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Exercise Physiology > Temperature Regulation And Conditions > Flashcards

Temperature Regulation And Conditions Flashcards

1
Q

What are environmental factors affecting athletes in Colorado

A
  1. Altitude
  2. Dry
  3. Seasons
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2
Q

How are humans Hemotherms?

A

They produce or maintain core body temp through metabolic heat production

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3
Q

2 key parts of humans being hemotherms

A
  1. They maintain constant body temperature
  2. Heat loss matches heat gain
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4
Q

What is the normal core temperature and the range

A

37 (34-45) degrees Celsius

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5
Q

What happens at temperature above 45 Celsius

A

Can damage proteins and enzymes and lead to death

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6
Q

What happens below temperatures of 34 degrees Celsius

A

Can cause decreased metabolism and cardiac arrhythmias

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7
Q

What is the thermal gradient

A

Gradient that exists between deep body core to skin surface

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8
Q

What temperature is the thermal gradient

A

Approximately 4 degrees celsius or 20 in extreme cold

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9
Q

How do you measure deep core temp

A

Rectum, ear esophagus

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10
Q

Voluntary heat production comes from

A

Exercise releases 70-80% energy expenditure as heat

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11
Q

Involuntary heat production comes from

A

Shivering and Non shivering thermogenesis

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12
Q

Shivering effect on heat production

A

Increases heat production by 5x

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13
Q

Non-shivering thermogenesis (NST) on heat production

A

From Thyroxine (thyroid hormone) and catecholamines

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14
Q

Where does NST happen

A

Brown adipose tissue which holds thyroxine

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15
Q

4 mechanisms of heat loss

A
  1. Evaporation
  2. Radiation
  3. Conduction
  4. Convection
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16
Q

What is the primary mechanism of heat loss in hot environments

A

Evaporation

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17
Q

Convection

A

Body heat is lost to surrounding air, which becomes warmer, rises and is replaced with cooler air

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18
Q

Conduction

A

Body heat is lost to nearby objects through direct physical touch

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19
Q

Radiation

A

Body heat is lost to nearby objects without physically touching them

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20
Q

Evaporation

A

Body heat causes perspiration which is lost from the body surface when the liquid sweat changes to vapors

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21
Q

What three things influence mechanisms of heat transfer?

A
  1. Temperature
  2. Relative humidity
  3. Vapor pressure
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22
Q

What 3 things does evaporation rate depend on?

A
  1. Temp and relative humidity
  2. Convective currents around the body
  3. Amount of skin surface exposed
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23
Q

High relative humidity effect on vapors pressure gradient

A

Will decrease the vapor pressure gradient between the skin and environment ultimately decreasing the rate of evaporation

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24
Q

What happens to vapor pressure as it gets warmer

A

The warmer the temp, the higher the vapor pressure

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25
Q

Higher vapor pressure effect on vp gradient

A

Higher the vapor pressure will decrease the vp gradient

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26
Q

Convective current on evaporation

A

Encourages evaporation through air flow

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27
Q

Vapor pressure effect on evaporation

A

Higher vapor pressure (heat) means less likely to encourage evaporation

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28
Q

Humid effect on evaporation

A

The more humid the air, the less likely you will evaporate

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29
Q

Increased skin surface exposed

A

less clothes more evaporation; more clothes will absorb sweat a cool without less evaporation

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30
Q

High relative humidity effect on evaporative heat loss

A

Higher humidity will reduce evaporative heat loss and increase your perception of how hot it is (why humidity adds heat)

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31
Q

Where is the body’s thermostat located

A

In the preoptic anterior hypothalamus

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32
Q

What does the Preoptic anterior hypothalamus (POAH) do

A

Responds to increased core temperature to stimulate sweat glads for evaporative heat loss;
Also cutaneous vasodilation

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33
Q

What is the purpose of cutaneous vasodilation in the PAOH

A

Increase heat loss from the skin to be evaporated

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34
Q

What controls the POAH in heat balance?

