CRANIAL NERVES
I, II, IV, VI, VIII, XI, XII
Modalities

SSS:
Special Sensory:
Special senses derived from ectoderm:
Sight, sound, balance.

SVS:
Special Visceral Sensory:
Special senses derived from endoderm:
Taste

SVM:
Special Visceral Motor:
Muscles derived from pharyngeal arches.
Modalities

GVS:
General Visceral Sensory:
General sensation from viscera.

GVM:
General Visceral Motor:
To smooth muscles of gut tract.
Autonomic motor

GSS:
General Somatic Sensory:
General senses from ectoderm (skin).

GSM:
General Somatic Motor:
Skeletal muscles.
Generalizations

Cranial nerves have same basic structure
as spinal nerves.
Dorsal root and ventral root.
Dorsal root ganglion.

Motor components of cranial nerves begin
within brain within motor nuclei.
Comparable to spinal cord anterior horns.

Cell bodies of sensory fibers are located in
dorsal root (cranial) ganglia.
Generalizations

Special sensory cranial nerves:
Are actually tracts.
No motor nuclei and no sensory ganglia.

Motor cranial nerves:
Begin in cranial motor nuclei.
Have no sensory roots and no sensory root ganglia.

Mixed cranial nerves:
Have both cranial motor nuclei and sensory ganglia.
Sensory ganglia are usually given specific names.
Generalizations

For each cranial nerve know:
Modality (modalities).
Function (functions).
Sensory areas and/or muscles innervated.
Foramen through which it passes.
Specific ganglion (if applicable).
Specific information included in this slide
presentation.
Olfactory Nerve (CN I)

Olfactory nerve fibers pass from:
Olfactory receptor cells.
Through:
Cribriform plate.
To:
Olfactory bulbs.

Modality:
SVS
Optic Nerve (CN II)
Begins in ganglionic layer of retina (not
rods and cones).
 Exits orbit through optic canal.
 50% decussation in optic chiasma:

Near pituitary gland.
Near internal carotid.

Modality:
SSS
Oculomotor Nerve (CN III)
Supplies four of the six extrinsic muscles
of the eye.
 Has a parasympathetic component.
 Will be discussed in a group with other
parasympathetic nerves.

Trochlear Nerve (CN IV)
Enters orbit through superior orbital
fissure.
 Innervates superior oblique muscle of the
eye.
 Modality:

GSM.
Only crossed cranial nerve.
 Only cranial nerve that emerges dorsally.

Abducens Nerve (CN VI)
Enters orbit through superior orbital
fissure.
 Lies on medial aspect of lateral rectus
muscle.
 Innervates lateral rectus muscle of the
eye.
 Modality:

GSM.
Vestibulocochlear Nerve (CN VIII)

Leaves cranial cavity via internal acoustic
meatus:
Accompanied by facial nerve.

Modality:
SSS

Auditory (cochlear) component:
Cell bodies in spiral ganglion of cochlea.
Function: Hearing.
Vestibulocochlear Nerve (CN VIII)

Vestibular component:
Cell bodies in vestibular ganglion.
From receptors for balance and equilibrium.
Function: Balance.
Spinal Accessory Nerve (CN XI)
Arises from C1-3 (4).
 Single trunk enters cranial cavity through
foramen magnum.
 Temporarily joins cranial root.

Cranial roots leave with vagus nerve.
Spinal Accessory Nerve (CN XI)
Spinal accessory trunk exits cranial cavity
via jugular foramen.
 Supplies:

Sternocleidomastoid and trapezius.

Modality:
SVM.
Hypoglossal Nerve (CN XII)
Exits cranial cavity via hypoglossal
foramen.
 Descends anteriorly in neck between
internal carotid and internal jugular.
 In neck gives rise to superior root of ansa
cervicalis and a nerve to thyrohyoid
muscle.
 Supplies extrinsic and intrinsic muscles of
tongue.
 Modality:

GSM.