Trapezius receives proprioceptive input from which spinal nerve roots?

Trapezius receives proprioceptive input from which spinal nerve roots?

• A. C5-C6
• B. C3-C4
• C. C1-C2
• D. C7-C8

Answer: (B)

Proprioceptive input from the trapezius comes from the upper cervical spinal levels, specifically the C3-C4 dorsal roots. The trapezius is motor via the spinal accessory nerve, but its muscle-spindle signals—the feedback that tells the brain how the muscle is length and moving—travel back to the spinal cord along the sensory fibers that enter at C3-C4. This arrangement lets the central nervous system monitor scapular position and coordinate shoulder girdle movements with arm actions. The other listed root levels don’t provide the trapezius’s proprioceptive input—C3-C4 is the typical source for this muscle’s sensory feedback.

Proprioceptive input from the trapezius comes from the upper cervical spinal levels, specifically the C3-C4 dorsal roots. The trapezius is motor via the spinal accessory nerve, but its muscle-spindle signals—the feedback that tells the brain how the muscle is length and moving—travel back to the spinal cord along the sensory fibers that enter at C3-C4. This arrangement lets the central nervous system monitor scapular position and coordinate shoulder girdle movements with arm actions. The other listed root levels don’t provide the trapezius’s proprioceptive input—C3-C4 is the typical source for this muscle’s sensory feedback.