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KIN 335 > Chapter 25 - Thermoregulation > Flashcards

Chapter 25 - Thermoregulation Flashcards

1
Q

What is the average core temperature?

A

36-37.8C

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2
Q

How much does metabolism rise in elite athletes during intense aerobic exercise?

A
  • 20-25 above resting levels
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3
Q

What does the increase in metabolism during intense exercise do regarding thermoregulation?

A
  • increases core temperature
  • Most of metabolisms results in heat production
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4
Q

What is the O2 consumption at rest?

A

0.25L/min

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5
Q

What is the O2 consumption during maximal exercise?

A

5L/min

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6
Q

How does heat loss occur in the body?

A
  • Radiation
  • Conduction
  • Convection
  • Evaporation
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7
Q

How is heat gained in the body?

A
  • Basal Metabolic Rate
  • Muscular Activity
  • Hormones
  • Thermic Effect of Food
  • Postural Changes
  • Environment
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8
Q

What does conduction heat exchange involve?

A
  • Direct heat transfer from one molecule to another through a liquid, solid, or gas
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9
Q

How does conduction contribute to a small amount of heat loss in the body?

A
  • Directly through deep tissues to cooler surface
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10
Q

What does the rate conductive heat loss depend on?

A
  • Temperature gradient between the skin and surrounding temperature
  • Thermal qualities of the surface
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11
Q

What does convection heat exchange involve?

A
  • Transferring heat by motion of gas or liquid across a heated surface
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12
Q

How does heat loss occur with convection?

A
  • Air moves around us, passes over the skin, heat is exchanged with the air molecules.
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13
Q

What contributes to the rate of heat exchange by convection?

A

The greater the movement, the greater the rate

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14
Q

What do all objects continually emit?

A
  • Electromagnetic heat waves or radiant energy
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15
Q

What are the primary methods for eliminating body heat during rest?

A
  • Radiation and Convection
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16
Q

Describe Radiation

A
  • Emission of electromagnetic heat waves or radiant energy
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17
Q

What is the primary avenue for heat dissipation during exercise?

A
  • Evaporation
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18
Q

What happens when a fluid evaporates and turns into a gaseous form?

A
  • Heat is lost (because its required)
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19
Q

What three factors influence the total amount of sweat vaporized from the skin and pulmonary surfaces?

A
  • Surface exposure to the environment
  • Temperature and relative humidity of the ambient air
  • Convection air currents about the body
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20
Q

How does the body gain heat from radiation?

A
  • Sky
  • Solar
  • Ground
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21
Q

How does the body lose heat from radiation?

A
  • From the body
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22
Q

How does the body lose heat through evaporation?

A
  • Respiratory
  • Sweat
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23
Q

How does the body lose heat through convection?

A
  • Muscle blood flow convection
  • Skin/Blood convection
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24
Q

How does the body lose heat through conduction?

A
  • Skin to surrounding area
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25
Q

What range of body temperature change can the human body tolerate?

A
  • Decline of 10C
  • Increase of 5C
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26
Q

What plays a primary role in the balance of body temperature?

A
  • Hypothalamus
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27
Q

What provides input to the central control center for temperature regulations?

A
  • Thermal receptors in the skin
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28
Q

What is the water vapor pressure gradient?

A
  • Difference between water vapor pressure on skin and in air
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29
Q

What is the heat produced in muscles an example of?

A
  • Conduction
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30
Q

What is the heat transported in the blood and example of?

A
  • Convection
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31
Q

Where are the central receptors located?

A
  • Hypothalamus
  • Other brain regions
  • Spinal Cord
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32
Q

What are central receptors sensitive to?

A
  • Blood temperature changes as small as 0.01C
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33
Q

What triggers the hypothalamus reflexes that conserve or eliminate body heat?

A
  • Very small changes in temperature changes of the blood passing through the hypothalamus
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34
Q

What happens at rest in the heat, regarding heat regulation?

A
  • Increase HR and Cardiac Output
  • Superficial and Venous Blood vessels dilate
  • Warm blood diverted to skin
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35
Q

What are the two competitive cardiovascular demands during exercise in heat?

A
  • Muscles require oxygen to sustain energy metabolism
  • Arterial blood that diverts to the periphery to cool the body cannot deliver its oxygen to active muscle
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36
Q

What happens to cardiac output during extreme heat stress?

