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HUBS192 Lectures 1-38 > HUBS192 Lecture 3 - Skin physiology > Flashcards

HUBS192 Lecture 3 - Skin physiology Flashcards

1
Q

5 touch receptors of the skin

A

1) free nerve endings
2) tactile discs
3) tactile (meissner) corpuscles
4) lamellar (pacinian) corpuscles
5) bulbous (ruffini) corpuscles

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2
Q

what are free nerve endings?

A

mostly unmyelinated small diameter fibres have sensory terminals located at the distal end

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3
Q

what are sensory terminals?

A

small swellings at distal ends

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4
Q

function of sensory terminals

A

have receptors that function as cation channels which depolarise to produce AP’s

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5
Q

what do free nerve endings respond to?

A

1) temperature
2) painful stimuli
3) movement
4) pressure

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6
Q

what are peritrichial endings?

A

free nerve endings wrapped around hair follicles

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7
Q

light touch receptors

A

peritrichial ending receptors that detect the bending of hairs

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8
Q

what are tactile (merkel) discs and where are the located?

A

free nerve endings associated with large disc shaped epidermal (merkel) cells located in the deepest layer of the epidermis

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9
Q

where is the tactile (merkel) disc abundant>

A

abundant in fingertips and very small receptive fields (good for two point discrimination)

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10
Q

what are tactile (merkel) discs sensitive to?

A

1) texture
2) fine touch
3) light pressure

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11
Q

tactile (meissner) corpuscles

A

branching unmyelinated sensory terminals surrounded by modified schwann cells which are then surrounded by a thin oval fibrous connective tissue capsule located in the papillary layer of the dermis

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12
Q

where is the tactile (meissner) corpuscles abundant?

A

abundant in hairless skin

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13
Q

what happens when the tactile (meissner) corpuscles capsule is deformed?

A

deformation of capsule triggers entry of Na+ ions into the nerve terminal inducing an AP

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14
Q

what do the tactile (meissner) corpuscles sense?

A

1) discriminative touch (movement of objects over the skins surface)
2) light pressure
3) low frequency vibration of 2 to 80 hertz

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15
Q

what are lamellar (pacinian) corpuscles and where are they located?

A

single dendrite lying within circular layers of collagen fibres and specialised fibroblasts scattered deep in the dermis and hypodermis

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16
Q

how are the layers of lamellar (pacinian) corpuscles seperated?

A

separated by gelatinous interstitial fluid

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17
Q

what happens when the lamellar (pacinian) corpuscles capsule is deformed?

A

deformation of capsule opens pressure sensitive Na+ channels in sensory axons
-inner layers covering axon terminal ‘relax’ quickly so AP’s discontinue (rapidly adapting)

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18
Q

what are the lamellar (pacinian) corpuscles stimulated by?

A

1) deep pressure when first applied

2) vibration

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19
Q

what are bulbous corpuscles (Ruffini’s endings) and where are they located?

A

network of nerve endings intertwined with a core of continuous collagen fibres surrounded by a capsule located in the dermis and subcutaneous tissue

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20
Q

what are the bulbous corpuscles (ruffini’s endings) sensitive to?

A

1) deep sustained pressure
2) skin stretching
3) skin distortion

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21
Q

what are bulbous corpuscles (ruffini’s endings) important for?

A

important for signalling continuous states of deformation of the tissue (heavy prolonged touch and pressure signals)
-involved in proprioception

22
Q

precapillary sphincters

A

bands of smooth muscle

23
Q

what does GPCR’s stand for?

A

G protein coupled receptors

24
Q

how is skin blood flow controlled?

A

controlled by smooth muscle in the walls of arteries and pre-capillary sphincters innervated by the SNS (sympathetic nervous system)

25
Q

what happens to reduce skin blood flow

A

-noradrenaline acts on alpha 1 adrenergic receptors on vascular smooth muscles in the skin
GPCR’s coupled to intercellular 2nd messengers increase intracellular Ca2+ causing vasoconstriction

26
Q

what happens to increase skin blood flow?

