Cranial Nerves 2x PDF

 Cranial Nerves CRANIAL NERVES 2  Cranial Nerves Ⅰ Olfactory nerve Ⅱ Optic nerve Ⅲ Oculomotor nerve Ⅳ Trochlear nerve Ⅴ Trigeminal nerve Ⅵ Abducent nerve Ⅶ Facial nerve Ⅷ Vestibulocochlear nerve...

 Cranial Nerves CRANIAL NERVES 2  Cranial Nerves Ⅰ Olfactory nerve Ⅱ Optic nerve Ⅲ Oculomotor nerve Ⅳ Trochlear nerve Ⅴ Trigeminal nerve Ⅵ Abducent nerve Ⅶ Facial nerve Ⅷ Vestibulocochlear nerve Ⅸ Glossopharyngeal nerve Ⅹ Vagus nerve Ⅺ Accessory nerve Ⅻ Hypoglossal nerve  7 Functional Types Motor 1. General Somatic Efferent (GSE) Activates Muscles from Somites (Skeletal, Extraocular, Glossal) 2. General Visceral Efferent (GVE) Activates Visceral Organs 3. Special Visceral Efferent (SVE) Activates Muscles of face, palate,mouth, pharynx and larynx excludes eye and tongue muscles Sensory 1. General Somatic Afferent (GSA) Mediates information from muscles, skin, ligament and joints 2. General Visceral Afferent (GVA) Mediates sensory innervation from visceral organs 3. Special Visceral Afferent (SVA) Mediates visceral sensation of taste from tongue, olfaction from Nose 4. Special Somatic Afferent (SSA) Mediates special sensations of vision from retina and audition and equilibrium from inner ear Classification of Cranial Nerves Sensory cranial nerves: contain only afferent (sensory) fibers – Ⅰ Olfactory nerve – Ⅱ Optic nerve – Ⅷ Vestibulocochlear nerve Motor cranial nerves: contain only efferent (motor) fibers – Ⅲ Oculomotor nerve – Ⅳ Trochlear nerve – ⅥAbducent nerve – Ⅺ Accessory nerve – Ⅻ Hypoglossal nerve Mixed nerves: contain both sensory and motor fibers--- – ⅤTrigeminal nerve, – Ⅶ Facial nerve, – ⅨGlossopharyngeal nerve – ⅩVagus nerve  III MOTOR NULCEI IV GSE SOMATIC MOTOR V oculomotor III trochlear IV extraocular mm. VII abducens VI hypoglossal XII tongue mm. VI GVE PARASYMPATHETIC VII IX Edinger Westphal III superior & inferior salivatory nuclei VII, IX XII dorsal motor nucleus of X X SVE BRANCHIOMOTOR Nucleus ambiguus motor nuc. V mastication IX, X and cXI facial nuc. VII facial expression nucleus ambiguus IX, X, cranial XI sXI pharynx, larynx accessory sXI trapezius, sternomastoid 7 7  V mesencehaplic SENSORY NULCEI V principal sensory SSA HEARING AND BALANCE vestibular VIII cochlear VIII VIII vestibular GSA SOMATOSENSORY VIII cochlear trigeminal V: mesencephalic proprioception principal sensory discriminative touch rost nuc solitarius spinal pain & temperature VII, IX, X caud nuc solitarius SVA TASTE IX, X nucleus solitarius, V spinal rostral VII, IX, X GVA PAIN, etc. nucleus solitarius caudal IX, X 8 8  Cranial Nerves Special Sense Nerves – I,II,VIII Somatic Motor Nerves – Eye—III,IV,VI – Tongue--XII “Rest of body” nerves – IX,X,XI Face and jaws – VII, V  Cranial Nerves (12 pair) I. Olfactory: smell II. Optic: vision III. Oculomotor: eyelid and eyeball movement IV. Trochlear: motor for vision (turns eye downward and laterally) V. Trigeminal: chewing, face and mouth touch and pain VI. Abducens: motor to lateral eye muscles VII. Facial: controls most facial expressions , taste, secretion of tears & saliva VIII. Vestibulocochlear: sensory for hearing and balance IX. Glossopharyngeal: sensory to tongue, pharynx, and soft palate; motor to muscles of the pharynx and stylopharyngeus X. Vagus Nerve: sensory to ear, pharynx, larynx, and viscera; motor to pharynx, larynx, tongue, and smooth muscles of the viscera, XI. Spinal Accessory Nerve: motor to sternocleidomastoid and trapezius XII. Hypoglossal Nerve: motor to intrinsic and extrinsic muscles of the tongue  Cranial Nerve Nuclei Midbrain (3)- Control Eye Muscles – Motor nuc. of oculomotor n. (motor & parasymphatetic) – Motor nuc. of trochlear n. Pons (6) – Three Sensory Nuc. of Trigeminal Mesencephalic nuc. (proprioceptive) Primary sensory nuc. (touch&pressure) Spinal trigeminal nuc. (pain&temperature) – Motor nuc. of trigeminal n. – Abducens Nuc. – Facial Motor Nuc.  Cranial Nerve Nuclei Medulla (9) 1. Cochlear nuc. (Hearing) 2. Vestibular nuc. (Equilibrium) 3. Salivary nuc. (Secretions) 4. Dorsal motor nuc. of vagus (Visceral Motor) 5. Hypoglossal nuc. (Tongue) 6. Nucleus tractus solitarius (Visceral Sensory) afferent swallowing 7. Spinal trigeminal nuc. (Sensory) 8. Nucleus ambiguus (Laryngeal & Pharyngeal Motor) efferent swallowing 12  Olfactory Nerve Special Sensory : smell Olfactory mucosa (SVA)→ Cribriform foramina → Olfactory bulb  Olfactory Nerve CN I Olfactory nerve is nerve of olfaction (smell) Peripheral processes of the primary olfactory neurons in the olfactory epithelium act as a sensory receptors. Primary olfactory neurons undergo continuous replacement throughout life. Secondary neurons are in the olfactory bulb. Without synapsing in the thalamus go to cortex Cortical areas involved in olfaction are ipsilateral.  