Skin and Temperature Regulation Flashcards
What is normal body temperature?
37 +/- 0.5C
At what temperature do proteins start to denature?
Above 41C
Below what temperature do you lose consciousness?
30C
What does temperature vary with?
External temperature
Activity
Circadian rhythm
Menstrual cycle
What is core temperature maintained by?
Balancing heat loss and heat gain
On a brisk walk, how much would the temperature raise by per 10 minutes?
1C
What is conduction?
Heat transfer directly between touching objects
Usually a source of heat loss but can be heat gain as well
What is convection?
Fluid conduction hence wind chill and water chill
What is lost via evaporation?
Respiration and sweating
How much fluid is lost from evaporation during the day at rest?
600 ml per day
What is the biggest source of heat loss from the skin?
Radiation
What is the cold receptors of the skins peak firing rate?
Below 30C
What is the range the cold receptors fire in?
10 - 40C
What is the peak firing rate for warm receptors?
Above 40C
What do the warm receptors fire in the range of?
30 - 50C
Where are peripheral thermoreceptors located?
Skin
especially in
- face
- scrotum
Where are central thermoreceptors located?
Spinal cord
Abdominal organs
Hypothalamus
What does the peripheral thermoreceptors detect?
A change in environmental temperature
What do the central thermoreceptors detect?
A change in body temperature
Where do changes detected by both of the receptors go?
To the hypothalamic thermoregulatory centre
What responses does the body have to cold stress?
General metabolism
Voluntary muscular activity
Shivering thermogenesis (involuntary)
Non shivering thermogenesis (only significant in infants due to brown adipose tissue)
What is heat loss from the body reduced by?
Vasomotor control - sympathetic arteriolar constriction reduces the delivery of blood flow to the skin Behavioural responses - reducing surface area - adding clothing - moving to warmer environment
Definition of hypothermia
A fall in deep body temperature to below 35C
Who is at risk of cold stress?
Neonates Elderly Vagrants Cold store workers North sea workers Outdoor pursuits
Treatment for cold stress
Dry / insulate to prevent further heat loss
Slow rewarming with bag/blanket
Intermetal rewarming with hot drinks and/or warm air
Pathology of frost bite
Vasoconstriction
increase in viscosity of blood so harder to push through
Promotes thrombosis
Causes anoxia
Ice crystals form in extracellular space
Increases extracellular osmolarity
Causes movement of water from intracellular space
Cell dehydration and death
What is the excess mortality in the winter?
40%
How is heat production minimised?
Decreased physical activity
Decreased food intake
Heat loss from the body is increased by…….
Vasomotor control - arteriolar dilation increases delivery of blood to the skin Sweating - sympathetic cholinergic fibres increase evaporate heat loss Behavioural responses - increasing surface area - remove clothing - move to shaded area/colder environment
Definition of heat exhaustion
Body temperature raised in range 37.5-40C
Another name for heat exhaustion
Heat illness
Pathology of heat exhaustion
Vasodilation and drop in central blood volume
Caused by disturbance of the bodys fluid/salt balance due to excess sweating
Presentation of heat exhaustion
Headache Confusion Nausea Profuse sweating Clammy skin Tachycardia Hypotension Weak pulse Fainting Collapse
What can heat exhaustion lead to?
Heat stroke
What is another name for heat stroke?
Heat injury
Definition of heat stroke?
Body temp raised above 40C
Pathology of heat stroke
Body temp control mechanisms fail
Presentation of heat stroke
Hot dry skin (sweating ceased)
Circulatory collapse
Who are those most at risk of overheating?
Neonates
Elderly
People doing physical work in hot humid environments
Workers wearing non breathable protective clothing
Why is humid environments not ideal to cool your body down?
You cannot get rid of heat using evaporation in humid environments
Treatment of heat stress
Move to cool environment Remove clothing Fan Sponge with tepid water Give fluids - oral - IV
What is fever a mechanism of?
Fighting infetion
Cause of fever
Endogenous pyrogens IL-1 and IL-6