A
  • 15-25% passes through the skin
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37
Q

What happens to stroke volume and heart rate at submaximal exercise in heat?

A
  • Lower Stroke Volume
  • Higher Heart Rate
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38
Q

What happens to cardiac output during submaximal exercise in heat?

A

Maximal Decrease
- Rise in HR does not offset drop in stroke volume

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39
Q

What circulatory adjustments during exercise in heat lead to increased blood lactate accumulation?

A
  • Decreased lactate uptake by the liver from reduced hepatic blood flow
  • Less muscle catabolism of circulating lactate because heat dissipation diverts cardiac output to the periphery
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40
Q

What does sweat do for hydration and electrolyte saturation in the body?

A
  • Reduces both
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41
Q

What does a single bout of activity in heat do to aldosterone?

A
  • Stimulates its release
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42
Q

What does aldosterone do?

A
  • act on renal tubules
  • Increase sodium reabosorption
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43
Q

What is aldosterone?

A
  • Sodium-conserving hormone
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44
Q

What is vasopressin?

A
  • Antiduretic hormone
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45
Q

What does exercise in heat do to vasopressin?

A
  • stimulates release
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46
Q

Where is vasopressin released from?

A
  • Hypothalamus
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47
Q

What does vasopressin do?

A
  • Increases permeability of collecting tubules of kidneys
  • facilitate fluid retention
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48
Q

Describe the pathway of fluid loss and retention during exercise

A
  • Muscular activity promotes sweating which causes loss of blood plasma, resulting in hemoconcentration and increased blood osmolality.
  • Increased blood osmolarity stimulates osmoreceptors in the hypothalamus which sends a neural signal to the posterior pituitary gland.
  • The posterior pituitary gland secretes ADH into blood which acts on the kidneys, increasing water permeability of the renal tubules and collecting ducts.
  • Leads to increased reabsorption of water and decreased urine output aids in minimizing body fluid loss.
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49
Q

How much sweat does moderate exercise for an hour produce?

A
  • 0.5-1L sweat loss
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50
Q

What places a demand on fluid reserves? what can it lead to?

A

Evaporative Cooling
- Lead to dehydration

51
Q

What are the 5 factors that coincide with fluid loss?

A
  • Lower plasma volume
  • Depressed skin blood flow for a given core temperature
  • Reduced Stroke Volume
  • Increased Heart Rate
  • General Deterioration in Circulatory and Thermoregulatory efficiency in exercise
52
Q

What does ingesting fluid during exercise do?

A
  • Increases blood flow to the skin for effective cooling
53
Q

What does fluid replacement during exercise need to focus on?

A
  • Maintaining plasma volume
  • Optimal circulation and sweating
54
Q

What provides the most effective defense against heat stress?

A
  • Adequate hydration
55
Q

What is hyperhydration?

A
  • Ingesting extra water
56
Q

Why might hyperhydration be beneficial before exercise in heat?

A
  • Offers thermoregulatory protection
57
Q

What are 3 practical ways to promote acute pre-exercise hyperhydration?

A
  • Consume 500mL H2O before sleeping
  • Consume 500mL upon awakening
  • Consume 500mL of cold water 20 min before exercise
58
Q

What do changes in body weight following exercise indicate?

A
  • Water loss
  • Adequacy of rehydration
59
Q

What are ideal conditions for rehydration?

A
  • Intake matches outtake
  • Water intake equal rate to loss through sweat
60
Q

What does each pound of weight lost represent?

A
  • 450mL dehydration
61
Q

How can you recover electrolytes lost during exercise through sweat?

A
  • Add them to rehydration drink
62
Q

What does the american college of sport medicine recommend for consuming sports drinks?

A
  • 0.5-0.7g Na/L of fluid during exercise
63
Q

What is urine volume inversely related to?

A
  • Beverage’s sodium content
64
Q

What does a modest rise in core temperature during exercise represent?

A
  • Favourable adjustment that optimizes physiologic and metabolic functions
65
Q

What 5 factors interact to improve physiologic adjustment and exercise tolerance during environmental heat stress?

A
  • Acclimatization
  • Training Status
  • Age
  • Gender
  • Body Fat Level
66
Q

What does repeated exposure to hot environments when combined with physical activity do?

