Group of neurons form a nerve.
Based on the diameter and conduction velocity, the nerves
are classified, which is known as Erlanger and Gasser’s classification.
Erlanger and Gasser’s classification of nerves
- Aα
- Aβ
- Aγ
- Aδ
- B
- C
Aα nerve
- They are the fastest conducting nerves
- They have diameter of 12-20 µm
- Their conduction velocity is 70-120 m/s
- They carry sensation of proprioception (Joint sense)
Aβ nerve
- They are the second fastest conducting nerves
- They have diameter of 5-12 µm
- Their conduction velocity is 30-70 m/s
- They carry sensation of touch and pressure
Aγ nerve
- They have diameter of 3-6 µm
- Their conduction velocity is 15-30 m/s
- They form motor innervation to muscle spindle
Aδ nerve
- They have diameter of 2-5 µm
- Their conduction velocity is 12-30 m/s
- They carry sensation of pain and temperature
B nerve
- They have diameter of <3 µm
- Their conduction velocity is 3-15 m/s
- They form preganglionic autonomic fibers
C nerve
- They are unmyelinated nerve fibers having have very slow conduction velocity
- They have diameter of 0.4-1.2 µm
- Their conduction velocity is 0.5-2.0 m/s
- They form first order sensory neurons carrying pain and temperature sympathetic fibers
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