Exam 2 - Cold Exposure

Question 1

Environmental Stressors that disturb homeostasis

Answer 1

Cold air temperature, air movement across the body, dry air, water immersion

Question 2

Cold Air Temperature

Answer 2

Disturbs homeostasis when air temperature is below skin and core temperature

Question 3

Air movement across the body

Answer 3

Accelerates the loss of body heat (windchill)

Question 4

Dry Air

Answer 4

Caused by low relative humidity

Question 5

Water Immersion

Answer 5

20-25x faster losing heat in water than air

Question 6

Behavioral Thermoregulation

Answer 6

Adding more layers of clothing, consuming hot beverages, moving to warmer location

Question 7

Physiological Thermoregulation

Answer 7

Thermoreceptors send impulses to posterior hypothalamus, inducing responses that allow for maintenance of homeostasis.

Question 8

Afterdrop

Answer 8

Occurs when an individual who has been exposed to a cold environment for a period of time and returns to a thermoneutral environment

Question 9

How do we increase heat production?

Answer 9

Shivering thermogenesis, mobilize fuels (glycogen, lipids), nonshivering thermogenesis (brown fat)

Question 10

How do we minimize heat loss?

Answer 10

Peripheral vasoconstriction, thermal gradient minimized (greater gradient = greater heat loss)

Question 11

Role of adipose tissue in heat loss

Answer 11

Lean people generate more heat but lose it fast. Fat people generate heat and keep it.

Question 12

Increased mobilization of metabolic fuels caused by

Answer 12

release of hormones EPI/NE/cortisol

Question 13

Cardiovascular responses at rest

Answer 13

Increased blood flow to the shivering muscles (increased oxygen and metabolic fuels), increased Q due to elevated CAT levels and baroreceptors detect increased pressure in central vessels inducing a reflex that lowers HR, increasing SV

Question 14

Cold-induced diuresis (CID)

Answer 14

Reduced peripheral blood flow, combined with increased central blood volume causes an increase in urine output.

Question 15

Body fluid alterations in a cold environment

Answer 15

Cold exposure (1-7 days) = reductions in plasma and blood volume may be an effect of hypohydration decreasing aerobic performance.
Cold exposure (11+ days) = no effect on body fluid regulation

Question 16

Metabolic Response to Cold

Answer 16

Cold exposure may alter resting metabolic rate and therefore TDEE. Increased hormonal secretion and increased shivering = increased RMR.

Question 17

Metabolic substrate use changes in a cold environment

Answer 17

CHO are preferred fuel for shivering

Question 18

Difficulties faced during exercise

Answer 18

Increased caloric expenditure (hobbling effect and frictional drag), shivering during exercise increases metabolic cost of exercise, intense cooling of the skin may impair motor skills requiring dexterity

Question 19

General exercise responses

Answer 19

Tcore will increase (unless at low-intensity), increased metabolic heat production, increased sweating, Tskin will be maintained (unless at low-intensity)

Question 20

Cardiorespiratory response

Answer 20

Decrease due to decreased Q (most important), hemoglobin will not diffuse oxygen like normal, decreased VO2max and decreased skeletal muscle blood flow

Question 21

Muscular endurance response

Answer 21

Nerve conduction velocity slows, decline in muscle fiber recruitment

Question 22

Muscular strength response

Answer 22

Increased time for fibers to reach maximal tension, increased viscosity of sarcoplasm, decreased rate of chemical reactions (lowered ATP from ATP-PC, glycolysis)

Question 23

What two activities suffer the most in the cold?

Answer 23

Jumping and sprinting

Question 24

Factors that determine survival in cold water

Answer 24

Duration of immersion, body mass, activity level, position in the water, clothing insulation, metabolic fuels

Question 25

What is critical temperature?

Answer 25

Related to body comp., below the CT there is an increase in energy metabolism that exceeds RMR.

Question 26

Effects of body fat on critical temperature

Answer 26

Fat = better!

Question 27

Effects of limb movement

Answer 27

Movement of legs provides better heat generation and decreased heat loss due to insulation

Question 28

Potential problems faced by athletes/laborers

Answer 28

Plunging into cold water can lead to ventricular arrythmias and hyperventilation. Mental performance can also suffer.

Question 29

What is habituation and when does it occur?

Answer 29

Desensitation to normal response to a stressor. Body heat isn’t lost and there is blunted shivering and cutaneous vasoconstriction. Takes about 21 days.

Question 30

Metabolic Acclimatization

Answer 30

If body heat is lost, and metabolic heat production is sufficient to protect body temperature: enhanced shivering thermogenesis/nonshivering thermogenesis will occur.

Question 31

Insulative Acclimatization

Answer 31

If body heat is lost and metabolic heat production IS NOT sufficient to protect body temperature: enhanced cutaneous vasoconstriction and improved muscle blood flow redistributes body heat toward subcutaneous shell during chronic or repeated cold stress.

Question 32

Role of autonomic nervous system

Answer 32

Sympathetic dominates during cold exposure. After 21 days PNS predominates. Increased vasodilation, fuel mobilization and skin temperature.

Question 33

What causes hypothermia?

Answer 33

When body temp falls between 32-35 degrees celsius. Accidental depression of Tcore, rapid cooling from CWI, exposure to dry/cold air for 6+ hours, drug and alcohol use and cold.

Question 34

Pathophysiology of hypothermia

Answer 34

Slowing of cardiovascular and respiratory systems, nerve conduction, mental acuity and metabolic rate. Thermoregulation ceases below 30 degrees celsius.

Question 35

S/S of Hypothermia

Answer 35

Increased metabolic rate, shivering ceases, loss of consciousness, decreased respiratory rate, pulmonary edema, and v-fib.

Question 36

Treatment of Hypothermia

Answer 36

Heating of the body’s outer shell, keep patient dry, inhale warm air, place hot water bottles on underarm and groin, provide radiant heat, provide warm fluids if patient is mildly impaired.

Question 37

Causes of frostbite/frostnip

Answer 37

Contact with cold metal, supercooled liquid, or from severe windchill. Exposed skin, moisture on skin and clothing, cramped position or posture, dehydration, localized pressure.

Question 38

Pathophysiology of frostbite/frostnip

Answer 38

Cold causes freezing of tissues, formation of ice crystals, and cell dehydration. Local vasoconstriction causes reduced blood flow leading to a clot, hypoxia and local metabolic acidosis. (Too much lactic acid)

Question 39

Treatment of frostbite/frostnip

Answer 39

Place frostbitten area in warm water or pour warm water on area (100-108 degrees F). Should not be placed next to heat source.

Question 40

Trench foot or immersion foot

Answer 40

Swollen, cold, irregularly colored extremity, skin may itch or tingle. Clean and dry feet, gently re-warm feet.

Question 41

Chillblain or Pernio

Answer 41

Swollen red areas or plaques which can progress to blisters or ulcers (chillblain). Superficial burning and pain (pernio).

Question 42

Recommendations for exposure to a cold environment

Answer 42

Dry your feet, do not walk through snow in low-cut shoes, gloves with five fingers are not made for cold weather, cold or nearly frozen extremities should be warmed with body heat by placing hands in armpit or groin area, wear insulative clothing, limit sweating, alcohol intoxication increases risk of cold injury.