Flashcards in Skin & Temperature Regulation Deck (35)
What is the normal temperature of the body?
36 +/- 0.5 degrees C
At what temperature do proteins start to denature?
Above 41 degrees C
At what temperature do people begin to lose consciousness?
Below 30 degrees C
What does temperature vary with?
• External temp
• Circardian rhythm
• Menstrual cycle
How is core temperature maintained?
By balancing heat loss and heat gain
By what four mechanism does the body maintain thermal balance?
What is the average heat produced per hour?
• 80kcal/hr at rest
• 600 kcal/hr at a brisk walk - raised temp by 1degreeC per 10min
Describe heat transfer in evaporation
Respiration + sweating
• 600ml/day at rest
• 4L/hour at extremes loses 600kcal/l
What accounts for 60% of heat loss?
What is conduction?
Heat transfer direct between touching objects
What two structure s in the body are responsible for detection of body temperature?
Cold receptors and warm receptors
Compare cold and warm receptors
Warm receptors will turn up their signal rate when they feel warmth—or heat transfer into the body. Cooling—or heat transfer out of the body—results in a decreased signal rate.
Cold receptors increase their firing rate during cooling and decrease it during warming.
What are the two types of thermoreceptors in the body and where are they located?
Located in the skin, especially in face, scrotum
Located in spinal cord, abdominal organs, hypothalamus
What do the peripheral thermoreceptors respond to?
Change in environmental temperature
What do the central thermoreceptors respond to?
Change in core body temperature
What do the peripheral and central thermoreceptor feed into?
Hypothalamic thermoregulatory centre which can produce responses to increased or decreased temperature
How is heat generated in response to cold stress?
• General metabolism (produces more heat)
• Voluntary muscular activity (skeletal muscle produces heat)
• Shivering thermogenesis (involuntary muscular activity)
• Non shivering thermogenesis (only significant in infants)
What is the non-shivering thermogenesis response to cold stress?
Neonates have high brown tissue -> protein gradient used to form ATP is stopped and is used to produce more heat
How is heat loss reducing in response to cold stress?
• Vasomotor control - sympathetic arteriolar constriction reduces delivery of blood to the skin
• Behavioural responses - reducing surface area, adding clothing, moving to warmth
How is hypothermia diagnosed?
A fall in deep body temperature to below 35
What types of people are at risk of hypothermia?
• Neonates (big surface area:volume as not able to produce much heat but large surface area to lose heat)
• Elderly (don't detect changes in body temperature so well)
• Cold store workers
• Outdoor pursuits
• North Sea workers
What is the treatment of 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
How does frostbit occur in response to cold stress?
• Increase in viscosity
• Promotes thrombosis
• Causes anoxia (no O2)
Cold causes stasis and highly viscous blood (risk of clotting and thrombosis)
1. Ice crystals form in extracellular space in body fluid is cold
2. Increases extracellular osmolality
3. Causes movement of water from intracellular space
cell dehydration and death
What are the causes of winter mortality?
• Partly due to increases in heart attacks and strokes following periods of cold weather (cold -> increase stasis and viscous blood)
• Increased vasoconstriction and increase blood viscosity
What are the three responses to heat stress?
• Heat production is minimised by:
• Decreased physical activity
• Decreased food intake
How is heat loss from the body increased in response to heat stress?
• Vasomotor control - arteriolar dilation increases delivery of blood to skin
• Sweating - sympathetic cholinergic fibres increase evaporative heat loss
• Behavioural responses - increasing surface area, removing clothing, moving to shaded area
Describe the development of heat exhaustion (heat illness)
• Body temp raised to 37.5-40C
• Results in vasodilation and drop in central blood volume
• Caused by a disturbance of body fluid/ salt balance due to excessive sweating
What are the symptoms of heat exhaustion?
• Confusion - reduction in preload and thus DV -> not enough lack of bloody supply to brain
• Profuse sweating
• Weak pulse
• Fainting and collapse
Who are the most at risk of heat stress?
• Neonates and elderly
• People doing physical work in hot humid environments
• Workers wearing non-breathable protective clothing