Cranial Nerves

Question 1

CN I

- Name, number, function, sensory/motor/mixed, central connection(s)

Answer 1

Olfactory
Sensory
Olfaction
Information collected in olfactory epithelium
Fibers of olfactory neurons
Central connection: olfactory bulb

Question 2

CN II

Answer 2

optic
*Sensory
*Transmits information from retina
*Central connection: lateral geniculate nucleus, pretectal nucleus
Vision, pupillary light reflex
The other cranial nerve that does not join up with the brainstem
CN of diencephalon

**Extracranial vs intracranial

Compression to the optic chiasm particularly affects the fibers that are crossing over from the nasal half of each retina.
This produces visual defect affecting the peripheral vision in both eyes, known as abitemporal hemianopia

Question 3

III

Name, number, function, sensory/motor/mixed, central connection(s)

Answer 3

Oculomotor
*MOTOR

*through innervation to different areas, plays a role in- raises/depresses/adducts the eyeball, elevates, abducts and laterally rotates the eyeball, raise upper eyelid

• Central connection: oculomotor nucleus
• Movement of eyeball, elevation of upper lid

(parasympathetic role- the central connection is the Edinger-Westphal nucleus (accessory oculomotor nucleus))

Question 4

The _____ nerve leaves the cranial cavity via the superior orbital fissure.

divisions

Answer 4

III: Oculomotor

-Divides intoSUPERIORandINFERIOR BRANCHES.
Once within the orbital cavity, both branches innervate accessory structures of the eye:
Superior branch Motor innervation to the superior rectus and levator palpabrae superioris.
Inferior branch Motor innervation to the inferior rectus, medial rectus and inferior oblique.
Parasympathetic fibers to the ciliary ganglion, which ultimately innervates the sphincter pupillae and ciliary muscles.

*Parasympathetic
Your sad pupils make my Edinger-Westphal nucleus make my pupils look sad, too.

Question 5

Parasympathetic & Oculomotor

Answer 5

Innervates sphincter pupillae and ciliary muscle of the eyeball via ciliary ganglion
*Central connection: Edinger-Westphal nucleus (accessory oculomotor nucleus)
Pupillary constriction and accommodation

The anatomical organization of the general somatic efferent (GSE) cell columns of the oculomotor nerve (CN III) complex
The Edinger-Westphal nucleus, whose axons (general visceral efferent) serve as preganglionic parasympathetic neurons, innervate the ciliary ganglia. The postganglionic parasympathetic neurons from the ciliary ganglia (not shown in figure) innervate the constrictor muscles of the pupil and the ciliary muscle.

Question 6

IV

Answer 6

• Trochlear
• Motor

*Central connection: trochlear nucleus
Movement of eyeball
Fewest axons, but longest intracranial axon path

Only CN to cross the midline

Arises from thetrochlear nucleusof the brain, emerging from the posterior aspect of the midbrain
Only cranial nerve to exit from the posterior midbrain
It runs anteriorly and inferiorly within thesubarachnoidspacebefore piercing the dura mater adjacent to theposterior clinoid processof the sphenoid bone.
The nerve then moves along the lateral wall of thecavernous sinus(along with the oculomotor nerve, the abducens nerve, the ophthalmic and maxillary branches of the trigeminal nerve and the internal carotid artery) before entering the orbit of the eye viathesuperior orbital fissure.

Origin and distribution of the trochlear nerve (cranial nerve IV) to the superior oblique muscle.

As indicated in the cross section of the brainstem, note that this nerve exits the brain from the dorsal aspect, and it is the only nerve that is crossed.
Arrow indicates direction of movement of the bulb downward and inward.

Question 7

Only CN to emerge from dorsal aspect of midbrain/brainstem

Answer 7

IV: Trochlear

Only CN to cross the midline

Question 8

Examination of the Trochlear Nerve

Answer 8

Examination of the Trochlear Nerve
Examined in conjunction with the oculomotor and abducens nerves by testing the movements of the eye.
Patient is asked to follow a point with their eyes without moving their head.
The target is moved in an ‘H-shape’ and the patient is asked to report any blurring of vision ordiplopia(double vision).

