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HUBS 192 > Lecture 3: Skin Physiology > Flashcards

Lecture 3: Skin Physiology Flashcards

1
Q

What are the different types of Touch receptors of the skin?

5

A
  • Free nerve endings
  • Tactile discs
  • Tactile corpuscles
  • Lamellar corpuscles
  • Bulbous corpuscles
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2
Q

How are receptors adapted to different stimuli?

2

A
  • Can often respond to several different stimuli

- Will be most sensitive to a particular type of stimulus

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3
Q

What is the most common receptor in the skin?

A

Free nerve endings

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4
Q

What is the structure of free nerve endings?

2

A
  • Mostly unmyelinated/small diameter fibres

- some myelinated/small diameter fibres

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5
Q

Where are Sensory Terminals found?

A

The distal ends of free nerve endings

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6
Q

What are Sensory Terminals?

A

Small swellings at the end of free nerve endings

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7
Q

What do sensory terminals possess?

A

Receptors that function as Cation channels leading to depolarisation and action potentials

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8
Q

What do Free Nerve endings mainly respond to?

4

A
  • Temperature
  • Painful stimuli
  • Some movement/pressure
  • Some itch
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9
Q

What are Peritrichial nerve endings?

A

Free nerve endings that wrap around hair follicles

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10
Q

What do Peritrichial endings do?

A

Act as light touch receptors, by detecting the bending of hairs

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11
Q

How do Free nerve ending sense itch?

A

Histamine receptors on sensory nerve endings detect histamine and alert your body

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12
Q

What are Tactile discs?

A

Free nerve endings located in the deepest layer of epidermis

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13
Q

What are Tactile discs associated with?

A

Large disc shaped epidermal (Merkel) cells

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14
Q

What does a Merkel cell do?

2

A
  • Detects stimulus

- Convert stimulus into a chemical message that is transmitted to sensory nerve endings

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15
Q

What is the chemical messenger used by Merkel cells?

A

Serotonin

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16
Q

Where are Tactile disks/Merkel cells most abundant in the body?

A

Finger tips

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17
Q

Are the receptor fields of Tactile disks/Merkel cells small or big?

A

Small

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18
Q

What are Tactile disks/Merkel cells good for?

A

Two point discrimination

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19
Q

What are Tactile disks/Merkel cells sensitive to?

A

An objects physical features e.g. texture, shape and edges

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20
Q

Where are Tactile Corpuscles located?

A

Papillary layer of the dermis

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21
Q

Where are Tactile Corpuscles especially prevalent in the body?

A 
Hairless skin e.g.
- finger pads 
- lips
- eyelids 
soles of feet
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22
Q

What can the structure of Tactile Corpuscles be described as?

A

Encapsulated

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23
Q

What are the structural features of an Encapsulated Tactile Corpuscle?
(3)

A
  • Branching unmyelinated sensory terminals
  • Terminals provided support by modified Schwann cells
  • surrounded by a thin oval fibrous connective tissue capsule
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24
Q

What do Tactile Corpuscles sense?

3

A
  • Delicate/discriminative touch
  • Light pressure
  • Low frequency vibration (2-80 Hz)
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25
Q

Where are Lamellar Corpuscles located?

A

Scattered deep in the dermis/hypodermis

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26
Q

What are the structural features of Lamellar Corpuscles?

3

A
  • Single dendrite
  • Inside layers of collagen fibres/specialised fibroblasts
  • Each layer separated by gelatinous interstitial fluid
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27
Q

What does deformation to the capsule of lamellar Corpuscles do?

A

opens pressure sensitive Na+ channels in sensory axons

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28
Q

What makes Lamellar Corpuscles rapidly adapting?

A

When inner layers covering the axon terminal are compressed they ‘relax’ quickly so action potentials are discontinued

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29
Q

What stimulates Lamellar corpuscles?

2

A
  • Deep pressure

- Vibration (around 250Hz)

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30
Q

Where are Bulbous Corpuscles located?

A

In the Demis/subcutaneous tissue

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31
Q

What are the structural features of Bulbous Corpuscles?

3

A
  • Network of nerve endings
  • Intertwined with a core of collagen fibres that are continuous with the dermis
  • Capsule surrounding entire structure
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32
Q

What stimulates Bulbous Corpuscles?

