Skip to content
FastestThings

Nerve Conduction

Aδ sensory fiber

Thinly myelinated afferents for sharp first pain, strong mechanical and thermal stimuli, conducting at 5–30 metres per second.

Also known as Group III, A-delta afferent
Post on X (opens in a new tab)

Conduction velocity

5–30m/s

Sensory afferent class. Textbook range 5–30 m/s. The rank uses the top of the range. The row shows the whole range.

OfficialFundamental Neuroscience for Basic and Clinical Applications (opens source in a new tab)

Mechanism

Why it's so fast

Aδ fibers are the fast pain channel because a thin myelin sheath still lets the impulse jump, just not as far or as fast as a touch fiber.

  1. Thin myelin

    The sheath is there, and the axon is only 1–5 µm across. Saltatory conduction survives. The shared band is 5–30 m/s, an order of magnitude below the large touch fibers.

  2. First pain

    River Publishers calls this the first, sharp pain, the signal that arrives before the burning sensation carried by unmyelinated fibers. The speed is the axon's, not a stopwatch on a blink.

  3. The whole range

    Three tables print 5–30 m/s. The rank uses 30. The row shows both ends, so a reader is not handed one cherry-picked edge.

The slow pain channel is the C fiber, at 0.5–2 m/s.

Provenance

Every measurement

Claimed, measured and official figures side by side, each with its source. The ranked figure is marked.

  1. 5–30m/sRanked figure

    Sensory afferent class. Textbook range 5–30 m/s. The rank uses the top of the range. The row shows the whole range.

    River Publishers describes this band as the first, sharp pain, at 5–30 m/s. The Haines table uses the same 5–30 m/s for Group III. A blink latency is a different measurement and is not stored here.

    Official
    Fundamental Neuroscience for Basic and Clinical Applications (opens source in a new tab)

Reference

Specs

Class
Aδ, Group III
Diameter
1–5 µm
Myelin
Thin
Range
5–30 m/s

Context

Background

Aδ fibers keep a thin myelin sheath. That is enough for saltatory conduction, and not enough to match the large touch fibers. They are the afferents of first pain: the sharp sensation that arrives before the slower burning signal.

All three tables print 5–30 m/s and a diameter of 1–5 µm. The rank uses 30 m/s. The row shows the whole range. This is a conduction velocity, not a reaction time and not a sneeze speed.

Spot a wrong number?

Every report is read by a person, and corrections are dated on the page.