Module 12: Cranial Nerves, Anatomy & physiology of normal swallow

Embryological Development: Branchial Origin of Speech-related Muscles (M12: 11, pic)(notes 12-2)

First Branchial Arch:(mandibular): CN V- Trigeminal : Mastication Muscles. temporalis, masseter media, lateral pterygoid, mylohyoid, anterior belly of digastric, tensor tympani, tensor veli palatini Second Branchial Arch: CN VII Facial : Facial expression muscles. Buccinator, auricularis, frontalis, platysma, orbicularis oris, orbicularis oculi, stapedius, stylohyoid, posterior belly of digastric Third Branchial Arch: CN IX Glosso- pharyngeal: stylopharyngeus Fourth & sixth Branchial Arch: CN X Vagus: Pharyngeal (4) & intrinsic laryngeal (6). Cricothyroid, levator veli palatini, pharyngeal constrictors, intrinsic laryngeal muscles - Early in human embryological development, 6 arches emerge. 1st & 4th well marked, 5th arch disappears during development, 6th arch present but not obvious. - Each of the Branchial Arches are related to a specific set of muscles. The muscles of facial expression. 3rd Arch - Stylopharyngeus. 4th Arch- (derived from) pharyngeal muscles (pharyngeal muscles derived from 4th arch). Intrinsic laryngeal muscles derived from 6th arch.

Foramina in Skull Base (M12: 22, pic)(notes 12-4)

Foramina in skull base- where the cranial nerves take a fixed path & exit the cranium through specific foramina in skull. Location of foramina in skull base.

Different Cranial Nerve Orientation & their Nuclei (M12: 21, pic)(notes 12-4)

Mid-sagittal Brainstem View (1,2,8 not pictured)

Location of Each Muscle & Embryonic Branchial Arch & Innervation by Cranial Nerve (M12: 12, pic)(notes 12-2)

Picture of Fetus further along & Muscle locations

Cranial Nerve VII: Facial: Special Sensory Component (M12: 56, pic)(notes 12-14)

Taste fibers for tongue & palate -Primary sensory neurons in geniculate ganglion -Joined by taste fibers from CN IX and X -Taste fibers split off in the middle ear (chorda tympani) -Joins lingual branch of CN V -Taste fibers terminate in nucleus of tractus solitaius -Fibers distributed to the taste buds of anterior 2/3 of tongue, hard palate and soft palate -Ascending fibers from nucleus solitarius travel to ventro- posterior thalamus, project to cortex (lower end of sensory strip in parietal lobe) - Function- for taste for tongue & palate - Pathway- involves primary sensory neurons in the geniculate ganglion which are joined by taste fibers from CN 9 & 10 (IX , X) - The taste fibers split off in the middle ear Chorda Tympani. - then the fibers join the lingual branch of CN V. - the taste fibers terminate in the nucleus of the Tractus Solitarius - Fibers are distributed to the taste buds in the anterior 2/3rds of the tongue, hard palate & soft palate. - Ascending fibers from Nucleus Solitarius travel to ventroposterior Thalamus & project to the cortex in the lower end of the sensory strip in the parietal lobe.

Medial Pterygoid (see Trigerminal Nerve: Branchial Motor Component) (M12: 40, pic)(notes 12- 10)

The Medial Pterygoid nerve branches off the main trunk then gives of 2 small branches to the Tensor Veli Palatnini & Tensor Tympani. The Medial Pterygoid nerve enters the deep surface of the medial pterygoid muscle. The Massetric Nerve branches from the manibular nerve & supplies the Masseter Muscle.

Olfactory receptors (see Clinical Correlates) (M12: 28)(notes 12-6)

are replaced 30-60 days

Bipolar Cells (see Cranial Nerve II: Optic Nerve) (M12: 29, pic)(notes 12-6,7)

bipolar cells (primary sensory neurons) - information is then passed to the bipolar cells these are the primary sensory neurons in the visual pathway.

Secretomotor fibers (see Cranial Nerve IX: Glossopharyneal) (M12: 63)(notes 12-16,17)

for parotid gland's saliva production

Cranial Nerves III-XII (M12: 17, pic)(notes 12-3)

full detail, nuclei of origin, & classifications graphic

Anosmia (see Clinical Correlates) (M12: 28)(notes 12-6)

impaired ability to smell

Rhinorrhea (see Clinical Correlates) (M12: 28)(notes 12-6)

leakage of CSF through the nose

Hyposmia (see Clinical Correlates) (M12: 28)(notes 12-6)

reduced olfactory sensation

Temporalis & Masseter Muscle (M12: 41, pic)(notes 12- 10)

(Deep & Superficial Parts of Masseter) - Temporalis Muscle- innervated by temporal branch of the mandibular nerve - Masseter Muscle- innervated by mandibular nerve

Ptosis (see Cranial Nerve III: Oculomotor) (M12: 30)(notes 12-7,8)

(droop) of the eyelid

Cranial Nerve VII: Facial Nerve: Visceral Motor Component superior salivatory nucleus lacrimal nucleus (M12: 52, pic)(notes 12-13)

(pic- red& dark orange lines) • Composed of preganglionic autonomic motor neuron cell bodies (known as superior salivatory nucleus & lacrimal nucleus) • Fibers from nucleus travel in the nervus intermedius • Divide in the facial canal becoming - chorda tympani & - greater petrosal nerve - Joins trigeminal fibers to lacrimal & mucosal glands of nasal & oral cavities stimulating secretions

