nerveconduction

Nerve conduction refers to the microscopic process by which electrical impulses propagate along neurons, enabling rapid communication within the nervous system. In peripheral nerves, impulses arise as action potentials that travel along axons and trigger neurotransmitter release at synapses. The speed and reliability of conduction depend on whether the fiber is myelinated, its diameter, and the temperature and metabolic state of the tissue.

In myelinated fibers, conduction is saltatory: action potentials are regenerated at discrete gaps called nodes of Ranvier. The myelin sheath, formed by glial cells, increases membrane resistance and decreases capacitance, allowing the impulse to leap between nodes and travel faster with less energy. Unmyelinated fibers conduct more slowly, with continuous depolarization along the axon. The overall conduction velocity can range from fractions of a meter per second to over 100 meters per second, depending on fiber type.

Nerve conduction studies (NCS) are clinical tests that measure how quickly electrical impulses move through peripheral nerves. By stimulating a nerve at one site and recording responses at another, clinicians obtain metrics such as conduction velocity, distal latency, and response amplitudes (CMAPs for motor fibers, SNAPs for sensory fibers). NCS can help distinguish demyelinating from axonal neuropathies and localize lesions, aiding diagnoses such as carpal tunnel syndrome, Guillain-Barré syndrome, and diabetic polyneuropathy. They are often performed with electromyography.

Limitations include limited assessment of proximal or small fibers, patient discomfort, and variability with temperature and anatomy. Nerve conduction is a foundational concept in neurophysiology and clinical neurology, reflecting the coordinated interplay of ion channels, membrane properties, and glial support that underpins rapid neural signaling.