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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***

***basal body temperature (BBT) chart.

during ovulation body temperature drops and after 24hrs rises again and stays raised for 6-7 days.

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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

****Evaporation is one way- heat loss only****

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

When a fluid, such as air or a liquid, is heated and then travels away from the source, it carries the thermal energy along.

****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

when temperature is raised, the warm thermoceptors increase their action potential firing and then settle in a new higher rate action potential, while the cold thermoceptors first stop firing their action potential and then settle on a new slower rate of action potential.

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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

19
Q

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

A

by increasing the fellowing:

  • 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
20
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
21
Q

How does vasomotor control reduce heat loss?

A
  • Sympathetic arteriolar constriction reduces delivery of blood to the skin
22
Q

What are some illnesses caused by cold stress?

A
  • Hypothermia
  • Frost bite
23
Q

When does hypothermia occur?

A

when deep body temperature is below 35

24
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
25
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)
26
Q

What does BAT stand for?

A

Brown adipose tissue

27
Q

Why are the elderly at risk of hypothermia?

A
  • Do not detect temperature change so well, less shivering capacity, more immobile
28
Q

What is the treatment of hypothermia?

A
  • insulation to prevent further heat loss
  • Slow re-warming with bag/blankets
  • Fast re-warming by immersion in water, extracorporeal circulation
  • Internal re-warming with hot drinks and/or warm air
29
Q

What is frostbite?

A

Injury caused by freezing of the skin and underlying tissues

30
Q

What are the two changes that occur in Forst bit which causes tissue death?

A

Vascular changes: Vasoconstriction and Increased viscosity ( thickness of blood) due to cold blood causes thrombosis and anoxia (an absence of oxygen).

Cellular changes: extreme cold cause ice crystals to form in the extracellular space. This increases extracellular osmolarity, which causes movement of water from intracellular space leading to Cell death and dehydration

31
Q

What is the percentage of excess deaths in winter due to cold stress?

A

40% excess in UK

32
Q

Why does mortality due cold stress increases in the winter?

A
  • Partially due to an increase in heart attacks and strokes caused by an increased vasoconstriction and increased blood viscosity due to the cold weather.
33
Q

How the body reduce heat production in response to heat stress?

A
  • By decreasing physical activity
  • By decreasing food intake
34
Q

How the body increases heat loss in response to heat stress?

A
  • Vasomotor control
    • Arteriolar dilation increases delivery of blood to the skin
  • Sweating
    • increases evaporation and heat loss
  • Behavioural responses
    • Increasing surface area, removing clothing, moving to shaded area
35
Q

What are some illnesses due to heat stress?

A
  • Heat exhaustion (heat illness) Body temperture is between 37.5 - 40 C
  • Heat stroke (heat injury) Body temperture is above 40 C
36
Q

Which age group is at risk of heat stress?

A
  • Neonates
  • Elderly
  • People doing physical work in hot humid environments
  • Workers wearing non-breathable protective clothing
37
Q

What is the treatment for heat stress?

A

Move to cool environment, Remove clothing, Fan, Give fluids (oral, IV)

38
Q

When does heat exhaustion and heat stroke occur?

A
  • Heat exhaustion: occurs when Body temperature is between 37.5-40 C
  • Heat Stroke: occurs when body temperture is above 40 C
39
Q

What are the clinical presentations of heat exhaustion?

A
  1. Headache
  2. Confusion
  3. Tachycardia
  4. Hypotension
  5. Fainting and collapse
40
Q

What causes heat stroke?

A

Body’s temperature control mechanism fails

41
Q

What is the clinical presentation of heat stroke?

A
  • Hot dry skin (sweating ceased)
  • Circulatory collapse due to the lack of central blood flow.
42
Q

What is a fever? What produce fever?

A
  • Is the body’s mechanism for fighting infection, because some pathogens don’t survive in high tempertures.
  • Caused by endogenous pyrogens interleukin-1 and Interleukin-6 (IL-1, IL-6) which are produced by the immune cells.
43
Q

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

A
  • Interleukin-1 and interleukin-6 controlle the the “set point” of the hypothalamus. When infection is detected in the body by the immune cells, immune cells release IL-1 and IL-6. In the hypothalamus prostaglandins is produced by cyclo-oxygenase which h shifts or changes the “set point” of the Hypothalamus to high (i.e 40C)t
  • Aspirin and Paracetamol inhibit cyclo-oxygenase which explains why aspirin and paracetamol reduce fever.
44
Q

Are fevers beneficial?

A
  • Mild fever is beneficial, sever fever is dangerous

Dermatology (10 decks)

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