A

Through sympathetic cholinergic control on the sweat glands and cutaneous vasculature

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35
Q

What stimulated sweating in the POAH

A

Ach binds to the eccrine sweat glands mAchR (muscarinic ach receptor) to produce sweat

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36
Q

What stimulates Vasodilation in the POAH

A

Ach binds to mAchR (muscarinic ach receptor) to dilate the blood vessels in the skin allowing for heat loss across the epidermis

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37
Q

Physiological response to heat load

A

Heat goes to the thermal receptors in the core and skin, is integrated in the POAH and sent to cutaneous vasodilation and sweating mechanism

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38
Q

What happens thermally as exercise intensity increases?

A

Heat production is increased due to muscular contraction causing a linear increase in body temperature

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39
Q

How does core temp change compared to amount of active muscle mass

A

Core temperature increases proportionally to the amount of active muscle mass

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40
Q

During steady state does exercise intensity or environmental temperature determine heat production

A

Exercise intensity

41
Q

Negative radiation and convection

A

Means you are gaining heat

42
Q

What actually changes heat production

A

Exercise work rate

43
Q

Higher core temperature due to submaximal exercise in a hot/humid environment risks what

A

Hyperthermia and heat injury

44
Q

Signs of heat cramps

A

Fatigue, thirst, profuse sweating, large muscle cramps

45
Q

Signs of heat exhaustion

A

Nausea; chills; headache

46
Q

Signs of heat stoke

A

Cessation of sweating; confusion; loss of consciousness

47
Q

What happens to oxygen consumption if you are not able to reach steady state

A

Oxygen consumption drifts

48
Q

What is the cardiovascular response maintain cardiac output while exercising in the heat

A

Heart rate will gradually increase to help compensate for decrease in stroke volume in order to maintain cardiac output

49
Q

What is the cardiovascular response to regulate blood flow while exercising in the heat

A

Blood flow is shunted away from working muscles and nonessential areas to the skin

50
Q

How high can sweat rates be?

A

Up to 4-5 L/hour

51
Q

Size effect on sweat rate

A

Larger individuals have higher sweat rates than smaller individuals

52
Q

What two things determine sweat rate?

A
  1. Genetic variation
  2. Size
53
Q

What is the endocrine responses to exercise in the heat

A

Increased release of vasopressin and aldosterone to retain blood volume and decrease urine output

54
Q

What factors contribute to impaired exercise performance?

A
  1. Central nervous system dysfunction
  2. Cardiovascular dysfunction
  3. Accelerated muscle fatigue
55
Q

What results from CNS dysfunction

A

Decreased motivation and reduced voluntary activation of motor units

56
Q

What results from Cardiovascular dysfunction in heat

A

Reduced stroke volume and CO during high intenity exercise; decreased muscle blood flow

57
Q

What causes accelerated muscle fatigue (3)

A
  1. Increased radical production
  2. Decreased muscle pH
  3. Muscle glycogen depletion
58
Q

Fluid intake role in core body temperature

A

Slows increase in core body temperature

59
Q

How much fluid should you consume during exercise

A

Hydrate prior; and consume 150 to 300 mL of fluid every 15 to 20 minutes

60
Q

How much fluid should you rehydrate per kg of fluid weight loss

A

1.5 L of fluid replacement

61
Q

Acclimation

A

Rapid physiological adaptation that occurs within days to a dew weeks, or is artificially induced in a climatic chamber

62
Q

Acclimatization

A

Gradual, long term adaptation that occurs within months to years of exposure to environmental stress

63
Q

What is the end result of heat acclimation

A

Lower heart rate and core temp during submaximal temperature

64
Q

5 adaptations during heat acclimation

A
  1. Increased plasma volume
  2. Earlier onset of sweating and higher sweat rate
  3. Reduced sodium chloride loss in sweat
  4. Reduced skin blood flow
  5. Increased cellular heat shock proteins
65
Q

Role of increased plasma volume during heat acclimation

A

(10-12%) maintains blood volume, stroke volume and sweating capacity

66
Q

Role of earlier onset sweating and higher sweat rate in heat acclimation

A

Less heat storage to maintain lower body temp

67
Q

Role of reduced sodium chloride loss in sweat in heat acclimation

A

Reduced risk of electrolyte disturbance

68
Q

Role of increased cellular heat shock proteins in heat acclimation

A

To prevent cellular damage due to heat

69
Q

How does the eccrine gland reduce sodium chloride loss in sweat

A

Parts of the eccrine gland can reabsorb electrolytes

70
Q

Why do you want a reduced skin blood flow in heat acclimation

A

Allows for core body temperature to be maintained better

71
Q

What do heat shock proteins do to prevent cellular damage due to heat?