Edinger-Westphal nucleus (CN III) (see 3 Cranial Nerve Nuclei in Midbrain Tegmentum (adult brain)) (M12: 18)(notes 12-3,4)

- (contains) parasympathetic efferents to(innervate the) ciliary muscle & constrictor fibers of the pupil (of the eye)

Trigerminal Nerve: Branchial Motor Component (M12: 40, pic)(notes 12- 10)

- Course of Motor component from the cortex, Pons, Motor mastication nucleus & Trigeminal ganglion. - Just outside the cranium, the motor & sensory branches of the Trigeminal unite to form a short, main trunk called the Mandibular Nerve. The Medial Pterygoid nerve branches off the main trunk then gives of 2 small branches to the Tensor Veli Palatnini & Tensor Tympani. The Medial Pterygoid nerve enters the deep surface of the medial pterygoid muscle. The Massetric Nerve branches from the manibular nerve & supplies the Masseter Muscle. - The 2-3 deep Temporal Nerves branch from Mandibular Nerve & enter the deep surface of the Temporalis Muscle.

Cranial Nerve VII: Facial: Brachial Motor Component (M12: 49, pic)(notes 12-12,13)

- Fibers in Motor Cortex descend to the motor nucleus in the brainstem, curve around the nucleus of the cranial nerve 6, the abducens, & exit the brainstem near the inferior margin of the Pons. - The fibers again join from the nucleus of Tractacellatereous??? & autonomic or Parasympathetic nuclei enter the Internal Auditory Meatus extend through the Petrosal bone facial canal, travels through the tympanic cavity innervating the Stapedius Muscle & exit the skull preceding to innervate the facial muscles, the Stylohyoid , & posterior belly of the digastric.

Cranial Nerve VII: Bilateral & Contralateral Nerve Projections (M12: 50, pic)(notes 12-13)

- Fibers that innervate the lower part of the face receive most corticobulbar fibers from the contralateral hemisphere. - Fibers supplying the upper part of the face receives fibers from both cerebral hemispheres.

Cranial Nerve IX: Glossopharyneal (M12: 67, pic)(notes 12-17,18)

- General Sensory Component Pathway - provides neural sensation for pain & temperature from posterior 1/3 of tongue, skin of external ear & internal surface of tympanic membrane. - Special Sensory Component Pathway- for taste for posterior 1/3 of tongue

Cranial Nerve Nuclei (M12: 15, pic)(notes 12-3)

- Group of nerve cell bodies in the brain, brainstem, or spinal cord serving the particular function (are displayed in diagram)(Except I, II, XI & salivary nucleus) -Note: both left & right nuclei for each cranial nerve listed. ******* Cranial Nerves are Paired ******

Clinical Correlates (M12: 28)(notes 12-6)

- Olfactory receptors- are replaced 30-60 days - damage from Cellular degeneration, skull fracture with CSF rhinorrhea(or leakage of CSF through the nose particularily), & as well as age can induced loss of smell - Anosmia- impaired ability to smell - Hyposmia- reduced olfactory sensation - Hyperosmia- abnormally acute smell - there are Implications of uni- & bilateral lesions - with regard to the sense of smell.

Cranial Nerve VII: Facial: General Sensory Motor Component (M12: 54, pic)(notes 12-13,14)

- Small cutaneous component • Nerve cells in geniculate ganglion in the temporal bone • Impulses travel in nervus intermedius descending in the spinal tract of the trigeminal nerve • Synapse in the upper medulla at the spinal nucleus of the trigeminal • Provides sensation from the wall of the acoustic meatus and surface of the tympanic membrane

Cranial Nerve VI: Abducens (M12: 44, pics)(notes 12- 11)

- Somatic Motor component of the Abducens nerve is highlighted. - Movements of the eyes produced by the 6 Intraocular muscles that are innervated by cranial nerve 6 (Abducens) & also cranial nerve 3 & CN 5. These eye movements allow visual fixations on objects & require a high degree of coordination of movement.

Cranial Nerve IV: Trochlear (M12: 32)(notes 12-8)

- Somatic motor nerve that innervates a single muscle of the eye • Categorization: General somatic efferent • Function: eyeball movement • Nucleus in midbrain tegmentum • Nerve innervates the superior oblique muscle - inward rotation & downward/lateral movement • Lesions cause diplopia (double vision) & weakness of downward gaze - Trochlear Nerve- crosses to the opposite side so the Superior Oblique muscle is innervated by the contralateral Trochlear Nucleus. - Trochlear Nucleus- located in midbrain tegmentum - Activation of the nerve causes the Superior Oblique muscle to contract resulting in inward rotation & downward & lateral movement of the eyeball. - Damage to Trochlear nerve- results in Diplopia(double vision) & weakness of the downward gaze (particularly important when going downstairs)

Mesencephalic Subnucleus (see Cranial Nerve V: Trigeminal ) (M12: 34)(notes 12- 9)

- Trigeminal- (Major sensory nerve of the face & motor nerve that innervates the muscles of mastication. ) Sensory Division- 3 Subnuclei- 1) Mesencephalic Subnucleus- consists of a thin column of primary sensory neurons that carry proprioceptive information from the muscles of mastication.

Pontine Trigeminal Nucleus (see Cranial Nerve V: Trigeminal ) (M12: 34)(notes 12- 9)

- Trigeminal- (Major sensory nerve of the face & motor nerve that innervates the muscles of mastication. ) Sensory Division- 3 Subnuclei- 2) Pontine Trigeminal Nucleus- large group of secondary sensory neurons in the Pons thought to be primarily concerned with discriminative touch sensation from head & face.

