PNS Disorders Flashcards
1
Q
Peripheral Nerve Structure
A
- Endoneurium: delicate CT, surrounds each fibre, important in nerve fibre regeneration
- Perineurium: surrounds bunches of axons + endoneurium sheath, nerve bundle now know as fascicle
- Epineurium: dense CT, surrounds nerve, binds fascicles together
2
Q
Motor Unit
A
- Motor neuron + group of muscle fibres it innervates
- Smaller units recruited first, followed by larger units as muscle force increases
3
Q
UMN vs LMN
A
- UMN: cell bodies in the cerebral cortex that issue commands to LMNs (via the corticospinal/bulbar tract)
- LMN: cells bodies in the SC and BS that directly innervate skeletal muscle
4
Q
UMN Disorders
A
+++++
- Spasticity
- Overactive tendon reflexes
- Abnormal Babinski sign
5
Q
LMN Disorders
A
- Flaccidity
- Atrophy
- Fasciculations (muscle twitches)
- decreased muscle tone
- Loss of tendon reflexes
6
Q
Disease of Motor Unit
A
Classified by component affected:
- Cell body: MND
- Axon: peripheral neuropathies
- Neuromusclar junction: myasthenia gravis, botulism
7
Q
Disease of the Axon Symptoms
A
Motor and sensory axons are bundles together, so both sensory and motor functions are affected
- symptoms: numbness, tingling, burning, ‘pins and needles’ - caused by hyper excitability of nerves
- symptoms: loss of sensation eg. pain and temp (more prominent distally - glove and stocking)
8
Q
Acute Disease of the Axon
A
Guillian-Barre Syndrome
- Often follows resp infection or infectious diarrheoa
- May be mild or so severe that ventilation is needed
- Autoimmune attack on peripheral nerves by circulating antibodies
9
Q
Pathogenesis of Guillian-Barre Syndrome
A
- Pathogens trigger humoral immune and autoimmune response through molecular mimicry
- Activates membrane attack complex
- Results in:
- > myelin detachment
- > disappearence of Na channels -> nerve cell dysfunction and symptoms