Question 9

Damage to the Trochlear Nerve

Answer 9

The most common cause iscongenital fourth nerve palsy, a condition of abnormal development. This may be curable with surgery.
Other causes of trochlear nerve damage includediabetic neuropathy,thrombophlebitis of the cavernous sinusandraised intracranial pressure

Question 10

V

Answer 10

Trigeminal

• Sensory and Motor
• General sensation and Opening and closing mouth (chew), tension on tympanic membrane

-plays a role in corneal reflex

Question 11

Central connection (for the sensory portion) of the Trigeminal CN:

Answer 11

trigeminal sensory nuclei
Three sensory nuclei(mesencephalic, principal sensory, spinal nuclei of trigeminal nerve)
At the level of thepons, the sensory nuclei merge to form a sensory root
Take up more CNS real estate than any other cranial nerve cell group

Question 12

(V2)

Answer 12

Maxillary Nerve (V2) (of CN 5)

• Maxillary nerve gives rise to 14 terminal branches, which innervate the skin, mucous membranes and sinuses of derivatives of theMAXILLARY PROMINENCE of the 1st pharyngeal arch:
• Lower eyelid and its conjunctiva
• Cheeks and maxillary sinus
• Nasal cavity and lateral nose
• Upper lip
• Upper molar, incisor and canine teeth and the associated gingiva
• Superior palate

Question 13

Abduction def

Answer 13

“Abductionis movement away from the mid-line of the body. … abductor - amuscle that can act to cause anabductionmovement at a joint is called an abductor. For example, the abductor pollicis longusmuscle. toabduct(verb) - e.g. “heabducted his right arm up to shoulder height”.

Question 14

VI

Answer 14

Abducens
Motor
Innervates lateral rectus muscle
*Central connection: abducens nucleus in the pons

Movement of eyeball

Question 15

Sensory Portion of the VII

Answer 15

(: Facial)

Innervates anterior 2/3 of tongue
Central connection: nucleus solitarius (solitary nucleus)
Taste

Question 16

Motor Portion of the VII: Facial

Answer 16

Motor Portion
Innervates muscles of facial expression, stapedius muscle
Central connection: facial nucleus
Facial movement, tension on bones of middle ear

Question 17

Parasympathetic Portion of the VII: Facial

Answer 17

Parasympathetic Portion
Technically falls under motor
Innervates salivary and lacrimal glands via submandibular and pterygopalatine ganglia
Central connection: superior salivatory nucleus
Salivation and lacrimation
Helps with this as a parasympathetic resposne
Production of tears and saliva

Question 18

Intracranial of the Facial

Answer 18

Intracranial
The nerve arises in thePONS
It begins as two roots; a largemotor root, and a smallsensory root.
The two roots travel through the internal acoustic meatus, a 1cm long opening in the petrous part of thetemporal bone. Here, they are in very close proximity to the inner ear.
Still within the temporal bone, the roots leave the internal acoustic meatus, and enter into theFACIAL CANAL
Within the facial canal, three important events occur:
Firstly the two rootsfuseto form the facial nerve.
Next, the nerve forms thegeniculate ganglion, L-shaped collection of fibers and sensory neurons of the facial nerve.
Lastly, the nerve gives rise to thegreater petrosal nerve(parasympathetic fibers to glands), the nerve tostapedius(motor fibers to stapedius muscle), and thechorda tympani(special sensory fibers to the anterior 2/3 tongue).
The facial nerve then exits the facial canal (and the cranium) via thestylomastoid foramen.This is an exit located just posterior to the styloid process of the temporal bone.

Question 19

Facial: Intracranial Damage/Lesions

Answer 19

Intracranial Damage/Lesions
The muscles of facial expression will be paralysed or severely weakened.The other symptoms produced depend on the location of the lesion, and the branches that are affected:
Chorda tympani– reduced salivation and loss of taste on the ipsilateral 2/3 of the tongue.
Nerve to stapedius– ipsilateral hyperacusis (hypersensitive to sound).
Greater petrosal nerve– ipsilateral reduced lacrimal fluid production.
The most common cause of an intracranial lesion of the facial nerve is middle ear pathology – such as a tumor or infection.
If no definitive cause can be found, the disease is termed Bell’s palsy.

Question 20

Nerve to stapedius damage

Answer 20

VII: Facial

Nerve to stapedius– ipsilateral hyperacusis (hypersensitive to sound).

