Cranial Nerves

Front 1

Olfactory nerve-cell bodies of origin, bony openings and its path to its terminal site

Back 1

o Cell bodies of origin – in ganglia located in olfactory mucosa in roof of the nasal cavity (no synapses here)
 These cell bodies are discrete (not a distinct ganglion)
o Central processes pass through cribiform plate to terminate in olfactory bulb in cranial cavity
 They synapse here with mitral cells whose axons form the olfactory tract
 Thse fibers go directly to the cerebrum

Front 2

Optic nerve-cell bodies of origin, path of its fibers, bony opening and terminal site.

Back 2

o Cell bodies of origin – ganglion cell layer of the retina
o Peripheral processes receive visual input from rods and cones (photoreceptor cells) via the bipolar cell layer
o Central processes leave retina as optic nerve to pass through the optic canal to enter the cranial cavity
 In the cranial cavity the nasal (medial) half of the optic nerves cross (at the optic chiasm located in the middle cranial fossa) to the join with uncrossed fibers from the temporal (lateral) half of the retina
 Posterior to the optic chiasm the two bundles of fibers are called optic tracts whose axons mostly terminate in the lateral geniculate bodies of the thalamus
 Fivers from the geniculate body prject to the visual cortices
 This results in the right optic tract conveying impulses from the left visual field and vice versa

Front 3

• Oculomotor nerve-cell bodies of origin, path of its fibers
o Cell bodies of origin and path to striated muscles from both its superior and inferior divisions

Back 3

 Cell bodies of origin
• Somatomotor – oculomtor nucleus in the midbrain
 Nerve emerges from midbrain, pierces dura lateral to sellar diaphragm roofing over the hypophysis, and runs through the roof and lateral wall of the cavernous sinus
 From there it leaves cranial cavity and enters orbit through superior orbital fissure where it divides into two divisions
• Superior division – innervates superior rectus and levator palpebra superioris
• Inferior division – innervates medial rectus, inferior rectus, and inferior oblique
o Also carries parasympathetic fibers whose cell bodies are located in the accessory oculomotor nucleus (see below)

Front 4

o Autonomic cell bodies of origin and complete path of its autonomic fibers.

Back 4

 Cell bodies of origin and fiber paths (parasympathetic innervation)
• Presynaptic – accessory ocuolmotor (Edinger-Wesphal) nucleus located rostra to the oculomotor nucleus
• Postsynaptic – ciliary ganglion (see below)
o Presynaptic fibers from the inferior division synapse onto
o Postsynaptic fibers from this ganglion pass to the eye in the short ciliary nerves to innervate the ciliary body and sphincter of the pupil
 Short ciliary nerves contain the following
• Postganglionic parasympathetic fibers (as described above)
• Postganglionic sympathetic fibers from superior cervical ganglion to innervate dilator pupillae
• General sensory fibers from cornea, iris and ciliary body (nasociliary nerve of V1)
 Long ciliary nerves are branches of the nasociliary nerve of V1 and do NOT pass through the ciliary ganglion
• Postgnaglionic sympathetic fibers innervating dilator pupillae and superior tarsal muscles (part of levator palpebrae superioris)
• Sensory fibers innervating cornea, iris and ciliary body

Front 5

• Trochlear nerve-cell bodies of origin, its path, bony opening, muscle it innervates

Back 5

o Cell body of origin – trochlear nucleus located in the midbrain immediately caudal to the oculomotor nucleus
 Fibers leave dorsal aspect of midbrain
o Path – longest intracranial (subarachnoid) course of the cranial nerves
 Pierces dura mater at margin of the cerebellar tentoirum and passes anteriorly in the lateral wall of the cavernous sinus
 Passes through the superior orbital fissure to supply the superior oblique