Lecture 9 Nerve Impulse conduction

Question 1

What is propagation of AP

Answer 1

Unidirectional (Refractory Period)

Question 2

What are the Factors affection speed

Answer 2

1. Axon diameter

2. myelination

Question 3

Axon Diameter characteristics

Answer 3

Larger Diameter= less resistance —> faster

Small Diameter= more resistance –> slower

Question 4

what is myelination ?

Answer 4

axons covered with myelin

allows AP ro transmit more efficiently (vs unmyelinated)

Question 5

What is Myelin

Answer 5

insulating layer of plasma membrane
formed by:
1. schwann cells
2.oligodendrocytes

Question 6

what are schwann cells

Answer 6

in peripheral nervous system (PNS)

once cell can myelinate only one axon

Question 7

what are oligodendrocytes

Answer 7

in the CNS

once cell can myelinate several axons

Question 8

Unmyelinated VS Myelinated axons

Answer 8

Each point along the axon must form an AP
more distance for AP –> slow
rate 2 m/sec

Question 9

what is myelinated axon conduction

Answer 9

-Voltage regualted gates concentrated on nodes of Ranvier
- Only nodes of ranvier form an AP
*Ions flow through myelinated regions
saltatory propagation : AP jumping from node to node
- Less distance for AP —> fast
Rate: 120 m/ sec

Question 10

Nodes of Ranvier

Answer 10

unmyelinated regions on axon