10.20.11+-+Cranial+Nerves


 * 1. Name the twelve cranial nerves:**

I. Olfactory II. Optic III. Oculomotor IV. Trochlear V. Trigeminal (Opthalmic, Maxillary, Mandibular) VI. Abducens VII. Facial VIII. Vestibulocochlear IX. Glossopharangeal X. Vagus XI. Accessory XII. Hypoglossal


 * 2. Describe the 6 types of fibers carried by the cranial nerves:**

Somatic Motor: Efferent, control skeletal muscles derived from somites Visceral Motor: Efferent, control smooth muscle, cardiac muscle, and glands Branchial Motor: Efferent, control skeletal muscles derived from branchial arches Somatic Sensory: Afferent, carry info to brain about touch, pain, temperature, pressure, vibration, and proprioception Visceral Sensory: Afferent, carry info to brain about distention, chemical content, and pain from viscera, blood vessels, etc. Special Sensory: Afferent, carry info to brain about smell, vision, taste, hearing, or balance.

There are three purely sensory cranial nerves: olfactory, optic, and vestibulocochlear. They go to the nose, eye, and ear respectively and all carry special sensory nerve fibers. There are five purely motor cranial nerves: occulomotor, trochlear, abducens, accessory, hypoglossal. They go to the muscles controlling the eyes (occulomotor, trochlear, and abducens); the superficial muscles of the deep fascia of the neck: sternocleidomastoid and trapezius (accessory); and all the muscles of the tongue except the palatoglossal muscle (hypoglossal). There are four nerves that carry both sensory and motor fibers: trigeminal, facial, glossopharangeal, and vagus. They do a big mix of everything but somatic motor. Those guys like to stay private.


 * 3. Compare and contrast sensory and motor ganglia of cranial nerves:**

Quick plug for the chart developed by Ethan available on Block 4's main page. It helps me remember this information.

There are six sensory ganglia and 5 motor ganglia. The sensory ganglia do not contain synapses. The motor ganglia do contain synapses. Special, visceral, and somatic sensory fibers pass through various sensory ganglia. Only visceral motor fibers pass through motor ganglia. All but two of the ganglia are associated with nerves that carry both fibers. Vestibulocochlear (sensory only) and Occulomotor (motor only) are the exceptions.

6 sensory ganglia: 5788910 (TGAV SISI)

CN-V (Trigeminal): Trigeminal (Semilunar) CN-VII (Facial): Geniculate CN-VIII (Vestibulocochlear): Auditory (Spiral) CN-VIII (Vestibulocochlear): Vestibular CN-IX (Glossopharyngeal): Superior and Inferior CN-X (Vagus): Superior and Inferior

5 motor ganglia: 377910 (CPSOI)

CN-III (Occulomotor): Ciliary CN-VII (Facial): Pterygopalatine CN-VII (Facial): Submandibular CN-IX (Glossopharyngeal): Otic CN-X (Vagus): Intramural (in wall of organ)


 * 4. For each pair of the twelve cranial nerves:**
 * a. Identify the nerve and its number**
 * b. List the type of fibers conveyed**
 * c. Name sensory or motor ganglion and the fiber types of each ganglion**
 * d. List muscles innervated by each cranial nerve**
 * e. Describe the course of each cranial nerve and the foramina and/or fossae traversed**

CN I - Olfactory Olfactory bulb projects many special sensory nerves thru cribriform plate into superior surfaces of nasal cavity

CN II - Optic Anatomically an extension of the brain. Two optic nerves carry special sensory fibers that meet at an optic chasm and then split into two optic tracts that are continuous with the retina

CN III - Occulomotor Exit the brain at the anterior aspect of the midbrain carrying somatic (superior, medial, and inferior rectus; inferior oblique, and levater papillae muscles) and visceral (constriction of the pupil) motor fibers and leave the neurocranium via the superior orbital fissure to enter the orbit. Splits into two branches, the superior and inferior rami.

CN IV - Trochlear Exits the brain at the lateral aspect of the midbrain, flows through the petrous ridges of the dura mater to leave the neurocranium via the superior orbital fissure to enter the orbit. Innervates the superior oblique muscle.

CN V - Trigeminal Gets its own lecture and page

CN VI - Abducens Exits the brain very medially, on the anterior aspect of the brain stem. Exits the neurocranium via the superior orbital fissure to enter the orbit. Innervates the lateral rectus muscle.

CN VII - Facial TBD

CN VIII - Vestibulocochlear Carries afferent sensory neurons from the vestibular apparatus and the cochlea to the brain. Enters the neurocranium via the internal acoustic meatus. Two ganglia (vestibular and cochlear) w/out synapses external to the neurocranium. The ganglia contain neuronal cell bodies from bipolar special sensory neurons. Vestibular apparatus - balance. Cochlea - hearing.

CN IX - Glossopharyngeal TBD

CN X - Vagus TBD

CN XI - Accessory Nerve Has 2 roots, the spinal and cranial roots. The cranial root fibers (branchial motor) join the spinal root to form the accessory n. then quickly switch to the vagus nerve. They then exit the vagus nerve via the recurrent laryngeal nerve and innervate all muscles of the pharynx but the stylopharyngeal muscle. The spinal root fibers enter the neurocranium via the foramen magnum and then merge with the cranial root to exit the neurocranium via the jugular foramen. They innervate the muscles of the investing fascial layer of the deep fascia of the neck, the trapezius and the sternocleidomastoid.

CN XII - Hypoglossal Leave the cranium via the hypoglossal foramen and then merges with some fibers from C1 to innervate 5 of the 6 intrinsic and extrinsic muscles of the tongue (not palatoglossus (vagus)).

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Rohen's 3rd Ed. p68