Maximus Gage
The sternocleidomastoid muscle is a muscle in the neck that tilts and rotates the head. It is innervated by the eleventh cranial nerve, also known as the spinal accessory nerve. This nerve is responsible for supplying motor control to the sternocleidomastoid and trapezius muscles, which are involved in neck and shoulder movements. The nerve has a complex anatomy and is believed to carry specific special visceral efferent (SVE) or general somatic efferent (GSE) information. Injury to the nerve can cause varying degrees of dysfunction in the sternocleidomastoid muscle, and it is important to identify the cause of the damage through a thorough medical history.
| Characteristics | Values |
|---|---|
| Nerve | Cranial nerve XI, spinal accessory nerve, accessory nerve |
| Origin | Nucleus ambiguus |
| Function | Rotates and tilts the head |
| Innervation | Ipsilateral, contralateral, or bilateral |
| Testing | Patient turns their head to the left or right against resistance |
Explore related products
What You'll Learn
The spinal accessory nerve
The cranial part of the nerve is smaller and arises from cells in the nucleus ambiguus. It ultimately joins and is distributed with the vagus nerve. This portion innervates the pharyngeal muscles, as well as the soft palate, larynx, and pharynx. The cranial component of the nerve provides motor control to these muscles.
Flexing and Muscle Growth: Is There a Link?
You may want to see also
Explore related products
Ipsilateral, contralateral, or bilateral innervation
The sternocleidomastoid muscle is innervated by the eleventh cranial nerve, also known as the spinal accessory nerve. This nerve has a complex and unique anatomy and is responsible for neck and shoulder movement, as well as the sensitive afferences of the trapezius and sternocleidomastoid musculature.
The spinal accessory nerve has two parts: a smaller cranial part and a main spinal portion. The cranial part arises from cells in the nucleus ambiguus and is distributed with the vagus nerve, innervating the pharyngeal muscles. The spinal portion, on the other hand, arises from a long column of nuclei in the ventral part of the medulla, extending to the fifth cervical segment or lower.
The spinal accessory nerve passes along the internal surface of the sternocleidomastoid muscle, sending branches without penetrating it. This nerve is responsible for the motor supply to the trapezius muscle, with some contribution from the cervical plexus. The trapezius muscle is involved in movements such as elevation, lowering, adduction, abduction, and external rotation of the scapula.
The spinal accessory nerve has been characterised as having ipsilateral, contralateral, or bilateral innervation. Ipsilateral and contralateral connections are both important for motor control. Ipsilateral motor activations have been observed during voluntary movements, and they play a role in the planning and execution of these movements. On the other hand, the contralateral hemisphere is classically understood to drive unilateral limb movements.
Muscle Recovery: Enhancing Healing and Performance
You may want to see also
Explore related products
The cranial nerve XI
The sternocleidomastoid muscle is innervated by the cranial nerve XI, also known as the spinal accessory nerve. This nerve has a complex and unique anatomy and is essential for neck and shoulder movement, as well as the intrinsic musculature of the larynx. It arises from two parts: a smaller cranial part and a main spinal portion.
The smaller cranial part of the nerve arises from cells in the nucleus ambiguus and is distributed with the vagus nerve. This portion innervates the pharyngeal muscles. The cranial component is considered part of the vagus nerve due to this shared pathway. The cranial nerve XI exits the skull through the jugular foramen, along with the vagus nerve and glossopharyngeal nerve.
The spinal portion, or main part, of the nerve arises from a long column of nuclei situated in the ventral part of the medulla, extending to the fifth cervical segment or lower. It begins in the precentral gyri and descends in the corticobulbar tract. The fibres join together and ascend through the foramen magnum, then exit through the jugular foramen. The nerve then descends in the neck near the jugular vein, supplying the sternocleidomastoid and trapezius muscles.
The Exciting Autonomy of Cardiac Muscle Cells
You may want to see also
Explore related products
The vagus nerve
The sternocleidomastoid muscle is innervated by the spinal accessory nerve, also known as the eleventh cranial nerve, or simply CN XI. This nerve is responsible for supplying motor control to the sternocleidomastoid and trapezius muscles, enabling movements such as rotating and tilting the head and shrugging the shoulders.
The spinal accessory nerve has a complex anatomy and can be divided into two parts: the spinal part and the cranial part. The spinal part arises from a series of roots, specifically C1-C5/6, and travels upwards to exit through the jugular foramen. This part of the nerve provides direct innervation to the sternocleidomastoid and trapezius muscles, ensuring their proper functioning.
The cranial part of the spinal accessory nerve is smaller and originates from the nucleus ambiguus of the medulla oblongata. This portion joins with the vagus nerve and contributes to the innervation of the pharyngeal, laryngeal, and palatal muscles. It carries special visceral efferent (SVE) information related to these muscles.
One of its important roles is in the parasympathetic innervation of the heart, where it helps regulate heart rate and cardiac function. The vagus nerve also contributes to the innervation of the respiratory system, including the pharynx and larynx, as well as the digestive system, where it stimulates peristalsis and secretion in the stomach and intestines. Additionally, the vagus nerve has sensory functions, providing sensory information from the throat, taste buds, and parts of the ear.
In summary, the sternocleidomastoid muscle is primarily innervated by the spinal accessory nerve, particularly its spinal part. The cranial part of the spinal accessory nerve, which joins the vagus nerve, has indirect effects on the sternocleidomastoid muscle through its involvement with other muscles and systems in the body. The vagus nerve, as one of the longest and most diverse nerves in the body, has a wide range of functions that extend beyond its connection with the spinal accessory nerve.
Herbs and Spices: Warming Up Muscles
You may want to see also
Explore related products
The trapezius muscle
The sternocleidomastoid muscle is innervated by the spinal accessory nerve or cranial nerve XI. This nerve is responsible for neck and shoulder movement and the intrinsic musculature of the larynx. It has a complex and unique anatomy.
Now, for the trapezius muscle:
The descending (upper) fibres of the trapezius muscle work with the levator scapulae muscle to elevate the scapula at the scapulothoracic joint. They also help maintain the level of the shoulders against gravity, such as when carrying a weight. When contracting unilaterally, the descending fibres produce a lateral flexion of the head and neck by acting on the atlanto-occipital and upper cervical vertebrae, respectively. This unilateral contraction can also result in a contralateral rotation of the head.
The transverse (middle) part of the trapezius muscle is involved in movements such as pushing, reaching forward, or pulling down, and it helps maintain scapular stability. It works in conjunction with the serratus anterior muscle to rotate the scapula upward during arm elevation, allowing the arm to lift smoothly above shoulder height. This coordination ensures efficient shoulder movement during pushing or punching actions.
The ascending (lower) part of the trapezius muscle is involved in movements such as side bending and turning the head, elevating and depressing the shoulders, and internally rotating the arm. It also works closely with the deltoid muscle for arm elevation and the supraspinatus muscle for shoulder abduction.
Loosening Tight Shoulder Muscles: Simple and Effective Techniques
You may want to see also
Frequently asked questions
The sternocleidomastoid muscle originates from the sternum and clavicle and inserts on the mastoid process. It rotates and tilts the head.
The sternocleidomastoid muscle is innervated by the spinal accessory nerve, also known as the eleventh cranial nerve or cranial nerve XI.
The nerve supplies motor control to the sternocleidomastoid muscle and is essential for neck and shoulder movement.
Injury to the nerve can cause varying degrees of dysfunction in the sternocleidomastoid muscle, ranging from benign to serious injuries. Benign injuries can occur from excessive stretching or carrying heavy weights, while more serious injuries can occur from extensive tumor mass-removal surgery in the neck area.
