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10. Year 2: Dermatology > Skin and Temperature Regulation > Flashcards

Skin and Temperature Regulation Flashcards

1
Q

What does homeothermic mean?

A

Maintains stable internal body temperature regardless of external influence

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2
Q

What is normal core body temperature?

A

37 +/- 0.5oC

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3
Q

At what temperature do proteins start to denature?

A

41oC

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4
Q

At what temperature do you lose consciousness?

A

Below 30oC

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5
Q

What does core body temperature vary with?

A
  • External temp
  • Activity
  • Circadian rhythm
  • Menstrual cycle
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6
Q

How is core body temperature maintained?

A

By balancing heat loss and heat gain

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7
Q

What are the different methods that thermal balance is achieved?

A

Convection

Conduction

Evaporation

Radiation

Heat production

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8
Q

What is evaporation in terms of thermal balance?

A

Respiration and sweating

About 600ml/day at rest

But 4L/hour at extremes and losses 600kcal/L

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9
Q

What is conduction in terms of thermal balance?

A

Heat transfer direct between touching objects

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10
Q

What is convection in terms of thermal balance?

A

Fluid conduction hence wind chill and water chill

Important in blood too

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11
Q

How is body temperature detected?

A

Cold and warm thermoreceptors

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12
Q

What are thermoreceptors divided into?

A
  • Peripheral thermoreceptors
    • Located in the skin, especially in face and scrotum
  • Central thermoreceptors
    • Located in spinal cord, abdominal organs and hypothalamus
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13
Q

Where are peripheral thermoreceptors located?

A

Skin, especially in face and scrotum

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14
Q

Where are central thermoreceptors located?

A

Spinal cord, abdominal organs and hypothalamus

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15
Q

How does an increases in temperature impact a warm receptor, and a decrease in temperature impact a cold receptor?

A

Increases frequency

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16
Q

Where do peripheral and central thermoreceptors feed their sensory information into?

A

Hypothalamic thermoregulatory centre

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17
Q

What do peripheral receptors detect?

A

Change in environmental temperature

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18
Q

What do central receptors detect?

A

Change in core body temperature

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19
Q

What are different ways that heat is generated within the body in response to cold stress?

A
  • General metabolism
    • Oxidative phosphorylation and other chemical reactions are not 100% efficient
  • Voluntary muscular activity
    • “Futile” muscular activity
  • Shivering thermogenesis
    • Involuntary muscular activity
  • Nonshivering thermogenesis
    • In humans is only significant in infants, due to brown adipose tissue
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20
Q

How does general metabolism generate heat?

A
  • Oxidative phosphorylation and other chemical reactions are not 100% efficient
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21
Q

For generating heat, what is voluntary muscular activity described as?

A
  • “Futile” muscular activity
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22
Q

What is shivering thermogenesis?

A
  • Involuntary muscular activity
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23
Q

In what age group is non-shivering thermogenesis significant in?

A

Infants due to brown adipose tissue

24
Q

How is heat loss from the body reduced?

A
  • Vasomotor control
    • Sympathetic arteriolar constriction reduces delivery of blood to the skin
  • Behavioural responses
    • Reducing surface area, adding clothing, moving to warmer environment
25
Q

How does vasomotor control reduce heat loss?

A
  • Sympathetic arteriolar constriction reduces delivery of blood to the skin
26
Q

What are some illnesses caused by cold stress?

A
  • Hypothermia
  • Frost bite
27
Q

When does hypothermia occur?

A

Is a fall in deep body temperature below 35

28
Q

Who is most at risk of hypothermia?

A
  • Neonates
    • Big SA:volume, not much fat, don’t shiver well, but do have brown adipose tissue (BAT)
  • Elderly
    • Do not detect temperature change so well, less shivering capacity, more immobile
  • Vagrants
  • Cold store workers
  • Outdoor pursuits
  • North sea workers
29
Q

Why are neonates at risk of hypothermia?

A
  • Big SA:volume, not much fat, don’t shiver well, but do have brown adipose tissue (BAT)
30
Q

What does BAT stand for?

