Peripheral Nerve system disorders Flashcards Preview

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Flashcards in Peripheral Nerve system disorders Deck (27)
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1
Q

what is a peripheral nerve

A

many bundles of nerve fibres
motor and sensory

2
Q

what is the structure of the peripheral nerve - epineurium

A

dense CT surrounds nerve
binds bundes (fascicles) togethe

3
Q

what is the structure of the peripheral nerve - perineurium

A

surrounds bunches of axons + endoneurium sheath
nerve bundle = fascicle (CT around each bundle with common destination)

4
Q

what is the structure of the peripheral nerve - enoneurium

A

delicate CT surrounds each axon
important for nerve fibre regeneration

5
Q

describe neuropraxia

A

blocked nerve conduction
transient = rapid recovery
cold, ischaemia, tourniquet, saturday night palsy

6
Q

decribe axonotmesis

A

axon + myelin sheath interrupted but endoneurium/nerve sheath intact
axon transmission interrupted
nerve crush, stretch injury

7
Q

describe neurotmesis

A

axon and nerve sheath interrupted
long term partial/complete loss of motor/sensory
nerve transection

8
Q

what are the 2 segments of PNS repair and the 4 series of changes

A

proximal (attached cell body) vs distal
cell body
proximal axon
distal axon
target muscle

9
Q

describe the proximal changes

A

chromatolysis = cell body wells, nucleus moves to eccentric position, rER fragments (breakdown Nissl bodies)
metabolic switch = from secretory to regenerating phase

10
Q

describe the distal changes

A

synatpic/NMJ stripping
wallerian degen of distal aon
myelin breakdown => mac clear debris
muscle atrophy
if endoneurium intact = good chance of recovery

11
Q

what’s a nissl body

A

clump of ER

12
Q

what happens to chances of recovery if endoneurium is intact

A

good chance of recovery

13
Q

what are the 4 steps for pn injury repair

A
  1. proximal axon sprouts
  2. axon sprouts find way to endoneurium tube schwann cells
  3. tube guides axonal growth
  4. complete recovery if possible
14
Q

what can happen without proper innervation

A

muscles can atrophy

15
Q

what happens when end of damaged nerve cells aren’t aligned

A

no repair
tangled axons form neuroma/glioma

16
Q

what are overall factors that affect nerve repair outcomes

A

type of injury
restoring contact with target muscle in periphery
proximal vs distal injury
age

17
Q

what is a motor unit

A

basic unit of motor function
a motor neuron + group of muscle fibres it innervates

18
Q

significance of motor unit

A

depends on dexterity of mvm + mass body part to be moved
smaller units recruited first, then larger units as muscle force increases

19
Q

what are the 3 disease targets of the motor unit

A

cell body (MN disease), can affect CNS + PNS
axon: peripheral neuropathies
nmj: myasthenia gravis, botulism

20
Q

what are the symptoms of peripheral neuropathy

A

motor + sensory axons are bundles together => sensory + motor functions affected
- Pos symptoms = numbness, tingling, pins/needles, hyperexcitability
- neg symptoms = weakness, loss of tendon reflexes (fasciculations and atrophy are rare), loss sensation eg pain + temp (prominent distally = glove and stocking)

21
Q

demyelinating vs axonal peripheral neuropathy classifications

A

demyelinating: conduction velocity of ap slows + conduction synchrony between diff axons of nerve is list. linked to mutations in genes that code for myelin proteins
axonal: linked to cellular proteins eg neurofilaments, microtubule motors (kinesin), cytosolic enzymes etc

22
Q

what is acute neuropathy - guillain-barre syndrome

A

often follows resp infection or infectious diarrhea, tho illness not always necessary
mild or sever => ventilator
spreading paralysis
autoimmune attack on peripheral nerved by circulating antibodies

23
Q

pathogenesis of guillain barre syndrome

A

pathogens trigger humoral immune = autoimmune response through molecular mimicry
antibodies produced cross-react with peripheral nerve proteins (for myelin)
activates membrane attack complex
results in myelin detachment, dec Na+ channels -> nerve dysfunction + symptoms

24
Q

describe chronic neuropathy - diabetic peripheral neuropathy

A
  • capillary damage = compromised vasculature
  • nerves dont get nutrient supply
  • impaired transmission of sensory input
  • loss sensation + circulation => increased risk infection
25
Q

what are the 2 categories of disease at NMJ

A

block ntsm action (myasthenia gravis)
block ntsm release (botulism)

26
Q

describe myasthenia gravis

A
  • weakness, fatigue of muscle groups (worse on sustained/repeated exertion)
  • autoimmune block of ACh receptors at nmj
  • autoimmune antibodies produced by muscle
  • reduced no. functional receptors
  • treat w/acetylcholinesterase inhibitors -> inc ACh availability
27
Q

describe botulism

A

botulinum toxin produced by clostridium botulinum bacteria
blocks vesicle binding to membrane -> blocks ACh release at nmj => muscle paralysis, dec sweat gland stim
therapeutic = spasticity, painful muscle spasms, wrinkles, reduce sweating
infection => respiratory paralysis & death