Temperature Regulation

What is the normal body temp range?

36.2(97.2) - 37.7(99.9)

What is cooler than the trunk of the body?

extermeties

Women exhibit wider fluctuation that follow

menstrual cycle

What controls thermoregulation?

preoptic area/anterior hypothalamus (areas receive sensory info from thermoreceptors on skin and core temps)

What are the 2 ways of body heat production?

Chemical reactions of metabolism, skeletal muscle tone/contraction

What is another name for body heat production: chemical reactions of metabolism?

chemical thermogenesis

what is another name for body heat production: skeletal muscle tone/contraction?

shivering thermogenesis

thyroxine acts on adrenal medulla to stimulate

catecholamine epinephrine secretion

Epinephrine secretion causes vasoconstriction and glycolysis which increases

metabolic rate, and body heat

What are some main mechanisms of heat loss?

radiation, conduction, peripheral vasodilation

what is peripheral vasodilation?

core warmed blood is diverted to the body surface where heat is lost by conduction from skin surface

What are some mechanisms of heat conservation?

vasoconstriction, voluntary mechanisms (curling into a ball)

What is the febrile response?

temporary re-setting of the hypothalamus thermostat in response to exogenous or endogenous pyrogens

What is the most common exogenous pyrogen?

pathogen produced endotoxin: liposaccharide complex

What is PGE2?

a mediator that acts on the hypothalamus to raise the temperature set point

what do pyrogenic cytokines do?

act on targets in the preoptic area/AH to increase heat production and heat conservation

what do endogenous cryogens (anti pyrectics) do?

diminish and control febrile response as a negative feedback

what is the final step in fever generation?

production of prostaglandin E2 (PGE2)

PGE2 acts on preoptic/AH ____________ neurons

warm-sensitive

Brain set-point for body temperature is increased, resulting in:

peripheral vasoconstriction, epi release, muscle tone/shivering increase

The acute response phase is due to

pyrogenic cytokine release

What else can cause the acute response phase?

fever, anorexia, fatigue, malaise

PGE2 can be controlled by

systemic antipyretics

the BBB is highly

selective and rigid

What are some benefits of moderate fever?

kills many microorganisms, deprives bacteria of nutrients

How long are febrile seizures?

brief

How to people get febrile seizures?

genetic predisposition

at what temperature do febrile seizures occur?

greater then 100.4 (most children experience at higher temps)

Hyperthermia =

too hot

Hyperthermia is not mediated by __________ and does not involve increase in ________________

pyrogens, HT set point

hyperthermia can be

accidental, therapeutic, associated with stroke/head trauma

What is the definition of heat cramps?

severe spasmodic abdominal/extremity cramps that follow prolonged sweating/sodium loss

Heat cramps is common individuals that are

not accustomed to heat or those preforming strenuous work in warm climates

what is the definition of heat exhaustion?

prolonged high core/enviromental temp

what does heat exhaustion cause?

profound vasodilation, profuse sweating

what are some manifestations of heat exhaustion?

dizziness, weakness, nausea, fainting, syncope (loss of consciousness)

Definition of heat stroke?

potentially lethal result of a breakdown in an overstressed thermoregulatory center

what is heat stroke caused by?

exertion, overexposure, or impaired physiological mechanisms for heat loss

what are some symptoms of heat stroke?

high core temp, absence of sweating, rapid pulse, confusion

what can heat stroke cause?

cerebral edema, CNS degradation, renal tubules necrosis, hepatic failure with delrium

Definition of hypothermia?

core temperature less than 35C

What can hypothermia cause

CNS, respiratory system depression

What happens to ATP in accidental hypothermia?

it is depleted

what happened to ATP in therapeutic hypothermia?

it is preserved

accidental hypothermia is caused by

sudden immersion in cold water or prolonged exposure to cold

therapeutic hypothermia is used to

slow metabolism and preserve ischemic tissue during surgery or limb reimplantation

therapeutic hypothermia may cause

ventricular fibrillation and cardiac arrest

who is at risk of accidental hypothermia

infants, elderly

what are some conditions wherein heat production is diminished?

hypothyroidism, hypopituitarism, decreased liver function, malnutrition, Parkinson's disease, RA

what is the definition of acute hypothermia?

peripheral vasoconstriction shunts blood away from cool skin to core in effort to decrease heat loss

what can acute hypothermia cause

peripheral tissue ischemia

what induces shivering to increase heat production?

hypothalamus

CNS trauma can cause

hyperthermia

trauma induced hyperthermia is highly resistant to

antipyretic therapy

accidental injuries can cause

hypothermia

some serious injuries can cause

peripheral vasodilation with decrease in surface and core temp

hemorrhagic shock can cause

hyperthermia

in hemorrhagic shock, blood loss elicits

peripheral vasodilation and slight increase in core temp

why can major surgery cause hypothermia?

open body cavity exposure

why can thermal burns cause hyperthermia

loss of skin barrier to evaporation