Thermoregulation

Question 1

What is a homeotherm?

Answer 1

A person or animal that maintains a constant core temperature

Question 2

Where is the temperature control center of the brain located?

Answer 2

Preoptic-anterior hypothalamus

Question 3

What are the 2 ways that heat production is classified?

Answer 3

Voluntary (exercise) and involuntary (shivering or biochemical heat that is caused by the secretion of hormones such as thyroxine and catecholamines)

Question 4

What are the four processes that can remove heat from the body?

Answer 4

Radiation, convection, conduction, and evaporation

Question 5

What is happens in heat loss during radiation?

Answer 5

Transfer of heat from one surface to another without needing contact aka heat transferred by infrared waves

Question 6

What happens in heat loss during conduction?

Answer 6

Heat from the body is transferred to the molecules of cooler objects that are in contact with its surface

Question 7

What happens in heat loss during convection?

Answer 7

Form in which heat is transmitted to air or water in contact with the body.

Question 8

What happens in heat loss through evaporation?

Answer 8

Heat is transferred from the body to water on the surface of the skin. Once it gains sufficient energy (heat), it is converted to gas vapor taking the heat away from the body

Question 9

What three factors is evaporation from the skin dependent on?

Answer 9

1) ambient conditions (ex. air temperature and relative humidity)
2) The convective currents around the body
3) the amount of skin exposed to the environment

Question 10

Why does evaporation occur?

Answer 10

Due to a difference in pressure gradients between the skin and the environment

Question 11

What is specific heat?

Answer 11

The amount of heat energy required to raise 1 kg of body tissue 1 degree in temperature

Question 12

How does the POAH react when an increase in core temperature is detected?

Answer 12

1) Hypothalamus stimulates sweat glands increasing evaporative heat loss
2) Vasomotor control center withdraws normal vasoconstrictor tone of skin increasing blood at surface

Question 13

How does the POAH react when a decrease in core temperature is detected?

Answer 13

1) Vasomotor control center tells peripheral blood vessels to constrict
2) involuntary shivering begins
3) pilomotor center is stimulated creating goosebumps
4) indirectly increases thyroxine production which increases cellular heat production

Question 14

What is the heat index?

Answer 14

The body’s perception of how hot it is

Question 15

What are the 3 major factors than can impair exercise performance during exercise in heat?

Answer 15

1) Accelerated muscle fatigue
2) cardiovascular dysfunction
3) CNS disfunction

Question 16

What are some strategies for preventing heat related injuries?

Answer 16

1) Exercise during the coolest part of the day
2) Minimize duration and intensity on hot days
3) expose maximal surface area of skin for evaporation
4) when removal of clothing not possible, provide frequent cool down breaks
5) rest/cool down breaks should not be in direct sunlight
6) Measure body weight at beginning and end of exercise session to determine fluid replacement required

Question 17

What three factors accelerate muscle fatigue?

Answer 17

1) Increased radical production
2) decreased muscle pH
3) muscle glycogen depletion

Question 18

Why do increased free radicals promote muscle fatigue?

Answer 18

Free radicals are produced during muscle contraction. React rapidly with muscle proteins resulting in oxidative damage. Heat induced increase in free radicals damages muscle proteins decreasing muscle force production

Question 19

How does muscle fatigue contribute to CNS dysfunction?

Answer 19

Muscle chemoreceptors are stimulated during fatiguing exercise. Results in afferent feedback to brain via type III/IV afferents. Neural feedback from fatiguing muscle exerts INH influences on central motor drive resulting in decreased recruitment of motor units.

Question 20

How does cardiovascular dysfunction contribute to impaired exercise performance in hot environments?

Answer 20

During maximal intensity exercise, there is a progressive decrease in blood flow to muscles due to a competition for blood between the skin and the muscles. As body temperature rises during exercise in a hot environment, blood rushes to surface away from contracting muscle

Question 21

What are some of the primary adaptations that occur during heat acclimitization?

Answer 21

Increased plasma volume, earlier onset of sweating, higher sweat rate, reduced salt loss in sweat, reduced skin blood flow, increased synthesis of heat shock proteins

Question 22

How much does blood plasma volume increase as a result of heat acclimitization?

Answer 22

10-12%

Question 23

Why does salt loss through sweat decrease with heat acclimitization?

Answer 23

Due to an increased secretion of aldosterone

Question 24

What are stress proteins?

Answer 24

Synthesized in response to stress (e.g. heat) and are designed to prevent cellular damage due to heat or other stresses

Question 25

How do athletes adapt to exercising in a cold environment?

Answer 25

1) Increased nonshivering thermogenesis
2) improved ability to prevent large decreases in skin temperature during cold exposure
3) improved ability to sleep in cold environments

Question 26

Define hypoxia, normoxia, and hyperoxia.

Answer 26

Hypoxia: Low PO2, ex. at altitude
Normoxia: PO2 at sea level
Hyperoxia: PO2 greater than at sea level

Question 27

How does altitude affect sprint performances?

Answer 27

Decreased air density at altitude decreases resistance to high speed movement. Sprint performances either not affected or improved.

Question 28

Why does VO2 max decrease at altitude?

Answer 28

Decreased oxygen extraction. Low atmospheric PO2 causes alveolar PO2 to be lower

Question 29

Why does maximal heart rate decrease at altitude?

Answer 29

Myocardial hypoxia may trigger a slower heart rate to decrease the work load and oxygen demand of the heart muscle

Question 30

What happens in the body when hypoxia inducible factor-1 is increased?

Answer 30

When the kidneys increase production of HIF-1, it inturn increases EPO. This then stimulates the production of more RBC

Question 31

What are two methods natives of high altitudes adapt to living at altitude?

Answer 31

1) Increased number of RBC

2) Increased hemoglobin sat of existing RBC

Question 32

Why do some athletes show an increase in VO2 max at altitude, but not all?

Answer 32

May be due to degree athlete was trained to prior to going to altitude

Question 33

Why do some athletes VO2 max experience a greater decline at altitude than others?

Answer 33

Some athletes experience desaturation quicker than others, even at sea level (blood too quick through lungs)