A
  • Improves exercise capacity with less discomfort upon subsequent heat exposure
67
Q

What does the term heat acclimatization describe?

A
  • Collective physiologic adaptations that improve heat tolerance
68
Q

When does a major portion of heat acclimatization occur?

A
  • First week of heat exposure
69
Q

What are the heat acclimatization responses? (8)

A
  • Improve Cutaneous Blood Flow
  • Effective distribution of Cardiac Output
  • Lowered Threshold for start of sweating
  • More effective distribution of sweat over skin surface
  • Increased sweat output
  • Lower salt concentration of sweat
  • Lower skin and core temp and HR for standard exercise
  • Less reliance on carbs during exercise
70
Q

What is the effect of the heat acclimatization response: improved cutaneous blood flow?

A
  • Transports metabolic heat from deep tissue (core) to shell
71
Q

What is the effect of the heat acclimatization response: Effective distribution of cardiac output?

A
  • Appropriate ciruclation to skin and muscles to meet demand of metabolism and thermoregulation
  • Greater blood pressure stability during exercise
72
Q

What is the effect of the heat acclimatization response: Lowered Threshold for start of sweating?

A
  • Evaporative cooling begins early in exercise
73
Q

What is the effect of the heat acclimatization response: More effective distribution of sweat over skin surface?

A
  • Optimum use of effective body surface for evaporative cooling
74
Q

What is the effect of the heat acclimatization response: Increased sweat output?

A
  • Maximizes evaporative cooling
75
Q

What is the effect of the heat acclimatization response: Lower salt concentration of sweat?

A
  • Dilute sweat preserves electrolytes in extracellular fluid
76
Q

What is the effect of the heat acclimatization response: Lower skin and core temperature and heart rate for standard exercise?

A
  • Frees greater proportion of cardiac output to active muscles
77
Q

What is the effect of the heat acclimatization response: Less reliance on carbohydrate catabolism during exercise?

A
  • Carbohydrate sparing
78
Q

How do trained individuals living in temperate climates respond to severe heat compared to sedentary counterparts?

A
  • More effectively
79
Q

What does training do for heat managment?

A
  • Increases sensitivity and capacity of the sweat response
  • Sweating begins at a lower temperature
80
Q

how do trained individuals differ from sedentary individuals regarding cutaneous blood flow?

A
  • Greater cutaneous blood flow at given internal temperature
  • Greater cutaneous blood flow at given percentage of VO2max
81
Q

Are there age-related decrements in thermoregulation for marathon runners?

A
  • NO
82
Q

Who has more heat-activated sweat glands per unit skin area, children or adults?

A
  • Children
83
Q

What do children do compared to adults regarding thermoregulation?

A
  • Sweat less
  • Maintain higher core temperature
84
Q

What are the recommendations for children regarding physical activity in high temperatures?

A
  • Intensity of effort decreased
  • Longer duration for acclimatization
85
Q

Who sweats more, men or women?

A
  • Men
86
Q

What do women typically have that helps them with thermoregulation? How?

A

Smaller, relatively larger body surface area per unit mass
- Favours greater heat dissipation through circulatory mechanisms

87
Q

What does excess body fat represent regarding thermoregulation?

A
  • Liability when exercising in heat
88
Q

How does increased fat mass reduce the capacity for thermoregulation?

A
  • Higher specific heat capacity
  • Acts as insulator
  • Limits heat conduction to the periphery
89
Q

How do larger people have a limited effectiveness of sweat evaporation?

A
  • Smaller surface area to body mass ratio
90
Q

What are Heat Cramps?

A
  • Severe involuntary, sustained, and spreading muscle spasms
91
Q

When do Heat Cramps occur?

A
  • During or after intense physical activity, usually in exercised muscles
92
Q

When does heat exhaustion occur?

A
  • ineffective circulatory adjustments compounded by depletion of extracellular fluid, principally plasma volume from excessive sweating
93
Q

What is the most complex problem from heat exposure?

A
  • Heat Stroke
94
Q

What does Heat Stroke Reflect?

A
  • Failure of heat-regulating mechanisms from an excessively high core temperature
95
Q

What are some warning signs of Heat-related Disorders?

