Thermoregulation

Question 1

What factors affect heat gain?

Answer 1

Exercise - 15-20% of expended, Nonexercise activity, Resting metabolism - 60-75% of expended, Hormone/CNS - thyroid makes T3 which increases O2 consumption and heat production, thermic effect or food - 10% expended, and Warm environments

Question 2

What factors affect heat loss?

Answer 2

Conduction - heat is exchagned between direct contact, Convection - transfer of heat via movement of air or water, Radiation - transfer of heat in form of infrared rays between warm and cool object, and Evaporation - conversion of liquid to vapor

Question 3

Best methods of cooling in order

Answer 3

Convection>Conduction>Radiation

Question 4

heat moving down a concentration gradient

Answer 4

radiation

Question 5

requires contact

Answer 5

conduction

Question 6

movement of environment drags heat out of the body; sweat

Answer 6

convection

Question 7

What’s normal body temp?

Answer 7

97-98.6 degrees

Question 8

How does homeostatic control work?

Answer 8

If body temperature exceeds 37C, thermoreceptors sense, and preoptic/ anterior hypothalamus is activated. Posterior region activated by cold and anterior region activated by warmth

Question 9

What are two types of thermoreceptors?

Answer 9

Peripheral sense surface temp and are part of skin, visceral structures, SP cord and central sense core temp are part of hypothalamus

Question 10

What are dual mechanisms for controlling heat dissipation and conservation?

Answer 10

the heat dissapatory center is in preoptic/anterior hypothalamus and by stimulsting, you get dilated blood vessels, panting and inhibition to shiver. Heat conservation of posterior thalamus leads to vasoconstriction, visceral vasodilation, shivering

Question 11

In hypothalamus and around spinal cord, viscera, and larger vessels. These monitor blood temperature

Answer 11

central receptors

Question 12

Under the skin, senses temperature changes in the environment and provides feedback to hypothalamus and cerebral cortex, controls conscious acts like curling up when cold

Answer 12

peripheral receptors

Question 13

sweating is driven by…

Answer 13

sympathetic post ganglionic neurons via ACh

Question 14

Decrease in sympathetic vasoconstriction and activation of parasympathetics

Answer 14

vasodilation

Question 15

What does sympathetic do when temperatures drop?

Answer 15

Activated by the hypothalamus, these neurons constrict arteries to keep warm blood away from cool skin, does metabolic heat production from brown adipose which uses uncoupled receptors, and increased secretion of TSH to bind B3 receptors on brown adipose

Question 16

Behavioral responses that maximize heat loss

Answer 16

use of fans to increases convective heat loss, immersion in water to increase conductive heat loss, stay out sun to prevent radiant gain, removing clothes

Question 17

What 3 mechanisms of hyporthermia?

Answer 17

Mild - (93.2-96.8) usually tachycardiac and high RR
Moderate - (86-93.2) decreased RR, HR, BP and decreased cerebral blood flow
Severe (less than 86) cardiac dysrhythmia like ventricular fibrillation, asystole, hypotension

Question 18

Raynauds Syndrome

Answer 18

vasoconstriction of the digital arterioles of fingers/toes. These areas turn white because of constricted flow (hypoxia). Can be triggered by stress, cold temp, smoking

Question 19

Hyperthermia

Answer 19

When temperature rises above 104° F (40° C). Unlike fever, it doesn’t respond to antipyretics, and can kill quickly. Caused by Excess heat production, excess heat from the environment, or impaired heat loss from the body and leads to higher oxygen demand so increased HR

Question 20

What happens during heat stroke?

Answer 20

If your body compensates: activation of muscarinics leads to sweating, depletion of Na+ (hyponatremia), water depletion and exhaustion
If your body can’t compensate: proteins denature, organ failure, inflammation, BP drops, cardiovascular collapse, physical damage to vasculature

Question 21

What happens during heat exhaustion?

Answer 21

Muscarinics lead to sweating, Na+ depletion, H2O loss, nausea, dehydration

Question 22

What are some influencing factors of hyperthermia?

Answer 22

High body mass is associated with more sweating, Heat adaption improve sweating, aerobic fitness improve sweating, ages over 40 have reduced sweating, females have reduced sweating, diabetes can decrease heat loss, fatness can also increase heat production

Question 23

excess calcium release from muscle triggered by depolarizing muscle relaxant succinylcholine and the inhalational anesthetic agent’s isoflurane, desflurane, sevoflurane, enflurane, halothane, ether, and methoxyflurane.

Answer 23

malignant hyperthermia

Question 24

What is mechanism of malignant hyperthermia?

Answer 24

exposure to triggering agent that binds to mutated muscle receptor leading to increased Ca2+ release. Leads to sustained contraction, rigidity, metabolism which increase heat. There’s oxygen depletion and ATP, so CO2 produced leading to acidosis. Anaerobic metabolism increases acidosis, ATP depleted, cells die and release K+ resulting in hyperkalemia which causes dysrhythmia

Question 25

What are 3 isoforms of RYRs?

Answer 25

RYR1 in adults, RyR2 in cardiac, and RyR3 in embryonic skeletal

Question 26

What are body and rectal fever temperatures?

Answer 26

Body is >100.4 rectal is >101.8

Question 27

Fever (pyrexia)

Answer 27

elevation in body temperature caused by a cytokine-inducing pyrogens, leading to upward displacement of the set point of the hypothalamic thermoregulatory center. Exogenous pyrogens microbial products, toxins or whole microbe.
Resolved when the factor responsible for set point increase is removed.

Question 28

induce leukocytes and macrophages, to release fever-producing endogenous pyrogens (inflammatory cytokines)
Pyrogenic cytokines increase set point of the hypothalamus

Answer 28

Triggered by exogneous pyrogens

Question 29

How do exogenous pyrogens lead to increase of endogenous pyrogens?

Answer 29

induce synthesis of PGE2 within the preoptic nucleus of the anterior hypothalamus, increases sympathetic activity, induces shivering, and impairing heat loss. 🡪 People with fever experience chills until the core body temperature rises to the new set point.

Question 30

What targets production of pyrogenic cytokines?

Answer 30

corticosteroids

Question 31

what inhibits cyclo-oxygenase?

Answer 31

Antipyretics such as aspirin which prevents more prostaglandin E2 production

Question 32

What are four stages of fever?

Answer 32

1. complaint of fatigue, malaise
2. Chills, raising of hypothalamic set point, vasoconstriction, shiver
3. vasodilation leads to flushed skin
4. decrease in pyrogens or treatment, sweating, vasodilation

Question 33

NSAID that blocks PGE production via cyclooxygenase inhibition, results in vasodilation, sweat

Answer 33

Ibuprofen

Question 34

Fever vs. Hyperthermia

Answer 34

fever you feel cold where hyperthermia you feel hot, need to take physical measures to treat hyperthermia, elevated set point in fever, hyperthermia has high mortality

Question 35

fever more than 106.7 (41.5)

Answer 35

Hyperyrexia which can develop in patients with severe infections or CNS hemorrhage