Question

For the following table, mark an X for all the actions performed by the listed muscles.

Muscles acting on the neck	Fibers	Flexion	Extension	Rotation	Lateral flexion
Sternocleidomastoid	Unilateral
	Bilateral
Scalenes	Unilateral
	Bilateral
Splenius	Unilateral
	Bilateral
Trapesius	Superior
Levator scapula
Longissimus capitus
Semispinalis capitis

Answer 1

Please find the below revised table with required information.

The last column has the explanation for each muscle action.

Muscles acting on the neck	Fibers	Flexion	Extension	Rotation	Lateral flexion	explanation
Sternocleidomastoid	Unilateral				X	A unilateral contraction of this muscle flexes the cervical vertebral column to the same side (lateral flexion)
	Bilateral	X				A bilateral contraction elevates the head by dorsally extending the upper cervical joints
Scalenes	Unilateral				X	A unilateral contraction bends the cervical spine to the side
	Bilateral	X				A bilateral contraction of this muscle allows a neck flexion
Splenius	Unilateral			X	X	Unilateral contraction causes lateral flexion of the head and neck and rotation of the head to the same side
	Bilateral		X			Bilateral action causes extension of the head and neck
Trapesius	Superior		X		X	The superficial muscles of the back including trapezuis contribute to extension and side flexion of the axial skeleton
Levator scapula				X	X	This muscle elevates and rotates the inferior angle medially, when the spine is fixed.When the unilateral shoulder is fixed , it rotates the scapulae to the same side and flexes the spine laterally.When bilateral shoulders are fixed the levator scapulae contracts causing flexion/extension of the cervical spine
Longissimus capitus			X		X	Laterally flexes the head and neck to the same side; Bilaterally extends the vertebral column
Semispinalis capitis			X	X		Acting bilaterally : extension of the head and neck Acting unilaterally : rotation of head and neck to opposite side

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