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| Table 2. Size and conduction velocity of nerve fibers | |||
| Name and function of type of fiber. (Letters are used for any nerve; Roman numerals are for sensory fibers in dorsal spinal roots.) | External diameter (micrometres) |
Conduction velocity (metres/second) | |
| Myelinated fibers | /tr>|||
| A-alpha or IA | Motor to skeletal muscle; sensory from muscle spindle proprioceptive endings (phasic, annulospiral type) | 12-20 | 70-120 |
| A-beta or IB | Sensory from tendons (tension); also Ruffini endings in skin | 10-15 | 60-80 |
| II | Sensory from Meissner's and pacinian corpuscles and similar endings in skin and connective tissue; from large hair follicles, and tonic proprioceptive endings (flower-spray type) of muscle spindles | 5-15 | 30-80 |
| A-gamma | Motor to intrafusal fibers of muscle spindles | 3-8 | 15-40 |
| A-delta or III | Sensory from small hair follicles and from free nerve endings for temperature and pain sensations | 3-8 | 10-30 |
| B | Preganglionic autonomic (white rami and cranial nerves 3, 7, 9, 10) | 1-3 | 5-15 |
| Unmyelinated fibers | /tr>|||
| C or IV | Pain & temperature; Olfaction; Postganglionic autonomic | 0.2-1.5 | 0.5-2.5 |
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Last updated: January 2003