Skin and Temperature Control Flashcards
What is normal body temperature?
37 degrees Celsius +/- 0.5 degrees
Man is homeothermic. What does this mean?
We can tightly regulate body temperature
What happens if body temperature rises over 41?
Proteins start to denature
What happens if body temperature falls below 30?
Lose consciousness
What are some factors which can cause variation within body temperature?
External temperature
Activity
Circadian rhythm
Menstrual cycle
How is core temperature maintained?
By balancing heat loss and gain
Radiation plays a role in thermal balance. Does it cause us to lose or gain heat?
Both!
If you took all your clothes off, you would be losing heat via radiation
If you were sunbeathing, you would gain heat from the rays
Evaporation plays a role in thermal balance. Does it cause us to lose or gain heat?
Lose
->via respiration and sweating
Conduction plays a role in thermal balance. Does it cause us to lose or gain heat?
Both!
->this is to do with heat transfer between touching objects e.g. hot water bottle, sleeping on a cold floor
Convection plays a role in thermal balance. Does it cause us to lose or gain heat?
Both
->can lose heat via wind or water chill but plays a role in heating of radiators hence how we can gain heat too
Which specialised neurons detect changes in body temperature?
Thermoreceptors
At what temperature is the peak firing rate of cold receptors?
25 oC
At what temperature is the peak firing rate of warm receptors?
40 oC
Where is the body are peripheral thermoreceptors located?
Skin, especially in the face and the scrotum
Where is the body are central thermoreceptors located?
Spinal cord
Abdominal organs
Hypothalamus
Which part of the brain is responsible for maintaining internal body temperature?
Hypothalamus
How does the body respond to cold stress be generating heat?
Increases metabolic rate
‘Futile’ muscular activity to produce heat e.g. jumping around to warm up
Shivering thermogenesis
Non-shivering thermogenesis (note this is only significant in infants due to brown adipose tissue)
How does the body respond to cold stress be reducing the amount of heat lost by the body?
Vasoconstriction
Behavioural responses e.g. adding more clothing
What happens in vasoconstriction?
Sympathetic arteriolar constriction reducing the delivery of blood to the skin
Hypothermia?
A fall in deep body temperature to below 35 oC
Who is at increased risk of hypothermia?
Neonates- less fat
Elderly- less mobile
Homeless people
Cold store workers
Outdoor pursuits
What is the treatment of cold stress?
Dry/insulate to prevent further heat loss
Slow re-warming with bags or blankets
Internal re-warming with hot drinks
Rapid re-warming by immersion in water
What happens as a consequence of cold stress?
Frost bite in the extremities
What occurs vascularly in frostbite?
Vasoconstriction
Increase in viscosity
Promotes thrombosis
Causes anoxia
What occurs cellularly in frostbite?
Ice crystals form in the extracellular space
Increase in extracellular osmolality
Movement of water from intracellular space
Cell dehydration and death
Why is there increased mortality rates in winter?
Increased MIs and stroke as there is increased vasoconstriction and blood viscosity
How is the body’s heat production minimised?
Decreased physical activity
Decreased food intake
How does the body increase the amount of heat it loses?
Vasodilation
Sweating
Behavioural responses e.g. taking off a jumper
What happens in sweating to lose heat?
Sympathetic cholinergic fibres increase evaporative heat loss
What are some consequences of heat stress?
Heat exhaustion
Heat stroke
At what body temperature does heat exhaustion occur?
37.5-40 oC
What does heat exhaustion result in?
Vasodilation and drop in central blood volume
What is heat exhaustion caused by?
Disturbance of the body’s fluid/salt balance due to excessive sweating
What are some of the symptoms of heat exhaustion?
Headache
Confusion
Nausea
Profuse sweating
Clammy skin
Tachycardia
Hypotension
Weak pulse
Fainting
Collapse
At what body temperature does heat stroke occur?
> 49oC
What are some of the symptoms of heat stroke?
Hot dry skin- sweating stops
Circulatory collapse
Soooo…. if heat exhaustion progresses, what can occur?
Heat stroke
Who is more at risk of heat stress?
Neonates
Elderly
People during physical work in hot, humid environment’s
Workers wearing non-breathable protective clothing e.g. firefighters
What is the treatment of heat stress?
Moving to a cool environment
Remove clothing
Fan
Sponge with tepid water
Give fluids, either orally or intravenously
What is fever caused by?
Endogenous pyrogens (IL-1, IL-6)
What happens by these endogenous pyrogens to cause fever?
Local production of prostaglandins by cyclo-oxygenase in the hypothalamus
->aspirin and paracetamol reduce fever as inhibit cyclo-oxygenase
Why do you feel cold and shivery at the start of a fever?
I find this interesting :)
The pyrogens shift the set point at which the body deems to be normal temperature.
Therefore, when trying to reach this new high temperature, the body thinks it’s cold so shivers to try and generate heat
Which mechanism allows heat loss through our blood?
Convection
-> This is where blood is warmed up in the core, goes out to the periphery where the heat can be lost then comes back to the core to be heated up again.
What happens to the firing rate of cold receptors in response to a decrease in temperature?
Cold receptors increase their firing rate
->The opposite is true for heat receptors which increase their firing rate in response to an increase in temperature.
