What is the key muscle function attributed to the C7 nerve root?

The key muscle function attributed to the C7 nerve root is the elbow extensors. This is primarily because the C7 nerve root plays a significant role in the innervation of the triceps brachii muscle, which is responsible for elbow extension. When considering the anatomy, the C7 nerve root contributes to the radial nerve, which innervates not only the triceps but also other extensors of the forearm. This function is critical for activities that involve pushing or straightening the arm, making it a vital motor function in upper limb movements.

In contrast to the other options, while finger abductors are innervated by the ulnar and radial nerves (primarily by the C8 and T1 roots), long toe extensors are influenced by the L5 and S1 nerve roots rather than the cervical roots. Ankle plantar flexors are mainly supplied by the S1 and S2 spinal nerves. Thus, the distinct role of the C7 nerve root in the functioning of the elbow extensors solidifies its primary association with that specific muscle action.