Neural Conduction

the movement of an action potential along an axon

propagation

What creates the normal directionality of an action potential?

refractory periods

Why would a signal weaken as it travels down an axon?

electrical charge leaks and resistance

What happens to a signal if it is not regenerated?

signal gets weaker and may fade

How do action potentials (APs) prevent signals from weakening?

regeneration

What happens to the signal strength when an action potential reaches the axon terminals?

remains at full strength

Action potential conduction velocity

1m/s to more than 100m/s

What two factors determine conduction speed

Axon diameter and myelination

Do larger myelinated axons or smaller unmyelinated axons conduct faster action potentials?

larger myelinated axona

Why is conduction speed important?

less time between stimulus and neural response for time critical functions

Why does a larger axon diameter allow the axon to travel faster?

less interal resistance

lipid-rich insulating layer surrounding portions of an axon

Myelin

Why does myelin allow for the axon to travel faster.

acts as an electrical insulation, reducing ion movement.

Does myelin make the cell energy efficent?

yes

Which cells produce myelin?

Oligodendrocytes and Schwann cells

Which cells produce myelin in the CNS?

Oligodendrocytes

Which cells produce myelin in the PNS?

Schwann Cells

How many axons can one oligodendrocyte myelinate?

multiple

How many axon segments does one Schwann cell myelinate?

one

What is another function of Schwann cells besides producing myelin?

metabolic support to axon

How is myelin arranged around an axon?

in segments

Small gaps between adjacent segments of myelin along an axon

nodes of ranvier

Where are voltage-gated ion channels concentrated in a myelinated axon?

at the nodes of ranvier

Where are action potentials (APs) regenerated in a myelinated axon?

nodes of ranvier

The process in which an action potential appears to jump from one node of Ranvier to the next.

saltatory conduction

Is continous or saltatory conduction quicker?

saltatory conduction

Does myelination stop when a person reaches adulthood?

No

What is social deprivation associated with in relation to myelin?

decreased myelin

What activities are associated with increased myelin?

Juggling, musical training, and learning a second language.

Damage to the myelin surrounding an axon

demyelination

What happens to electrical current when myelin is damaged?

More electrical current leaks

How does demyelination affect conduction speed?

slows down conduction speed

Multiple sclerosis (MS) attacks which system?

CNS

Guillain-Barré syndrome (GBS)

PNS

What do both Guillain-Barré syndrome (GBS) and Multiple sclerosis (MS) have in common?

Demyelination disrupts nerve signals

Vision problems, numbness, weakness, fatigue, balance problems

Common symptoms of Multiple Sclerosis

Severe pain, numbness, weakness, loss of reflexes

Common symptoms of Guillain-Barré syndrome