Nerve Supply To Head

Question 1

Efferent activity

Answer 1

Nerves transmitting away from the CNS and controls muscular or secretory activity

Question 2

Afferent activity

Answer 2

Nerve transmission going towards CNS and controls sensory activity

Question 3

Oculomotor nerve

Answer 3

CN III

Somatic/visceral efferents only

Pre-ganglionic parasympathetic fibers synapse on ciliary ganglion. Post-ganglionic parasympathetic fibers go to pupillary constrictor muscle and to ciliary body

Fibers go to all eye muscles except dorsal oblique, lateral rectus, and retractor bulbi

Clinical signs= pupillary dilation, lateroventral strabismus, ptosis

Question 4

Trigeminal nerve

Answer 4

CN V

Largest cranial nerve

Mixed nerve

Branches are mandibular, maxillary, and ophthalmic

Sensory to skin of head, and oral/nasal cavities

Motor to chewing muscles

Question 5

Mandibular division of trigeminal nerve

Answer 5

Somatic afferent and efferent fibers to skeletal muscles

Main responsibilities is chewing reflexes and sensory on face

Exits skull via oval notch of foramen lacerum

Clinical signs= jaw drop, no feeling of lower face and lower teeth, oral mucosa, or tongue

Question 6

Branches of mandibular branch of trigeminal

Answer 6

Afferent pathway of chewing:

• Lingual branch provides sensation ( not taste) to rostral 2/3 of tongue
• Mandibular alveolar branch provides sensation to lower teeth
• Buccal branch provides sensation to inside of cheek

Efferent pathway of chewing

• motor innervation of muscles that close jaw (masseter, temporalis, pterygoid)
• motor innervation to rostral belly of digastricus and mylohyoideus

Afferent innervation of face
-mental branch and auriculotemporal branch provide sensation to skin on lower face

Question 7

Maxillary division of trigeminal

Answer 7

Somatic afferents only
Emerges from the round foramen and enters the pterygopalatine fossa

Innervates lateral angle of eye, skin of rostral face, upper teeth, all skin of muzzle and nostril part of nasal cavity

Clinical signs= insensitive muzzle, no lateral palpebral reflexes

Question 8

Branches of maxillary division of trigeminal

Answer 8

• infraorbital branch cutaneously innervates upper lip, nostril, and skin in upper face
• zygomatic branch supplies lower eyelid, lateral canthus, and skin rostral to the ears (in cows, cornual branch off zygomatic branch innervates horns)
• caudal and internal nasal branches supply lining of nasal cavity
• maxillary alveolar nerve and palatine nerves innervate upper teeth and hard palate, respectively.

Question 9

Ophthalmic division of trigeminal

Answer 9

Somatic afferents only
Emerges from orbital fissure

• lacrimal, frontal, and infratrochlear branches innervate skin of forehead; also involved in innervation of horn in cattle
• ethmoidal branch innervates mucosa covering ethmoturbinates in nasal cavity
• long ciliary branch innervates cornea
• infratrochlear branch innervates conjunctiva
• long ciliary and infratrochlear together provide afferent pathway of corneal reflex

Clinical signs= no corneal reflex

Question 10

Facial nerve

Answer 10

CN VII
Both afferent and efferent

Enters cranium via stylomastoid foramen

Motor to muscles of facial expression, jaw opening, and parasympathetic to salivary glands, tear glands, and eye lids

Sensory to inner pinna and rostral 2/3
 of tongue (taste)

Clinical signs= facial paralysis

Involved in yellow star thistle poisoning

Question 11

Motor control of facial muscles

Answer 11

Branches of facial nerve- dorsal and ventral buccal, auriculopalpebral, and caudal auricular innervates skeletal muscles of nostril, lips, cheek, eyelid, and external ear

Question 12

Afferent pathways of salivary reflexes

Answer 12

Branches of facial nerve- chorda tympani

Carries info from rostral 2/3 of tongue

Question 13

Efferent pathway of salivary reflexes

Answer 13

Parasympathetic pathways carried by facial and glossopharyngeal nerves. Facial nerve goes to mandibular and sublingual salivary glands

Question 14

Other functions of facial nerve

Answer 14

Parasympathetic motor innervation of glands in nasal cavity (via major petrosal branch)

Parasympathetic motor innervation of lacrimal gland

Somatic afferent innervation of skin on inner ear (via internal auricular branch)

opens jaws via branch to caudal belly of digastricus and occipitomandibularis

Question 15

Glossopharyngeal nerve

Answer 15

CN IX
Afferent and efferent
Enters cranium via foramen lacerum

Clinical signs= dysphagia

Lines guttural pounch

Question 16

Branches of glossopharyngeal nerve

Answer 16

Lingual branch- sensory and taste to caudal 1/3 of tongue

Pharyngeal branch- sensory to pharynx and motor to pharynx

Caudal sinus nerve- chemoreceptors to carotid body

Also send pre-ganglionics to otic ganglion which then sends post-ganglionic to parotid salivary gland

Question 17

Vagus nerve

Answer 17

CN X
Afferent and efferent
Enters cranium via foramen lacerum
Innervates pharynx/larynx and associated muscles
Clinical signs= laryngeal hemiplagia and dysphagia

Question 18

Afferent fibers of vagus nerve

Answer 18

Pharyngeal branch to pharynx produces swallowing or gagging

Cranial laryngeal branch gives sensory to larynx and elicits cough and choke reflex

Sensory fibers to esophagus and upper digestive tract

Sensory fibers to baroreceptors in heart

Question 19

Efferent fibers of vagus

Answer 19

Supplies striated muscle of larynx via recurrent laryngeal nerves

Preganglionic parasympathetic fibers supply terminal ganglion from esophagus to distal colon, cardiac muscle, and glands/smooth muscle of respiratory tract