Diseases of PNS & Skeletal Muscles Flashcards
2 Main Components of PNS
Axons
Myelin Sheaths
Function Carried out by motor unit
Somatic Motor Function
Somatic Motor Function consists of
Lower Motor Neuron - Located at Ant Horn
Axon
NMJ]
Myofibers
Somatic Sensory function
Contain specialized structures that serve to register specific sensory modalities
Distal nerve endings
How Fast:
Unmyelinated fibers mediate autonomic function as well as pain and temp sensation
Slowest Conduction
How Fast:
Large diameter axons with thick myelin sheaths
transmit light touch and motor signals
Fast Conduction:
Myelinated segment
Internode
Unmyelinated Gaps
Nodes of Ranvier
Intracellular protein that has role in myelin corporation
Myelin basic protein
Dysfunction of Schwann cell
Guillain Barre Syndrome
Damage to the myelin sheath
Hereditary motor and sensory neuropathy
Disintegrating myelin is engulfed initially by
Schwann Cells
Disintegrating myelin is engulfed Later by
Macrophages
Stimulus for remyelination
Denuded axon
Primary target of the damage in peripheral neurophathies
Axons
Prototypcal pattern of injury when cutting a peripheral nerve the portions of axons that are distal to the point of transections are disconnected from the central neuron and degenerate
Wallerian Degeneration
Electrophysiologic hallmark of axonal neuropathies
Reduction in signal strength owing to the dropout of axon from affected peripheral nerves
Pattern of Pheripheral nerve damage where Type I and Type II myofibers are arranged in checker board distribution and the internodes along the motor axons are uniform in thickness and lenght
Normal Motor Units
Pattern of Pheripheral nerve damage where result in degeneration of the distal axon and its associated myelin sheath with atrophy of denervated myofibers
Acute Axonal Injury
Pattern of Pheripheral nerve damage where in acute demyelinating disease produces random segmental degeneration of individual myelin internodes, while sparing the axons
Acute Axonal Injury
Pattern of Pheripheral nerve damage where it allows reinnervation of myofibers, the regenerated axon is myelinated by proliferating schwann cells but the new internodes are shorter and the myelin sheaths are thinner thatn the origineal ones
Regeneration of axons after Injury
Pattern of Pheripheral nerve damage where remission of demyelinating disease allows remyelination to take place, but new internodes are also shorter and thinner myelin sheaths than flanking normal undamaged internodes
Regeneration of Axons after injury
Generalized abnormality of axons affecting the neuron cell body
Neuronopathy
Generalized abnormality of axons affecting the axon
Axonopathy
Electrophysiologic hallmark of demyelinating neuropathies
Slowed nerve conduction velocity, reflective loss of myelin
Common causes of mononeuropathies
Trauma, Entrapment and infections
Disease process that damages several nerves in haphazard fashion
Mononeuritis multiplex
An affected patiend might have a right wrist drop from involvement of the right radial nerve and left foot drip from peroneal nerve damage. Vasculitis is a common cause of this injury
Mononeuritis multiplex
affect nerve roots as well as peripheal nerves, leading to diffuse symmetric symptoms in proximal and istal parts of the body
Polyradiculoneuropathies
Diseases that are infectious polyneuropathies
Leprosy, Diptheria, Varicella xoster virus
Characterized clinically by weakness: distal to proximal (Ascending Paralysis)
Guillian Barre Syndrome
Inflammation of peripheral nerves, manifested as perivenular and endoneural infiltrationby lymphocytes macrophages and plasma cell
Guillian-Barre Syndrome
inflammation and demyelination of spinal nerve roots and Peripheral Nerves
Guillian Barre Syndrome
