Nerve conduction velocity is the speed at which an electrochemical signal propagates down a neural pathway. Many things can affect this, including axon diameter, myelination, the internal resistance of the axon, and temperature. Nerve conduction velocity differs from species to species, and to a lesser degree, from individual to individual.
These impulses are extremely fast, with some myelinated neurons conducting at speeds up to 120 m/s (432 km/h)
Type | Erlanger-Gasser Classification |
Diameter | Myelin | Conduction velocity | Associated muscle fibers |
---|---|---|---|---|---|
α | Aα | 13-20 µm | Yes | 80–120 m/s | Extrafusal muscle fibers |
γ | Aγ | 5-8 µm | Yes | 4–24 m/s | Intrafusal muscle fibers |
Different sensory receptors are innervated by different types of nerve fibers. Proprioceptors are innervated by type Ia, Ib and II sensory fibers, mechanoreceptors by type II and III sensory fibers and nociceptors and thermoreceptors by type III and IV sensory fibers.
Type | Erlanger-Gasser Classification |
Diameter | Myelin | Conduction velocity | Associated sensory receptors |
---|---|---|---|---|---|
Ia | Aα | 13-20 µm | Yes | 80–120 m/s | Responsible for proprioception] |
Ib | Aα | 13-20 µm | Yes | 80–120 m/s | Golgi tendon organ |
II | Aβ | 6-12 µm | Yes | 33–75 m/s | Secondary receptors of muscle spindle All cutaneous mechanoreceptors |
III | Aδ | 1-5 µm | Thin | 3–30 m/s | Free nerve endings of touch and pressure Nociceptors of neospinothalamic tract Cold thermoreceptors |
IV | C | 0.2-1.5 µm | No | 0.5-2.0 m/s | Nociceptors of paleospinothalamic tract Warmth receptors |
Type | Erlanger-Gasser Classification |
Diameter | Myelin | Conduction velocity |
---|---|---|---|---|
preganglionic fibers | B | 1-5 µm | Yes | 3–15 m/s |
postganglionic fibers | C | 0.2-1.5 µm | No | 0.5-2.0 m/s |
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