Nucleus of Spinal Tract (see Cranial Nerve V: Trigeminal ) (M12: 34)(notes 12- 9)

- Trigeminal- (Major sensory nerve of the face & motor nerve that innervates the muscles of mastication. ) Sensory Division- 3 Subnuclei- 3) Nucleus of Spinal Tract- senses pain & temperature. It is a long column of cells extending from the Pons caudally into the spinal cord where it merges with the dorsal grey matter of the spinal cord.

Cranial Nerve VII: Facial: General Sensory Motor Component (M12: 55, pic)(notes 12-14)

- blue pathway

Cochlear Fibers (see Cranial Nerve VIII: Vestibulocochlear Cochlear Component) (M12: 62, pic)(notes 12-16)

- cochlear fibers divide into 2 branches in pons 1) Dorsal cochlear nucleus 2) Ventral cochlear nucleus -Fibers decussate after cochlear nucleus, a few are ipsilaterally projected as well

Trochlear nucleus (CN IV) (see 3 Cranial Nerve Nuclei in Midbrain Tegmentum (adult brain)) (M12: 18)(notes 12-3,4)

- contains Lower Motors Neurons (that) innervating superior oblique, (eye muscle)- one of the muscles of the eye

Oculomotor nucleus (CN III) (see 3 Cranial Nerve Nuclei in Midbrain Tegmentum (adult brain)) (M12: 18)(notes 12-3,4)

- contains Lower Motors Neurons that control (most of the) eye muscles

Cranial Nerve X: Vagus Nucleus ambiguous (NA) Dorsal (parasympathetic) nucleus Nucleus solitarius (M12: 69)(notes 12-18)

- great importance for voice production & swallowing 3 nuclei in the medulla - Nucleus ambiguous (NA) Axon from cell body of NA has 2 branches: - pharyngeal branch - & laryngeal branch » (laryngeal) Gives rise to recurrent laryngeal nerve & superior laryngeal nerves that (terminates in larynx) - Dorsal (parasympathetic) nucleus • Efferents innervate involuntary muscles of bronchi, esophagus, heart, stomach, small intestine & portion of large intestine - Nucleus solitarius • Afferents follow similar path to the glossopharyngeal nerve • Fibers terminate in postcentral gyrus Innervation Nucleus Ambiguous receives equal number of corticonuclear fibers from both hemispheres

Cranial Nerve V: Trigeminal (M12: 33)(notes 12-8, 9)

- means "3 twins" refers to 3 major divisions (O,M, M) Categorization: 1. Special visceral efferent 2. General somatic afferent Function: 1. jaw movement for mastication ; tension of tympanic membrane; flattening and tensing the soft palate; opening the Eustachian tube assists upper & anterior laryngeal movement 2. general sensation from head: face, scalp, eye, oral & nasal cavities, tympanic membrane, meninges • 3 major divisions: ophthalmic, maxillary & mandibular -Nuclei - Motor (masticator) nucleus: located in the pons - Sensory nucleus: extends from the midbrain caudally into the spinal cord - 3 subnuclei • Mesencephalic (proprioception) • Pontine trigeminal nucleus (discriminative sensation from head & face) • Nucleus of the spinal tract (pain & temperature)

Tensor (Veli) Palatini (see CN V: The Trigeminal Nerve: Motor) (M12: 38, pic)(notes 12- 10)

- prevents food from entering the nasal pharynx (behind nasal cavity)

Cranial Nerve VII: Facial LMN &UMN Lesions (M12: 51, pics)(notes 12-13)

- with LMN Lesions of the facial nerve, there is involvement of the entire side of the face Ipsilaterally. - Unilateral Facial Paralysis. - In Upper Motor Neuron Lesions there is complete involvement of lip & neck muscles. Some degree of involvement around the eyes, little difficulty with the forehead or Frontalis Muscle. - Upper Motor Neuron Paralysis- occurs on voluntary movement with almost normal movements for emotionally initiated movements. Like a 'true smile'. But remember that the person would not be able to lateralize their lips or retract their lips to smile on command.

Cranial Nerve VIII: Vestibulocochlear Cochlear Component (M12: 62, pic)(notes 12-16)

-(cochlear nerve) nerve cells and fibers in spiral ganglion around the modiolus(of cochlea) - nerve fibers enter the brainstem at lower pons lateral to facial nerve - cochlear fibers divide into 2 branches in pons 1) Dorsal cochlear nucleus 2) Ventral cochlear nucleus -Fibers decussate after cochlear nucleus, a few are ipsilaterally projected as well -Fibers form lateral lemniscus tract- through the posterior pons in midbrain -Before fibers terminate in the medial geniculate body, fibers take one of several paths synapsing at 1 or more of these structures: Superior olives, Trapezoid body, Inferior colliculus Nucleus of the lateral lemniscus -Project to auditory radiations & auditory cortex

Cranial Nerve VIII: Vestibulocochlear (M12: 60, pic)(notes 12-15)

-Afferents from utricle, saccule, semicircular canal & cerebellum -Vestibular nerve: nerve cells and fibers in the vestibular ganglion located in the internal acoustic meatus. The nerve cells & fibers in vestibular nerve are located in vestibular ganglion in Internal Acoustic Meatus. -Fibers enter the brainstem between the lower pons and upper medulla -Most axons enter the vestibular nuclear complex- which consists of a group of nuclei in the floor of the 4th ventricle.

