Please enable JavaScript.
Coggle requires JavaScript to display documents.
NS 47 - Temperature Control (ii) (Physiological temp regulating mechanisms…
NS 47 - Temperature Control (ii)
Physiological temp regulating mechanisms
metabolism
vasomotor responses
vasoconstriction of arterioles in skin
heat conservation
keeps warm blood in core
bloodless skin = excellent insulator
vasodilation of arterioles in skin
heat loss
thermoneutral zone = temp range that can be maintained by vasomotor responses alone
sweating
regulated + continuously adjusted heat loss
evaporation
dilute salt solution
affected by environment humidity
high humidity -> air H2O-saturated -> limited ability to take up additional moisture from skin -> less sweating
sweat glands innervated by symp Ns BUT NT=ACh
in dermis: gland secretes, duct absorbs
pore in epidermis
shivering
primary involuntary heat production mechanism
rhythmic skeletal muscle activity
oscillates @ 10-20 shakes/s
increased tone
all energy converted to heat, as no work is achieved
can increase core temp 2-5 fold in 5 min
brown fat metabolism
generates heat in animals + newborns
unclear role in adults
hair-raising
contraction of muscles @ base of hair
hair lifts + traps air
ineffective in humans (low hair density)
voluntary behaviour
dressing appropriately
drinking water
staying in shade
Temp detection + set point
peripheral (skin) + core (hypothal, CSN, int ab organs) thermoRs
thermoRs send afferents to hypothal (central control)
ant hypothal has temp detectors that receive info from core + periphery - triggers heat loss via vasodilation
responds to v small changes (0.01 degrees)
hypothalamic neurons are warm-sensitive or cold-sensitive
post hypothal triggers heat production (shivering) + conservation
ablation/lesion results in hypothermia when patient in area below room temp
N ending channels open (@ R): increases temp sensitivity + changes neuron firing rate
Hypothermia
core temp below acceptable range
causes: mountaineering, diving, old age, hypothyroidism,. hypopituitarism, malnutrition, stroke, trauma, drugs, burns, surgery
cooling exceeds heat producing/conserving mechanisms
metabolism slows, higher order thinking affected, depression of resp + cardiac centres
Hyperthermia
core temp above acceptable range
causes: exercise, hyperthyroidism, adrenaline, malfunctioning hypothal
treatment = cooling (ice, water, fanning)
Fever
a REGULATED increase in core temp as a result of infection/inflamm
Why? stimulates immune system + decreases pathogen's ability to replicate
thermoregulatory system not malfunctioning
temp set point has been reset to a higher value (hence shivering even though warm)
triggered by endogenous pyrogens (IL1, TNFalpha) in response to pathogens
act on hypothal
increase set-point, PG production, heat generating response
antipyretics (e.g. aspirin) block pyrogens' pathway to hypothal (block COX)