental condition that threatens temp homeostasis by decreasing core temp

75
Q

What are some physiological responses to exercise in the cold?

A
  • low core temp > slow HR
  • muscle function decreased
  • superficial muscle fibers numbed
  • as fatigue increases, metabolic heat production decreases
76
Q

Windchill factor takes into account:

A

air temp and air movement (wind)

77
Q

The lower the windchill factor value, the ___ the chance of freezing tissues

A

higher

78
Q

Heat loss is __x faster in cold water versus cold air

A

4x

79
Q

Heat loss is ___ in moving water

A

increased

80
Q

Hypothermia from cold water occurs well above ___ ___

A

freezing point (0 celcius)

81
Q

What is the treatment for hypothermia?

A
  • get person out of the cold
  • remove all wet clothing
  • provide warm drinks and dry clothing
  • put person into sleeping bag
  • find a source of heat
  • prepare for emergency treatment and/or evacuation
  • may require hospital facilities
82
Q

What are two health risks during exercise in the cold?

A
  • frostbite
  • exercise-induced asthma
83
Q

What is frostbite?

A
  • peripheral tissue freezing
  • excess vasoconstriction > lack of O2 nutrients > tissue death
84
Q

What happens if frostbite goes untreated?

A

gangrene (tissue death/rotting), tissue loss

85
Q

How do you treat frostbite?

A

gradually rewarm only when no risk of refreezing

86
Q

Exercise-induced asthma is caused by:

A

excessive airway drying

87
Q

Exercise-induced asthma is treated by:

A

steroid inhalers

88
Q

Cold related illness mitigation strategies:

A
  • dress in layers and remove as you warm-up
  • stay dry
  • avoid prolonged cold exposure after exercise
89
Q

What changes allow your body to acclimate to the cold?

A
  • lower skin temp at which shivering begins (increased non-shivering thermogenesis)
  • maintain higher hand and foot temp
  • adaptations begin in one week

Ex Phys (10 decks)

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