Skin + Temperature Flashcards
What is core body temp
37 degrees +- 0.5
Why is this important
>41 = proteins denature <30 = LOC
What does body temp vary with
External temp
Activity
Circadian rhythm
Menstrual cycle
What do we produce all the time
Heat
How do you we manage heat
Conduction - heat transfer between touching
Convection - fluid conduction e.g. wind / water chill
Evaporation - respiration / sweating taking heat energy with it (main loss in body)
Radiation - can be loss or gain
What do cold receptors do
Respond to cold temp
Peak fire at 30 degrees (10-40 range)
What do warm receptors do
Respond to warm temp
Peak fire at 40 degrees (30-50)
How do you tell apart
Dynamic response to change in temp
Warm receptors fire more when temp increases
What are peripheral thermoreceptors
Located in the skin
Face and scrotum sensitive
Respond to environmental temp
What are central thermoreceptors
Located in spinal cord, abdominal organs and hypothalamus
Tell core temperature
What happens
Nerves go to hypothalamic thermoregular centre
Response generated
What nerve fibres detect cold
A delta
What nerve fibres detect warm
C fibres
What is fever
Body’s response to infection
What causes fever
Endogenous pyrogenes (IL) Increase set point on hypothalamus of where body temp should be by producing prostaglandins So feel cold when temp increases to this point
What helps fever
NSAID + Aspirin
Block cycle-oxygenase which stops prostaglandin production which turns up set point
How are prostaglandins produced
Cyclo-oxygenase in hypothalamus
How does body generate heat in cold stress
Cell metabolism
Voluntary muscle activity
Shivering thermogenesis - involuntary
Non-shivering thermogenesis in infants
What is nonshinvering thermogenesis
Brown adipose tissue
Uses protein gradient to produce heat
How is heat loss reduced in cold stress
Sympathetic arteriolar construction - A1
Behaviour - add clothes, move to warmth, reduce SA
What is hypothermia
<35 degrees
Who is at risk
Neonates
Elderly
Outdoor workers/ North Sea
How are neonates at risk
Big SA to volume
Little fat
Don’t shiver
How are elderly at risk
Do not detect temp well
Immobile
Less shivering capacity
What does cold stress do to vascularity
Vasoconstriction so slow flow
Increased viscosity
Increased thrombosis
Hypoxia
What does cold stress to cellular
Ice crystals in extra-cellular space
Increased osmotic conc
Movement of water from intracellular space
Cell dehydration
What are complications
Increased heart attack and stroke due to vasoconstriction and viscosity
How do you Rx hypothermia
Dry + insulate to prevent further loss Slow re-warming Internal rewarming with hot drinks Fast re-warming by immersion in water Extra-corporeal circulation
How is heat production minister
Decreased physical activity
Decreased food intake
How is heat loss increased
Arteriolar dilation
Sweating
Increase SA
Remove clothes
How do we sweat
Sympathetic cholinergic fibres
Release Ach
NOT Na
What is heat exhaustion
Body temp >37.5-40
Results in vasodilation and drop in blood volume
Distance of fluid / salt balance due to sweat
What are the symptoms
Headache Confusion Nausea Sweating Clammy skin Tachy as low BP Hypotension Weak pule Faint Collapse
What is heat stroke
If temp above 40 and body’s control measures fail
Hot dry skin as sweating ceased and circulatory collapse
Who is at risk
Neonates
Elderly
Protective clothing
Physical work in hot environment
How do you Rx
Move to cool Remove clothing Fan Sponge with tepid water Give fluids - oral or IV
