cranial nerves 2

The facial nerve (CN VII) is primarily motor but also has what other types of fibres?

Special sensory (for taste) and autonomic (parasympathetic) fibres.

What muscles are innervated by the motor component of the facial nerve (CN VII)?

The muscles of facial expression, the stapedius (a small muscle in the middle ear), and the caudal digastric muscle (which opens the jaw).

What is the function of the stapedius muscle, and which nerve innervates it?

It is a small muscle in the middle ear, innervated by the facial nerve (CN VII).

What does the auriculopalpebral branch of the facial nerve innervate?

the muscles closing the eyelids (orbicularis oculi muscles) and muscles of the ear (auricular)

What do the dorsal and ventral buccal branches of the facial nerve innervate?

Muscles of the cheek, lips (orbicularis oris), and nostrils.

What is the function of the cervical branch of the facial nerve?

Motor to the caudal belly of the digastricus muscle.

What is the function of the caudal auricular branch of the facial nerve

Sensory to the skin around the ear.

what parasympathetic functions does the facial nerve (CN VII) provide?

Parasympathetic innervation to the mandibular and sublingual salivary glands, and to the lacrimal gland (tear production).

How does the special sense of taste travel in the facial nerve?

Via the chorda tympani.

What taste sensation is carried by the chorda tympani of the facial nerve?

Special taste sensation from the rostral two-thirds of the tongue.

Through which opening does the facial nerve exit the neurocranium, and through which canal does it pass?

It exits via the internal acoustic meatus and passes through the facial canal in the petrosal portion of the temporal bone.

Why may lesions in the middle ear cause dysfunction of CN VII?

The portion of the facial canal adjacent to the tympanic cavity lacks a bony wall, and the nerve is separated from the cavity by only a few micrometres of loose connective tissue.

What condition is a common cause of facial nerve dysfunction in dogs with floppy ears (e.g., cocker spaniel)?

Otitis media.

What is a clinical sign of complete facial paralysis, as shown in the horse with otitis media?

Complete right facial paralysis (drooping of the right side of the face).

What can cause compression of the buccal branches of the facial nerve in horses?

Prolonged lateral recumbency for surgery (compression at the ramus of the mandible).

What are the two functions of the vestibulocochlear nerve (CN VIII)?

Hearing and vestibular (balance) function.

After passing through the internal acoustic meatus, into which two branches does CN VIII divide?

The vestibular and cochlear branches.

Which cranial nerve provides motor innervation to the stylopharyngeus muscle, and what is the special function of this muscle?

The glossopharyngeal nerve (CN IX). It is the only pharyngeal muscle that dilates the pharynx during swallowing.

What are the sensory functions of the glossopharyngeal nerve (CN IX)?

General sensory to the pharynx, palate, and caudal one-third of the tongue; taste (special sensory) to the caudal one-third of the tongue.

What is the motor function of the glossopharyngeal nerve (CN IX)?

Motor to pharyngeal muscles (via the pharyngeal plexus

What is the parasympathetic function of the glossopharyngeal nerve (CN IX)?

Supplies parasympathetic innervation to the parotid salivary gland.

What clinical sign results from damage to the glossopharyngeal nerve?

Difficulty in swallowing.

Through which opening does the vagus nerve (CN X) exit the skull, and how does it travel down the neck?

It exits through the jugular foramen and travels down the neck in the vagosympathetic trunk.

What motor contribution does the vagus nerve (CN X) make in the pharynx?

It contributes motor fibres to the pharyngeal plexus (along with CN IX) to innervate the caudal pharyngeal muscles.

What is the function of the cranial laryngeal nerve (a branch of the vagus)?

Motor to the cricothyroid muscle to adjust tension in the vocal cords; sensory to the larynx rostral to the vocal cords.

Describe the path of the left and right recurrent laryngeal nerves

Left — around the aortic arch and back up the trachea to the larynx. Right — around the right subclavian artery and up the trachea to the larynx.

What is the function of the recurrent laryngeal nerves (which terminate as caudal laryngeal nerves)?

Both are motor to all cricoarytenoid muscles and sensory to the larynx caudal to the vocal cords.

What parasympathetic functions does the vagus nerve (CN X) provide?

Parasympathetic innervation to smooth muscle in the thorax (heart, trachea, bronchi, esophagus) and in the abdomen (the gut).

What are the two components of the spinal accessory nerve (CN XI), and where does each originate?

Cranial component — from nuclei in the medulla oblongata. Spinal component — from 4–5 cervical segments of the spinal cord.

What does the cranial component of the accessory nerve (CN XI) do?

Combines with the vagus nerve to give it motor fibres to the larynx.

What muscles are innervated by the spinal component of the accessory nerve (CN XI)?

Brachiocephalicus, trapezius, and sternocephalicus muscles.

What muscles are innervated by the hypoglossal nerve (CN XII)

The extrinsic and intrinsic muscles of the tongue.