Neuroanatomy of Cranial Nerves

CNS

Brain and Spinal Cord

Information processing/Interneurons

Sensory/Afferent

•General Sensory (Somatic and Visceral)

•Special Sensory

RECEPTORS

Motor/Efferent

•Somatic Motor

•Visceral Motor (ANS)

PNS

Nerves

EFFECTORS

Overview

Functional Components of Nerves• General sensory

– Somatic sensory (GSA)– Visceral sensory (GVA)

• Special sensory (SSA, SVA)• Somatic motor (GSE)

– Branchial motor (SVE) to skeletal muscles derived from branchial arches

– Somatic motor (GSE) to skeletal muscles derived from other sources

• Visceral motor (GVE) to smooth muscle and glands

Cranial Nerves

• Carry 1-4 functional components– General sensory– Special sensory– Somatic motor– Visceral motor

What to Know About Cranial Nerves• Name and Number• Origin from brain• Functional components• Location of cell bodies

– Nucleus– Ganglion

• Foramen of exit from cranial cavity• Distribution: branches, targets, and

functions• Testing and lesions

Cell Bodies of Cranial Nerves

• General sensory neurons – in a sensory ganglion (no synapses, pseudounipolar)

• Special sensory neurons – in a sensory ganglion or in the sensory organ

• Somatic motor neurons – in a nucleus

• Visceral motor neurons– – Preganglionic – in a nucleus– Postganglionic – in an autonomic ganglion

(synapses)

General Sensory Pathways• Neurons

– Primary/peripheral– Secondary– Tertiary (cell body in

thalamus)

L 1-23

Voluntary Motor Pathway

• AKA Pyramidal system

• Upper motor neurons• Lower motor neurons

L Fig 1-23

• I Olfactory• II Optic• III Oculomotor• IV Trochlear• V Trigeminal• VI Abducens• VII Facial• VIII Vestibulocochlear• IX Glossopharyngeal• X Vagus• XI Spinal accessory• XII Hypoglossal

Special Sensory

• CN I – Olfactory (olfaction)

• CN II – Optic (vision)

• CN VIII – Vestibulocochlear (hearing, equilibrium)

• CN’s VII, IX, X - taste

General Sensory

• CN V – Trigeminal– V1

– V2

– V3

– Sensory neuron cell bodies in trigeminal ganglion

• Other cranial nerves with general sensory fibers – CN’s VII, IX, and X

Somatic Motor

• CN’s III, IV and VI ocular muscles• CN XI SCM and trapezius• CN XII tongue muscles

• CN V3 (arch I) muscles of mastication, etc.

• CN VII (arch II) m’s of facial expression, etc.• CN IX (arch III) stylopharyngeus• CN X (arches IV, VI) m’s of soft palate, pharynx,

and larynx

Visceral Motor(Parasympathetic)

• CN’s III, VII, IX, X• Ganglia:• Targets:• Postganglionic

parasympathetics tend to follow branches of the trigeminal nerve.

L 1-25

Sympathetics to the Head• Origin:• Ganglia:• Targets:• Postganglionic

sympathetics follow branches of carotid arteries (in a perivascular plexus)

L 1-26

CN’s Carrying All Four Functional Components

• CN VII

• CN IX

• CN X

Branches of Cranial Nerves May Serve Different Functions

V3

Netter Plate 42

References

• Regional anatomy – Liebgott Chapter 7

• Systemic anatomy – Liebgott Chapter 8

• Images – Netter Plates 112-125