A
  • Nausea
  • Chills, Goose Bumps
  • Headaches
  • Fatigue
  • Excessive Thirst
  • Cessation of Sweating
  • Profuse Sweating
  • Confusion
  • Painful Large Muscle Cramps
  • Loss of Consciousness
96
Q

Is Oral temperature reliable for testing core temperature?

A
  • NO
97
Q

What does the hypothalamus sense regarding thermoregulation?

A
  • Increased Temperature
98
Q

Where does the hypothalamus send signals when it senses an increase in temperature?

A
  • Sweat glands become active
  • Vasodilation in skin blood vessels
99
Q

How does the hypothalamus activating the sweat glands help with thermoregulation?

A
  • Increase evaporative heat loss
100
Q

How does the hypothalamus vasodilating skin blood vessels help with thermoregulation?

A
  • More Heat lost from the skin
101
Q

What vascular adjustments occur in response to cold?

A
  • Cutaneous cold receptors constrict peripheral blood vessels
102
Q

How does the cutaneous cold receptors constricting peripheral blood vessels in the cold help?

A
  • Reduce flow of warm blood to the body’s surface
  • Redirecting warm blood to core
103
Q

What is the greatest contribution to defending against the cold?

A
  • Physical Activity
104
Q

Exercise energy metabolism can sustain constant core temperature in the cold up to what air temperature?

A

-30C

105
Q

What does shivering in the cold do?

A
  • Generates metabolic heat
106
Q

Describe Shivering

A
  • Rapid, involuntary cycle of contraction and relaxation of skeletal muscle
107
Q

How much can shivering increase the body’s heat production by?

A
  • four to five times
108
Q

What neurotransmitters increase the heat production during cold exposure?

A
  • Epinephrine
  • Norepinephrine
109
Q

What does cold stress stimulate from the thyroid?

A
  • Release of Thyroxine
110
Q

What does the release of thyroxine from the thyroid during cold stress do?

A
  • Increases resting metabolism
111
Q

What is normothermia?

A

98.6F

112
Q

What temperature range is mild hypothermia?

A

95-91.4F

113
Q

What changes might occur during mild hypothermia?

A
  • Max Shivering
  • Increased Blood Pressure
  • Amnesia
  • Dysarthria
  • Poor Judgement
  • Behaviour Change
  • Ataxia
  • Apathy
114
Q

What temperature range signifies moderate hypothermia?

A

89-85F

115
Q

What changes might occur during moderate hypothermia?

A
  • Stupor
  • Shivering Ceases
  • Pupils Dilate
  • Cardiac Arrhythmias
  • Decreased Cardiac Output
  • Unconsciousness
116
Q

What temperature range signifies severe hypothermia?

A

82-56F

117
Q

What changes might be seen in severe hypothermia?

A
  • Ventricular fibrillation likely
  • Hypoventilation
  • Loss of reflexes and voluntary motion
  • Acid-base disturbances
  • No Response to pain
  • Reduced cerebral blood flow
  • Hypotension
  • Bradycardia
  • Pulmonary Edema
  • No Corneal Reflexes
  • Areflexia
  • Electroencephalographic Silence
  • Asystole
  • Lowest Infant Survival
  • Lowest Adult Survival
118
Q

How does the hypothalamus help in thermoregulation during cold temperatures?

A
  • Senses drop in blood temperature
  • Sends signal to skin blood vessels for vasoconstriction
  • Sends signals to skeletal muscles for shivering
119
Q

Does cold ambient air pose special danger to the respiratory passages?

A
  • NO
120
Q

What happens when extremely cold ambient air enters the respiratory tract?

A
  • Reaches 26-32C before it reaches the bronchi
121
Q

What evidence contradicts the theory that cold ambient air poses no threat to damaging the respiratory passages?

A
  • Athletes who exercise in very cold environments have a higher occurrence of hyper-reactivity or asthma compared to those who exercise in warmer environments
122
Q

What did the study on Alaskan sled dogs support?

A
  • Strenuous exercise in cold environments can lead to lower airway disease
123
Q

What did the study on airway remodeling from cold-weather exercise in elite athletes find?

A
  • Prolonged repeated exposure of the airways to inadequately conditioned air may induce inflammation and remodeling in competitive skiers
124
Q
A

KIN 335 (12 decks)

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