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45 Cards in this Set

  • Front
  • Back
Moderate demyelination results in a decreased what?
Moderate demyelination results in an increased what? x2
1. Response latency

2. Temporal Dispersion (slowed and inconsistent AP timing)
List the four categories of sensory nerve fibers.
Ia & Ib
Describe Ia & Ib nerve fibers.
Large myelinated sensory fibers
Describe II nerve fibers
Medium myelinated sensory fibers
Describe III nerve fibers
Largest unmyelinated sensory fibers
Describe IV nerve fibers
Smallest unmyelinated sensory fibers
Which nerve fibers are the slow pain fibers? AKA?
Type IV nerve fibers

AKA - C fibers
Types of motor axon nerve fibers.
Alpha - large
Gamma - small
In a mixed nerve with multiple fibers, which nerve fibers tend to be demyelinated first?
Largest, and fastest
Increased current threshold caused by demyelination is due to what?
Exposed internodal ion channels ("leakiness").
Input resistance (Rin) is affected how by demyelination?
Will decrease due to demyelination along with membrane resistance
Ephaptic transmission causes what?
Ephaptic transmission is caused by what?
Electrical cross talk
What is electrical cross talk.
If nerve becomes demyelinated, another local circuit axon can transfer to that demyelinated nerve.
Severe demyelination can cause what?
Conduction block.
Only extensive damage causes conduction block. Why?
Sodium current at node of ranvier is so large.
T/F - Mammalian myelinated axons have delayed rectifier channels.
What do myelinated mammalian axons use instead of DRC?
Passive potassium channels.
What is responsible for repolarization?
Passive potassium channels
What allows for higher AP frequencies?
Shorter refractory period
Where is the only place to record extracellular AP currents?
Nodes of ranvier
For single AP, about how many nodes are active at different stages of AP cycle?
A new node becomes active every how many seconds?
15 microseconds
Saltatory conduction occurs in what type of axons?
myelinated axons
Demyelination of a few nodes typically does not cause conduction block because why? x2
1. Saltatory conduction

2. Safety factor
What is the typical safety factor for mammalian AP?
Demyelination of where occurs in MS?
Demyelination of where occurs in Guillain Barre syndrome?
Neurophysiological symptoms of demyelination worsen when?
At increased body temperature
What are neurophysiological symptoms of demyelination?
1. Slowed CV
2. Temporal dispersion
3. Parasthesia
4. Sometimes (if bad) conduction block
What is the critical hallmark of MS?
Multiple lesions separated by time and space
Chronic demyelination leads to what?
Axonal degeneration
What is the reason for progressive irreversible disability?
Axonal degeneration at new lesions.
Compare remyelination by schwann cells vs. remyelination in MS
Lasts longer
In Guillain Barre Syndrome, axonal degeneration is often associated with what organism?
Campylobacter jejuni
Incidence of Charcot-Marie-tooth disease?
What is the etiology of type 1b Charcot-Marie-tooth disease?
Point mutation in PMP (Peripheral Myelin Protein) gene
What is the etiology of type 1a Charcot-Marie-tooth disease?
Gene duplication causing over-expression of PMP22
What is the inheritance pattern of 1a Charcot-Marie-tooth disease?
What is the etiology of X-linked Charcot-Marie-tooth disease?
Defect in gap junction protein of myelin lamellae (connexin32)
What are symptoms of Charcot-Marie-tooth disease?
1. Decreased CV
2. Cyclical demyelination/myelination
3. Impaired gait with deformed contracted foot.
What is the long term hallmark symptom for Charcot-Marie-tooth disease?
Impaired gait with deformed contracted foot.
Define leukodystrophy.
Genetic diseases of CNS myelin
What is the etiology of Pelizaeus-Merzbacher disease?
Defect in proteolipid protein (PLP)