A

Brown adipose tissue

31
Q

Why are the elderly at risk of hypothermia?

A
  • Do not detect temperature change so well, less shivering capacity, more immobile
32
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
33
Q

What is frostbite?

A

Injury caused by freezing of the skin and underlying tissues

34
Q

What kinds of changes does frost bite cause?

A

Vascular changes:

  • Vasoconstriction
  • Increase in viscosity
  • Promotes thrombosis
  • Causes anoxia (an absence of oxygen)

Cellular changes:

  • Ice crystals form in extracellular space
  • Increases extracellular osmolarity
  • Causes movement of water from intracellular space
  • Cell death and dehydration
35
Q

What are some vascular changes due to frost bite?

A
  • Vasoconstriction
  • Increase in viscosity
  • Promotes thrombosis
  • Causes anoxia (an absence of oxygen)
36
Q

What are some cellular changes due to frostbite?

A
  • Ice crystals form in extracellular space
  • Increases extracellular osmolarity
  • Causes movement of water from intracellular space
  • Cell death and dehydration
37
Q

How does mortality change in winter?

A

40% excess mortality in winter in UK

38
Q

Why does mortality increases in the winter?

A
  • Partly due to increase in heart attacks and strokes following periods of cold weather
  • Increased vasoconstriction and increased blood viscosity contribute
39
Q

How is heat production minimised in response to heat stress?

A
  • Decreased physical activity
  • Decreased foot intake
40
Q

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

A
  • 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
41
Q

How does vasomotor control increase heat loss?

A
  • Arteriolar dilation increases delivery of blood to the skin
42
Q

How does sweating increase heat loss?

A
  • Sympathetic cholinergic fibres increase evaporative heat loss
43
Q

How do behaviour reponses increase heat loss?

A
  • Increasing surface area, removing clothing, moving to shaded area
44
Q

What are some illnesses due to heat stress?

A
  • Heat exhaustion (heat illness)
  • Heat stroke (heat injury)
45
Q

Who are some people at risk of heat stress?

A
  • Neonates
  • Elderly
  • People doing physical work in hot humid environments
  • Workers wearing non-breathable protective clothing
46
Q

What is the treatment for heat stress?

A
  • Move to cool environment
  • Remove clothing
  • Fan
  • Sponge with tepid water
  • Give fluids (oral, IV)
47
Q

When does heat exhaustion occur?

A

Body temperature raised in range of 37.5-40

48
Q

What changes in the body does heat exhaustion cause?

A

Results in vasodilation and drop in central blood volume

Caused by disturbance of the body’s fluid/salt balance due to excessive sweating

49
Q

What is the clinical presentation of heat exhaustion?

A
  • Headache
  • Confusion
  • Nausea
  • Profuse sweating
  • Clammy sin
  • Tachycardia
  • Hypotension
  • Weak pulse
  • Fainting and collapse
50
Q

When does heat stroke occur?

A

Body temperature raised above 40

51
Q

What causes heat stroke?

A

Body’s temperature control mechanism fails

52
Q

What is the clinical presentation of heat stroke?

A
  • Hot dry skin (sweating ceased)
  • Circulatory collapse
53
Q

What is a fever?

A

Part of body’s mechanism for fighting infection, caused by endogenous pyrogens (IL-1, IL-6)

54
Q

What is a fever caused by?

A

Endogenous pyrogens (IL-1, IL-6)

55
Q

Explain the concept of ‘set point’ controlled by hypothalamus?

A
  • Endogenous pyrogens shift the set point
  • Caused by local production of prostaglandins by cyclo-oxygenase in hypothalamus
  • Explains why aspirin and paracetamol reduce fever
  • Analogy of a thermostat that has been reset, body temperature regulates around a higher than normal body temperature
  • Mild fever is beneficial, sever fever is dangerous
56
Q

Are fevers beneficial?

A
  • Mild fever is beneficial, sever fever is dangerous
57
Q

What is changing of the set point during a fever caused by?

A
  • Caused by local production of prostaglandins by cyclo-oxygenase in hypothalamus

10. Year 2: Dermatology (11 decks)

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