Temperature Regulation And Conditions Flashcards
1
Q
What are environmental factors affecting athletes in Colorado
A
- Altitude
- Dry
- Seasons
2
Q
How are humans Hemotherms?
A
They produce or maintain core body temp through metabolic heat production
3
Q
2 key parts of humans being hemotherms
A
- They maintain constant body temperature
- Heat loss matches heat gain
4
Q
What is the normal core temperature and the range
A
37 (34-45) degrees Celsius
5
Q
What happens at temperature above 45 Celsius
A
Can damage proteins and enzymes and lead to death
6
Q
What happens below temperatures of 34 degrees Celsius
A
Can cause decreased metabolism and cardiac arrhythmias
7
Q
What is the thermal gradient
A
Gradient that exists between deep body core to skin surface
8
Q
What temperature is the thermal gradient
A
Approximately 4 degrees celsius or 20 in extreme cold
9
Q
How do you measure deep core temp
A
Rectum, ear esophagus
10
Q
Voluntary heat production comes from
A
Exercise releases 70-80% energy expenditure as heat
11
Q
Involuntary heat production comes from
A
Shivering and Non shivering thermogenesis
12
Q
Shivering effect on heat production
A
Increases heat production by 5x
13
Q
Non-shivering thermogenesis (NST) on heat production
A
From Thyroxine (thyroid hormone) and catecholamines
14
Q
Where does NST happen
A
Brown adipose tissue which holds thyroxine
15
Q
4 mechanisms of heat loss
A
- Evaporation
- Radiation
- Conduction
- Convection
16
Q
What is the primary mechanism of heat loss in hot environments
A
Evaporation
17
Q
Convection
A
Body heat is lost to surrounding air, which becomes warmer, rises and is replaced with cooler air
18
Q
Conduction
A
Body heat is lost to nearby objects through direct physical touch
19
Q
Radiation
A
Body heat is lost to nearby objects without physically touching them
20
Q
Evaporation
A
Body heat causes perspiration which is lost from the body surface when the liquid sweat changes to vapors
21
Q
What three things influence mechanisms of heat transfer?
A
- Temperature
- Relative humidity
- Vapor pressure
22
Q
What 3 things does evaporation rate depend on?
A
- Temp and relative humidity
- Convective currents around the body
- Amount of skin surface exposed
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
24
Q
What happens to vapor pressure as it gets warmer
A
The warmer the temp, the higher the vapor pressure
25
Higher vapor pressure effect on vp gradient
Higher the vapor pressure will decrease the vp gradient
26
Convective current on evaporation
Encourages evaporation through air flow
27
Vapor pressure effect on evaporation
Higher vapor pressure (heat) means less likely to encourage evaporation
28
Humid effect on evaporation
The more humid the air, the less likely you will evaporate
29
Increased skin surface exposed
less clothes more evaporation; more clothes will absorb sweat a cool without less evaporation
30
High relative humidity effect on evaporative heat loss
Higher humidity will reduce evaporative heat loss and increase your perception of how hot it is (why humidity adds heat)
31
Where is the body’s thermostat located
In the preoptic anterior hypothalamus
32
What does the Preoptic anterior hypothalamus (POAH) do
Responds to increased core temperature to stimulate sweat glads for evaporative heat loss;
Also cutaneous vasodilation
33
What is the purpose of cutaneous vasodilation in the PAOH
Increase heat loss from the skin to be evaporated
34
What controls the POAH in heat balance?
Through sympathetic cholinergic control on the sweat glands and cutaneous vasculature
35
What stimulated sweating in the POAH
Ach binds to the eccrine sweat glands mAchR (muscarinic ach receptor) to produce sweat
36
What stimulates Vasodilation in the POAH
Ach binds to mAchR (muscarinic ach receptor) to dilate the blood vessels in the skin allowing for heat loss across the epidermis
37
Physiological response to heat load
Heat goes to the thermal receptors in the core and skin, is integrated in the POAH and sent to cutaneous vasodilation and sweating mechanism
38
What happens thermally as exercise intensity increases?
Heat production is increased due to muscular contraction causing a linear increase in body temperature
39
How does core temp change compared to amount of active muscle mass
Core temperature increases proportionally to the amount of active muscle mass
40
During steady state does exercise intensity or environmental temperature determine heat production
Exercise intensity
41
Negative radiation and convection
Means you are gaining heat
42
What actually changes heat production
Exercise work rate
43
Higher core temperature due to submaximal exercise in a hot/humid environment risks what
Hyperthermia and heat injury
44
Signs of heat cramps
Fatigue, thirst, profuse sweating, large muscle cramps
45
Signs of heat exhaustion
Nausea; chills; headache
46
Signs of heat stoke
Cessation of sweating; confusion; loss of consciousness
47
What happens to oxygen consumption if you are not able to reach steady state
Oxygen consumption drifts
48
What is the cardiovascular response maintain cardiac output while exercising in the heat
Heart rate will gradually increase to help compensate for decrease in stroke volume in order to maintain cardiac output
49
What is the cardiovascular response to regulate blood flow while exercising in the heat
Blood flow is shunted away from working muscles and nonessential areas to the skin
50
How high can sweat rates be?
