Final Exam - Thermoregulation Flashcards
heat production
thermogenesis
heat loss
thermolysis
maintenance - thermogenesis
Vasoconstriction
Shivering
Piloerection
Curling up
maintenance - thermolysis
vasodilation
sweating
pilorelaxation
stretching out
Effect of shivering
increase metabolism –> similar to light exercise
increase heat production by 500%
Target organs of nonshivering thermogenesis
brown adipose tissue (BAT) + skeletal muscle
- skeletal muscle = primary in adults
- BAT = primary in infants
Net energy moves from ____ to _____
warmer object to cooler object
Mechanisms of heat loss
Radiation
Evaporation
Convection
Conduction
Latent heat of vaporization
Evaporization
Most heat loss occurs d/t
radiation
Radiation
Heat loss by transfer of photons
NOT to surrounding air
Evaporization
insensible water evaporation from skin/lungs
1/2 d/t respiratory loss
Decrease radiation heat loss by
incubator/barrier between patient/object
decrease evaporation heat loss by
humidification, covering exposed skin, using warm preps
conduction
heat loss thru contact with cooler object
conduction requires
direct contact
conduction heat loss can be minimized by
insulation, bair hugger, warming mattress under patient
convection
heat loss thru moving cool air
primary terminal organ for cold sensation
Krause’s end bulb
Krause’s end bulb - range of stimulation
15-25*C
Below = only pain receptors active
primary terminal organ for warm sensation
Ruffini’s Corpuscle
Ruffinis Corpuscle - range of stimulation
25-45*C
Cold sensation transmitted to spinal cord via
small-diameter, myelinated, A delta nerve fibers
Warm sensation transmitted to spinal cord via
unmyelinated C nerve fibers
Peripheral sensors: afferent temp
terminal organ –> nerve fibers –> substantia gelatinosa of posterior horn (spinal cord)
–> anterolateral spinothalmic tract to thalamus
Central sensors: afferent temp
anterior hypothalamus
outside CNS: receptors in muscles + splanchnic/vagal afferents
earliest warning of external temperature changes
come from peripheral temperature sensors
central receptors take over once
skin temperature has reached maximum variability
Efferent systems: involves 2 pathways
neurologic, endocrine
neurologic efferent system
SNS regulates cutaneous blood flow/nonshivering thermogenesis via adrenergic efferents/diaphoresis (via cholinergic efferents)
skeletal muscle shivering is stimulated by
direct motor response from posterior hypothalamus
Long term efferent control of temp
Endocrine system
Short term efferent control of temp
Neurologic control via ANS
Endocrine control of temp
ACTH, GH, ADH, TSH
Physiologic response to hyperthermia
inhibition of heat production, increase heat dissipation
most important mechanism for transferring heat between core/periphery
cutaneous vasodilation
major mechanism for evaporative heat loss
diaphoresis
*via sympathetic cholinergic fibers
body responds to hypothermia via
increasing heat production, decreasing heat loss
Body not capable of countering heat loss at what temp
32-33*C
Body decrease by 1*C results in
6% reduction in metabolism
8% reduction in O2 consumption
7% CBF/brain O2 consumption
7% MAC reduction
