Thermoregulation

Question 1

Homeotherm

Answer 1

animals that regulate internal temp for optimal biochemical reaction rates

Question 2

Circadian rhythm temperature swings

Answer 2

lowest in morning and highest in evening

Question 3

Homeostasis

Answer 3

balance of heat generation and heat dissipation

Question 4

Why does metabolic transformations generate heat

Answer 4

inherent inefficiency (20% efficient and 80% heat release)

Question 5

Resting metabolic rate

Answer 5

metabolic rate necessary to maintain function - adds to metabolic heat production (increased by thyroxin and EPI)

Question 6

Thermal neutral environment

Answer 6

environment that a naked body would not lose nor gain heat

Question 7

Avenues for heat transfer form the body

Answer 7

Conduction, convection, radiation, and evaporation

Question 8

Conduction

Answer 8

heat transfer b/w 2 SOLID OBJECTS (ice pack)

Question 9

Convection

Answer 9

fluid carries heat b/w body and environment (air, water)

Question 10

Radiation

Answer 10

exchange occurs in the infrared portion of the EM energy spectrum (gain: surrounding objects have higher surface temp than body; loss: surrounding objects have lower surface temp than body)

Question 11

Evaporative

Answer 11

phase change from liquid to gas (berthing, perspiration) INDEPENDENT of the thermal gradient b/w body and environment; DEPENDENT on water vapor pressure b/w skin and environment (humidity)

Question 12

Balance of het production and heat loss

Answer 12

M (metabolic heat) - R - C - E = S (stored heat/current temp)

Question 13

Physiological response to heat transfer

Answer 13

heat production (shivering), heat distribution (vasoconstriction), sweating

Question 14

Negative feedback loop for thermal regulation

Answer 14

thermal sensors, hypothalamic integrative center and thermal effector

Question 15

Thermal sensors

Answer 15

free-nerve endings cutaneous and hypothalamic thermal sensors to heat and cold

Question 16

Hypothalamus and thermal regulation

Answer 16

skin and hypothalamic thermal receptor information is compared to “set point” and efferent thermal commands are send to re-establish set-point

Question 17

Anterior hypothalamus is in charge of

Answer 17

decreases in body temp

Question 18

Posterior hypothalamus is in charge of

Answer 18

increased in body temp

Question 19

Thermal effectors

Answer 19

autonomic nervous system via vasoconstriction or vasodilation, stimulation of eccrine sweat glands, shivering, brown adipose activation

Question 20

eccrine sweat glands

Answer 20

sympathetic cholinergic fibers for evaporative heat loss

Question 21

What happens to the thyroid gland during thermoregulation

Answer 21

too hot = decreased thyroid stimulation = decreased metabolic activity

Question 22

Hyperthermia

Answer 22

increased environmental temperature and humidity (heat index) reduces the body’s ability to loss heat through radiation, convection, and evaporation

Question 23

Exposure to high temp and exercise

Answer 23

heat exhaustion and heat stroke

Question 24

Risk factors for hyperthermia

Answer 24

lack of acclimatization, low fitness, obese, dehydrated

Question 25

Malignant hyperthermia

Answer 25

genetic abnormality of skeletal muscle reaction to anesthetics (halothane or succinylcholine)

Question 26

Treatment for hyperthermia

Answer 26

cold compresses and IV to rehydrate

Question 27

Hypothermia

Answer 27

exposure to prolonged low temperatures, immersion in cold water, and wind bursts that increase het loss by conduction and convection

Question 28

Reaction to hypothermia

Answer 28

shivering, increased muscle tone, vasoconstriction, Brown adipose tissue activity

Question 29

Thermoregulation and exercise

Answer 29

Initially exercise increases core temperature because heat production > heat dissipation; heat loss mechanisms are activated and temperature plateaus at an elevated steady-state

Question 30

What happens to the O2 dissociation curve during exercise

Answer 30

increased body temperature cause shift to the right, facilitating O2 unloading into peripheral tissues

Question 31

Why is exercising in the heat potentially fatal (other than inability to release body heat)?

Answer 31

vasodilation to reduce body temp causes a decrease in the return venous flow to the heart, decreasing CO, heart pumps harder and faster to maintain CO (blood flow to viscera decreases = nausea) eventually decreased BV results in dizziness and fatigue

Question 32

Heat acclimatization and physical training

Answer 32

trained individuals sweat earlier and more profusely and contains less Na ( increased evaporative heat loss reduced the need for conductive heat loss (vasodilation) maintaining high BV for circulation

Question 33

Fever and body temp elevation

Answer 33

hypothalamus actively elevates core temp setpoint

Question 34

Pyrogen

Answer 34

any substance that causes a fever

Question 35

Prostaglandin E2 are elevated

Answer 35

elevation of PGE2 in the hypothalamic tissue increases the set-point for core temp and remains elevated until the pyrogen subsides