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Dermatology > Skin & Temperature Regulation > Flashcards

Skin & Temperature Regulation Flashcards

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Dermatology Board Prep flashcards
1
Q

What is the normal temperature of the body?

A

36 +/- 0.5 degrees C

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2
Q

At what temperature do proteins start to denature?

A

Above 41 degrees C

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3
Q

At what temperature do people begin to lose consciousness?

A

Below 30 degrees C

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4
Q

What does temperature vary with?

A
  • External temp
  • Activity
  • Circardian rhythm
  • Menstrual cycle
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5
Q

How is core temperature maintained?

A

By balancing heat loss and heat gain

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6
Q

By what four mechanism does the body maintain thermal balance?

A
  • Convection
  • Conduction
  • Evaporation
  • Radiation
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7
Q

What is the average heat produced per hour?

A
  • 80kcal/hr at rest

* 600 kcal/hr at a brisk walk - raised temp by 1degreeC per 10min

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8
Q

Describe heat transfer in evaporation

A

Respiration + sweating
• 600ml/day at rest
• 4L/hour at extremes loses 600kcal/l

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9
Q

What accounts for 60% of heat loss?

A

Radiation

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10
Q

What is conduction?

A

Heat transfer direct between touching objects

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11
Q

What two structure s in the body are responsible for detection of body temperature?

A

Cold receptors and warm receptors

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12
Q

Compare cold and warm receptors

A

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.

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13
Q

What are the two types of thermoreceptors in the body and where are they located?

A

Peripheral thermoreceptors:
Located in the skin, especially in face, scrotum

Central thermoreceptors:
Located in spinal cord, abdominal organs, hypothalamus

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14
Q

What do the peripheral thermoreceptors respond to?

A

Change in environmental temperature

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15
Q

What do the central thermoreceptors respond to?

A

Change in core body temperature

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16
Q

What do the peripheral and central thermoreceptor feed into?

A

Hypothalamic thermoregulatory centre which can produce responses to increased or decreased temperature

17
Q

How is heat generated in response to cold stress?

A
  • General metabolism (produces more heat)
  • Voluntary muscular activity (skeletal muscle produces heat)
  • Shivering thermogenesis (involuntary muscular activity)
  • Non shivering thermogenesis (only significant in infants)
18
Q

What is the non-shivering thermogenesis response to cold stress?

A

Neonates have high brown tissue -> protein gradient used to form ATP is stopped and is used to produce more heat

19
Q

How is heat loss reducing in response to cold stress?

A
  • Vasomotor control - sympathetic arteriolar constriction reduces delivery of blood to the skin
  • Behavioural responses - reducing surface area, adding clothing, moving to warmth
20
Q

How is hypothermia diagnosed?

A

A fall in deep body temperature to below 35

21
Q

What types of people are at risk of hypothermia?

A
  • 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)
  • Vagrants
  • Cold store workers
  • Outdoor pursuits
  • North Sea workers
22
Q

What is the treatment of hypothermia?

A
  • 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
23
Q

How does frostbit occur in response to cold stress?

A 
Vascular:
• Vasoconstriction 
• Increase in viscosity 
• Promotes thrombosis 
• Causes anoxia (no O2)

Cellular
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

24
Q

What are the causes of winter mortality?

A
  • 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
25
Q

What are the three responses to heat stress?

A
  • Heat production is minimised by:
  • Decreased physical activity
  • Decreased food intake
26
Q

How is heat loss from the body increased in response to heat stress?

A
  • 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
27
Q

Describe the development of heat exhaustion (heat illness)

A
  • 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
28
Q

What are the symptoms of heat exhaustion?

A
  • Headache
  • Confusion - reduction in preload and thus DV -> not enough lack of bloody supply to brain
  • Nausea
  • Profuse sweating
  • Tachycardia
  • Hypotension
  • Weak pulse
  • Fainting and collapse
29
Q

Who are the most at risk of heat stress?

A
  • Neonates and elderly
  • People doing physical work in hot humid environments
  • Workers wearing non-breathable protective clothing
30
Q

What is the treatment of heat stress?

A
  • Move to cool environment
  • Remove clothing
  • Fan
  • Sponge with tepid water
  • Give fluids (oral, IV)
31
Q

Describe the development of heat stroke (heat injury)

A
  • Body temp raised > 40C

* Body temp control mechanisms fail

32
Q

What are the symptoms of heat stroke?

A
  • Hot dry skin (sweating ceased as you run out of fluid)

* Circulatory collapse

33
Q

What happens in a fever?

A
  • Bodys mechanism for fighting infection
  • Caused by endogenous pyrogens (IL-1, IL-6)
  • Increase in the ‘set point’ controlled by the hypothalamus
  • Body temperature regulates around high than normal temp
  • Beneficial in order to fight infection
34
Q

What happens to the set point in a fever?

A
  • Endogenous pyrogens shift the set point
  • Caused by local production of prostaglandins by cyclo-oxygenase in the hypothalamus
  • Explains why aspirin & paracetamol reduce fever
35
Q

Describe the relationship of the set point in exercise in comparison to it in a fever

A

Exercise – produce heat within and core increases above set point temperature causing sweat

Fever – increase in set point and then your body actively doing everything it can to increase body temp up to that body – set point is above body temperature temperature

Dermatology (8 decks)

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