Thermoregulation and pyrexia L8 Flashcards
at what temp does denaturing occur
above 45 degrees
range of temps where there is conscious intelligence
35-40 degrees
when in the day are you coolest
just before you wake up
when in the day are you hottest
mid afternoon
rise in temperature in the menstrual cycle
0.5 degrees at ovulation
what fibres transmit temperature
A delta and C fibres (same as pain)
coordinator of thermoregulation
anterior hypothalamus
do we have more hot or cold receptors
more cold receptors (we are a cold species)
normal body temp=
37.5 degrees
heat production=
metabolism
what type of response is most important to maintain temperature
voluntary actions
e.g of voluntary actions
wearing a coat
wearing less clothing in the sun
what disadvantage do the very old and very young have
often can’t put clothing on themselves
5 changes when too cold
shivering brown fat skin blood flow piloerection neuroendocrine
how much can shivering increase heat production
5%
what body movement is shivering predominately
truncal
disadvantage of shivering
metabolically expensive
can lose vital energy
who has brown fat
neonates and animals
what is brown fat (3)
- adipose tissue with lots of mitochondria
- higher blood supply than normal fat
- Beta 3 receptors
what does brown fat do
burns fat into energy
2 changes in skin blood flow
vasodilation
vasoconstriction
how much can skin blood flow alter heat loss
8%
what happens to skin blood flow in prolonged cold exposure
paradoxical increased flow
what Nervous system mediates skin blood flow
sympathetic
piloerection=
hairs stand on end
erector pili under what control
sympathetic
effect of erector pili
minimal effect in humans
what neuroendocrine effect happens when you’re cold
increased catecholamines (adrenaline/ noradrenaline)
heat loss by conduction/convection=
60%
heat loss by radiation=
25%
heat loss by evaporation
15%
what system controls sweat glands
sympathetic
most neurotransmitters of sympathetic=
noradrenaline
whats different about the neurotransmitters in sweat glands
cholinergic (muscarinic)
3 substances filtered across in sweat
sodium
chloride
urea
what is sweat like in people who have acclimatised to heat
sweat more but more concentrated so lose less sodium
how much does heat loss increase by sweat
10x
2 abnormalities in thermoregulation
hypothermia
hyperthermia
hypothermia=
core temp <35 degrees
severe hypothermia=
<28 degrees
3 causes of hypothermia
behavioural
hypothyroidism
dermatological
3 clinical features of hypothermia
confusion
coma
cardiovascular
common cardio complication of hypothermia
atrial fibrillation
what is not advised when someone is hypothermic
defibrillation
management of hypothermia
ABC; airways, breathing , circulation
-controlled warming (via warming blankets
what can be used for extreme hypothermia in big hospitals
bypass
hyperthermia=
> 38 degrees
life threatening hyperthermia=
> 40 degrees
4 causes of hyperthermia
exertion (exercise)
situational (heat stroke)
Drugs
pyrexia
4 clinical signs of hyperthermia
confusion
seizures
coma
cardiovascular
what is pyrexia usually due to
altered set point
causes of pyrexia (5)
- infection
- blood transfusion
- inflammation
- malignancy
- hypothalamic insult
what in the body is a major contributor to pyrexia (drug target)
prostaglandins
drugs that treat pyrexia
NSAID
Aspirin
paracetamol
why do we get a fever
to get rid of pathogens
when is a fever bad
head injury
post cardiac arrest
why do we treat fever
to make people feel better
