Cranial nerves Flashcards
Where are the GSE cell bodies of CN III located?
Oculomotor nucleus in the rostral mesencephalon at the level of the rostral colliculi
The oculomotor nucleus is responsible for innervating several extraocular muscles.
What muscles does CN III innervate?
- Medial rectus
- Dorsal rectus
- Ventral rectus
- Ventral oblique
- Levator palpebrae superioris
These muscles control eye movement and eyelid elevation.
How does CN IV exit the cranial cavity?
Through the orbital fissure
In some horses, it may exit through the trochlear foramen.
What is unique about CN IV regarding muscle innervation?
It is the only cranial nerve with GSE neurons that innervate a muscle solely on the side opposite its nucleus
This means that the dorsal oblique muscle is innervated from the opposite side of the brain.
What muscles does CN VI innervate?
- Lateral rectus
- Retractor bulbi
These muscles are involved in eye movement.
What is the physiological response of nystagmus?
A move to the right results in fast phase jerk to the right
This involves coordinated movement of the eyes in response to head movement.
What results from lesions of CN VI?
Paralysis of lateral rectus leading to medial strabismus
Medial strabismus is characterized by the eye deviating medially.
What are the GSE cell bodies of CN V located?
In the motor nucleus in the pons
The trigeminal nerve is responsible for sensations in the face and motor functions such as biting and chewing.
What muscles does CN VII innervate?
- Muscles of facial expression
- Caudal digastricus
These muscles are responsible for movements such as smiling and frowning.
What is the function of the nucleus ambiguous?
Contains GSE neuronal cell bodies for CN IX, X, and XI
This nucleus plays a crucial role in regulating muscles involved in swallowing and speech.
What branches does CN IX provide?
Pharyngeal branches to pharyngeal muscles
These branches form part of the pharyngoesophageal plexus with CN X.
How does CN X exit the cranial cavity?
Through the jugular foramen
It is involved in various autonomic functions.
What does the internal branch of CN XI join?
Joins the vagus nerve
The accessory nerve has both cranial and spinal roots.
What does the external branch of CN XI innervate?
- Intrinsic muscles of the larynx
- Cervical and cranial thoracic esophagus
- Trapezius
- Sternocephalicus
- Cleidocephalicus
These muscles are involved in neck movement and swallowing.
Where are the GSE cell bodies of CN XII located?
In the motor nucleus in the medulla
This nerve is primarily responsible for tongue movement.
What muscles does CN XII innervate?
- Styloglossus
- Hyoglossus
- Genioglossus
- Intrinsic tongue muscles
- Geniohyoideus
These muscles are essential for movements such as speaking and swallowing.
What cranial nerves are involved in the parasympathetic GVE LMN of the Medulla?
CN VII, IX, X, XI
Where are the preganglionic GVE LMN nuclei located in relation to the hypoglossal nucleus?
Dorsal, adjacent to the floor of the fourth ventricle, and lateral to the hypoglossal nucleus
What is the location of the parasympathetic nucleus for CN VII?
Rostral in the medullary column
What do the preganglionic axons of CN VII join to enter the internal acoustic meatus?
CN VII GSE motor neurons
What structure do the preganglionic axons of CN VII join with to form the nerve of the pterygoid canal?
Major petrosal nerve and deep petrosal nerve
Where do the preganglionic parasympathetic axons of CN VII synapse?
Pterygopalatine ganglion
What glands are innervated by the ganglionic axons from CN VII?
- Lacrimal gland
- Gland of the 3rd eyelid
- Palatine glands
- Lateral and mucosal nasal glands
What does the chorda tympani branch off from in CN VII?
Other preganglionic axons within the facial canal
What nerve does the chorda tympani join to synapse on sublingual and mandibular ganglia?
Lingual nerve
What glands are innervated by the CN VII ganglionic axons after synapsing on sublingual and mandibular ganglia?
Sublingual and mandibular salivary glands
Where is the parasympathetic nucleus for CN IX located?
Just caudal to the PS nucleus of CN VII
What do the preganglionic axons of CN IX join to form a motor component?
GSE axons from nucleus ambiguous
Where do the preganglionic axons of CN IX terminate?
Otic ganglion
What glands are innervated by the ganglionic axons from CN IX?
- Parotid gland
- Zygomatic salivary glands
What is the largest nucleus in the parasympathetic medullary column?