Cranial Nerves (M12: 1,2, pic)(notes 12-1)

-Originate- in brainstem & innervate the muscles of the head, neck, face, larynx, tongue, pharynx, & glands. - numbered anterior to posterior & in the order in which they enter the brain. - Cranial nerves essential for speech, resonance & phonation as well as swallowing, vision, hearing, smell & taste.

Cranial Nerve X: Vagus (M12: 70)(notes 12-18,19)

-Vagus emerges from medulla as several rootlets - which converges into 2 roots - that exits the skull through jugular foramen. as the vagus continues to descend it is joined. -joined by fibers from the nucleus ambiguus -Vagus travels through neck - below base of neck, vagus takes a different path on each side of body to reach cardiac, pulmonary & esophageal plexuses

Masticator Nucleus (see Trigeminal Nerve: Clinical Corner: UMN Lesion) (M12: 42)(notes 12- 10,11)

-composed of lower motor neurons , therefore damage to the masticator nucleus or its axons or anywhere peripheral or distal will constitute a LMN Lesion.

Cranial Nerve IX: Glossopharyneal Nucleus Ambiguus Inferior Salivatory Nucleus Nucleus Solitarius (M12: 65)(notes 12-17)

1) Nucleus Ambiguus • Receives corticonuclear fibers both hemispheres • Efferent innervation to stylopharyngeus muscle (elevates pharynx & larynx) 2) Inferior Salivatory Nucleus • Receives afferents from hypothalamus, olfactory system & taste from mouth • Efferents supply - otic ganglion of ear - parotid salivary gland 3) Nucleus Solitarius • Visceral afferents from inferior ganglia (this mediates sensation to pharynx, soft palate, posterior 1/3 of tongue, fauces(arches at back of mouth) , tonsils, ear canal & tympanic cavity • Fibers decussate, travel to thalamic & hypothalamic nuclei • Thru internal capsule • (on to) Lower postcentral gyrus

6 Cranial Nerve Nuclei in Pons (Pontine Tegmentum) (M12: 19)(notes 12-4)

3 Sensory nuclei of trigeminal (CN V) - Primary sensory nucleus - Spinal trigeminal nucleus - Mesencephalic nucleus - Trigeminal motor nucleus -(Cranial Nerve 5 responsible for muscles of mastication) - muscles of mastication • Abducens motor nucleus - innervates lateral rectus muscle of the eye • Facial motor nucleus - contains lower motor neurons that innervate the muscles of facial expression

Cranial Nerve IX: Glossopharyneal (M12: 64)(notes 12-17)

3 brainstem nuclei concerned with glossopharyngeal nerve function - Nucleus ambiguus, - Inferior salivatory nucleus - Nucleus solitarius

Cranial Nerve Nuclei in Medulla (M12: 20)(notes 12-4)

9 major nuclei (in medulla) - Cochlear & vestibular nuclear complexes, solitarius nucleus, salivatory nucleus (ANS), hypoglossal nucleus, ambiguus nucleus, and spinal trigeminal nucleus - Cochlear & Vestibular nuclear complexes- Located laterally at junction of Pons & Medulla (Pontomedullary Junction) - Solitarius Nucleus- Visceral sensory nucleus responsible for taste, heart rate, respiration & blood pressure. - Salivatory Nucleus (ANS)- responsible for glands hypoglossal nucleus- whose LMN's innervate intrinsic & extrinsic muscles of the tongue is also another nucleus. - Ambiguus Nucleus- controls muscle movements of larynx & pharynx. - Spinal Trigeminal Nucleus- receives sensory input from head,neck, sinuses & meninges.

Cranial Nerve III: Oculomotor (M12: 31, pics)(notes 12-8)

B- Ptosis- left eyelid drooping C- Impairment in moving of eyeball indicated by lack of symmetry.

Basomedial temporal cortex (see Cranial Nerve I: Olfactory) (M12: 26, pic)(notes 12-5,6)

Basomedial temporal cortex- olfactory brain • Plexus of thin fibers that unite in about 20 small bundles - Olfactory receptors situated in mucous membrane of nasal cavity

Cranial Nerve X: Vagus: Branchial Motor Component Pharyngeal Nerve Branch Superior Laryngeal Nerve Recurrent Laryngeal Nerve (M12: 71, pic)(notes 12-19,20)

Branchial Motor Component - Axons from premotor, motor, & other cortical areas descend as corticonuclear fibers through the internal capsule - to synapse on motor neurons in nucleus ambiguous in the medulla. - The LMNs leave the nucleus ambiguus & exit the medulla as 8-10 rootlets - The Nerve exits the skull through the Jugular Foramen - Reaches constrictor muscles of the pharynx(which is the throat) & as well as intrinsic laryngeal muscles( Larynx/voice box) - Branchial motor fibers the divide into 3 Major branches : 1) Pharyngeal Nerve 2) Superior Laryngeal 3) Recurrent Laryngeal Nerves 1) Pharyngeal Nerve Branch : is the principle motor nerve of the pharynx. it enters the pharynx at the middle constrictor & breaks up into the Pharyngeal Plexus to supply all the muscles of the pharynx and soft palate except for Stylopharyngeous ( which is supplied by CN XI (11)) and also does not supply Tensor Veli Palatini ( which is supplied by CN v (5) - Trigeminal). Pharyngeal branch also supplies the Palatoglossus muscle of the tongue. 2) Superior Laryngeal Nerve: branches off from the interior vagal ganglion. It descends and dividing into the internal and external laryngeal nerves. External Laryngeal Branch: supplies the inferior constrictor muscle and then supplies the Cricothyroid muscle of the larynx. It also sends branches to the Pharyngeal Plexus & the superior cardiac nerves. 3) Recurrent Laryngeal Nerves: takes a different path on the right and left sides of the body. -The Right Recurrent laryngeal nerve arises from the Vagus nerve anterior to the Subclavin Artery then hooks back under the artery and ascends posterior to it. - The Left Recurrent laryngeal nerve arises from the left Vagus the aortic arch. It hooks back posteriorly under the arch and ascends through the superior media Stynum and travels between the trachea and esophagus on the left side. - Both Recurrent laryngeal nerves- supply the intrinsic muscles of the larynx except for the Cricothyroid. It's not uncommon that surgeons may stretch or Nick the Vagus nerve (the recurrent laryngeal nerve on the left side) when a person is having cardiac surgery. This would leave a person sometimes with a unilateral vocal fold paralysis because of the denervation of the nerves to the intrinsic muscle of the larynx.

