Anatomy and Physiology of the Cranial Nerves

Question 1

Cranial nerve 1

Answer 1

Olfactory nerve
Special sense of smell
Somatic

Question 2

Cranial nerve 2

Answer 2

Optic nerve
Vision
Somatic

Question 3

Cranial nerve 3

Answer 3

Oculomotor nerve
Movement of eye and pupil constriction
Motor

Autonomic- parasympathetic

Question 4

Cranial nerve 4

Answer 4

Trochlear nerve
Movement of eye
Motor

Question 5

Cranial nerve 5

Answer 5

Trigeminal nerve
Sensation of the face, motor to muscles of mastication
Both sensory and motor

Question 6

Cranial nerve 6

Answer 6

VI. Abducens nerve
Movement of eye
Motor

Question 7

Cranial nerve 7

Answer 7

VII. Facial nerve
Facial expressions, special sense of taste
Both. lacrimal and salivary glands
Sensory and motor 
 Autonomic- parasympathetic

Question 8

Cranial nerve 8

Answer 8

VIII. Vestibulocochlear nerve
Hearing and balance
Somatic

Question 9

Cranial nerve 9

Answer 9

IX. Glossopharyngeal
Sensation to pharynx, tongue, including taste and swallowing salivary glands
Both motor and somatic
Autonomic- parasympathetic

Question 10

Cranial nerve 10

Answer 10

X. Vagus nerve
Larynx, heart, viscera of gastrointestinal tract
BOth sensory and somatic

Autonomic- parasympathetic

Question 11

Cranial nerve 11

Answer 11

XI. Accessory nerve
Movement of neck
Motor

Question 12

Cranial nerve 12

Answer 12

XII. Hypoglossal nerve
Movement of tongue
MOtor

Question 13

Optic nerve

Answer 13

• 3 neurons in sequence
• The first neuron is the bipolar cell that receives information from the neuroepithelium of the retina
• The second neuron is the ganglion cell, it’s axon continues through the optic chiasm and along the optic tract on the opposite side
• The third neuron has it’s cell body in the lateral geniculate nucleus. It’s axons project through the optic cortex in the occipital cortex in what is called the optic radiation
66% fibres decussate ( cross over ) in cats and 75% in dogs

Question 14

Clinical Test: Pupillary light reflex

Answer 14

• A light is shone into one eye.
• This is detected by the retina and conveyed by the optic nerve though the optic chiasm and along the optic tract.
• Parasympathetic fibres of the oculomotor nerve are stimulated to signal to the pupil via the ciliary ganglion and ciliary nerves to the muscles of the pupil.

Question 15

Innervation of the extraocular muscles

Answer 15

• SR superior rectus- 3
• IO inferior oblique- 3
• MR medial rectus- 3
• LR lateral rectus- 6
• IR inferior rectus- 3
• SO superior oblique- 4

Question 16

Three roots of the trigeminal nerve

Answer 16

The semilunar (gasserian or trigeminal) ganglion is the great sensory ganglion of CN V. It contains the sensory cell bodies of the 3 branches of the trigeminal nerve (the ophthalmic, mandibular, and maxillary divisions). The ophthalmic and maxillary nerves are purely sensory.

Question 17

Analgesia of the trigeminal nerve – Nerve blocks

Answer 17

• Disbudding and de-horning • Dentistry:
• Cornual nerve block, V2 • Infraorbital nerve block- V2
• Mental nerve block – V3

Question 18

Cranial Nerve VII – Facial nerve

Answer 18

• Motor
• muscles of facial expression
• caudal belly of digastric (equines)
• stapedius mm.
• Parasympathetic
• Glands
• Special sense
• Taste (Chordae tympani branch)
• Sensory
• ear

Question 19

Facial nerve paralysis

Answer 19

• Clinical signs:
• Inability to blink • Drooping of face • Dry eye
• Often unilateral
• Can be caused by ear infection

Question 20

Cranial Nerve VII – Facial nerve

Answer 20

• Motor
• muscles of facial expression
• caudal belly of digastric (equines)
• stapedius mm.
• Parasympathetic
• Glands
• Special sense
• Taste (Chordae tympani branch)
• Sensory • ear

Question 21

Autonomic innervation of the head

Answer 21

• Cranial Nerves III, VII, IX, X have parasympathetic components
• No cranial nerves have sympathetic components
• Sympathetic innervation to the head travels up the neck
from T1 and T2 via the cranial cervical ganglion
• Pupil
• Lacrimal gland
• Salivary glands