M2-C2-L11 --> Neurophysiology Ii

Front 1

Moderate demyelination results in a decreased what?

Back 1

CV

Front 2

Moderate demyelination results in an increased what? x2

Back 2

1. Response latency

2. Temporal Dispersion (slowed and inconsistent AP timing)

Front 3

List the four categories of sensory nerve fibers.

Back 3

Ia & Ib
II
III
IV

Front 4

Describe Ia & Ib nerve fibers.

Back 4

Large myelinated sensory fibers

Front 5

Describe II nerve fibers

Back 5

Medium myelinated sensory fibers

Front 6

Describe III nerve fibers

Back 6

Largest unmyelinated sensory fibers

Front 7

Describe IV nerve fibers

Back 7

Smallest unmyelinated sensory fibers

Front 8

Which nerve fibers are the slow pain fibers? AKA?

Back 8

Type IV nerve fibers

AKA - C fibers

Front 9

Types of motor axon nerve fibers.

Back 9

Alpha - large
Gamma - small

Front 10

In a mixed nerve with multiple fibers, which nerve fibers tend to be demyelinated first?

Back 10

Largest, and fastest

Front 11

Increased current threshold caused by demyelination is due to what?

Back 11

Exposed internodal ion channels ("leakiness").

Front 12

Input resistance (Rin) is affected how by demyelination?

Back 12

Will decrease due to demyelination along with membrane resistance

Front 13

Ephaptic transmission causes what?

Back 13

Parasthesia

Front 14

Ephaptic transmission is caused by what?

Back 14

Electrical cross talk

Front 15

What is electrical cross talk.

Back 15

If nerve becomes demyelinated, another local circuit axon can transfer to that demyelinated nerve.

Front 16

Severe demyelination can cause what?

Back 16

Conduction block.

Front 17

Only extensive damage causes conduction block. Why?

Back 17

Sodium current at node of ranvier is so large.

Front 18

T/F - Mammalian myelinated axons have delayed rectifier channels.

Back 18

False

Front 19

What do myelinated mammalian axons use instead of DRC?

Back 19

Passive potassium channels.

Front 20

What is responsible for repolarization?

Back 20

Passive potassium channels

Front 21

What allows for higher AP frequencies?

Back 21

Shorter refractory period

Front 22

Where is the only place to record extracellular AP currents?

Back 22

Nodes of ranvier

Front 23

For single AP, about how many nodes are active at different stages of AP cycle?

Back 23

30

Front 24

A new node becomes active every how many seconds?

Back 24

15 microseconds

Front 25

Saltatory conduction occurs in what type of axons?

Back 25

myelinated axons

Front 26

Demyelination of a few nodes typically does not cause conduction block because why? x2

Back 26

1. Saltatory conduction

2. Safety factor

Front 27

What is the typical safety factor for mammalian AP?

Back 27

5

Front 28

Demyelination of where occurs in MS?

Back 28

CNS

Front 29

Demyelination of where occurs in Guillain Barre syndrome?

Back 29

PNS

Front 30

Neurophysiological symptoms of demyelination worsen when?

Back 30

At increased body temperature

Front 31

What are neurophysiological symptoms of demyelination?

Back 31

1. Slowed CV
2. Temporal dispersion
3. Parasthesia
4. Sometimes (if bad) conduction block

Front 32

What is the critical hallmark of MS?

Back 32

Multiple lesions separated by time and space

Front 33

Chronic demyelination leads to what?

Back 33

Axonal degeneration

Front 34

What is the reason for progressive irreversible disability?

Back 34

Axonal degeneration at new lesions.

Front 35

Compare remyelination by schwann cells vs. remyelination in MS

Back 35

Lasts longer

Front 36

In Guillain Barre Syndrome, axonal degeneration is often associated with what organism?

Back 36

Campylobacter jejuni

Front 37

Incidence of Charcot-Marie-tooth disease?

Back 37

1:2,500

Front 38

What is the etiology of type 1b Charcot-Marie-tooth disease?

Back 38

Point mutation in PMP (Peripheral Myelin Protein) gene

Front 39

What is the etiology of type 1a Charcot-Marie-tooth disease?

Back 39

Gene duplication causing over-expression of PMP22

Front 40

What is the inheritance pattern of 1a Charcot-Marie-tooth disease?

Back 40

AD

Front 41

What is the etiology of X-linked Charcot-Marie-tooth disease?

Back 41

Defect in gap junction protein of myelin lamellae (connexin32)

Front 42

What are symptoms of Charcot-Marie-tooth disease?

Back 42

1. Decreased CV
2. Cyclical demyelination/myelination
3. Impaired gait with deformed contracted foot.

Front 43

What is the long term hallmark symptom for Charcot-Marie-tooth disease?

Back 43

Impaired gait with deformed contracted foot.

Front 44

Define leukodystrophy.

Back 44

Genetic diseases of CNS myelin

Front 45

What is the etiology of Pelizaeus-Merzbacher disease?

Back 45

Defect in proteolipid protein (PLP)