Cranial Nerve IX: Glossopharyneal Branchial Motor Component (M12: 66, pic)(notes 12-17)

Branchial motor component - begins at cortex - fibers descend along corticonuclear fibers - thru internal capsule - thru basis pedunculi - synapse bilaterally on LMNs in rostral nucleus ambiguus - (onto the) in medulla,(where glossopharyngeal) emerges as 3 or 4 rootlets - then nerve passes laterally to exit thru jugular foramen - then axons descend in neck to stylopharyngeus muscle

Cranial Nerve X: Vagus "the Wanderer" (M12: 68)(notes 12-18)

Categorization • Special visceral efferent, general visceral efferent • Visceral afferent, general somatic afferent Functions: 90% sensory, 10% motor function • Motor to the viscera (heart, respiratory system, most of digestive system) • Primary efferents to the palatal muscles (except: tensor palatine) • Primary efferents for pharyngeal constrictors • Afferent for middle and inferior portion of the pharynx • Mediates sensation of the epiglottis (one laryngeal cartilage) • Innervates intrinsic muscles of the larynx

Cranial Nerve IX: Glossopharyneal (M12: 63)(notes 12-16,17)

Categorization- as both motor & sensory nerve • 2 motor components: special visceral efferent & general visceral efferent • 3 sensory components: general visceral afferent, general somatic afferent, special afferent Function - (to be) Efferent to 1 muscle, stylopharyngeus • Stylopharyngeus Dilates pharynx laterally (or to the sides) • (it also) Contributes to elevation of pharynx & larynx for swallowing - Secretomotor fibers for parotid gland's saliva production - Sensory fibers for taste from posterior 1/3 of tongue - General sensation from posterior 1/3 tongue, skin of external ear, internal surface of tympanic membrane - Mediates sensory portion of pharyngeal gag - Sensation (visceral) from carotid body & from carotid sinus

Cranial Nerve III: Oculomotor Impaired visceral component (M12: 30)(notes 12-7,8)

Categorization: 1. General somatic efferent 2. General visceral efferent Function: 1. eye muscles for movement 2. parasympathetic supply to pupil constrictors & lens accommodation • Somatomotor component innervates the extraocular muscles to move the eyeball • Visceral component responsible for pupil constriction & shape of lens - Impaired visceral component = loss of pupillary reflex & pupil dilation • Also, innervates the levator palpebrae superioris that elevates the upper eyelid - Dysfunction causes ptosis (droop) of the eyelid - movements of the eyes are produced by 6 extra ocular muscles. To change in visual fixation, or to maintain fixation, on a moving object, the eyes need precision in movement & must move together requiring a high degree of coordination of the eye muscles. - The nuclei of Cranial nerve 3, 4, 6, are controlled as a group by higher centers in the cortex & brainstem. - The oculomotor nerve plays a major role in eye movement. - The General Somatic Motor Efferent component innervates 4 of the 6 extra-ocular extrinsic muscles & Visceral Motor Component innervates the Intrinsic -Ocular Muscles which control the size of the pupil & the shape of the lens. - Oculomotor nerve also innervates levator palpebrae superioris that elevates the upper eyelid. - Dysfunction of this muscle (LPS) causes ptosis (droop) of the eyelid

Cranial Nerve II: Optic Nerve (M12: 29, pic)(notes 12-6,7)

Categorization: Special Afferent (sensory) nerve Function: Conveys visual information from the retina • 1) light energy transduced into electrical signal by rods and cones - Light enters the pupil & travels to the back of the eye passing through the retina where light energy is "transduced into electoral signals by rods & cones" • 2) to bipolar cells (primary sensory neurons) - information is then passed to the bipolar cells these are the primary sensory neurons in the visual pathway. • 3) to ganglion cells in anterior layers of the retina - they pass the signal to the secondary sensory neurons called ganglion cells in anterior layers of the retina. • 4) axons of ganglion cells converge (toward) on the optic disc • 5) exit from the eye (ball)-"as the optic nerve" • 6) form the optic nerve • 7) half of the fibers cross at the optic chiasm & travel as the optic tract (to travel as the right & left optic tract) • 8)(they then) synapse with nerve cells in the lateral geniculate body of the thalamus • 9) (and) form the optic radiations (geniculocalcarine tract)- that travel to the visual cortex • terminate in the visual cortex with integrated visual signals sent to the visual association cortex for interpretation

Cranial Nerve VIII: Vestibulocochlear Nerve (M12: 59, pics)(notes 12-15)

Categorization: special sensory afferent Afferent information from the internal ear to the CNS 2 parts: vestibular nerve cochlear (acoustic nerve) Function: -audition(hearing) (from cochlea) -balance, equilibrium, proprioception of head semicircular canals)

Classification of Cranial Nerves (M12: 9)(notes 12-1,2)

Classification of Cranial Nerves • Information types - General & special • Muscle types - Skeletal & visceral - Fiber types - Afferent & efferent - Serving general motor & general sensory functions with Somatic & Visceral functions, the cranial nerves also use special receptors & neurons to serve special functions. - Somatic- components of cranial nerves with special functions contain only Afferent fibers whereas the Visceral component contains Afferent & Efferent fibers.

