Excitable Cell Physiology

5.

Propagation of the Action Potential

5.1.

Local Circuit Currents

5.1.1.

Current Flow Mechanisms

5.1.1.1.

Intracellular Current Flow

5.1.1.2.

Extracellular Return Path

5.1.1.3.

Membrane Current

5.1.2.

Depolarization of Adjacent Membrane

5.1.2.1.

Threshold Activation

5.1.2.2.

Sequential Excitation

5.1.2.3.

Propagation Direction

5.2.

Conduction in Unmyelinated Axons

5.2.1.

Continuous Conduction

5.2.1.1.

Stepwise Depolarization

5.2.1.2.

Adjacent Membrane Activation

5.2.1.3.

Uniform Channel Distribution

5.2.2.

Factors Affecting Conduction Velocity

5.2.2.1.

5.2.2.1.1.

Internal Resistance Effects

5.2.2.1.2.

Length Constant Changes

5.2.2.2.

5.2.2.2.1.

Channel Kinetics

5.2.2.2.2.

Membrane Properties

5.2.2.3.

Membrane Resistance

5.2.2.3.1.

Channel Density

5.2.2.3.2.

Leak Conductance

5.2.2.4.

Membrane Capacitance

5.2.2.4.1.

5.2.2.4.2.

Time Constant Effects

5.2.3.

Conduction Velocity Calculation

5.2.3.1.

Cable Theory Application

5.2.3.2.

Velocity-Diameter Relationship

5.3.

Myelinated Axon Conduction

5.3.1.

Myelin Sheath Structure

5.3.1.1.

Lipid Composition

5.3.1.2.

Protein Components

5.3.1.3.

Insulation Properties

5.3.2.

Myelin-Forming Cells

5.3.2.1.

Schwann Cells in PNS

5.3.2.1.1.

Single Axon Myelination

5.3.2.1.2.

Regeneration Capacity

5.3.2.2.

Oligodendrocytes in CNS

5.3.2.2.1.

Multiple Axon Myelination

5.3.2.2.2.

Limited Regeneration

5.3.3.

Nodes of Ranvier

5.3.3.1.

Unmyelinated Regions

5.3.3.2.

High Sodium Channel Density

5.3.3.3.

Clustering Mechanisms

5.3.3.4.

Nodal Structure

5.3.4.

Saltatory Conduction

5.3.4.1.

Node-to-Node Jumping

5.3.4.2.

Passive Conduction in Internodes

5.3.4.3.

Active Regeneration at Nodes

5.3.4.4.

Mechanism and Efficiency

5.3.5.

Advantages of Myelination

5.3.5.1.

Increased Conduction Velocity

5.3.5.1.1.

Velocity-Diameter Relationship

5.3.5.1.2.

Energy Efficiency

5.3.5.2.

Metabolic Benefits

5.3.5.2.1.

Reduced Ion Flux

5.3.5.2.2.

Lower ATP Requirements

5.3.5.3.

Space Efficiency

5.3.5.3.1.

Smaller Axon Diameter

5.3.5.3.2.

Compact Nervous System

5.3.6.

Demyelinating Diseases

5.3.6.1.

Conduction Block

5.3.6.2.

Velocity Reduction

5.3.6.3.

Clinical Manifestations

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4. The Action Potential

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6. Synaptic Transmission