2

A
  • sustained deep pressure

- stretching/distortion of the skin

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33
Q

What are Bulbous Corpuscles important for?

A

signalling continuous states of:

  • deformation to tissue
  • heavy prolonged touch/pressure signals
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34
Q

What are Bulbous corpuscles involved in at joint capsules?

A

Proprioception - degree of joint rotation

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35
Q

Where on the body is there a high density of Bulbous Corpuscles?

A

Around fingernails

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36
Q

What do Bulbous Corpuscles allow your grip to do?

A

Be modulated

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37
Q

What do Arteries do in context of the skin?

A

Supply blood to the skin and subcutaneous layer

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38
Q

Where do the branches of arteries extend?

A

They extend into the superficial layers of the dermis

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39
Q

What is the role of capillary loops?

2

A
  • supply blood to the upper dermis/underside of the epidermis
  • Drain blood into the venous plexus
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40
Q

Where is smooth muscle located?

A

In the walls of blood vessels

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41
Q

What controls smooth muscle in blood vessels?

A

Sympathetic nervous system

42
Q

Where are Precapillary sphincters located?

A

At the start of capillary beds

43
Q

What does Contracting smooth muscle of the Precapillary sphincter/Arteries do?

A

Restricts blood flow to the upper layers of the skin

44
Q

What does Noradrenaline from the SNS act on in vascular smooth muscle in the skin?

A

Alpha 1 adrenergic receptors

45
Q

What are Alpha 1 adrenergic receptors an example of?

A

G-protein coupled receptor (GPCR)

46
Q

How do G-protein coupled receptors work?

A

They activate a secondary messenger system in the cell

47
Q

How do GPCR’s work on vascular smooth muscle tissue in the skin?
(3)

A
  • Secondary messenger system leads to increased intracellular calcium
  • Intracellular calcium leads to constriction
  • Constriction leads to reduced skinflow
48
Q

What is the result of less SNS activity in the skin?

2

A
  • Relaxation/dilation of arteries to the skin

- Increased skin bloodflow flow

49
Q

What is the optimal body temperature?

A

37ºC

Range of 36.5 - 37.5ºC

50
Q

What happens to cells at 40 degrees?

2

A
  • They become denatured

- Lose ability to thermoregulate

51
Q

What happens to cells when your body becomes too cold?

A

Nervous tissue lose function

52
Q

What are the Primary mechanisms of heat transfer?

4

A
  • Radiation
  • Evaporation
  • Convection
  • Conduction
53
Q

How is heat Transferred through radiation?

A

It is lost/gained through infrared rays

54
Q

What % of heat loss is through Radiation?

A

60%

55
Q

How is heat Transferred through Conduction?

A

Heat is transferred from/to objects that are in contact with the body

56
Q

What % of heat loss to the air is due to Conduction?

A

15%

57
Q

How is heat transferred through convection?

3

A
  • Firstly by conduction
  • Then warm air moves away and is replaced by cold air
  • constant temperature gradient is maintained
58
Q

How is heat lost through Evaporation?

A

Heat energy is transferred from the body to convert water from liquid to gas

59
Q

What is the difference between water and air as a heat acceptor?

A

Water can absorb far more heat than air

60
Q

What are Eccrine sweat glands innervated by?

A

Sympathetic cholinergic nerves

61
Q

What are Sympathetic cholinergic nerves?

A

Nerves that release Acetylcholine

62
Q

What is a muscarinic acetylcholine receptor?

A

Acetylcholine receptors that forms G protein-coupled receptor complex

63
Q

What are only some Eccrine sweat glands stimulated by?

A

Adrenaline acting on Beta receptors

64
Q

What is a results of Adrenaline acting on Beta receptors?

A

Nervous sweating

65
Q

What are the bodily responses to temperature increase?

4

A
  • Behavioural changes
  • Vasodilation and shunting of blood to skin surface
  • Sweat production
  • Respiratory heat loss
66
Q

What is the Preoptic area of the hypothalamus?

A

Area containing heat/cold sensitive receptors (central thermoreceptors)

67
Q

What happens if blood temperature goes above set point?

A

Heat loss centre is activated

68
Q

What are induced responses by the heat-loss centre?

