Skin and Temperature Control Flashcards
what . is the normal body temperature and what happens when the body gets too hot and what happens when the body gets too cold?
- Man is homeothermic
- Core body temp is normally 37 ± 0.5°C
- Above 41°C proteins start to denature
- Below 30°C lose consciousness
what does body temperature vary with?
• Varies with
- external temp
- activity
- circadian rhythm
- menstrual cycle
Core temperature is maintained by balancing heat ____ and heat ____
loss
gain
what is involvedi n thermal balance?
what is responsible for the detection of body temperature?
“Cold” receptors and “warm receptors
Warm receptors fire when it is hotter when it should be and vice verse for cold receptors
thermoreceptors are responsible for the detection of body temperature, where are they?
Peripheral thermoreceptors - located in the skin, especially in face, scrotum
Central thermoreceptors - located in spinal cord, abdominal organs, hypothalamus
changes in the environmental temperature are detected by what?
changes in the core body temperature are detected by what?
and where deos this information go?
one response to cold stress is increases the heat generated inside the body, how is this done?
General metabolism - oxidative phosphorylation and other chemical reactions are not 100% efficient
Voluntary muscular activity - “futile” muscular activity
Shivering thermogenesis - involuntary muscular activity
Nonshivering thermogenesis - in humans, only significant in infants, due to brown adipose tissue
one response to cold stress is decreasing tthe heat loss form the body, how is this done?
Vasomotor control - sympathetic arteriolar constriction reduces delivery of blood to the skin
Behavioural responses - reducing surface area, adding clothing, moving to warmer environment
Hypothermia - a fall in deep body temperature to below 35ºC
who is at risk?
neonates - big SA:volume, not much fat, don’t shiver well, but do have BAT
elderly - do not detect temp change so well, less shivering capacity, more immobile
vagrants (homeless)
cold store workers
outdoor pursuits
North Sea workers
what is the treatment of hypothermia or cold stress
dry/insulate to prevent further heat loss
slow re-warming with bag/blankets
internal re-warming with hot drinks and/or warm air
fast re-warming by immersion in water, extracorporeal circulation
what vascular changes happen in frost bite?
vasoconstriction
increase in viscosity
promotes thrombosis
causes anoxia
what cellular changes happen in frost bite?
ice crystals form in extracellular space
increases extracellular osmolality
causes movement of water from intracellular space
cell dehydration and death
describe the winter mortality in the UK?
40% excess mortality in winter in UK
partly due to increases in heart attacks and strokes following periods of cold weather
increased vasoconstriction and increased blood viscosity contribute
is response ot heat sress, heat production is minimised by what?
Decreased physical activity
Decreased food intake
is response ot heat sress, heat loss form the body is increased by what?
Vasomotor control - arteriolar dilation increases delivery of blood to the skin
Sweating - sympathetic cholinergic fibres increase evaporative heat loss
Behavioural responses - increasing surface area, removing clothing, moving to shaded area
what is heat exhaustion (heat illness) and what does it cause?
body temperature raised in range 37.5-40ºC
results in vasodilation and drop in central blood volume
caused by a disturbance of the body’s fluid/salt balance due to excessive sweating
symptoms include headache, confusion, nausea, profuse sweating, clammy skin, tachycardia, hypotension, weak pulse, fainting & collapse
what is heat stroke (heat injury) and what does it cause?
body temperature raised above 40ºC
body’s temperature control mechanisms fail
symptoms include hot dry skin (sweating ceased) & circulatory collapse
who is most at risk of heat exhaustion or heat stroke?
neonates & the elderly
people doing physical work in hot humid environments
workers wearing non-breathable protective clothing
what is the treatment of heat exhaustion or heat stroke?
move to cool environment
remove clothing
fan
sponge with tepid water
give fluids (oral, intravenous)
what is a fever?
Part of the body’s mechanism for fighting infection
Caused by endogenous pyrogens (IL-1, IL-6)
Concept of ‘set point’ controlled by the hypothalamus:
- endogenous pyrogens shift the set point
- caused by local production of prostaglandins by cyclo-oxygenase in the hypothalamus
- explains why aspirin & paracetamol reduce fever
Analogy of a thermostat that has been reset
Body temperature regulates around a higher than normal body temperature
Mild fever is beneficial
Severe fever is dangerous
why may you feel cold in a fever even though your body core temperautre is increased?
If in fever the set point is shifted up so for the period of set higher then core then you feel cold as your core temp is lower than the set point