Cranial Nerve VII: Facial Nerve (M12: 46, chart)(notes 12- 11, 12)

Cranial Nerve VII: Facial : 2 motor & 2 sensory components : Categorization: Branchial motor Component (yellow) (special visceral efferent): Function: Innervates : stapedius, stylohyoid, posterior belly of digastric; muscles of facial expression including buccinator, platysma; occipitalis muscle -Categorization: Visceral motor component (general visceral efferent): Function: Stimulation of the lacrimal, submandibular & sublingual glands; innervates mucous membranes of the nose, hard palate & velum (soft palate) - Categorization: - General sensory component (general somatic afferent) Function: From skin of the auricle 's concha; area of skin behind ear - Categorization: - Special sensory component (special afferent): Function: Taste from the anterior 2/3 of the tongue, hard palate & velum (soft palate - Several nuclei (nuclear complex) located in the pons near the reticular formation including - Superior salivatory nucleus - Lacrimal nucleus - Facial motor

Cranial Nerves Chart (M12: 7, graphic)(notes 12-1)

Cranial Nerve, Fibers, structures innervated, functions, brainstem nucleus (fill in or print chart) - Cranial nerves 1 & 2- Part of the forebrain (not in nucleus) - Brainstem Nucleus- CN (3-12) attached to the brainstem & have their nuclei located in the brainstem. Cranial Nerve functions- vision, hearing, olfaction, & gustation. Some only sensory,(8-vestibulocochlear) & some only motor (12- hypoglossal) & some mixed

Greater Petrosal Nerve Chorda Tympani (see Cranial Nerve VII: Facial Nerve: Visceral Motor Component) (M12: 52, pic)(notes 12-13)

Divide in the facial canal becoming - chorda tympani & greater petrosal nerve - Joins trigeminal fibers to lacrimal & mucosal glands of nasal & oral cavities stimulating secretions

Cranial Nerve VII: Facial (M12: 58)(notes 12-14,15)

Function: -(important for) speech, swallowing, muscles of facial expression & pulling larynx superiorly & posteriorly - of interest- all facial apertures- are openings guarded by muscles innervated by the facial nerve. These apertures are the eyes, the nose, the mouth & external auditory canal. -(provides motor) innervation to the sublingual and submaxillary salivary glands -guards the middle ear by innervating the stapedius muscle dampening excessive movement of the ossicles to loud noise. When a person has damage to the facial nerve, they may complain that sounds are too loud. -partially responsible for taste (IF 4 primary tastes: salty, sour, bitter & sweet) Assessment • Muscles of facial expression • Wrinkle forehead • Close your eyes tightly • Close your mouth tightly • Retract corners of mouth and tense cheeks • Clinician pull s down corners of mouth; client resists & tenses anterior neck - Facial Nerve can be assessed by an SLP during an oral mechanism exam. Some of the assessment tasks would be for the person to smile, & produce other facial expressions. These tasks can be helpful in identifying impairments in the facial nerve functioning.

Cranial Nerve Nuclei (M12: 14, chart)(notes 12-3)

Graph: Modality, Associated Nucleus, Associated Cranial Nerves, Function Chart. - Motor = Efferent - Sensory = Afferent - Nucleus (plural, nuclei): a group of nerve cell bodies in the brain, brainstem,or spinal cord that are anatomically discrete and typically serve a particular function

Left Abducens (VI) Nerve Paralysis (M12: 45, pics)(notes 12- 11)

Left Abducens (VI) Nerve Paralysis(pic)- left eye is deviated medially because of unopposed action of medial rectus muscle. - Diplopia (double vision) disappears on eye movement to the right(pic). When eye movements to the right are made. Diplopia present when lateral movements are made to the side of Paralysis (in this case, the left side) - Diplopia on lateral movement to the left (pic).

Vestibular Nuclear Complex (see Cranial Nerve VIII: Vestibulocochlear) (M12: 60, pic)(notes 12-15)

Most axons enter the vestibular nuclear complex- which consists of a group of nuclei in the floor of the 4th ventricle.

CN V: The Trigeminal Nerve: Motor (M12: 38, pic)(notes 12- 10)

Motor (Yellow) Component: - innervates muscles of mastication & soft palate - To muscles of mastication • tensor typani • tensor (veli) palatini - prevents food from entering the nasal pharynx (behind nasal cavity) • mylohyoid • anterior belly of digastric

MNemonic for Type of Cranial Nerve (Motor, Sensory, both) (M12: 8)(notes 12-1)

Olfactory (CN I) Some (sensory) Optic (CN II) Say (sensory) Oculomotor (CN III) Marry (motor) Trochlear (CN IV) Money (motor) Trigeminal (CN V) But (both) Abducens (CN VI) My (motor) Facial (CN VII) Brother (both) Vestibulocochlear (CN VIII) Says (sensory) Glossopharyngeal (CN IX) Bad (both) Vagus (CN X) Business (both) Accessory (CN XI) Marry (motor) Hypoglossal (CN XII) Money (motor)

Olfactory Bulb, Olfactory Tract Stria (M12: 27, pic)(notes 12-6)

Olfactory Bulb, Olfactory Tract Stria: Lateral, Intermediate, Medial Pyriform - Olfactory Nerve can contain the nerve cell bodies of the Secondary Sensory Neurons. - From the Olfactory Bulb the fibers form the Olfactory Tract. - Traditional, the bulb & the tract of the secondary sensory axons, are known as Olfactory nerve. - The Medial Olfactory Area is thought to mediate emotional responses to odors through it's connects with the limbic system.

