A muscle that prevents unwanted movement of a bone is called?

Question

The prime mover of neck flexion is a prominent muscle on the said of the neck called-------------

Answer 1

A muscle that prevents unwanted movement is called a synergist. Some antagonists also act to stabilize a joint when the agonist is contracting. The prominent muscle you are referring to is called the sternocleidomastoid muscle aka SCM.

Answer 2

No idea about the first question but the prime flexor of the neck is the sternocleidomastoid. Origin  of the two heads are the sternum (manubrium) and clavical, insertion is at the mastoid process.

Answer 3

Tendon?

Answer 4

The fixator muscles prevents any unecessary movement,

Neck flexor muscle