Question 21

VIII:

Answer 21

Vestibulocochlear
Sensory
Innervates vestibular apparatus, cochlea
Central connection: vestibular nuclei, cochlear nuclei
Vestibular sensation (position and movement of head), hearing

Question 22

VIII: Vestibulocochlear damage

Answer 22

Vestibular neuritis: inflammation of thevestibular branchof the vestibulocochlear nerve.
Some cases are thought to be due to reactivation of the herpes simplex virus.
It presents with symptoms of vestibular nerve damage:
Vertigo– a false sensation thatoneself or the surroundings are spinning or moving.
Nystagmus– a repetitive, involuntary to-and-fro oscillation of the eyes.
Loss of equilibrium(especially in low light).
Nauseaandvomiting.
The condition is usually self-resolving. Treatment is symptomatic, usually in the form of anti-emetics or vestibular suppressants

Question 23

inflammation of the_____ of the vestibulocochlear nerve leads to Vestibular neuritis:

Answer 23

vestibular branch

Question 24

Tinnitus

Answer 24

The perception of chronic tinnitus has also been associated with hyperactivity in the central auditory system, especially in the auditory cortex.
In such cases, the tinnitus is thought to be triggered by damage to the cochlea (the peripheral hearing structure) or the vestibulocochlear nerve.

Question 25

IX: Glossopharyngeal

Answer 25

One of the smallest cranial nerves Has many functional components: Taste Sensation from 1/3 of tongue Sensation from pharyngeal wall Sensation from carotid sinus (baroceptors/blood pressure) Sensation from external ear Branchiomotor innervation of the stylopharyngeus muscle (swallowing) Parasympathetic innervation to parotid gland (major salivary gland)

Question 26

Functional parts of the IX: Glossopharyngeal

Answer 26

Functional parts SVA (special visceral afferent)- taste Inferior glossopharyngeal ganglion (or solitary nucleus) GVA (general visceral afferent)- sensation from posterior tongue, pharyngeal wall, carotid sinus Inferior glossopharyngeal ganglion GSA (general somatic afferent)- sensation from external ear Superior glossopharyngeal ganglion *SVE (special visceral efferent)- branchiomotor to stylopharyngeus muscle -Nucleus ambiguus GVE (general visceral efferent)- parasympathetic to parotid (salivary gland) Inferior salivatory nucleus

Question 27

IX: Glossopharyngeal very important to help with

Answer 27

swallowing

Question 28

IX: Glossopharyngeal

Answer 28

Supplies sensory innervation to the oropharynx, and thus carries the AFFERENT information for the gag reflex. When a foreign object touches the back of the mouth, this stimulates CNIX, beginning the reflex. The efferent nerve in this process is the vagus nerve. An absent gag reflex signifies damage to the glossopharyngeal nerve.

Question 29

X: Vagus

Answer 29

Large nerve Largest !!! Cranial nerve Has the most extensive distribution in the body of all cranial nerves Innervates all the way down into the abdomen Also has 5 functional components like the glossopharyngeal nerve (SVA, GVA, GSA, SVE, GVE) 2 rootlets that originate from the brain and join together

Question 30

X: Vagus (In the Head)

Answer 30

In the Head Originates from the medulla of the brainstem. Exits the cranium via the jugular foramen, with the glossopharyngeal and accessory nerves (CN IX and XI respectively). Within the cranium, the auricular branch arises. This supplies sensation to the posterior part of the external auditory and canal external ear.

Question 31

X: Vagus = In the Neck

Answer 31

In the Neck Passes into the carotid sheath, travelling inferiorly with the internal jugular vein and common carotid artery. At the base of the neck, the right and left nerves have differing pathways: The right vagus nerve passes anterior to the subclavian artery and posterior to the sternoclavicular joint, entering the thorax. The left vagus nerve passes inferiorly between the left common carotid and left subclavian arteries, posterior to the sternoclavicular joint, entering the thorax.

Question 32

X: Vagus - Several branches arise in the neck:

Answer 32

Several branches arise in the neck: Pharyngeal branches – Provides motor innervation to the majority of the muscles of the pharynx and soft palate. Superior laryngeal nerve – Splits into internal and external branches. The external laryngeal nerve innervates the cricothyroid muscle of the larynx. The internal laryngeal provides sensory innervation to the laryngopharynx and superior part of the larynx. Recurrent laryngeal nerve (right side only) – Hooks underneath the right subclavian artery, then ascends towards to the larynx. It innervates the majority of the intrinsic muscles of the larynx.

