Skin and temperature control Flashcards
What is the normal core body temperature? How is it maintained?
37 +/- 0.5°C
Core temperature is maintained by balancing heat loss and heat gain
At what temperature do proteins start to denature?
Above 41°C
At what temperature do humans lose consciousness
Below 30°C
Hypothermia = below 35°C
What does our body temp vary with?
External temp
Activity
Circadian rhythm
Menstrual cycle
Where are Peripheral thermoreceptors located? What do they detect?
Located in the skin, especially in face, scrotum
Detect a change in the environmental temperature
Where are Central thermoreceptors located?
What do they detect?
Located in spinal cord, abdominal organs, hypothalamus
Detect a change in core body temperature
In which ways is heat lost from the body
Convection
Evaporation - respiration + sweating
Radiation - 60% heat loss
Conduction - heat transfer through touch
Sources of heat for the body through…
Convection
Conduction
Radiation
Response to cold stress: How is heat generated in the body (4)
General metabolism
Voluntary muscular activity
Shivering thermogenesis - involuntary
Non-shivering thermogenesis - only significant in infants due to brown adipose tissue
How is heat loss from the body reduced in response to cold stress? (2)
Vasomotor control
- sympathetic arteriolar constriction reduces delivery of blood to the skin
Behavioural responses
- reducing surface area, adding clothing, moving to warmer environment
Who is at risk of hypothermia? (6)
Neonates
Elderly - do not detect temp change so well, less shivering capacity, more immobile
Vagrants - homeless/beggars
Cold store workers
Outdoor pursuits
North Sea workers
Why are Neonates at risk of hypothermia?
Babies have a big SA:volume ratio
This means they dehydrate quicker due to having a bigger surface area than fluid in them.
They don’t have much fat, don’t shiver well, but do have BAT (brown adipose tissue) to produce heat
Treatment for hypothermia
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
Vascular response to cold stress
vasoconstriction
increase in viscosity
promotes thrombosis
causes anoxia
Cellular response to cold stress
ice crystals form in extracellular space
increases extracellular osmolality
causes movement of water from intracellular space
cell dehydration and death
How is there an increase in heart attacks and strokes following periods of cold weather?
Cold response causes increased vasoconstriction and increased blood viscosity which contribute
How is heat production minimised? (2)
Decreased physical activity
Decreased food intake
How is heat loss from the body increased? (3) ie how to cool down
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
Heat exhaustion (heat illness)
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.
Heat stroke (heat injury)
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 stress
Neonates & the elderly
People doing physical work in hot humid environments
Workers wearing non-breathable protective clothing
Treatment of someone exposed to heat stress of some sort
Move to cool environment
Remove clothing
Fan
Sponge with lukewarm water
Give fluids (oral, intravenous)
What is a Fever? What causes it?
Part of the body’s mechanism for fighting infection
Caused by endogenous pyrogens (IL-1, IL-6)
Endogenous pyrogens shift the ‘set point’ (controlled by hypothalamus). Caused by local production of prostaglandins by cyclo-oxygenase in the hypothalamus
Body temperature regulates around a higher than normal body temperature
Mild fever can be beneficial but severe fever is dangerous
Difference in core temp and set temp during exercise and when you have a fever
Exercise: Tset is normal but your Tcore increases
Fever: Tset increases to about the same as your Tcore
