The Human Brain : From Neurone to Nervous System

NERVE CELLS : The Classification of Nerve Fibres

  1. Neurones provide a rapid means of communication over long distances, by passing impulses (action potentials) very rapidly along their axonal membranes. They can be separated into several groups with different physiological functions.

  2. Neurones provide a rapid means of communication over long distances within the body by passing action potentials - electrical impulses - along their axonal membranes.

  3. Myelinated axons have larger diameters, lower thresholds and higher conduction velocities than unmyelinated axons; the speed of conduction of the impulse is directly related to the degree of myelination.

  4. Nerve trunks contain many axons with different degrees of myelination. They are classified according to diameter or conduction velocity into two systems: A-alpha, A-beta, A-delta, and C; or Groups I, II, III and IV.

  5. Key Words: Action potential, 'Spike', voltage gated sodium channels, voltage gated potassium channels, saltatory conduction, myelin, the relation between conduction velocity and axon diameter