A

They protect cells from thermal injury by stabilizing and remolding damaged proteins

72
Q

How many days does it take for heart rate to acclimate to heat

A

Around 4

73
Q

How many days does it take for plasma volume to acclimate to heat

A

3 days

74
Q

How many days does it take for perceived exertion to decrease when acclimating to heat

A

4 days

75
Q

How many days does it take for sweat rate to acclimate to heat

A

6 days

76
Q

what are the sex differences in thermoregulation?

A

They are small when matched for body composition and level of acclimation

77
Q

What are the age differences in thermoregulation?

A

Skin blood flow is reduced in older individuals (>60) resulting in reduced ability to lose heat during exercise

78
Q

How long does it take to lose acclimation?

A

Significant decline in 7 days with complete loss in 28 days.

79
Q

Skin blood flow adaptation during cold stress

A

Decrease in skin blood flow; at a lower temp for the same work load requiring less blood being redistributed from muscle working so less blood near skin

80
Q

How does the POAH respond to a decrease in core temp?

A

Through shivering and a decreased skin blood flow

81
Q

How is shivering stimulated?

A

When core temp dramatically drops, Somatic motor neurons stimulate skeletal muscle contraction to produce heat

82
Q

How does non-shivering thermogenesis increase body temperature?

A

By releasing NE and thyroxine from brown adipose tissue to increase the rate of cellular metabolism

83
Q

What happens to blood vessel regulation in the cold

A

Cutaneous Vasoconstriction

84
Q

How does the POAH regulate vasoconstriction?

A

By NE acting on alpha 1 adrenergic receptors causing the blood vessels to vasoconstrict and conserve heat

85
Q

Physiological response to cold stress

A

Clod stimulates the skin and core receptor; POAH integrates signal; Effectors for shivering, cutaneous vasoconstriction, catecholamine release, thyroxin release

86
Q

Subcutaneous fat as an insulator

A

Effective in cold water; primary fuel for shivering in well-fed individuals

87
Q

Water immersion rate of heat loss

A

25x greater than air of same temperature

88
Q

Blood flow response to the cold

A

Blood flow is shunted through cutaneous vasoconstriction away from the skin to the core

89
Q

Hand muscle function in cold

A

Cold exposure to the hands can cause numbness by a reduce in blood flow and a depressed rate of neural transmission and numb; can lose dexterity and negatively impact motor skills

90
Q

What happens when body temperature declines from 37 to 25 degrees Celsius or lower

A

Level of hypothermia is associated with life threatening cardiac arrhythmias

91
Q

Breathing cold air effects

A

Will not impact respiratory tract but can trigger exercise induced asthma because of cooling and drying of airways

92
Q

What 3 things happen in cold adaption?

A
  1. Lower skin temperature
  2. Maintain higher hand temperature
  3. Improved ability to sleep in the cold
93
Q

What happens to skin in adaptation to cold

A

Shivering begins at a lower skin temperature because of the increase in utilizing non-shivering thermogenesis

94
Q

Why do hands and feet have higher temperature in cold acclimation?

A

To improve peripheral blood flow

95
Q

Why do you sleep better in cold after acclimating?

A

There is a reduction in shivering

96
Q

How do cold-acclimatized people maintain heat production

A

Less shivering by increasing non-shivering thermogenesis

97
Q

Sex differences in responses to cold exposure

A

At rest women reduce body temp faster than men but show a similar decrease in cold water

98
Q

Age responses to cold exposure

A

Older >60 become less tolerant to cold. Children have a faster fall in body temp

99
Q

During cold stress what caused vasoconstriction of blood vessels of the skin?

A

Norepinephrine acting on alpha 1 ADR

Exercise Physiology (12 decks)

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