Explain how an action potential is propagated down an axon in continuous conduction. Why is saltatory conduction faster than continuous conduction?

Verified step by step guidance

1. Step 1: Understand the concept of an action potential. An action potential is a rapid rise and subsequent fall in voltage or membrane potential across a cellular membrane with a characteristic pattern.
2. Step 2: Describe continuous conduction. In continuous conduction, the action potential travels down an unmyelinated axon. The depolarization of one segment of the axon membrane causes the adjacent segment to depolarize, propagating the action potential along the axon.
3. Step 3: Explain the process of depolarization and repolarization. During depolarization, sodium channels open, allowing Na+ ions to enter the neuron, making the inside more positive. Repolarization follows as potassium channels open, allowing K+ ions to exit, restoring the negative membrane potential.
4. Step 4: Define saltatory conduction. Saltatory conduction occurs in myelinated axons, where the action potential jumps from one node of Ranvier to the next, bypassing the myelinated sections of the axon.
5. Step 5: Compare the speed of conduction. Saltatory conduction is faster than continuous conduction because the action potential jumps between nodes, reducing the number of times the membrane must depolarize and repolarize, thus speeding up the transmission of the signal.

Key Concepts

Action Potential

An action potential is a rapid, temporary change in the electrical membrane potential of a neuron, allowing it to transmit signals. It occurs when a neuron reaches a certain threshold, leading to the opening of voltage-gated ion channels. This results in a rapid influx of sodium ions, followed by the outflow of potassium ions, creating a wave of depolarization and repolarization along the axon.

Continuous Conduction

Continuous conduction refers to the unmyelinated propagation of action potentials along an axon. In this process, the action potential is regenerated at every segment of the axon membrane, leading to a slower transmission speed. This method is typical in smaller, unmyelinated fibers where the entire membrane is involved in the conduction process.

Saltatory Conduction

Saltatory conduction occurs in myelinated axons, where action potentials jump from one node of Ranvier to another, bypassing the myelinated sections. This significantly increases the speed of signal transmission compared to continuous conduction, as the electrical impulse travels faster through the insulated segments. The presence of myelin sheaths reduces capacitance and increases resistance, allowing for more efficient signal propagation.