A

SNS activity is reduced to cause vasodilation (relaxation) to the arteries of the skin

27
Q

normal range of body temperature

A

between 36.5 and 37.5 degrees

28
Q

what is radiation?

A

causes heat loss in the form of infared rays

29
Q

what is evaporation?

A

heat is lost from the phase change of water form a liquid to a gas

30
Q

what is convection?

A

the movement of heated air away from the skin to be replaced with cooler which results in heat loss

31
Q

what is conduction?

A

transfer of heat by direct contact to another object/surface

32
Q

what are eccrine sweat glands innervated by

A

innervated by the sympathetic nervous system

33
Q

what happens at sympathetic cholinergic eccrine sweat glands?

A

ACh is released onto the GPCR - mAChRs

34
Q

what happens when eccrine glands are stimulated by adrenaline?

A

when stimulated by adrenaline in the blood it acts upon beta receptors to cause ‘nervous sweating’

35
Q

relationship between beta receptors secretion and body temperature

A

beta receptors can release adrenaline independent to body temperature

36
Q

pre optic area of the hypothalamus contains

A

thermoreceptors for the

1) heat loss centre
2) heat gain centre

37
Q

what happens when the heat loss centre is activated?

A

1) decreased SNS activation of alpha 1 on skin blood vessels causing vasodilation
2) increased SNS cholinergic activation of mAChR’s on sweat glands causing sweating
3) increased respiratory rate

38
Q

what happens when the heat gain centre is activated in terms of increased generation of body heat?

A

1) non shivering thermogenesis

2) shivering thermogenesis

39
Q

what happens when the heat gain centre is activated to conserve body heat?

A

vasoconstriction thereby reducing losses by radiation and convection

40
Q

what happens to cause shivering?

A

when the tone of muscles exceeds critical level, shivering begins due to contractions of agonist and antagonist muscles mediated by the muscle spindle (stretch receptors)

41
Q

what is non-shivering thermogenesis?

A
  • increased sympathetic nerve activity
  • increased circulating adrenaline/noradrenaline from the adrenal medulla
  • increased cellular metabolism
  • ‘uncoupling’ of oxidative phosphorylation
42
Q

what causes increased thyroxine (a heat generating mechanism)?

A
  • in response to TRH and TSH

- increases basal metabolic rate

43
Q

what is an arrector pili muscle?

A

smooth muscle innervated by the SNS (alpha 1 receptors) that attaches the hair follicle to the upper dermis

44
Q

what happens when the arrector pili muscle contracts?

A

1) goosebumps

2) compresses sebaceous glands which lubricates skin

45
Q

what is a first-degree burn and what are the features of it?

A

superficial burn to the outer layers of the epidermis that is red/pink, dry and painful

46
Q

3 features of a first-degree burn

A

1) no blisters
2) skin remains a water and bacterial barrier
3) heals in 3-10 days

47
Q

what is a second-degree burn?

A

burn to the epidermis + varying amounts of the dermis that is painful, moist, red and blistered

48
Q

2 features of a second-degree burn

A

1) heals in 1-2 weeks

2) needs absorptive dressings

49
Q

what is a deep second-degree burn?

A
  • may include whiteish, waxy areas
  • hair follicles, sweat glands may remain intact
  • some tactile receptors lost
  • heal in 1 month with possible loss of sensation and scarring
50
Q

third-degree burn

A

burn that extends into subcutaneous tissue (may involve muscle and bone) that has varied colour

51
Q

4 features of a third-degree burn

A

1) hard, dry and leathery
2) no pain due to destroyed nerve endings
3) if more than a few cms, skin grafting is required
4) weeks to regenerate + scarring

52
Q

3 potential complications of severe burns

A

1) dehydration and hypovolemic shock
2) infection/sepsis
3) hypothermia

HUBS192 Lectures 1-38 (38 decks)

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