Parasympathetic nucleus of CN X
Where do the preganglionic axons of CN X exit after joining GSE axons?
Jugular foramen and tympano-occipital fissure
What structures do the preganglionic axons of CN X follow to reach the heart, lungs, and esophagus?
Branches of the vagus nerve
Where do the preganglionic axons of CN X synapse in the abdomen?
Ganglia within the wall of organs
What system is associated with the GI wall innervation from CN X?
Enteric nervous system
What are the two functional classifications of cranial nerves?
Motor and sensory
Which cranial nerves are associated with the GSE component not associated with branchial arches?
- III (Oculomotor)
- IV (Trochlear)
- VI (Abducent)
- XI (Accessory)
- XII (Hypoglossal)
What is the special visceral efferent (SVE) component?
Motor fibers that innervate muscles associated with branchial arches
Which cranial nerves are associated with the SVE component?
- V (Trigeminal)
- VII (Facial)
- IX (Glossopharyngeal)
- X (Vagus)
- XI (Accessory)
What is the general visceral efferent (GVE) component?
Autonomic nervous system fibers that innervate intrinsic muscles of the eye, heart, vessels, viscera, and glands
Which cranial nerves are associated with the GVE component?
- III (Oculomotor)
- VII (Facial)
- IX (Glossopharyngeal)
- X (Vagus)
- XI (Accessory)
What is the general somatic afferent (GSA) component?
Sensory fibers coming from the skin and musculoskeletal receptors
Which cranial nerves are associated with the GSA component?
- V (Trigeminal)
- VII (Facial)
- X (Vagus)
What is the special somatic afferent (SSA) component?
Fibers for the sense of sight, equilibrium, and hearing
Which cranial nerves are associated with the SSA component?
- II (Optic)
- VIII (Vestibulocochlear)
What is the general visceral afferent (GVA) component?
Sensory fibers from viscera and heart
Which cranial nerves are associated with the GVA component?
- VII (Facial)
- IX (Glossopharyngeal)
- X (Vagus)
What is the special visceral afferent (SVA) component?
Fibers for the sense of taste and smell
Which cranial nerves are associated with the SVA component?
- VII (Facial)
- IX (Glossopharyngeal)
- X (Vagus)
- I (Olfactory)
What type of axons form the olfactory nerves (I cranial nerve)?
Unmyelinated axons surrounded by olfactory ensheathing cells
Where do the olfactory nerves transmit sensations to?
Olfactory bulb (paleocortex) of the cerebrum
What is the function of the vomeronasal organ?
Detects odors associated with reproductive functions
What is the main function of the optic nerve (II cranial nerve)?
Vision
What structure do the optic nerve fibers form after crossing at the optic chiasm?
Optic tract
Which cranial nerve is responsible for innervating the extrinsic muscles of the eye?
Oculomotor nerve (III cranial nerve)
What does the trochlear nerve (IV cranial nerve) innervate?
Dorsal oblique muscle
What are the three branches of the trigeminal nerve (V cranial nerve)?
- Ophthalmic
- Maxillary
- Mandibular
Which nerve carries sensory fibers to the upper eyelid?
Frontal nerve (branch of ophthalmic nerve)
What is the role of the maxillary nerve?
Sensory innervation to the midface and upper teeth
What type of fibers does the mandibular nerve carry?
Special visceral efferent (SVE) and general somatic afferent (GSA)
True or False: The lingual nerve is sensory for the rostral two thirds of the tongue.
True. This is a branch of the mandibular nerve
What muscle does the mylohyoid nerve innervate?
Mylohyoid muscle and rostral belly of the digastricus. This is a branch of the mandibular nerve
Which nerve innervates the tensor tympani muscle? Where does it branch from?
Tensor tympani nerve, a branch of the mandibular nerve.
Fill in the blank: The _______ nerve innervates the tensor veli palatini muscle.
[tensor veli palatini nerve], a branch of the mandibular nerve
What is the function of the auriculotemporal nerve?
Sensory to the external acoustic meatus and tympanic membrane
Branch of the mandibular nerve
What nerve opens the orifice of the auditory tube into the pharynx?
Glossopharyngeal nerve
The glossopharyngeal and vagus nerves are responsible for this function.
What is the main function of the auriculotemporal nerve?
Innervates the salivary parotid gland and provides sensory innervation to the ear and tympanic membrane
It receives postganglionic parasympathetic fibers from the otic ganglion.
What muscles does the abducent nerve innervate?