2

A
  • Decreased activation of SNS alpha 1 receptors leads to vasodilation
  • Increase SNS cholinergic activation of mAChRs leads to sweating
69
Q

Are radiation, conduction and convection effective heat loss mechanisms?

A

No

70
Q

What happens when central thermoreceptors detect temperature below set point?

A

Heat gain centre is activated

71
Q

What are induced responses by the heat-gain centre?

2

A
  • Increased generation of body temperature

- Conservation of body temperature

72
Q

What are examples of Heat generating mechanism?

3

A
  • Shivering
  • Non-shivering thermogenesis
  • increased thyroxine increase
73
Q

What are the features of shivering?

3

A
  • increased tone of skeletal muscles
  • Above critical level shivering occurs due to oscillatory contractions between agonist and antagonist
  • muscles are mediated by muscle spindles
74
Q

What are the features of Non-Shivering Thermogenesis?

4

A
  • Increased sympathetic nerve activity
  • Increased circulating adrenaline/noradrenaline
  • Increased cellular metabolism
  • ‘uncoupling’ of oxidative phosphorylation
75
Q

What are features of increased thyroxine in generating heat?

3

A
  • Occurs in response to TRH/TSH
  • Increased basal metabolic rate
  • May take several weeks of cold exposure to ensue
76
Q

What are Arrector Pili muscles innervated by?

A

Sensory nervous system Alpha 1 receptors

77
Q

How do Arrector Pili muscles attach to hair follicles?

A

By linking the hair follicle to the upper Dermis

78
Q

What happens when Arrector Pili muscle contracts?

4

A
  • Pulls hair upright
  • dimples the skin
  • leads to goose bumps
  • Compresses Sebaceous gland
79
Q

What are examples of different types of burns?

4

A
  • First-degree burn
  • Second-degree burn
  • Deeper Second-degree burn
  • Third-degree burn
80
Q

What layer(s) of skin do First-degree burns effect?

A

superficial, outer layer of the Epidermis

81
Q

What are symptoms of First degree burns?

4

A
  • Red/pink colouring
  • Dry skin
  • Pain
  • Usually no blisters
82
Q

What is the healing time of a First degree burn?

A

3-10 days

83
Q

What layer(s) of skin do Second-degree burns effect?

A

Epidermis + varying amounts of dermis

84
Q

What are symptoms of Second-degree burns?

4

A
  • Red
  • Blisters
  • Moist
  • Painful
85
Q

What is required to aid healing a second-degree burn?

A

Good dressings, initially absorptive ones

86
Q

What layer(s) of skin do Deeper second-degree burns effect?

A

Epidermis + dermis

87
Q

What are symptoms of Deeper Second-degree burns?

5

A
  • Red
  • Blisters
  • Moist
  • Painful
  • May include whiteish, waxy areas
88
Q

What are effects of Deeper second-degree burns?

2

A
  • Hair follicles/Sweat glands may remain intact

- Some tactile receptors may be lost

89
Q

What is the healing time of a Second-degree burn?

A

1-2 weeks

90
Q

What is the healing time of a Deeper second-degree burn?

2

A
  • One month

- May have some loss of sensation/scarring

91
Q

What layer(s) of skin do Third-degree burns effect?

A

Full thickness extending into the subcutaneous tissue

92
Q

What are symptoms of Third-degree burns?

5

A
  • Varied colour from waxy white to deep red or black
  • Hard
  • Dry
  • Leathery
  • No pain
93
Q

Why is there no pain in the area of Third-degree burns?

A

Sensory nerve endings have been destroyed

94
Q

What is the healing time of a Third-degree burn?

A

Weeks to regenerate skin and for scarring to occur

95
Q

What may be an additional requirement to heal from a Third degree burn?

A

Skin grafting

96
Q

What % of Total body surface area would the face be?

A

9%

97
Q

What % of Total body surface area would each Upper limb be?

A

9%

98
Q

What % of Total body surface area would the trunk (front and back) be?

A

36%

99
Q

What % of Total body surface area would the Genitalia be?

A

1%

100
Q

What % of Total body surface area would each Lower limb be?

A

18%

101
Q

What are potential complications of Severe burns?

3

A
  • Dehydration/Hypovolemic shock
  • Infection/Sepsis
  • Hypothermia

HUBS 192 (38 decks)

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