Question 33

X: Vagus - In the Thorax

Answer 33

In the Thorax The right vagus nerve forms the posterior vagal trunk, the left forms the anterior vagal trunk.  Branches from the vagal trunks contribute to the formation of the oesophageal plexus, which innervates the smooth muscle of the oesophagus. Two other branches arise in the thorax: Left recurrent laryngeal nerve – hooks under the arch of the aorta, ascending to innervate the majority of the intrinsic muscles of the larynx. Cardiac branches – these innervate regulate heart rate and provide visceral sensation to the organ. This leads to ? Referred pain ? The vagal trunks enter the abdomen via the oesophageal hiatus, (opening in the diaphragm)

Question 34

X: Vagus -In the Abdomen

Answer 34

In the Abdomen In the abdomen, the vagal trunks terminate by dividing into branches that supply the oesophagus, stomach and the small and large bowel (up to the splenic flexure).

Question 35

X: Vagus

Answer 35

Sensory Innervates pharynx, larynx, trachea, esophagus, external ear Central connection: trigeminal sensory nucleus General sensation Sensory (special sensory) Innervates thoracic and abdominal viscera, aortic bodies, aortic arch Central connection: solitary nucleus Visceral sensation, chemoreception, baroreception Motor Innervates soft palate, pharynx, larynx, upper esophagus Central connection: nucleus amibiguus Speech, swallowing Parasympathetic Innervates thoracic and abdominal viscera Central connection: dorsal motor nucleus of vagus Innervation of cardiac muscle, smooth muscle, and glands of cardiovascular system, respiratory, and gastrointestinal tracts For example, in the stomach, the vagus nerve increases the rate of gastric emptying, and stimulates acid production.

Question 36

X: Vagus - Sensory

Answer 36

Sensory Innervates pharynx, larynx, trachea, esophagus, external ear Central connection: trigeminal sensory nucleus General sensation

Question 37

XI: (Spinal) Accessory

Answer 37

Motor Innervates sternomastoid and trapezius muscle Central connection: spinal cord Movement of head and shoulder Examined by asking the patient to rotate their head and shrug their shoulders, both normally and against resistance.

Question 38

XI: Accessory - why should not call cranial

Answer 38

Originally believed to have two roots- cranial and spinal Turns out, the cranial root is actually mostly made of vagal nerve fibers The spinal root gets fibers from the spinal accessory nucleus of the ventral cervical spinal cord So, XI is not the most cranial Cranial nerve

Question 39

XI: Accessory

Answer 39

slide 27ish through 31

Question 40

XII: Hypoglossal

Answer 40

Motor Innervates intrinsic and extrinsic muscles of tongue Central connection: hypoglossal nucleus (medulla oblongata) Found in the medulla Movement of tongue Not just talking or chewing Varies in size among animals: in cats/dogs it will be smaller because they do not make elaborate vowels/speech. In a whale it will be even smaller Passes laterally across the posterior cranial fossa, within the subarachnoid space. Exits the cranium via the hypoglossal canal. Now extracranial, the nerve receives a branch of the cervical plexus that conducts fibers from C1/C2 spinal nerve roots. They do not combine with the hypoglossal nerve – they merely travel within its sheath. It then passes inferiorly to the angle of the mandible, crossing the internal and external carotid arteries, and moving in an anterior direction to enter the tongue.

Question 41

XII: Hypoglossal (Role of the C1/C2 Roots)

Answer 41

Role of the C1/C2 Roots The C1/C2 roots that travel with the hypoglossal nerve also have a motor function. Branch off to innervate the geniohyoid (elevates the hyoid bone) and thryohyoid (depresses the hyoid bone) muscles. Another branch containing C1/C2 fibers descends to supply the ansa cervicalis – a loop of nerves that is part of the cervical plexus. From the ansa cervicalis, nerves arise to innervate the omohyoid, sternohyoid and sternthyroid muscles. These muscles all act to depress the hyoid bone.

Question 42

XII: Hypoglossal

Answer 42

The hypoglossal nerve is examined by asking the patient to protrude their tongue. Other movements such as asking the patient to push their tongue against their cheek and feeling for the pressure on the opposite side of the cheek may also be used if damage is suspected. Patients will present with deviation of the tongue towards the damaged side on protrusion, as well as possible muscle wasting and fasciculations (twitching of isolated groups of muscle fibers) on the affected side.

