Skin & Temperature control Flashcards

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1
Q
  • what is core body temp
  • what does it vary with?
  • what happens above 41°C
  • what happens below 30°C
A
  • CBT is normally 37 +/- 0.5°C
  • varies with
  • external temperature
  • activity
  • menstrual cycle
  • circadian rhythm
  • above 41°C, proteins denature
  • below 30°C, lose consciousness
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2
Q

how is core body temp maintained?

A

by balacing heat loss and heat gain

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3
Q

What are the 4 factors that affect thermal balance and explain them

A
  • evaporation
  • respiration + sweating
  • radiation
  • radiation of heat, both into body ie through sun and out ie after exercise
  • accounts for 60% of heat loss
  • conduction
  • heat transfer direct between touching objects
  • convection
  • heat transfer due to bulk movement of molecules within gases and liquids
  • blood causes convection as it transfers heat from core to periphery ie skin
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4
Q

how do we detect body temperature?

A
  • cold and warm receptors
  • some receptors that fire when cold and others when warm
  • Range in middle when cold and warm fire at same rate
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5
Q

How can you tell warm and cold receptors apart?

A

via their dynamic response to change in temp: diagram

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6
Q

What are the different classes of thermoreceptors & where are they located?

A
  • peripheral thermoreceptors

located in skin, especially in face, scrotum as sperm needs to be kept cool

  • central thermoreceptors

located in spinal cord, abdominal organs, hypothalamus

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7
Q

In response to cold stress, how is heat generation within the body increased?

A
  • increased metabolism & background metabolic rate
  • Voluntary muscular activity
  • Shivering thermogenesis
  • involuntary muscle activity: use skeletal muscle, make it contract to produce heat as by-product
  • Non-shivering thermogenesis
  • only significant in infants, due to brown adipose tissue
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8
Q

in response to cold stress, how is heat loss from the body reduced?

A
  • sympathetic arterial constriction
  • behavioural responses ie adding clothing, moving to warmer environment
  • hypothermia- body temp reduced to 35°C
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9
Q

who are those at risk with the cold?

A
  • neonates
  • elderly
  • homeless
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10
Q

why are neonates at risk in the cold?

A
  • not much fat
  • don’t shiver well
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11
Q

why are the elderly at risk in the cold?

A
  • don’t detect temp change so well
  • less shivering capacity
  • more immobile
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12
Q

what is the treatment of cold stress?

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
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13
Q

what is a condition which arises as a response to cold stress?

A

frost bite

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14
Q

in frost bite, why may tissue damage occur?

A

may result from

  • direct cellular damage

or

  • secondary effects of vascular damage
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15
Q

how does vascular damage contirbute to frostbite?

A
  1. vasoconstriction
  2. increase in blood viscosity
  3. increase chance of clot
  4. thrombosis –> anoxia
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16
Q

how does cellular damage contribute to frostbite?

A
  1. ice crystals form in ECF
  2. increases extracellular osmolality
  3. draws fluid out of cells, they get dehydrated
  4. cell death
17
Q

what does cold stress cause?

A

increase in mortality

18
Q

in response to heat stress, heat production is minimised by what?

A
  • reduced food intake
  • decreased physical activity
19
Q

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

A
  • arteriolar dilation
  • sweating - sympathetic cholinergic fibres increase evaporative heat loss
  • behavioural responses

-removing clothing, moving to shaded area

20
Q

what are some consequences of heat stress?

A
  • heat exhaustion
  • heat stroke
21
Q

what is heat exhaustion?

A
  • body temp raised in range 37.5- 40 degrees celsius
  • results in vasodilation and drop in central blood volume
  • caused by a disturbance of the body’s fluid/salt balance due to excessive sweating
22
Q

what are symptoms of heat exhaustion?

A
  • headache
  • confusion
  • nausea
  • clammy skin/profuse sweating
  • tachycardia
  • hypotension
  • fainting & collapse
23
Q

what is heat stroke?

A
  • body temperature raised to above 40degrees Celsius
  • body’s temp control mechanisms fail
24
Q

what are symptoms of heat stroke?

A

hot dry skin & circulatory collapse

25
Q

who are the most at risk in heat?

A
  • neonates & elderly
  • people doing physical work in hot humid environment
  • workers wearing non-breathable protective clothing
26
Q

treatment of heat stress?

A
  • move to cool environment
  • remove clothing
  • fan
  • sponge with tepid water
  • give fluids
27
Q
  • what is fever?
  • what is it caused by?
A
  • part of body’s mechanism for fighting infection
  • caused by endogenous pyrogens ie IL-1, IL-6
28
Q

how does fever occur?

A
  • endogenous pyrogens shift set point
  • caused by local production of prostaglandins by cyclo-oxygenase in hypothalamus
29
Q

how do anti-pyretics such as aspirin and paracetamol reduce fever ?

A

by inhibiting enzyme cyclo-oxygenase & reducing levels of prostaglandins

30
Q

what is fever’s effect?

A

to increase set point so to regulate it around 39, so start doing things to increase core temperature to reach that ie shivering