12 pairs, Roman numerals I to XII
• All passes through foramina in base of skull (Foramen magnum - largest
foramina)
• Mainly control anatomic structures of the head except:
o Vagus (X) – extends into the thoracic (controls the heart) and
abdominal cavities (controls abdominal organs)
o Accessory (XI) – Controls Sternocleidomastoid and Trapezius (the
one that turns the head from right to left or shrugging of the
shoulders)
• All arise from the brainstem (Nuclei) EXCEPT CN I and II
Cranial Nerves Nuclei (Nerve Cell Body/Soma Origin)
• Cranial nerves are collection of axons.
• Most cranial nerves emerge from the brainstem except I and II
• CN I: Basal forebrain
• CN II: Diencephalon (Thalamus)
• CN III – XI: Brainstem
FORAMINA OF THE CRANIAL VAULT
Cranial nerve exit foramina in summary
• Anterior Fossa:
o I - perforations in cribriform plate
• Middle Fossa:
o II – optic foramen
o III, IV, VI and ophthalmic division of V – superior orbital fissure
"Frozen eye" - tumor in the superior orbital fissure
o Maxillary division of V – foramen rotundum
o Mandibular division of V – foramen ovale
• Posterior Fossa:
o VII and VIII – internal auditory meatus
o IX, X and XI – jugular foramen
o XII – hypoglossal foramen
SOMATIC vs. VISCERAL FUCNTIONS
A. Sensory Division
1. Somatic Sensory – Skeletal Muscles
▪ General – Touch, pain, pressure, vibration, temperature,
proprioception in skin, body wall and limbs
▪ Special – Hearing, equilibrium, vision, smell
2. Visceral Sensory – Smooth Muscles and Glands
▪ General – Stretch, pain, temp., chemical changes, and
irritation in viscera; nausea and hunger
▪ Special – Taste
Motor Division
1. Somatic Motor
▪ General - Motor innervation of all skeletal muscles
2. Visceral Motor
▪ General – motor innervation of smooth and cardiac muscle,
glands; equivalent to Autonomic Nervous System (ANS)
(parasympathetic and sympathetic division)
SOMATOMOTOR FUNCTIONS: Part of the Pyramidal System
• Involved in control of motor functions in the body (Voluntary)
• Originate from the motor cortex
• Pyramidal pathways - pyramidal: motor
o Corticospinal tract (Spinal cord-spinal nerves)
▪ Movement of muscles below the head with control
from opposite side of the brain
▪ Direct innervation of motor neurons of spinal cord thru
Anterior (ventral horn cell)
o Corticobulbar/Corticonuclear tracts (Brainstem/Cranial nerve)
▪ Movement of muscle with control from opposite side
of brain
▪ Some movement of muscle in here is with control from
both cortical sides (bilateral) of the brain.
▪ Direct innervation of motor neurons of cranial nerve
nuclei thru brainstem. E.g.: facial expression, turning
head side to side
Overview:
• Somato-motor
• Somato-sensory
• Viscero-motor
• Viscero-sensory
• Special sensory (smell, sight, taste, hearing, balance
1. Somato-Motor
• Voluntary, originates from the pre-central gyrus
• Pyramidal
o 2 neuron (generally) Pathway – UMN (CNS) to LMN (PNS)
o Upper Motor Neuron (UMN) - Cortex to brainstem
o Lower Motor Neuron (LMN) - Brainstem nuclei to
neuromuscular junction
o Efferent pathway (away from the brain)
o Decussates to the other side at the medullary pyramids
o Cranial nerve decussates pyramid
o Some cranial nerves have bilateral somatic motor control
coming from the cortex
▪ Example: CN VII, CN XI
Example of Bilateral Motor Cortex Control:
Accessory Nerve
• The motor cortex sends control to both Sternocleidomastoid and
Contralateral Trapezius
o Motor cortex damage will present with weakness to contralateral
trapezius and bilateral sternocleidomastoid (that means if there is
damage on the right cortex, there will be difficulty turning the
neck on both sides)
• Damage to the Accessory nerve itself – present with Ipsilateral weakness/
paralysis on both muscles.
2. Somato-Sensory
o 3 neuron pathways
o Afferent pathway
o Via Sensory Ganglia:
a. Semilunar ganglion (V)/ Trigeminal ganglion
b. Geniculate ganglion (VII)
c. Vestibular and Cochlear ganglia (VIII)
d. Glossopharyngeal Nerve ganglia (IX)
e. Vagus nerve ganglion (X)
o Somato-sensory innervation:
a. Primary neuron: Cranial Nerve Ganglia
b. Secondary neuron: Brainstem
c. Tertiary neuron: Thalamus
Viscero-Motor
o Motor to the Viscera (Smooth muscles and Glands)
a. Sympathetic – C8 to T5 to the head
- Note: no sympathetic innervation from the
Cranial Nerves
b. Parasympathetic – Brainstem (CN: III, VII, IX, X)
c. 3 neuron system
- Primary neuron – hypothalamus to the
viscero-motor nuclei in the brainstem
- Secondary neuron (Preganglionic) –
brainstem nuclei to a parasympathetic
ganglion
- Tertiary neuron (Post-Ganglionic) –
Parasympathetic ganglion to effector organ
viscero motor (cont)
Four Parasympathetic Nuclei in the Brainstem
1. Located inside brainstem
2. Edinger Westphal nucleus: Oculomotor nerve (III)
3. Superior Salivatory nucleus: Facial nerve (VII)
4. Inferior Salivatory nucleus: Glossopharyngeal nerve
(IX)
5. Dorsal Vagal nucleus: Vagus nerve (X)
Four Parasympathetic Ganglia
1. Located outside the CNS
2. Ciliary Ganglion: Oculomotor nerve (III)
3. Pterygo-palatine Ganglion: Facial nerve (VII)
4. Submandibular Ganglion: Facial nerve (VII)
5. Otic Ganglion: Glossopharyngeal nerve (IX)
6. Note: Sympathetic innervation to the head – Lateral
horn of the spinal cord segments C8 – T5
▪ Via Superior Cervical ganglion along the internal
carotid artery
▪ No sympathetic supply coming from the cranial
nerves
Viscero-Sensory
➢ Primary Sensory Ganglions:
- Glossopharyngeal nerve ganglion (IX) receives info
about blood pressure
- Vagus nerve ganglion (X) receives info about heart
rate
➢ Secondary Nuclei
- Solitary tract nucleus (Tractus Solitarius)
▪ Assimilates the viscero-sensory information
from CN IX and X
5. Special Sensory
➢ Smell: Olfactory nerve (I)
➢ Sight/Vision: Optic nerve (II)
➢ Taste: Facial nerve anterior 2/3b of the tongue (VII),
Glossopharyngeal nerve posterior 1/3 of the tongue (IX), and
Vagus nerve at back of the tongue (X)
➢ Hearing: Vestibulocochlear nerve (VIII)
➢ Balance: Vestibulocochlear nerve (VIII)
According to Function
• Purely Sensory Nerves
✓ Olfactory (I) – Smell
✓ Optic (II) – Vision
✓ Vestibulocochlear (VIII) – Hearing and Balance
• Purely Motor Nerves
✓ Oculomotor (III)
✓ Trochlear (IV)
✓ Abducens (VI)
✓ Spinal Accessory/Accessory (XI)
✓ Hypoglossal (XII)
Mixed Sensory and Motor Nerves
✓ Trigeminal Nerve (CN V)
✓ Facial Nerve (CN VII)
✓ Glossopharyngeal Nerve (CN IX)
✓ Vagus Nerve (CN X)
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