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Exercise Physiology > Lecture 12 > Flashcards

Lecture 12 Flashcards

1
Q

Lecture 12:

Define Thermoregulation

A

The regulation of body temperature around a [physiological set point

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2
Q

Lecture 12:

How do humans regulate their body temperature?

A

Humans are homeothermic - internal body temperature is regulated & nearly constant despite environmental temperature changes

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3
Q

Lecture 12:

What is Acclimation when discussion body temperature regulation?

A

The short-term adaptation to environmental stressors (days or weeks)

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4
Q

Lecture 12:

What is Acclimatization when discussion body temperature regulation?

A

The long-term adaptation to environmental stressors (months to years)

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5
Q

Lecture 12:

What is Metabolic Heat Production (M)?
- how does it occur? 75% from what & 25% from what?

A

M = the transfer of heat between the body & environment (heat moves from core to shell of body via blood)
- 25% of ATP breakdown comes from cellular work (With) & 75% from metabolic heat

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6
Q

Lecture 12:

How is heat lost/dissipated from the body when it reaches the skin?

A

1.) conduction
2.) convection
3.) radiation
4.) evaporation

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7
Q

Lecture 12:

How is heat gained?

A

1.) metabolic heat
2.) environmental heat (conduction, convection, & radiation)

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8
Q

Lecture 12:

When discussing body temp regulation & transfer of body heat, What is Conduction (K)?

A

The transfer of heat from one solid material to another through direct molecular contact (negligible)
-Eg; siting on cold or hot metal bleachers

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9
Q

Lecture 12:

When discussing body temp regulation & transfer of body heat, What is Convection (C)?

A

Transfer of heat through movement of gas/liquid across a surface
*increased movement across skin causes increased heat exchange
- this is a major daily thermoregulatory factor

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10
Q

Lecture 12:

When discussing body temp regulation & transfer of body heat, What is Radiation (R)?

A

Heat loss in the form of infrared rays/energy (eg; from sun)
- body can give or receive radiant heat
- is a daily thermoregulatory factor

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11
Q

Lecture 12:

Conduction, Convection, and radiation are all types of what category of heat exchange?
- what is resistant to this type of exchange?

A

All avenues of dry heat exchange
- Insulation (I) = resistance to dry heat exchange

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12
Q

Lecture 12:

When discussing body temp regulation & transfer of body heat, What is Evaporation (E)?

A

Loss of heat as liquids change to gas
- primary form of heat loss during exercise (~80%)
- clothing = resistance to E

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13
Q

Lecture 12:

When discussing the heat balance equation…
- what happens if it = 0?
- if it is <0?
- if it is >0?

A

= 0 —> heat balance (core temp doesnt change)
<0 —> heat loss
>0 —> heat gain

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14
Q

Lecture 12:

What is humidity & how does it lead to heat loss?

A

Humidity is essentially evaporated heat loss as it is water vapour pressure that affects Evaporation
- increase in humidity = decrease E; decrease humidity = increase E
- prolonged evaporation through sweat can cause dehydration

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15
Q

Lecture 12:

What is the cooling capacity of sweat?

A

If air temp is greater than or = to skin temp than convection will not rid sweat & evaporation will be used

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16
Q

Lecture 12:

What is the bodies core temperature regulated around?

A

Core temp regulated around 37deg C
*if core temp goes above 40deg C than it inhibits physiological thermoregulateion function

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17
Q

Lecture 12:

What is Thermoregulatory Function controlled by?

A

Preoptic-anterior Hypothalamus (POAH) regulates thermoregulatory control as it is the body’s thermostat located in the brain

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18
Q

Lecture 12:

How does the Preoptic-anterior Hypothalamus (POAH) work?

A

It receives input from sensory thermoreceptors & when body temperature deviates from normal levels, POAH activates thermoregulatory mechanisms
- once stimulated, it signals SNS effectors

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19
Q

Lecture 12:

What are 2 types of sensory receptors for temperature regulation?

A

1.) Peripheral thermoreceptors - in skin
2.) Central thermoreceptors - in brain & spinal cord

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20
Q

Lecture 12:

How do skin arteriole effectors of the SNS work?

A

1.) Cause SNS vasoconstriction (VC) which reduces heat loss
2.) Cause SNS vasodilation (VD) which increases heat loss

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21
Q

Lecture 12:

How do Eccrine Sweat Gland Effectors of the SNS help with thermoregulatory control?

A

SNS stimulates sweating to cause heat loss through evaporation
- glands are more responsive to changes in core temp than skin temp
- Acetlycholine causes sympathetic cholinergic stimulation

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22
Q

Lecture 12:

How do skeletal muscle effectors help regulate temperature?

A

Generate heat through shivering when cold through involuntary contraction & relaxation
- only produces heat (doesnt reduce it)

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23
Q

Lecture 12:

How do endocrine glands work as effectors for temperature regulation?

