Muscles responsible for Neck Extension
Longissimus Capitis
Action: Extension of the head and cervical spine Nerve: Dorsal primary rami of C4 to T5
Semispinalis Capitis
Action: Extension, rotation and lateral flexion of the head and cervical spine Nerve: Dorsal primary rami of C4 to T6
Splenius Capitis
Action: extend and laterally flex head and neck, slight rotation Nerve: Dorsal Rami of (C3, C4)
Obliquus Capitis Superior and Inferior
Action: extend and rotate the atlantoaxial joint Nerve: Suboccipital Nerve, Dorsal Ramus of C1
Rectus Capitis Posterior Major and Minor
Action: extends and rotates the head Nerve: Suboccipital Nerve, Dorsal Ramus of C1
Sternocleidomastoid
Action: flexes neck, extends head, turns head side to side Nerve: CN XI, C2,3
Levator Scapulae
Action: flexes the neck Nerve: Dorsal Scapular nerve C5
Trapezius
Action: hyperextends the neck Nerve: Spinal root of CN XI, Ventral Rami of C3,4
Splenius Cervicis
Action: laterally flex and extend neck Nerve: Dorsal primary rami of C5 to C7