Up to 4-5 L/hour
51
Size effect on sweat rate
Larger individuals have higher sweat rates than smaller individuals
52
What two things determine sweat rate?
1. Genetic variation
2. Size
53
What is the endocrine responses to exercise in the heat
Increased release of vasopressin and aldosterone to retain blood volume and decrease urine output
54
What factors contribute to impaired exercise performance?
1. Central nervous system dysfunction
2. Cardiovascular dysfunction
3. Accelerated muscle fatigue
55
What results from CNS dysfunction
Decreased motivation and reduced voluntary activation of motor units
56
What results from Cardiovascular dysfunction in heat
Reduced stroke volume and CO during high intenity exercise; decreased muscle blood flow
57
What causes accelerated muscle fatigue (3)
1. Increased radical production
2. Decreased muscle pH
3. Muscle glycogen depletion
58
Fluid intake role in core body temperature
Slows increase in core body temperature
59
How much fluid should you consume during exercise
Hydrate prior; and consume 150 to 300 mL of fluid every 15 to 20 minutes
60
How much fluid should you rehydrate per kg of fluid weight loss
1.5 L of fluid replacement
61
Acclimation
Rapid physiological adaptation that occurs within days to a dew weeks, or is artificially induced in a climatic chamber
62
Acclimatization
Gradual, long term adaptation that occurs within months to years of exposure to environmental stress
63
What is the end result of heat acclimation
Lower heart rate and core temp during submaximal temperature
64
5 adaptations during heat acclimation
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
Role of increased plasma volume during heat acclimation
(10-12%) maintains blood volume, stroke volume and sweating capacity
66
Role of earlier onset sweating and higher sweat rate in heat acclimation
Less heat storage to maintain lower body temp
67
Role of reduced sodium chloride loss in sweat in heat acclimation
Reduced risk of electrolyte disturbance
68
Role of increased cellular heat shock proteins in heat acclimation
To prevent cellular damage due to heat
69
How does the eccrine gland reduce sodium chloride loss in sweat
Parts of the eccrine gland can reabsorb electrolytes
70
Why do you want a reduced skin blood flow in heat acclimation
Allows for core body temperature to be maintained better
71
What do heat shock proteins do to prevent cellular damage due to heat?
They protect cells from thermal injury by stabilizing and remolding damaged proteins
72
How many days does it take for heart rate to acclimate to heat
Around 4
73
How many days does it take for plasma volume to acclimate to heat
3 days
74
How many days does it take for perceived exertion to decrease when acclimating to heat
4 days
75
How many days does it take for sweat rate to acclimate to heat
6 days
76
what are the sex differences in thermoregulation?
They are small when matched for body composition and level of acclimation
77
What are the age differences in thermoregulation?
Skin blood flow is reduced in older individuals (>60) resulting in reduced ability to lose heat during exercise
78
How long does it take to lose acclimation?
Significant decline in 7 days with complete loss in 28 days.
79
Skin blood flow adaptation during cold stress
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
How does the POAH respond to a decrease in core temp?
Through shivering and a decreased skin blood flow
81
How is shivering stimulated?
When core temp dramatically drops, Somatic motor neurons stimulate skeletal muscle contraction to produce heat
82
How does non-shivering thermogenesis increase body temperature?
By releasing NE and thyroxine from brown adipose tissue to increase the rate of cellular metabolism
83
What happens to blood vessel regulation in the cold
Cutaneous Vasoconstriction
84
How does the POAH regulate vasoconstriction?
By NE acting on alpha 1 adrenergic receptors causing the blood vessels to vasoconstrict and conserve heat
85
Physiological response to cold stress
Clod stimulates the skin and core receptor; POAH integrates signal; Effectors for shivering, cutaneous vasoconstriction, catecholamine release, thyroxin release
86
Subcutaneous fat as an insulator
Effective in cold water; primary fuel for shivering in well-fed individuals
87
Water immersion rate of heat loss
25x greater than air of same temperature
88
Blood flow response to the cold
Blood flow is shunted through cutaneous vasoconstriction away from the skin to the core
89
Hand muscle function in cold
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
What happens when body temperature declines from 37 to 25 degrees Celsius or lower
Level of hypothermia is associated with life threatening cardiac arrhythmias
91
Breathing cold air effects
Will not impact respiratory tract but can trigger exercise induced asthma because of cooling and drying of airways
92
What 3 things happen in cold adaption?
1. Lower skin temperature
2. Maintain higher hand temperature
3. Improved ability to sleep in the cold
93
What happens to skin in adaptation to cold
Shivering begins at a lower skin temperature because of the increase in utilizing non-shivering thermogenesis
94
Why do hands and feet have higher temperature in cold acclimation?
To improve peripheral blood flow
95
Why do you sleep better in cold after acclimating?
There is a reduction in shivering
96
How do cold-acclimatized people maintain heat production
Less shivering by increasing non-shivering thermogenesis
97
Sex differences in responses to cold exposure
At rest women reduce body temp faster than men but show a similar decrease in cold water
98
Age responses to cold exposure
Older >60 become less tolerant to cold. Children have a faster fall in body temp
99
During cold stress what caused vasoconstriction of blood vessels of the skin?
Norepinephrine acting on alpha 1 ADR
