Lecture 3: Skin Flashcards

1
Q

What are Free Nerve Endings?

A

– small swellings at distal ends of axons = sensory terminals
- mostly unmyelinated (C fibers) but some small myelinated ones (As)
– Sensory Terminals have receptors that can respond tovarious painful (nociceptive), thermal and chemical stimuli.
- Some are chemically activated, some cation channels (both send signals to somato)

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2
Q

Where are Tactile (Merkel) discs located?

A

Free nerve endings located in deepest layerof epidermis

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3
Q

What do Tactile (Merkel) discs detect?

A

Sensitive to:
* touch and light pressure
* texture, shape and edges
* Low frequency vibration (5-15 Hz)

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4
Q

How do Tactile (Merkel) discs communicate?

A

Seratonin:
– Associated with large disc shaped epidermal (Merkel) cells
* Communication between the tactile epithelial cell and nerve ending possible via serotonin (5HT)

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5
Q

Where are Tactile (Meissner) Corpuscles located?

A

– Located in papillary layer of dermis, Especially in hairless skin

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6
Q

What are Tactile (Meissner) Corpuscles?

A

(Encapsulated)
• Spiralling / branching unmyelinated sensory terminals surrounded by modified Schwann cells and then by a thin oval fibrous connective tissue capsule
• Deformation of capsule triggers entry of Na+ ions into nerveterminal&raquo_space; Action Potential

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7
Q

What do Tactile (Meissner) Corpuscles detect?

A

Delicate ‘fine’ or discriminative touch eg. braille reading
– Movement of objects over the surface of the skin
• Light pressure
• Low frequency vibration (most sensitive 10 to 50 Hertz)

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8
Q

Where are Lamellar (Pacinian) corpuscles found?

A

Found deep in dermis and hypodermis

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9
Q

What do Lamellar (Pacinian) corpuscles detect?

A

Stimulated by deep pressure (when first applied)
Also vibration because rapidly adapting. Optimal stimulation frequency is around 250Hz

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10
Q

What are Lamellar (Pacinian) corpuscles?

A
  • Single sensory axon terminal lying within concentric layers of collagen fibres and specialized fibroblasts.
  • Layers separated by gelatinous interstitial fluid
  • isolated from stimulation apart from deep pressure (Na+ channels) rapidly adapting
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11
Q

Where are Bulbous (Ruffini) corpuscles located?

A

Located in dermis and subcutaneous tissue

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12
Q

What do Bulbous (Ruffini) corpuscles detect?

A
  • Sensitive to sustained deep pressure and stretching or distortion of the skin
  • Found in joints (proprioception)
  • Slippage of objects in hands
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13
Q

What are Bulbous (Ruffini) corpuscles?

A
  • Network of nerve endings intertwined with a coreof collagen fibres.
  • continuous with those of the surrounding dermis.
  • Capsule surrounds entire structure
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14
Q

How do we control Skin Bloodflow?

A
  • Smooth muscle in walls of arteries and pre-capillary sphincters innervated by the sympathetic nervous system (SNS)
  • Noradrenaline acts on α1 adrenergic receptors on this vascular smooth muscle in the skin
  • Activation of a1 adrenergic receptors = vasoconstriction so less blood flow and vice versa
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15
Q

Eccrine sweat glands are innervated by?

A
  • sympathetic nervous system - Sympathetic cholinergic i.e. release ACh onto mAChRs (GPCRs)
  • Some eccrine sweat glands can also be stimulated by Adrenaline in blood acting on β receptors – (nervous sweating)
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16
Q

What happens when body temprature increases?

A
  • Preoptic area of hypothalamus contains heat and cold sensitive neurons (central thermoreceptors)
  • If too hot, decreased SNS a1 activation of blood vessels (vasodilation) (more skin bloodflow)
  • Increased SNS cholinergic activation of mAChRs on sweat glands -> sweating
  • respiratory rate increases and also -behavioural changes
17
Q

What are the three Heat Generating Mechanisms?

A
  • Shivering
  • Non-Shivering Thermogenesis (adrenaline and fat burn)
  • Thyroxine (increases basal metabolic rate)
18
Q

What is shivering?

A

– Oscillatory contractions of agonist and antagonist muscle
– ATP → ADP + Pi + movement + heat

19
Q

What are Arrector Pili muscles and what do they do?

A
  • Smooth muscle innervated bySNS (α1 receptors)
  • Attach hair follicle to upperdermis
  • Contraction pulls hairs upright and dimples skin > goosebumps (insulation)
  • Also compresses sebaceous glands which lubricates skin
20
Q

Rule of 9’s

A

Head = 9%
Upper limb = 9%
Trunk = 36%
Genitalia = 1%
Lower limbs = 18%

21
Q

Potential Complications of Severe Burns

A
  • Dehydration and hypovolemic shock
  • Infection / Sepsis
    -Hypothermia