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EPHE 441 - Midterm (A) > Thermoregulation > Flashcards

Thermoregulation Flashcards

1
Q

Heat gain factors

A 
BMR 
Muscular Activity 
Hormones 
Thermic effect of food 
Postural changes of the environment
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2
Q

Heat loss factors (4)

A

Radiation
Conduction
Convection
Evaporation

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3
Q

Hypothalamic Temperature Regulation: What is it and how is it activated (2)

A

Acts as thermostat set and regulated at 37°C ±1°C
initiates responses to protect from gain or loss of heat

CANNOT TURN OFF HEAT, initiates responses to protect from gain or loss of heat

Activation of heat-regulating mechanisms:

  1. Thermal receptors in skin =input to central control center
  2. Changes in Tblood perfusing hypothalamus directly stimulate central control centre
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4
Q

Heat Gain Factors (6)

A 
BMR 
Muscular Activity 
Hormones 
Thermic effect of food 
Postural changes 
Environment
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5
Q

Increased Body temperature during exercise

A

Increase in body temperature with work rate

Linear across wide range of temperatures

Linear for both arm and leg exercises

Temperature proportional to active muscle mass

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6
Q

Effects of Clothing on thermoregulation (6)

A
  1. Wind Speed: Higher speed disturbs zone of insulation
  2. Body movements: Moving disturbs zone of insulation
  3. Chimney Effect: Loosely hanging clothing ventilates trapped air layers away from body
  4. Bellows Effect: vigorous body movements increase ventilation of air layers that conserve body heat
  5. Water vapor transfer: clothes resist water vapor exit
  6. Permeation efficiency factor: how well clothing absorbs liquid by capillary action
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7
Q

Football uniforms

A

Football equipment and clothing seal off 50% of body from evaporative cooling benefits
-Football gear exacerbates increase in rectal and skin temp with exercise

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8
Q

Is ear temp a good measurement of core temp

A

Ear temp generally measures lower than actual core temperature.

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9
Q

Effect of Ambient Temperature (3)

A
  1. Heat production remains constant
  2. Lower convective and radiant heat loss
  3. Higher evaporative loss
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10
Q

Evaporation

A

In order for heat to be lost by sweat it MUST evaporate

Wiping sweat is wastful and innefective

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11
Q

Three Factors influence total amount of sweat vaporized from skin and/or pulmonary surfaces

A
  1. Surface exposed to environment
  2. Temperature and relative humidity of ambient air
  3. Convective air currents about the body
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12
Q

Most important factor determining effectiveness of evaporative heat loss

A

Ratio of water in ambient air (at a given temperature) to total quantity of moisture that air could contain.

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13
Q

Sweat Production & Electrolyte Loss

A
  1. Sodium (Dominant): Loss will be noticed in kidneys, which will affect nerve transmission, muscle activation and blood volumes
  2. Potassium (Limited)
  3. Magnesium
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14
Q

Pathway Heat takes to escape

A

Tissues -> Skin -> Blood -> Environment

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15
Q

Fatigue and Core Temperature

A

Generally coincides with core temperatures between 38 to 40 C

Impairs muscle activation from high brain temperature

Decreases central drive to exercise

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16
Q

Impaired exercise performance with inefficient thermoregulation

A

Fluid and electrolyte loss
Metabolic changes

Impairs ability to deliver glucose and fatty acids

17
Q

Water Loss in heat

A

Moderate exercise > 1 hour = 0.5-1.0 L sweat loss

18
Q

Such fluid loss coincides with (5)

A

Fluid loss of 2% body mass adversely affects exercise

  1. Lower plasma volume
  2. Depressed skin blood flow for a given core temperature 3. Reduced stroke volume
  3. Increased near-compensatory heart rate
  4. General deterioration in circulatory and thermoregulatory efficiency in exercise
19
Q

Mechanisms contributing to dehydration-mediated physical performance degradation:

A
  1. Augmented hyperthermia
  2. Increased cardiovascular strain
  3. Altered metabolic & central nervous system functions
  4. Increased perception of effort (RPE)
20
Q

Factors that Modify Heat tolerance

A
  1. Acclimatization
  2. Trainingstatus
  3. Age
  4. Gender
  5. Bodyfatlevel
21
Q

Acclimatization Response and its effects: Improved cutaneous blood flow

A

Transports metabolic heat from deep tissues to shell

22
Q

Acclimatization Response and its effects: Effective distribution of cardiac output

A

Appropriate circulation to skin and muscles to meet demands of metabolism and thermoregulation; greater blood pressure stability during exercise

23
Q

Acclimatization Response and its effects: Lowered threshold for start of sweating

A

Evaporative cooling begins early in exercise

24
Q

Acclimatization Response and its effects: More effective distribution of sweat over skin surface

A

Optimum use of effective body surface for evaporative cooling

25
Q

Acclimatization Response and its effects: Increased sweat output

A

Maximizes evaporative cooling

26
Q

Acclimatization Response and its effects: Lowered salt concentration of sweat

A

Dilute sweat preserves electrolytes in extracellular fluid

27
Q

Acclimatization Response and its effects: Lower skin and core temperatures and heart rate for standard exercise

A

Frees greater proportion of cardiac output to the active muscles

28
Q

Acclimatization Response and its effects: Less reliance on carbohydrate catabolism during exercise

A

Carbohydrate sparing

29
Q

Physical Activity in the Cold

A 
Chronic exertional fatigue 
Sleep loss
Inadequate nourishment 
Reduced tissue insulation
Depressed shivering heat production
30
Q

Fat and Physiologic Function in the Cold

A

Successful ocean swimmers possess large amount of subcutaneous fat than highly trained non ocean swimmers

Additional Fat increases effective insulation in cold water

31
Q

Cold Stress and Children

A

A child’s large body surface area-to-mass ratio facilitates heat loss in a warm environment but becomes a liability during cold stress because body heat dissipates rapidly

Rely on two mechanisms to compensate for their relatively large surface area-to-mass ratio:
– Augmented energy metabolism
– More effective peripheral vasoconstriction in limbs

32
Q

Cold Acclimatization

A

Humans adapt poorly to long-term cold exposure compared to prolonged heat exposure

Adaptations:
Hand and feet blood flow can increase
Shivering occurs at lower body temp
Improved ability to sleep in the cold 
Changes in peripheral blood flow distribution
33
Q

Predisposing factors to frost bite

A 
Alcohol Use
Low physical fitness 
Fatigue
Dehydration 
Poor peripheral circulation

EPHE 441 - Midterm (A) (6 decks)

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