Cranial Nerve Nuclei (M12: 16, pic)(notes 12-3)

Sensory & Motor Nuclei pic Dorsal View of brain stem (only 1 paired nuclei displayed in diagram) Sensory- left side & Motor- right side Paired- nuclei on both sides

CN V: The Trigeminal Nerve: Sensory (M12: 37, pic)(notes 12- 9,10)

Sensory (Blue) • From the face and scalp, eye, mucous membranes of paranasal sinuses • Nasal and oral cavities including tongue, teeth, external aspect of the tympanic membrane, meninges of anterior & middle cranial fossa

Sensory (Afferent) Pathways (M12: 24, pic)(notes 12-5)

Sensory Pathways - Three-order nuclei & fibers • First-order fibers- outside the CNS •Second-order fibers- brainstem gray matter - Decussating second- order fibers •Third-order fibers- - Projections from the thalamus to the motor cortex - Most of the sensory pathways of the Cranial Nerves consist of 3- Order Nuclei & their fibers. Traveling from the most distal sensory fibers, the 1st Order Fibers are peripheral fibers outside the CNS. - 2nd Order Fibers- have cell bodies in the gray matter of the brainstem & these fibers cross the midline and terminate in the Thalamus. - 3rd Order Fibers- have cell bodies in the central posterior- medial nucleus of the Thalamus & project to the lower region of the sensory cortex in the parietal lobe. - Exceptions- 3-order cell organization are the special sensory functions of smell, audition & vision.

Superior salivatory nucleus (see Cranial Nerve VII: Facial Nerve) (M12: 46, chart)(notes 12- 11, 12)

Several nuclei (nuclear complex) located in the pons near the reticular formation including Superior salivatory nucleus, Lacrimal nucleus, Facial motor nucleus SSN- receives afferent information from the hypothalamus & olfactory system and taste information from the mouth - Supplies submandibular sublingual salivary glands, nasal & palatine glands

Facial Motor Nucleus (see Cranial Nerve VII: Facial Nerve) (M12: 46, chart)(notes 12- 11, 12)

Several nuclei (nuclear complex) located in the pons near the reticular formation including Superior salivatory nucleus, Lacrimal nucleus, Facial motor nucleus • Facial Motor nucleus innervates the - muscles of facial expression: orbicularis oculi, zygomatic, buccinator, orbicularis oris and labial muscles - Other muscles: platysma, stylohyoid, stapedius, posterior belly of digastric

Lacrimal nucleus (see Cranial Nerve VII: Facial Nerve) (M12: 46, chart)(notes 12- 11, 12)

Several nuclei (nuclear complex) located in the pons near the reticular formation including Superior salivatory nucleus, Lacrimal nucleus, Facial motor nucleus • Lacrimal nucleus - Receives information from afferent fibers from trigeminal sensory nuclei for reflex response to corneal irritation - Receives taste information from anterior 2/3 of tongue, floor of mouth, soft and hard palates

Spinal Accessory Nerve (CN IX) (M12: 13, pic)(notes 12-3)

Spinal Accessory Nerve (CN IX) • (these LMN's) Innervate neck muscles - (specifically) Sternocleidomastoid muscle - Trapezius muscle • Branchial in origin - LMN's exiting C1-C5 segments form the spinal accessory nerve - Accessory nerve also Branchial in Origin. Commonly referred to as Spinal Accessory nerve.

Mandibular nerve (see Cranial Nerve V: Trigeminal ) (M12: 34)(notes 12- 9)

Trigeminal- Sensory fibers have 3 main branches 3) Mandibular nerve (sensory to the tongue, mandible, lower teeth, lower lip, part of the cheek and part of the external ear )

Ophthalmic nerve (see Cranial Nerve V: Trigeminal ) (M12: 34)(notes 12- 9)

Trigeminal- Sensory fibers have 3 main branches • 1) Ophthalmic nerve (sensory to forehead, eyes & nose)

Maxillary nerve (see Cranial Nerve V: Trigeminal ) (M12: 34)(notes 12- 9)

Trigeminal- Sensory fibers have 3 main branches • 2) Maxillary nerve (sensory to upper lip mucosa, maxilla, upper teeth, cheeks, palate, and maxillary sinus

Cranial Nerve VIII: Vestibulocochlear (M12: 61, pic)(notes 12-16)

Vestibular nerve : - Efferents to • cerebellum thru inferior cerebral peduncles • spinal cord via the vestibulospinal tract medial longitudinal fasciculus. - all nuclei in vestibular complex contribute fibers to MLF.

Hyperosmia (see Clinical Correlates) (M12: 28)(notes 12-6)

abnormally acute smell

Facial Apertures (see Cranial Nerve VII: Facial) (M12: 58)(notes 12-14,15)

all facial apertures- are openings guarded by muscles innervated by the facial nerve. These apertures are the eyes, the nose, the mouth & external auditory canal.

