Cranial Nerves & the Eye

26 October 2006

Cranial Nerves

Peripheral nerves that originate from nuclei located in the brain rather than from the spinal cord are called cranial nerves

Nerves emanate from surface of brain

Designated by names and numbers (in Roman numerals)

They can be sensory or motor

Unusual because some have special sensory organs as their sensory receptors

Special vs. General Senses

General senses convey stimuli from

- Exteroceptors

- Enteroceptors

- Proprioceptors

Located in the skin, muscles, joints and in viscera

Special senses convey stimuli from special sensory organs, sensitive to:

- Light

- Vibratory energy (sound)

- Gravity and body motion

- Chemical stimulation

Special senses are associated only with cranial nerves


Cranial Nerves

I - Olfactory

- Sense of smell

II - Optic

- Vision

III - Occulomotor

- Motor control of the position of the eyes and of pupillary dilation

IV - Trochlear

- Motor control of the position of the eyes (one muscle)

V - Trigeminal

- General sensory to face and motor to muscles of mastication

VI - Abducens

- Motor control of the position of the eyes (one muscle)

VII - Facial

- Motor to muscles of face; sense of taste to anterior 2/3rds of tongue

VIII - Vestibulocochlear

- Hearing and equilibrium

IX - Glossopharyngeal

- Sensory to pharynx, sense of taste to posterior 1/3rd of tongue, motor to one muscle of the pharynx

X - Vagus

- Sensory and motor to pharynx & larynx, motor to thoracoabdominal viscera

XI - Spinal Accesory

- Motor to trapezius and sternocleidomastoid

XII - Hypoglossal

- Motor to intrinsic muscles of tongue


- Point of attachment to brain

- Foramen of skull through which it passes

- Function

See Tables on pp 124-125 of lab manual for this information

See Martini Figures 15.21 through 15-30


The Eye

Extraoccular structures

Lacrimal gland

Nasolacrimal sac

- Lacrimal canaliculi

- Nasolacrimal duct

Levator palpebrae superioris

Superior rectus m.

Lateral rectus m.

Medial rectus m.

Inferior rectus m.

Superior oblique m.

Inferior oblique m.

Martini, Figs. 18.18, 18.19


Anatomy of the Eye

Globe of eye contained by Fibrous tunic

- Sclera - white (muscle attachment)

- Cornea - transparent covering of pupil

Vascular Tunic provides passage for blood supply & muscles

- Choriod layer

- Ciliary body

Ciliary muscles - act on lens

- Pupillary muscles



Anatomy of the Eye

Nervous tunic

- Retina

- Optic disc - exit point of retinal neurons

- Optic nerve

Ectodermal structures

- Lens

- Suspensory (zonular) ligaments

Connect ciliary muscles to lens

Spaces of Eye

- Posterior cavity - posterior to lens

Vitreous body

Thick, gelatinous

Formed at birth

Anterior cavity - between lens and cornea

- Aqueous humor

Anterior chamber, anterior to iris

Posterior chamber, posterior to iris

- Always being formed new and resorbed

- Production & resorption must be balanced

Martini Figs 18.20, 18.21