5.3 Muscles & Nerves of the Head, Face & Neck
Key Takeaways
- The three muscle types are skeletal (striated, voluntary), smooth (nonstriated, involuntary), and cardiac (found only in the heart)
- A muscle's origin is its fixed attachment; the insertion is the movable attachment, and muscles pull but never push
- The epicranius (occipitofrontalis) has a front portion that raises the eyebrows and a back portion that draws the scalp backward
- The masseter and temporalis are the muscles of mastication that close the jaw; the zygomaticus major and minor elevate the corner of the mouth when smiling
- The fifth cranial nerve (trigeminal) is the largest cranial nerve and chief sensory nerve of the face with three branches; the seventh cranial nerve (facial) is the chief motor nerve of facial expression; the eleventh cranial nerve (accessory) supplies the sternocleidomastoid and trapezius
Why Muscles and Nerves Are Heavily Tested
Facial massage, scalp massage, and client positioning all depend on knowing what lies under the skin. The PSI exam draws a steady stream of questions from myology (the study of muscles) and neurology (the study of nerves) — usually asking you to match a muscle or nerve to its location, action, or name. This section gives you the complete tested set.
Muscle Types and Properties
There are three types of muscle tissue:
- Skeletal muscle is striated (striped in appearance) and voluntary — it is attached to the bones and is controlled by the will. Every muscle you manipulate during massage is skeletal muscle.
- Smooth muscle is nonstriated and involuntary — it is found in the internal organs such as the stomach and intestines, and in the blood vessels. It functions automatically.
- Cardiac muscle is the involuntary muscle of the heart; it is striated but not under conscious control, and it is found nowhere else in the body.
Muscle tissue has three working properties: contractility (the ability to shorten), extensibility (the ability to be stretched), and elasticity (the ability to return to its original shape after stretching). A muscle's origin is the part that does not move — the fixed attachment, usually closer to the skeleton. The insertion is the movable attachment, the part farthest from the skeleton. Muscles contract and pull on the insertion; they pull but never push.
Muscles of the Scalp and Face
The epicranius, also called the occipitofrontalis, is the broad muscle that covers the top of the skull. It has two bellies connected by the epicranial aponeurosis, a broad tendon: the front portion (frontalis) raises the eyebrows, draws the scalp forward, and causes wrinkles across the forehead; the back portion (occipitalis) draws the scalp backward.
Key facial expression muscles:
| Muscle | Location | Action |
|---|---|---|
| Corrugator | Between the eyebrows | Draws the eyebrow down and wrinkles the forehead vertically (frowning) |
| Procerus | Covers the bridge of the nose | Lowers the eyebrows; causes wrinkles across the bridge of the nose |
| Orbicularis oculi | Completely surrounds the margin of the eye socket | Closes the eyelid |
| Orbicularis oris | Flat band around the upper and lower lips | Closes the lips, compresses and purses them (as in kissing and whistling) |
| Zygomaticus major and minor | Extend from the zygomatic bone to the corner of the mouth | Elevate the corner of the mouth, as in laughing and smiling |
| Buccinator | Thin, flat muscle of the cheek between the upper and lower jaw | Compresses the cheeks and expels air between the lips, as in blowing; assists chewing |
Muscles of Mastication, the Neck, and the Back
The muscles of mastication (chewing) that the exam tests are the masseter and the temporalis: they coordinate in opening and closing the mouth, working to close the jaw. The platysma is a broad muscle extending from the chest and shoulder muscles to the side of the chin; it is responsible for pulling down the corner of the mouth and lowering the jaw, as in an expression of sadness or doubt, and it wrinkles the skin of the neck.
Larger muscles of the neck and upper back:
| Muscle | Location | Action |
|---|---|---|
| Sternocleidomastoid | Side of the neck | Rotates the head from side to side and bends the head toward the chest |
| Trapezius | Covers the back of the neck and upper-middle region of the back | Draws the head backward and to the side; moves the shoulder blades (shrugging) |
| Latissimus dorsi | Broad, flat superficial muscle covering the lower back | Controls the swinging of the arm backward and forward |
In the forearm and hand — relevant to your grip on shears, razors, and blow dryers — the extensors straighten the wrist, hand, and fingers to form a straight line along the forearm, while the flexors bend the wrist and draw the fingers closed, as in gripping. The supinator turns the hand palm-upward; the pronators turn the hand palm-downward. Grip fatigue after a day of cutting is a flexor story, and ergonomics training exists to protect exactly these muscles.
The Nervous System: Divisions You Must Know
The nervous system is divided into the central nervous system (CNS) — the brain and spinal cord, the control center — and the peripheral nervous system (PNS), which connects the CNS to the rest of the body and includes twelve pairs of cranial nerves originating in the brain and thirty-one pairs of spinal nerves.
Nerves are classified by the direction they carry messages. Sensory nerves (afferent) carry impulses from the sense organs to the brain, registering touch, heat, cold, and pain. Motor nerves (efferent) carry impulses from the brain to the muscles and glands, producing movement and activity. The autonomic nervous system controls the involuntary muscles and regulates heart action, digestion, and glandular activity.
The Cranial Nerves the Exam Tests
| Nerve | Key facts |
|---|---|
| Fifth cranial nerve (trigeminal) | The largest of the cranial nerves and the chief sensory nerve of the face; also a motor nerve to the muscles of mastication. It has three branches: ophthalmic (eye and forehead area), maxillary (upper jaw, cheek, nose, and upper lip), and mandibular (lower jaw, lower lip, and chin) |
| Seventh cranial nerve (facial) | The chief motor nerve of the face; emerges near the lower part of the ear and controls the muscles of facial expression — including the epicranius, orbicularis oculi, orbicularis oris, and platysma |
| Eleventh cranial nerve (accessory) | Motor nerve that controls the sternocleidomastoid and trapezius, producing movements of the head, neck, and shoulders |
Massage Direction and Nerve Points
Every massage manipulation is applied in a specific direction, and that direction follows the muscle fiber direction — you massage from the insertion toward the origin of the muscle. Stroking with the grain of the muscle relaxes it; working against it can overstretch tissue. Motor nerve points are specific points where motor nerves enter muscles; pressure applied to a nerve point during massage affects the entire muscle, which is why properly placed pressure in a scalp or facial massage produces whole-muscle relaxation. Numbness, tingling, or sharp pain during any service means pressure is affecting a nerve incorrectly — ease off immediately.
Exam tip: Lock in the number-name pairs by function: the 5th (trigeminal) feels the face (sensory), the 7th (facial) moves the face (motor to expression muscles), and the 11th (accessory) moves the neck and shoulders.
Which statement correctly describes the fifth cranial (trigeminal) nerve?
During a facial service, a client chews gum, and you notice the thick muscle at the side of the jaw contracting to close the mouth. Which muscle of mastication is primarily responsible for closing the jaw?