Retractor bulbi muscle and lateral rectus muscle
It is the sixth cranial nerve.
What components make up the facial nerve?
SVE, GVE, GVA, SVA, GSA
The facial nerve has a complex structure with multiple functional components.
Where does the facial nerve enter the cranial cavity?
Internal acoustic meatus
This is located in the petrosal part of the temporal bone.
What is the role of the major petrosal nerve?
Carries GVE and GVA fibers from the facial nerve
It innervates the lacrimal gland and other structures through the pterygopalatine ganglion.
What does the chorda tympani innervate?
Mandibular and sublingual salivary glands and taste in the rostral two thirds of the tongue
It is a branch of the facial nerve.
What sensory information does the vestibulocochlear nerve transmit?
Stimuli from receptors in the inner ear
It is responsible for balance and hearing.
What is the function of the glossopharyngeal nerve?
Innervates the tonsils, root of the tongue, and forms the pharyngeal plexus
It has components for special visceral and general visceral functions.
Where does the vagus nerve primarily send its sensory fibers?
To the skin of ear canal and visceral organs
It has a significant role in autonomic functions.
What is the composition of the vagus nerve?
SVE, GVE, GVA, SVA, GSA
It has a diverse range of functions related to visceral motor and sensory innervation.
What does the accessory nerve consist of?
Cranial and spinal roots
It innervates specific muscles in the neck and shoulder.
Fill in the blank: The _______ nerve innervates the cricothyroideus muscle.
Cranial laryngeal nerve
Branch of CN X
True or False: The facial nerve has proprioceptive afferents for the mimic muscles of the face.
False
Proprioceptive afferents are thought to be part of the trigeminal nerve.
True or False: The vagus nerve sends branches to the bronchi and heart.
True
What ganglion contains the bodies of sensory neurons for the glossopharyngeal nerve?
Jugular ganglion
This ganglion is located at the level of the jugular foramen.
What is the function of the auricular branch of the vagus nerve?
Sensory innervation to the external ear canal
It joins the facial nerve for this purpose.
What does the cranial laryngeal nerve (GVE and GVA components) innervate?
Mucosa of the larynx and taste buds of the epiglottis
It has both motor and sensory components.
Where are the bodies of the neurons of the spinal roots of the accessory nerve located?
In the motor nucleus of the accessory nerve, dorsolateral portion of the ventral horn of cervical spinal cord segments (C1 to C7)
This location is crucial for the function of the accessory nerve.
What is the pathway of the spinal roots of the accessory nerve?
They leave the spinal cord between the dorsal and ventral roots of cervical spinal nerves, lie dorsal to the denticulate ligament, run rostrally to enter the cranial cavity through the foramen magnum
This pathway is essential for the integration of spinal and cranial nerve functions.
What do the cranial and spinal accessory nerve roots unite to form?
The external branch of the accessory nerve (GSE)
This branch is responsible for motor innervation to specific muscles.
How does the internal branch of the accessory nerve form?
Some fibers from the cranial roots join the vagus nerve
This internal branch becomes part of the recurrent laryngeal nerve (SVE).
What muscles does the external branch of the accessory nerve innervate?
- Trapezius
- Omotransversarius
- Sternocephalicus
- Cleidocephalicus
The sternocephalicus and cleidocephalicus are also innervated by ventral branches of the cervical spinal nerves.
What is the primary function of the hypoglossal nerve (XII cranial nerve)?
Motor to muscles of the tongue (intrinsic and extrinsic) and to genihyoideus and thyrohyoideus muscles
This nerve is crucial for tongue movements and swallowing.
Where does the hypoglossal nerve leave the medulla oblongata?
Laterally to the pyramids via several rootlets
This exit point is vital for its subsequent pathway.
Through which canal does the hypoglossal nerve exit the skull?
Hypoglossal canal
This canal is specifically designed for the passage of the hypoglossal nerve.
What does the hypoglossal nerve communicate with during its course?
The ventral branch of the first cervical spinal nerve forming the cervical loop (ansa cervicalis)
This communication is important for motor control of neck and tongue muscles.
True or False: The hypoglossal nerve has a sensory ganglion.
False
The hypoglossal nerve is primarily a motor nerve and lacks sensory ganglia.
Where are the afferent neurons that respond to stretch in the hypoglossal nerve proposed to be located?
At the dorsal root ganglion of C1
This connection occurs through the ansa cervicalis.
