Brief Answer:
there are different muscles involved
Detailed Answer:
HI, thanks for using healthcare magic
Myotomes are groups of muscles that are controlled or innervated by specific
nerve roots such as the nerve roots that you mentioned - C4 to C7.
(1)C4 - this is involved in elevation of the shoulder. The muscles involved aret trapezius and levator scapulae
(2)C5-this is involved in abduction/flexion of the shoulder and flexion at the elbow.
There are a number of muscles innervated including the
biceps brachii, bracialis, deltoid,supraspinatus, infraspinatus,
brachioradialis, pectoralis major (clavicular head). teres major, teres minor
(3) C6 is involved in , adduction of the shoulder, flexion of the elbow as well , extension of the wrist, flexion of the wrist
The muscles are teres major and teres minor, deltoid, triceps brachaii, extensor carpi radialis longus and brevis, flexi carpi radialis,
(4) c7-involved in extension at the elbow, shoulder adduction, medial rotation of the shoulder, flexion and extension of the fingers, flexion and extension at the wrist.
There are also a host of muscles involved.
I hope this helps, feel free to ask any other questions