| A | B |
|---|
| Aa (alpha) fiber | motor to extrafusal |
| Group 1a | primary muscle spindle afferent |
| Group 1b | GTO afferent |
| AB (beta) fiber | motor to intra/extrafusal |
| Group II | secondary muscle spindle afferent; corpuscular mechanoreceptor afferent |
| Ay (gamma) fiber | motor to muscle spindles (intrafusal muscle) |
| Group III | nociceptor |
| B fiber | IML to para/prevertebral ganglia (or adrenal gland) |
| C fiber | para and prevertebral ganglia to effector |
| Group IV | nociceptor |
