Neuroscience: Electrotonic Conduction and Myelination

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Questions and Answers

What is a primary role of the Nodes of Ranvier in a myelinated axon?

To allow for the jumping of action potentials between nodes (correct)

To facilitate continuous conduction along the axon

To provide insulation to the entire axonal length

To increase the diameter of the axon

Which statement correctly describes the myelination process in the central nervous system?

Each axon is surrounded by individual oligodendrocytes

Myelin is produced exclusively by satellite cells

One oligodendrocyte myelinates multiple segments of a single axon (correct)

A single Schwann cell myelinates multiple axons

How does saltatory conduction enhance the speed of action potential propagation?

By enabling action potentials to jump from one node of Ranvier to another (correct)

By allowing action potentials to propagate continuously without jumping

By reducing the frequency of action potentials generated

By decreasing the gap between myelinated segments

Where are voltage-gated sodium channels primarily located in a myelinated axon?

At the nodes of Ranvier and the axon hillock Signup and view all the answers

What role does myelination play in the nervous system?

It serves as an insulator, preventing ion movement across the myelinated sections. Signup and view all the answers

What is the effect of myelin on the neighboring tissue in a myelinated axon?

It allows the action potential to pass undiminished between nodes Signup and view all the answers

What are the Nodes of Ranvier important for?

They contain the voltage-gated Na channels located in myelinated axons. Signup and view all the answers

How does myelination affect the speed of action potential propagation?

It increases the speed through saltatory conduction. Signup and view all the answers

What initiates the regeneration of an action potential in adjacent membrane during electrotonic conduction?

The depolarization of the adjacent membrane to threshold. Signup and view all the answers

What happens to voltage-gated Na channels immediately after an action potential?

They inactivate and must recover from this inactivation. Signup and view all the answers

Which of the following glial cells is responsible for myelination in the central nervous system?

Oligodendrocytes Signup and view all the answers

What is the characteristic of saltatory conduction?

It involves the action potential jumping from one Node of Ranvier to another. Signup and view all the answers

Which statement is true regarding the parts of a neuron that are myelinated?

Myelin acts as an insulator along the axon but not at the terminals. Signup and view all the answers

What is the primary role of voltage-gated sodium channels in the propagation of an action potential?

They open to allow Na+ influx, leading to depolarization. Signup and view all the answers

What effect does myelination have on the speed of action potential propagation?

It increases the speed by enabling saltatory conduction. Signup and view all the answers

What ensures that the action potential propagates in one direction along the axon?

The refractory period after each action potential. Signup and view all the answers

What is the role of local depolarization in the generation of an action potential?

It causes neighboring sodium channels to activate at threshold. Signup and view all the answers

What initiates the opening of voltage-gated sodium channels during an action potential?

A local depolarization triggered by Na+ entering through stretch receptors. Signup and view all the answers

How does electrotonic conduction differ from action potential propagation?

Electrotonic conduction is slower than action potential propagation. Signup and view all the answers

What characteristic of nodes of Ranvier contributes to saltatory conduction?

They are areas with a high concentration of voltage-gated Na+ channels. Signup and view all the answers

Which factor does NOT influence the conduction speed of an action potential?

Concentration of Na+ in the extracellular fluid. Signup and view all the answers

Study Notes

Electrotonic Conduction

Electrotonic Conduction is the spread of current inside the axon.
It is a passive process, meaning it doesn't require energy.
Current spreads electrotonically to adjacent membrane.
Action Potentials can only move in one direction because of the refractory period.
Action Potential is initiated at one point in the membrane, leading to depolarization of adjacent membrane to threshold, resulting in a new action potential.

Myelination

It is a process where the axon is wrapped with myelin, insulating the axon and preventing ions from moving across.
Made by oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system.
The axon is the only part of a neuron that is myelinated.

Nodes of Ranvier

They are the regions of a myelinated axon that are unmyelinated.
They contain voltage-gated Na channels, which are responsible for generating action potentials.
In the peripheral nervous system, a single Schwann cell myelinates one segment of the axon.
In the central nervous system, a single oligodendrocyte myelinates several axons and several regions within a given axon.

Saltatory Conduction

The propagation of action potentials along a myelinated axon, where action potentials jump from one node of Ranvier to the next.
It's faster than continuous conduction because it only occurs at the nodes of Ranvier.
The action potential is generated at the first node of Ranvier and then passes to the second node of Ranvier, where further depolarization of neighboring tissue occurs, generating the next action potential.

Speed of Propagation

The speed of propagation is influenced by the diameter of the axon.
Larger axons have a lower internal resistance, allowing for faster conduction.
The presence of myelin significantly increases the speed of conduction due to saltatory conduction.
Voltage-gated Na channels are concentrated at the Nodes of Ranvier, allowing for efficient propagation of action potentials.

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Description

This quiz covers concepts related to electrotonic conduction, myelination, and the structure of myelinated axons, including the Nodes of Ranvier. It explores how action potentials propagate and the role of myelin in neuronal signaling. Test your knowledge on these essential neuroscience topics.