Question 43

Cranial Nerves attach directly to forebrain_____(while the rest attach to the midbrain/brainstem Remember that sensory nerves are afferents and motor nerves are efferents Pons: nuclei for CN V, VI, VII Major part contains neurons that send axons to cerebellum Motor control, especially of upper limb Midbrain: nuclei for CN III and IV

Answer 43

I and II attach directly to forebrain, while the rest attach to the midbrain/brainstem Remember that sensory nerves are afferents and motor nerves are efferents Pons: nuclei for CN V, VI, VII Major part contains neurons that send axons to cerebellum Motor control, especially of upper limb Midbrain: nuclei for CN III and IV

Question 44

why is the image on slide 2 a lie

Answer 44

Nearly Impossible to See the Olfactory Nerve (see slide 6)

Question 45

olfactory tract

Answer 45

The lateral stria sends carries the axons to the primary olfactory cortex. The medial stria carry the axons across the medial plane of the anterior commissure where they meet the olfactory bulb of the opposite side.

Question 46

Most CN nerves are wrapped in by epi-, peri- and endoneurium... what CN are not?

Answer 46

- optic: Due to its unique anatomical relation to the brain, the optic nerve is surrounded by cranial meninges - Olfactory nerve too

Question 47

bitemporal hemianopia*

Answer 47

CN II Compression to the optic chiasm particularly affects the fibers that are crossing over from the nasal half of each retina. This produces visual defect affecting the peripheral vision in both eyes, known as a bitemporal hemianopia

Question 48

II: Optic: Extracranial

Answer 48

Extracranial The optic nerve is formed by the convergence of axons from the RETINAL GANGLION CELLS Receive impulses from the photoreceptors of the eye (the rods and cones). The nerve leaves the bony orbit via the OPTIC CANAL, a passageway through the sphenoid bone. It enters the cranial cavity, running along the surface of the middle cranial fossa (in close proximity to the pituitary gland).

Question 49

Intracranial (CN II)

Answer 49

CN II Within the middle cranial fossa, the optic nerves from each eye unite to form the OPTIC CHIASM. At the chiasm, fibers from the nasal (medial) half of each retina cross over, forming the optic tracts So, optic nerve is before crossing, optic tract is after crossing

Question 50

CN III innervates what to affect what?

Answer 50

*Innervates superior/inferior/medial rectus muscles (raises/depresses/adducts the eyeball), inferior oblique muscle (elevates, abducts and laterally rotates the eyeball) , levator palpebrae superioris muscle (raise upper eyelid)

Question 51

CN III innervates

Answer 51

* superior rectus muscles * inferior rectus muscles * medial rectus muscles * inferior oblique muscle * levator palpebrae superioris muscle

Question 52

CN 4 innervates

Answer 52

Innervates a single muscle, the superior oblique muscle A muscle of oculomotion. As the fibers from the trochlear nucleus cross in the midbrain before they exit, the trochlear neurons innervate the CONTRALATERAL superior oblique.

Question 53

***Only cranial nerve to exit from the posterior midbrain

Answer 53

CN 4

Question 54

diplopia

Answer 54

double vision | CN 4

Question 55

Sensory Portion of CN V - innervates

Answer 55

Sensory Portion | Innervates face, scalp, cornea, nasal cavity, oral cavity, cranial dura mater

Question 56

Motor Portion of CN V

Answer 56

*Innervates muscles of mastication, tensor tympani *Central connection (for motor): trigeminal motor nucleus At the level of the PONS, the motor nucleus continues to form a motor root. The motor root passes inferiorly to the sensory root, along the floor of the trigeminal cave. Its fibers are only distributed to the mandibular division. Opening and closing mouth (chew), tension on tympanic membrane

Question 57

CN V - divisions ****

Answer 57

In middle cranial fossa, the sensory root expands into the trigeminal ganglion. The peripheral aspect of the trigeminal ganglion gives rise to 3 divisions: ophthalmic (V1), maxillary(V2) and mandibular (V3).

Question 58

trigeminal ganglion | CV V

Answer 58

The trigeminal ganglion is located lateral to the cavernous sinus, in a depression of the temporal bone (trigeminal cave)

Question 59

(V1)