A

They increase metabolism to increase heat production & use hormonal stimulation for heat production
- they release thyroxine & catecholamines to cool body

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24
Q

Lecture 12:

What are some affects exercising in the heat has on cardiovascular function? (3)

A

1.) exercise in heat causes skin arterioles to VD & increase conventional heat loss (this requires increase in blood flow compared to in the cold)
2.) POAH triggers the SNS to increase cardiac output through HR & contractility to increase VC of nonessential tissues
3.) blood volume decreases causing sweat, SV doesnt increase causing blood to pool, thereby HR increases even more to compensate

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25
Q

Lecture 12:

What is the Cardiovascular Overload limitation when exercising in the heat?

A

Heart doesnt supply enough blood flow to exercising muscle & skil which impairs performance & increases risk of over heating
- especially impacts untrained athletes

26
Q

Lecture 12:

What is the Critical temperature theory when discussing limitations to exercising in the heat?

A

The brain shuts down/stops exercise at 40-41deg C which helps explain the limitations of trained athletes

27
Q

Lecture 12:

How does exercising in the heat further influence dehydration?

A
  • sweat rate & skin blood flow is reduced
  • small reductions in blood volume & BP due to dehydration
  • large reductions in SV & cardiac output
  • blood flow is reduced to active and inactive muscles/skin/brain
28
Q

Lecture 12:

What is precooling & its impact on sports performance?

A

Pre-cooling artificially lowers core temp before exercise such as cold water immersion, cooling vests, & icy drinks
- cooling can improve sport performance, particularly during endurance exercise but may be detrimental for sprint events or power exercises as could cause injury

29
Q

Lecture 12:

How is sweating used to maintain the bodies fluid balance?

A

Sweating occurs when hot environmental temperatures exceed the skin/core temperatures
- C, K, R all cause heat gain & only E causes heat loss
- eccrine sweat glands are controlled by POAh

30
Q

Lecture 12:

Which is more dilute… light or heavy sweating?

A

Light sweating = very dilute sweat & heavy sweating = less dilute sweat (more Na+ & Cl- loss)

31
Q

Lecture 12:

How is sweat composition affected by training?

A

Sweat becomes more sensitive to aldosterone & more Na+ & Cl- is reabsorbed/conserved
- loss of K+, Ca2+, & Mg2+ remains unchanged

32
Q

Lecture 12:

How much sweat is lost during exercise?

A

Possible hourly loss of 1.6-2.0L of sweat (2.5-3.2% of body weight)
- increased sweating leads to decreased blood volume & lowered cardiac output
- severe dehydration from sweating can lead to heat-related illnesses

33
Q

Lecture 12:

How is fluid balance controlled during exercise in the heat?

A

Fluid balance is maintained by hormones
- water loss causes electrolytes to trigger aldosterone & ADH release
- Aldosterone retains Na+ at kidneys & ADH retains water at the kidneys (vasopressin)

34
Q

Lecture 12:

What are the 6 risk factors to consider when exercising in the heat?

A

1.) Metabolic heat production
2.) Air temperature
3.) ambient water vapour pressure (humidity)
4.) air velocity
5.) radiant heat sources
6.) clothing

35
Q

Lecture 12:

How is external heat stress measured?

A

Heat index does not reflect on physiological stress
- wet-bulb globe temperature (WBGT) measures external heat stress & includes C, E, & R

36
Q

Lecture 12:

What is the WBGT (wet-bulb globe temperature) equation & what is it used for?

A

WBGT equation gauges thermal stress
- dry-bulb T is the actual sir temperature (C)
- Wet-bulb T reflects the evaporative potential (E)
- Globe T measures radiant heat load (R)
* WBGT = 0.1T + 0.7T + 0.2T

37
Q

Lecture 12:

What are the 3 main heat illnesses?
- rank from least to most dangerous

A

1.) Heat cramps
2.) Heat Exhaustion
3.) Heatstroke

38
Q

Lecture 12:

What are heat Cramps?
- caused by what? Prevented by what?

A

Severe, painful cramping of large muscles & most common in heavy sweaters
- triggered by Na+ losses & dehydration
- prevented by liberal intake of Na+ & water

39
Q

Lecture 12:

What is Heat Exhaustion?
- caused by what?

A

Fatigue, dizziness, nausea, committing, fainting, weka, & rapid pulse caused by severe dehydration from sweating & heat
- blood flow needs of muscle & skin are not met due to low blood volume
- thermoregulatory mechanisms are functional but overwhelmed

40
Q

Lecture 12:

What is Heatstroke?
- characterized by what?

A

Life-threatening impact of heat caused by thermoregulatory mechanism failure
- Characterized by; core temperature above 40deg Ch & confusion, disorientation, & unconsciousness
- death & coma if untreated - whole body cooling ASAP

41
Q

Lecture 12:

How can Hyperthermia be prevented?

A

Avoiding outdoor activities when WBGT is greater than 28deg C
- practice early morning or evening
- do not restrict fluid intake - have fluids available to replace fluid lost through sweat, drink every 15-30mins, minimize HR rise & core temp rise
- wear minimal clothing (especially for football)

42
Q

Lecture 12:

What are 5 Guidelines for Practicing/Competing in the Heat?

