Thermoregulation

Question 1

What is temp regulation related to?

Answer 1

metabolic heat production

Question 2

What is homeosthermic temp (average temp) ?

Answer 2

Range: 35.5-37.7
Average: 37

Question 3

Maintain heat balance

Answer 3

Mass balance (input=output)
Sources of input:
-External (from the environment)
-Internal (metabolism sufficient to maintain temp)
Heat Exchange Mechanisms
-Radiant 60%(given off by anything greater than 0)
-Conductive 3% (touching)
-Convection 12% (air currents)
-Evaporation 25% (heat loss in water at same temp as air is 2-4x greater)
insensible evaporation

Question 4

What causes variation on body temperature?

Answer 4

PA level
Emotions
Eating
Environmental conditions

Question 5

If ambient temperatures are above…

If ambient temperatures are below…

Answer 5

=Heat gain>heat loss

=Heat gain less than heat loss

Question 6

What controls autonomic temp?

Answer 6

Hypothalamus determines appropriate response (acts as a thermostat and can detect changes of 0.1-0.5)

Question 7

What do thermoreceptors do and where are they located?

Answer 7

monitor change in body temp
send info to the skin (peripheral) and hypothalamus (central)
Deep neural receptors in abdomen and great veins that can sense temp changes

Question 8

What are the mechanisms that regulate body temp?

Answer 8

1) adjust blood flow distribution
2) sweating
3) Increase metabolism
4) Hormonal regulation

Question 9

1) Adjust blood flow distribution

Answer 9

Convective heat loss/gain through blood distribution
Cutaneous vessels can either
-Gain or lose heat to or from the environment
Change diameter through neural control
Some local vasodialtion
Decrease temp = increase sympathetic neurons = vasoconstriction = more blood to core
Increase temp = sympathetic cholinergic neurons innervate cutaneous vessels = vasodialtion = blood to peripheral

Question 10

2) Sweating

Answer 10

Heat lost though skin by evaporation
increase core temp = sympathetic cholinergic neurons stim sweat glands (secrete hypotonic sweat)
Evaportation is affected by
-Exposed skin area
-Temp and humidity(greatest impact - increase = decrease evap)
-Convective currents

Question 11

3) Increase Metabolism

Answer 11

Increase heat production
Unregulated
-increase voluntary muscle contraction (moving)
Regulated- shivering (hypothalamic thermoregulatory center initiates contractions
-Non-shivering thermogenesis (increased heat from brown fat)

Question 12

4) Hormonal Regulation

Answer 12

Increase release of epinephrine and norepinephrine increase heat production
Cold exposure thyroid releases more thyroxine to elevate RMR
Cold exposure = many physiological and psychological challenges

Question 13

Thermoregulation and Exercise

Exercise in the cold

Answer 13

Body loses heat 2-4x faster in water at the same temp of air due to conduction
Metabolic heat generated by muscular activity contributes to thermoregulation during cold stress
Better adaptations to heat than cold

Question 14

Wind Chill

Answer 14

The affect of cooling associated with increase velocity

Effects increase with increase exercise velocity

Question 15

Thermal Balance in Response to heat

Answer 15

Peripheral vasodilation
Increase sweating
Conscious acts (choosing to wear lighter clothes)
Acclimatization

Question 16

What is thermal effector response?

Answer 16

Regulation of heat loss and heat gain to control body temp at rest during exercise and in response to the environment

Question 17

Exercise in heat

Answer 17

core temp above 42 degrees can be fatal
Core temp above 44 proteins start to denature
Increase in core temp = breakdown of nervous tissue, local hemorrhage and organ failure

Question 18

What is hyperthermia?

Answer 18

core temperature above 41 degrees

Question 19

How is fluid loss determined?

Answer 19

Pre-exercise weight- post exercise weight

1kg = 1L of fluid lost

Question 20

What is sweat rate?

Answer 20

Change in weight (fluid loss)/exercise time

Question 21

What is Cardiac Drift?

Answer 21

Gradual increase in HR during prolonged exercise especially in heat even with no increase in intensity
Increased core temp=increased blood flow to the skin
Blood volume is reduced
Decrease SV increase HR to compensate for constant Q

Question 22

Considerations for elderly and children in heat

Answer 22

reduced circulation, efficiency, degenerative diseases

Higher rate of heat, lower sweat, lower heat transfer

Question 23

What are gender differences in heat?

Answer 23

Women have slower sweating response, decrease sweat volume, increase sweat glands,
Larger surface area allows for better cooling

Question 24

Acclimatization in the heat

Answer 24

Take 10-24 days for full
increase circulation
increase sweat response

Question 25

Practical considerations for exercise in the heat

Answer 25

Avoid prolonged exercise
Stay hydrated
wear light colors
be conscious of sign and symptoms
reduce expectation
acclimatize

Question 26

Exercise in the cold

Answer 26

lose heat through radiation, conduction, convection, evaporation

Question 27

What is hypothermia?

Answer 27

core below 35 degree

Question 28

What are physiological response to cold temp?

Answer 28

1) Non-shivering thermogenesis
increase in sympathetic stim. release of epinephrine and thyroxine
2) Peripheral vasoconstriction
3)Involuntary shivering
4) Goose bump

Question 29

Gender differences in the cold

Answer 29

Women increased peripheral vasoconstriction during the cold. Larger body surface, less muscle mass.
Advantages: increased body fat aides in insulation

Question 30

Cold acclimatization

Answer 30

Starts in 7 days. complete in a month
Increase non-shivering thermogenesis
Intermittent vasodialtion of the vessels

Question 31

Practical consideration of exercise in the cold?

Answer 31

Dress in layers
Consider wind chill
First half into the wind
Use head like a radiator

Question 32

Wicking and Evaporation

Answer 32

Wicking sweat away form the skin reduces cooling