Answer 59

``` Ophthalmic Nerve (V1) Gives rise to 3 terminal branches: frontal, lacrimal and nasociliary, which innervate the skin and mucous membrane of derivatives of the frontonasal prominence derivatives: Forehead and scalp Frontal and ethmoidal sinus Upper eyelid and its conjunctiva Cornea (see clinical relevance) Dorsum of the nose ```

Question 60

V3

Answer 60

CN V: Mandibular Nerve Mandibular nerve gives rise to four terminal branches in the infra-temporal fossa: buccal nerve, inferior alveolar nerve, auricotemporal nerve and lingual nerve. These branches innervate the skin, mucous membrane and striated muscle derivatives of the mandibular prominence of the 1st pharyngeal arch. Sensory supply: Mucous membranes and floor of the oral cavity External ear Lower lip Chin Anterior 2/3 of the tongue (only general sensation; special taste sensation supplied by the chorda tympani, a branch of the facial nerve) Lower molar, incisor and canine teeth and the associated gingiva Motor Supply: Muscles of mastication; medial pterygoid, lateral pterygoid, masseter, temporalis Anterior belly of the digastric muscle and the mylohyoid muscle (these are suprahyoid muscles) Tensor veli palatini Tensor tympani

Question 61

The corneal reflex

Answer 61

The corneal reflex is the involuntary blinking of the eyelids – stimulated by tactile, thermal or painful stimulation of the cornea. In the corneal reflex, the ophthalmic nerve (V1) acts as the afferent – detecting the stimuli. The facial nerve is the efferent limb, causing contraction of the orbicularis oculi muscle. If the corneal reflex is absent, it is a sign of damage to the trigeminal/ophthalmic nerve, or the facial nerve.

Question 62

VI central connections

Answer 62

Central connection: abducens nucleus in the pons -Exits at border between pons and medulla -Enters the subarachnoid space and pierces the dura mater to run in a space known as Dorello’s canal.   Travels through the cavernous sinus at the tip of the petrous temporal bone, before entering the orbit of the eye through the SUPERIOR ORBITAL FISSURE

Question 63

VI

Answer 63

Any pathology which leads to downward pressure on the brainstem (e.g. brain tumor, extradural hematoma) can lead to the nerve becoming stretched along the clivus of the skull.  Wernicke-Korsakoff syndrome (caused by thiamine deficiency and generally seen in alcoholics) is a rare cause of sixth nerve palsy. Other causes of abducens nerve damage include diabetic neuropathy Patients will present with diplopia and a medially rotated eye which cannot be abducted past the midline. The patient may attempt to compensate by rotating their head to allow the eye to look sideways.

Question 64

VII

Answer 64

both sensory and motor

Question 65

Extracranial Damage/Lesions VII: Facial

Answer 65

Extracranial Damage/Lesions Only the motor function of the facial nerve is affected, resulting in paralysis or severe weakness of the muscles of facial expression. There are various causes of extracranial lesions of the facial nerve: Parotid gland pathology – e.g a tumour, parotitis, surgery. Infection of the nerve  – particularly by the herpes virus. Compression during forceps delivery – the neonatal mastoid process is not fully developed, and does not provide complete protection of the nerve. Idiopathic – If no definitive cause can be found, the disease is termed Bell’s palsy.

Question 66

VIII: Vestibulocochlear divsions (does not seem that important to alex)

Answer 66

The vestibular and cochlear portions of the vestibulocochlear nerve are functionally discrete, and so they originate from different nuclei in the brain: Vestibular component – arises from the vestibular nuclei complex in the pons and medulla. Cochlear component – arises from the ventral and dorsal cochlear nuclei, situated in the inferior cerebellar peduncle. Both sets of fibers combine in the pons to form the vestibulocochlear nerve. The nerve emerges from the brain at the cerebellopontine angle and exits the cranium via the internal acoustic meatus of the temporal bone

Question 67

IX: Glossopharyngeal | *******functional parts ********

Answer 67

SVA (special visceral afferent)- taste Inferior glossopharyngeal ganglion (or solitary nucleus) GVA (general visceral afferent)- sensation from posterior tongue, pharyngeal wall, carotid sinus Inferior glossopharyngeal ganglion GSA (general somatic afferent)- sensation from external ear Superior glossopharyngeal ganglion SVE (special visceral efferent)- branchiomotor to stylopharyngeus muscle Nucleus ambiguus GVE (general visceral efferent)- parasympathetic to parotid (salivary gland) Inferior salivatory nucleus

Question 68

IX: Glossopharyngeal

Answer 68

