Day 4 Muscles of the Skull KH 2220 Laura Abbott, MS, LMT Day 4 Muscles of the Skull

Meninges 3 protective layers of brain Dura Mater Arachnoid Mater External; tough, thick covering Arachnoid Mater Web-like, shock absorption, intermediate Pia Mater Deep and vascular Meningitis – compression/pressure on brain- usually involving the arachnoid mate and pia mater 2 types: viral and bacterial (touch chin to neck)

MENINGES Subarachoid space contains cerebrospinal fluid

The Cranial Nerves There are 12 pairs of cranial nerves, each designated by a name and a Roman numeral. Most cranial nerves are mixed, meaning they have both sensory and motor fibers. The cell bodies of the motor fibers are situated within the brain. The cell bodies of the sensory fibers are located (for the most part) just outside the brain where they cluster together into a ganglion.

I Olfactory nerves sensory There are actually many tiny olfactory nerves, each originating in the roof of the nasal cavity and terminating in the olfactory bulb. The olfactory nerves conduct impulses from the nasal cavity to the olfactory area of the cerebral cortex, which interprets these impulses as smell.

II Optic nerve Sensory The fibers of the optic nerve originate in the retina (back of the eye). From there, the fibers conduct impulses to the midbrain. From the midbrain, the impulses are relayed to the visual area of the cerebral cortex where the impulses are interpreted as sight.

III Oculomotor nerve Mixed The sensory and motor fibers of this nerve supply the muscles that produce movements of the eye ball, as well as the eye lid muscles. It also supplies the iris (the sphincter muscle through which light enters the eye) and the ciliary muscles, which change the shape of the lens to accommodate for near and far vision. Damage to this nerve may result in double vision, dilated pupils, blurred vision, and droopy eyelids (ptosis).

IV Trochlear nerve Mixed This is the smallest of the cranial nerves. Its sensory and motor fibers supply the superior oblique muscles for oblique eye movements.

V Trigeminal nerve Mixed This is the largest of the cranial nerves. It supplies the tissues of the face, eyes, nasal cavity, and mouth. Sensory fibers conduct impulses for touch, heat, cold, and pain (including tooth pain). Motor fibers supply the chewing muscles. Its name is taken from the fact that it consists of three main branches: The ophthalmic nerve (supplies the scalp, eyes, outer nose, and nasal cavity), the maxillary nerve (supplies the nasal cavity, palate, and upper teeth) the mandibular nerve (supplies the lower jaw and teeth).

FYI Trigeminal Neuralgia is believed to be the most severely painful condition there is. It is caused by inflammation of the trigeminal nerve. Pain may last for a few seconds of a few minutes, but it may occur many times during the day. Severing the nerve just proximal to its ganglion treats the most severe cases.

VI Abducens nerve Mixed The sensory and motor fibers of this nerve supply the lateral rectus muscles for lateral eye movements.

VII Facial nerve Mixed Sensory fibers conduct impulses from the taste buds on the anterior two-thirds of the tongue. Motor fibers supply the facial muscles.

FYI Bell’s palsy is a dysfunction of the facial nerve. The muscles are paralyzed on one side of the face, and the person loses sensation on that side of the face, the lower eyelid droops, the corner of the mouth sags, there is partial loss of taste, and the eyes tear constantly. The cause is unknown, symptoms could disappear spontaneously, and massage can help

VIII Vestibulocochlear nerve Sensory Also known as the statoacoustic nerve and auditory nerve. It originates in the ear. It has two portions: the vestibular portion conducts impulses which the brain uses to get a sense of balance. The cochlear portion carries impulses to the auditory area of the cerebral cortex which interprets the impulses as “sound.” Damage to this nerve results in impaired hearing (nerve deafness), dizziness, and nausea.

IX Glossopharyngeal nerve Mixed This nerve supplies the back of the tongue (glosso) and the throat (pharynx). Sensory fibers provide general sensation for these areas as well as taste information from the back of the tongue. Sensory fibers originating from the carotid artery gives the brain information about blood pressure. Motor fibers supply swallowing muscles of the throat. Damage to this nerve results in loss of gag reflex and impaired ability to swallow and taste (sour and bitter).

X Vagus nerve Mixed This nerve supplies most of the visceral organs in the thoracic and abdominopelvic cavity. Damage results in hoarseness, loss of voice, difficulty in swallowing, and impaired digestion. Innervates smooth muscle of heart and lungs.

XI Accessory nerve Motor Motor fibers supply the sternocleidomastoid muscle (SCM), traps, and swallowing muscles. Damage may result in turning of the head to one side (SCM) and impaired ability to shrug shoulder (traps).

XII Hypoglossal nerve Motor Motor fibers supply muscles of the tongue. Damage results in impaired ability to speak and swallow.

Pneumonic Device to Remember Cranial Nerves: Oh – Olfactory Oh – Optic Oh – Oculomotor To – Trochlear Touch – Trigeminal And – Abducens Feel – Facial Very – Vestibulocochlear Green – Glossopharyngeal Veggies – Vagus Ah – Accessory Ha - Hypoglossal

Temporalis Muscle O: temporal fossa SIDES OF SKULL I: coronoid process of mandible A: Elevates mandible

Frontalis O: frontal bone I: Skin of the eyebrows Wrinkle eyebrows, forehead elevation, raise eyebrows

Occipitalis Muscle O: lateral 2/3 of superior nuchal line external occipital protuberance I: galea aponeurosis, over the occipital bone A: draws back the scalp to raise the eyebrows and wrinkle the brow

Masseter Muscle O: zygomatic process and its arch I: angle and ramus of mandible A: Closes jaw and elevates mandible Unilaterally – moves jaw to same side

Buccinator Muscle O: molar region of maxilla and mandible alveolar near teeth I: orbicularis oris A: draws corner of mouth lateral (compresses cheek/whistling/food between teeth)

Orbicularis Oris O: maxilla and mandible I: encircles mouth, angles at mouth A: closes mouth/kissing muscle

Medial Pterygoid O: medial surface of lateral pterygoid plate of the sphenoid palatine bone pterygoid fossa I: inner surface of mandibular ramus angle of the mandible A: closes the lower jaw (clenches the teeth) ; can protrude the mandible in combination with the lateral pterygoid

Lateral Pterygoid O: Superior head: lateral surface of the greater wing of the sphenoid; Inferior head: lateral surface of the lateral pterygoid plate I: neck of the mandibular condyle; articular disk of the TMJ A: deviates mandible to side opposite of contraction (during chewing); opens mouth by protruding mandible