Nerve impulse conduction

Question 1

Propagation of action potentials

Answer 1

-unidirectional (refractory period)

Question 2

factors affecting speed

Answer 2

• axon diameter

- myelination

Question 3

axon diameter

Answer 3

• larger diameter= less resistance –> faster

- smaller diameter= more resistance –> slower

Question 4

myelination

Answer 4

• axons covered with myelin

- allows AP to transmit for efficiently

Question 5

Myelin (what it is and types)

Answer 5

• insulating layer of plasma membrane
• formed by:

1. schwann cells
   - in peripheral nervous system (PNS)
   - one cell can myelinated one axon
2. oligodendrocytes
   - in central nervous system (CNS)
   - one cell can myelinated several axons

Question 6

unmyelinated axon conduction

Answer 6

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

Question 7

myelinated axon conduction

Answer 7

• voltage regulated gates concentrated on nodes of ranvier (unmyelinated regions)
• only nodes of ranvier form an AP
• ion flows through myelinated regions faster than AP
• solitary propagation: AP jumping from node to node
• less resistance for AP –> fast
• rate: 120 m/sec