slide 8 helps One of the smallest cranial nerves Has many functional components: Taste Sensation from 1/3 of tongue Sensation from pharyngeal wall Sensation from carotid sinus (baroceptors/blood pressure) Sensation from external ear Branchiomotor innervation of the stylopharyngeus muscle (swallowing) Parasympathetic innervation to parotid gland (major salivary gland) The glossopharyngeal nerve originates in the medulla oblongata It emerges from the anterior aspect of the medulla, moving laterally in the posterior cranial fossa.   The nerve leaves the cranium via the jugular foramen. At this point, the tympanic nerve arises. Sensory from middle ear and *The glossopharyngeal nerve terminates by splitting into several sensory branches: Pharyngeal branch – combines with fibers of the vagus nerve to form the pharyngeal plexus. It innervates the mucosa of the oropharynx (middle part of throat behind mouth) Lingual branch – provides the posterior 1/3 of the tongue with general and taste sensation Tonsillar branch – forms a network of nerves, known as the tonsillar plexus, which innervates the palatine tonsils.

Question 69

• SVA

Answer 69

* SVA (special visceral afferent)- taste | * Inferior glossopharyngeal ganglion (or solitary nucleus)

Question 70

IX: *

Answer 70

Glossopharyngeal Sensory (special sensory) Innervates posterior 1/3 of tongue, carotid body, carotid sinus Central connection: solitary nucleus Taste, chemoreception, baroreception Motor Innervates stylopharyngeus muscle (acts to shorten and widen the pharynx, and elevate the larynx during swallowing) Central connection: nucleus ambiguus Swallowing *Parasympathetic Innervates parotid salivary gland via otic ganglion Central connection: inferior salivatory nucleus Salivation Supplies sensory innervation to the oropharynx, and thus carries the afferent information for the gag reflex. When a foreign object touches the back of the mouth, this stimulates CNIX, beginning the reflex. The efferent nerve in this process is the vagus nerve. An absent gag reflex signifies damage to the glossopharyngeal nerve.

Question 71

GVA

Answer 71

GVA (general visceral afferent)- sensation from posterior tongue, pharyngeal wall, carotid sinus

Question 72

*SVE

Answer 72

* SVE (special visceral efferent)- branchiomotor to stylopharyngeus muscle - Nucleus ambiguus

Question 73

X: Vagus

Answer 73

Large nerve Largest !!! Cranial nerve Has the most extensive distribution in the body of all cranial nerves Innervates all the way down into the abdomen Also has 5 functional components like the glossopharyngeal nerve (SVA, GVA, GSA, SVE, GVE) 2 rootlets that originate from the brain and join together In the Head Originates from the medulla of the brainstem. Exits the cranium via the jugular foramen, with the glossopharyngeal and accessory nerves (CN IX and XI respectively). Within the cranium, the auricular branch arises. This supplies sensation to the posterior part of the external auditory and canal external ear. In the Neck Passes into the carotid sheath, travelling inferiorly with the internal jugular vein and common carotid artery. At the base of the neck, the right and left nerves have differing pathways: The right vagus nerve passes anterior to the subclavian artery and posterior to the sternoclavicular joint, entering the thorax. The left vagus nerve passes inferiorly between the left common carotid and left subclavian arteries, posterior to the sternoclavicular joint, entering the thorax.

Question 74

exits out the jugular foramen

Answer 74

glossopharyngeal and accessory nerves (CN IX and XI respectively). Within the cranium, the auricular branch arises. X: Vagus XI

Question 75

X: Vagus

Answer 75

Several branches arise in the neck: Pharyngeal branches – Provides motor innervation to the majority of the muscles of the pharynx and soft palate. Superior laryngeal nerve – Splits into internal and external branches. The external laryngeal nerve innervates the cricothyroid muscle of the larynx. The internal laryngeal provides sensory innervation to the laryngopharynx and superior part of the larynx. Recurrent laryngeal nerve (right side only) – Hooks underneath the right subclavian artery, then ascends towards to the larynx. It innervates the majority of the intrinsic muscles of the larynx. In the Thorax The right vagus nerve forms the posterior vagal trunk, the left forms the anterior vagal trunk.  Branches from the vagal trunks contribute to the formation of the oesophageal plexus, which innervates the smooth muscle of the oesophagus. Two other branches arise in the thorax: Left recurrent laryngeal nerve – hooks under the arch of the aorta, ascending to innervate the majority of the intrinsic muscles of the larynx. Cardiac branches – these innervate regulate heart rate and provide visceral sensation to the organ. This leads to ? Referred pain ? The vagal trunks enter the abdomen via the oesophageal hiatus, (opening in the diaphragm) In the Abdomen In the abdomen, the vagal trunks terminate by dividing into branches that supply the oesophagus, stomach and the small and large bowel (up to the splenic flexure).

Question 76

X: Vagus