A

1.) Events should not take place during the hottest time of day (avoid 28+)
2.) Keep adequate supply of fluids
3.) Adjust fluid intake based on fluid losses
4.) Be aware of signs of heat illness
5.) Organizers get final call on stopping events, & excluding athletes who have heat illness

43
Q

Lecture 12:

What is Acclimation?

A

Repeated exercise in the heat that leads to rapid changes for better performance in hot conditions
- acclimation = short term (9-14days)
- acclimitization = long term (months to years)

44
Q

Lecture 12:

What are 3 key effects of Acclimation?

A

1.) Cardiovascular function is optimized
2.) Changes in sweating rate, sweat distribution, & sweat content
3.) Lower core temperature during exercise

45
Q

Lecture 12:

What are some sex differences to consider when exercising in the heat?

A

1.) Men & women have to same capacity of exercising in the heat at same relative intensity
2.) women have lower sweat rates than men
3.) women have more active sweat glands but less production per gland (advantage in humidity, disadvantage in hot/dry climates)

46
Q

Lecture 12:

What are some effects of exercising in the cold?

A

Cold stress comes from any environmental condition causing loss of body heat
- decreased core/skin temps triggers physiological/behavioural mechanisms
- POAH triggers; peripheral VC, no shivering thermogenesis, skeletal muscle shivering…
- Cerebral cortex triggers behavioural adaptations

47
Q

Lecture 12:

What is Cold Habituation?

A

Occurs after epeated exposures to cold with no significant heat loss
- VC & shivering is blunted & core temps allowed to decrease more

48
Q

Lecture 12:

When exercising in the cold, what is Metabolic Acclimation?

A

Occurs after repeated exposures to heat loss & enhances metabolic shivering for heat production

49
Q

Lecture 12:

When exercising in the cold, what is Insulative Acclimation?

A

Occurs when an increase in metabolism cannot prevent heat loss thus, skin VC is enhances and there’s an increase in peripheral tissue insulation

50
Q

Lecture 12:

How is heat loss impacted by windchill?

A

Windchill is the air movement not the airs temperature
- windchill index is based on cooling effect of wind
- C heat loss increased
- Increased windchill = increased risk of freezing tissues

51
Q

Lecture 12:

When discussing exercise in the cold, how does cold water compare to air?

A
  • considering C, K, E, + R, heat loss id 4x faster in cold water than in cold air
  • core temp is constant until water temp is below 32
  • core temp decreases by 2.1C per hour in 15C water
  • heat loss increases in moving water & decreases with exercise
    *Hypothermia occurs from cold water well above 0
52
Q

Lecture 12:

What happens to muscle function while exercising in the cold?

A

Muscle function decreases as fibre recruitment is altered & contractile forces decrease
- shortening velocity & power of muscle decreased
- superficial muscles are affected & deep muscles spared

53
Q

Lecture 12:

In the cold, how does fatigue relate to heat production?

A

As fatigue increases, metabolic heat production decreases as energy reserves are depleted with endurance exercise causing potential for hypothermia

54
Q

Lecture 12:

What happens to FFA metabolic responses when exercising in the cold?

A

Normally, catecholamines increase which increases FFA oxidation but in the cold, catecholamines secretion increases but does not increase FFA count
- VC occurs in subcutaneous fat causing FFA mobilization to decrease

55
Q

Lecture 12:

What happens to glucose metabolic responses when exercising in the cold?

A

Blood glucose is maintained during exposure to cold & muscle glycogen utilization increase
- hypoglycemia causes shivering to become suppressed

56
Q

Lecture 12:

When discussing health risks of exercising in the cold, what is Hypothermia?

A

When core temp is between34.5-29.5deg C & POAH function is compromised
- core temp below 29.5deg C means POAH thermoregulation is completely lost, metabolism is slowed, & coma is possible

57
Q

Lecture 12:

When discussing exercise in the cold, what are some Cardiorespiratory health risks/effects?

A

HR slows due to low core temp
- cold may decrease ventilation (rate & volume) but does not damage ventilators tissues

58
Q

Lecture 12:

What are the treatments for mild hypothermia?

A

Remove from cold & [or vide dry clothing, blankets, & warm beverages

59
Q

Lecture 12:

What are the treatments for severe hypothermia?

A

Handle gently to avoid arrhythmias, reward gradually, & may need to take to hospital or provide medical care

60
Q

Lecture 12:

When discussing exercising in the cold, what is Frostbite?
- treatment & cause?

A

Freezing of peripheral tissues in air temps below -29deg C
- excess VC leading to lack of O2/nutrients causing tissue death
*if untreated, tissue loss may occur
- treat by gradually re-warming once there is no risk of re-freezing

61
Q

Lecture 12:

When discussing health risks of exercising in the cold, what is Exercise-induced Asthma?
- treated how?

A

Affects ~50% winter athletes
- involves excessive airway drying & treated with beta-agonists or steroidal inhalers

Exercise Physiology (12 decks)

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