Cranial Nerve I: Olfactory (M12: 26, pic)(notes 12-5,6)

• Categorization: Special Afferent (sensory) • Function: olfaction (smell) - Structures: Olfactory mucosal membrane, olfactory bulbs, olfactory nerve/tract Basomedial temporal cortex- olfactory brain • Plexus of thin fibers that unite in about 20 small bundles - Olfactory receptors situated in mucous membrane of nasal cavity - CN: made up of olfactory epithelium bulbs, tracts & together with the olfactory areas of the brain & their communications provides with the sense of smell. - The Primary Sensory neurons in Olfactory epithelium transmit sensation via the Plexus fibers which assemble into approximately 20 small bundles that synapse on the secondary sensory neurons in the olfactory bulb.

Cranial Nerve VI: Abducens (M12: 43)(notes 12- 11)

• Categorization: general somatic efferent / motor nerve • Function: movement of eyeball • Abducens Nucleus located near floor of the fourth ventricle in the pontine tegmentum • Dysfunction of Abducens prevents lateral movements of the eyeball • Innervates one muscle of the eye: the lateral rectus muscle

Motor (Efferent) Pathways (M12: 23, pic)(notes 12-5)

• Corticonuclear (bulbar) fibers - Motor cells (UMNs) in precentral gyrus - Descend through internal capsule - Activation of CN motor nuclei (LMN) in the brainstem • Most corticonuclear fibers cross the midline at different brainstem locations - Corticonuclear fibers- arise in precentral motor cortex, descend thru Internal Capsule & synapse on lower motor neuron motor cranial nerve nuclei in the brainstem. - Most cortioconuclear fibers cross the midline at different brainstem locations, before reaching cranial nerve nuclei. - Substantial bilateral cortical innervation of the cranial motor nuclei exists for the muscles of the face, the jaw, the larynx, & the pharynx.

3 Cranial Nerve Nuclei in Midbrain Tegmentum (adult brain) (M12: 18)(notes 12-3,4)

• Edinger-Westphal nucleus (CN III) - (contains) parasympathetic efferents to(innervate the) ciliary muscle & constrictor fibers of the pupil (of the eye) • Oculomotor nucleus (CN III) - contains Lower Motors Neurons that control (most of the) eye muscles • Trochlear nucleus (CN IV) - contains Lower Motors Neurons (that) innervating superior oblique, (eye muscle)- one of the muscles of the eye

Cranial Nerve VII: Facial: Brachial Motor Component (M12: 48, pic)(notes 12-12)

• Fibers of the nucleus extend to floor of ventricle, curve around nucleus of abducens (CN VI), exit brainstem near inferior margin of pons • Fibers join fibers from the nucleus of the tractus solitarius & autonomic or parasympathetic nuclei, enter the internal auditory meatus, extend through the petrosal bone facial canal, travels through the tympanic cavity innervating the stapedius muscle, exit the skull

Cranial Nerve V: Trigeminal (M12: 34)(notes 12- 9)

• Innervation - Motor part of trigeminal innervates these muscles: • Masseter, temporalis, lateral & medial pterygoids, tensor tympani, tensor veli palatine, mylohyoid, & anterior belly of the digastric - Sensory fibers have 3 main branches • 1) Ophthalmic nerve (sensory to forehead, eyes & nose) • 2) Maxillary nerve (sensory to upper lip mucosa, maxilla, upper teeth, cheeks, palate, and maxillary sinus 3) Mandibular nerve (sensory to the tongue, mandible, lower teeth, lower lip, part of the cheek and part of the external ear ) - Trigeminal- Major sensory nerve of the face & motor nerve that innervates the muscles of mastication. Sensory Division- 3 Subnuclei- 1) Mesencephalic Subnucleus- consists of a thin column of primary sensory neurons that carry proprioceptive information from the muscles of mastication. 2) Pontine Trigeminal Nucleus- large group of secondary sensory neurons in the Pons thought to be primarily concerned with discriminative touch sensation from head & face. 3) Nucleus of Spinal Tract- senses pain & temperature. It is a long column of cells extending from the Pons caudally into the spinal cord where it merges with the dorsal grey matter of the spinal cord.

Cranial Nerve VII: Facial Nerve Innervation (M12: 47)(notes 12-12)

• Superior salivatory nucleus - receives afferent information from the hypothalamus & olfactory system and taste information from the mouth - Supplies submandibular sublingual salivary glands, nasal & palatine glands • Lacrimal nucleus - Receives information from afferent fibers from trigeminal sensory nuclei for reflex response to corneal irritation - Receives taste information from anterior 2/3 of tongue, floor of mouth, soft and hard palates • Facial Motor nucleus innervates the - muscles of facial expression: orbicularis oculi, zygomatic, buccinator, orbicularis oris and labial muscles - Other muscles: platysma, stylohyoid, stapedius, posterior belly of digastric

Trigeminal Nerve: Clinical Corner: UMN Lesion LMN Lesion (M12: 42)(notes 12- 10,11)

• UMN Lesion - No significant change in (the action of) muscles of mastication. Since the masticator & masticator nucleus is innervated by both cerebral hemispheres & also by numerous inputs from brainstem nuclei. - Masticator Nucleus- composed of lower motor neurons , therefore damage to the masticator nucleus or its axons or anywhere peripheral or distal will constitute a LMN Lesion. • LMN Lesion - Paralysis and eventual atrophy of muscles of mastication on the affected side; decreased strength of biting - Most common cause of LMN lesions are vascular damage, tumors & trauma.****