Answer 76

Sensory Innervates pharynx, larynx, trachea, esophagus, external ear Central connection: trigeminal sensory nucleus General sensation Sensory (special sensory) Innervates thoracic and abdominal viscera, aortic bodies, aortic arch Central connection: solitary nucleus Visceral sensation, chemoreception, baroreception Motor Innervates soft palate, pharynx, larynx, upper esophagus Central connection: nucleus amibiguus Speech, swallowing Parasympathetic Innervates thoracic and abdominal viscera Central connection: dorsal motor nucleus of vagus Innervation of cardiac muscle, smooth muscle, and glands of cardiovascular system, respiratory, and gastrointestinal tracts For example, in the stomach, the vagus nerve increases the rate of gastric emptying, and stimulates acid production.

Question 77

helps with swallowing

Answer 77

X: Vagus and more!!

Question 78

should not be called a cranial nerve

Answer 78

XI: (Spinal) Accessory | and really olfactory

Question 79

Cranial Part Immediately after leaving the skull, cranial part combines with the vagus nerve (CN X) at the inferior ganglion of vagus nerve (a ganglion is a collection of nerve cell bodies). The fibers from the cranial part are then distributed through the vagus nerve. For this reason, the cranial part of the accessory nerve is considered as part of the ________

Answer 79

vagus nerve.

Question 80

XII: Hypoglossal

Answer 80

Motor Innervates intrinsic and extrinsic muscles of tongue Central connection: hypoglossal nucleus (medulla oblongata) Found in the medulla Movement of tongue Not just talking or chewing Varies in size among animals: in cats/dogs it will be smaller because they do not make elaborate vowels/speech. In a whale it will be even smaller Passes laterally across the posterior cranial fossa, within the subarachnoid space. Exits the cranium via the hypoglossal canal. Now extracranial, the nerve receives a branch of the cervical plexus that conducts fibers from C1/C2 spinal nerve roots. They do not combine with the hypoglossal nerve – they merely travel within its sheath. It then passes inferiorly to the angle of the mandible, crossing the internal and external carotid arteries, and moving in an anterior direction to enter the tongue.

Question 81

Role of the C1/C2 Roots The C1/C2 roots that travel with the hypoglossal nerve also have a motor function. Branch off to innervate the geniohyoid (elevates the hyoid bone) and thryohyoid (depresses the hyoid bone) muscles. Another branch containing C1/C2 fibers descends to supply the ansa cervicalis – a loop of nerves that is part of the cervical plexus. From the ansa cervicalis, nerves arise to innervate the omohyoid, sternohyoid and sternthyroid muscles. These muscles all act to depress the hyoid bone

Answer 81

Role of the C1/C2 Roots The C1/C2 roots that travel with the hypoglossal nerve also have a motor function. Branch off to innervate the geniohyoid (elevates the hyoid bone) and thryohyoid (depresses the hyoid bone) muscles. Another branch containing C1/C2 fibers descends to supply the ansa cervicalis – a loop of nerves that is part of the cervical plexus. From the ansa cervicalis, nerves arise to innervate the omohyoid, sternohyoid and sternthyroid muscles. These muscles all act to depress the hyoid bone

Question 82

sensory nerves are ____ and motor nerves are _____

Answer 82

sensory nerves are afferents and motor nerves are efferents

Question 83

___ nerves are afferents and ___ nerves are efferents

Answer 83

sensory nerves are afferents and motor nerves are efferents

Question 84

Shortest cranial nerve

Answer 84

CN1 Does not emanate from brainstem CN of telencephalon Olfactory receptor cells are bipolar nerve cells with a peripherally directed dendrite which terminates in a knob from which numerous cilia project. The olfactory chemoreceptors are located on these cilia. Synapse on mitral cells of olfactory bulb *Olfactory tract: Unmyelinated, covered by olfactory Schwann cells (olfactory ensheathing glia) Nerve capable of regeneration Information passed on to olfactory cortex and amygdala Damage --> Inability to smell Age: the older you get, the less you can smell Possibly due to repeated damage and infections over time

Question 85

Oculomotor: originates, path

Answer 85

* Originates from the anterior aspect of the midbrain. - Moves anteriorly, passing below the posterior cerebral artery, and above the superior cerebellar artery. - Pierces the dura mater and enters the lateral aspect of the cavernous sinus. *The nerve leaves the cranial cavity via the superior orbital fissure.

Question 86

CNII does not join up with the brainstem | -is it part of the CNS or PNS?

Answer 86

The other cranial nerve that does not join up with the brainstem CN of diencephalon Technically part of the CNS rather than the PNS because it is derived from an out-pouching of the diencephalon (optic stalks) during embryonic development.