Olfactory epithelium- Specialized area of nasal mucosa. 4 cell types – Primary olfactory neurons are bipolar, receptor cells 20 or more bundles or filaments traverse cribriform plate – Basal cells- source of new receptor cells, regeneration of 60 days – Supporting cells – Secretory cells in olfactory glands,solvent for odorants  Olfactory Bulb Rostral enlargement of olfactory tract Contain cell bodies of mitral and tufted cells- secondary neurons o o Glomeruli- 1 and 2 olfactory neurons contact Interneurons  Postsynaptic fibers of mitral & tuft cells form the olfactory tract and trigone (rostral to anterior perforated substance) Lateral (primary) olfactory stria to primary olfactory area (uncus, entorhinal area, limen insula, part of amygdala) Conscious appreciation of smell  From primary olfactory areas to entorhinal cortex (secondary olfactory cortex) Subjective appreciation of olfactory stimuli  Some collaterals terminate in anterior olfactory nucleus Postsynaptic fibers project to contralateral olfactory bulb via anterior commissure Inhibitory effect on contralateral olfactory bulb Serves to enhance more active bulb & provide directional cues to the source of the olfactory stimulation  Anosmia-loss of sense of smell – Nerve trauma – Age etc.  Optic nerve Special Sensory: Sight Optic nerve nuclei are located in the lateral geniculate body Ganglion cell (SSA) → Optic canal → Lateral geniculate body  Optic Nerve (II) Special somatic afferent Retina to Optic Nerve to Optic Chiasm To Lateral Geniculate Body To Optic Radiations To Visual Cortex in Occipital Lobe Clinically: – Injury results in visual field loss 28  Optic Nerve course Arises from the retina of the eye Optic nerves pass through the optic canal, located in the lesser wing of sphenoid and enters middle cranial fossa Joins the optic nerve fibers of other side and form the optic chiasm Small number of fibers from each eye and leave the chiasm and goes to suprachiamatic nucleus of hypothalamus (circadan rhythm)  At the chiasm, ½ cross and ½ do not cross Crossed fibers from opposite side and uncrossed fibers form optic tract 80-90 %of fibers continue to the lateral geniculate body of thalamus where they synapse Small number of fibers leave tract and synapse – in pretectal nucleus (pupillary light reflex) – in superior colliculus (orient eye and head movement to visual stimuli)  Functions solely by carrying afferent impulses for vision Cranial Nerve III: Oculomotor  Oculomotor nerve Components – General somatic efferent fibers (GSE) – General visceral efferent fibers (GVE) Main action－supplies – Superior, inferior and medial recti; inferior obliquus; levator palpebrae superioris – Sphincter pupillea and ciliary muscle Ciliary ganglion: lies between optic nerve and lateral rectus Oculomotor nerve  Oculomotor Nerve (III) General somatic efferent – Innervate extrinsic muscles of eye General visceral efferent – Provides parasympathetic projections to constrictor fibers of iris and ciliary muscles – Provides motor innervation for iris to adjust to light and lens to focus – Edinger-Westphal Nucleus 38  Functions in raising the eyelid, directing the eyeball, constricting the iris, and controlling lens shape The latter 2 functions are parasympathetically controlled Parasympathetic cell bodies are in the ciliary ganglia  Nuclei of Oculomotor Nerve Edinger-Westphal Somatic Motor Located in midbrain at the level of superior colliculus near midline and ventral to cerebral aqueduct 41 Oculomotor Nerve  Course Fibers extend from the ventral midbrain, Emerges from the interpeduncular fossa on ventral aspect of fossa Pass between posterior cerebral and superior cerebellar arteries, course anteriorly Pierces dura and passes in the cavernous sinus superior to trochlear nerve  Course of CN III pass through the superior orbital fissure in tendinous ring, splits into superior and inferior branches Superior division- superior rectus muscle & levator palpebrae Inferior division-medial rectus, inferior rectus, inferior oblique muscles Visceral motor fibers run with branches to inferior oblique and then leave to synapse in ciliary ganglion Postganglionic fibers leave as 8 to 10 short ciliary nerves to enter the eye at the posterior aspect. Terminate in the constrictor pupillae and ciliary muscles Course of Oculomotor Nerve  Clinical Info: Oculomotor Nerve (III) Clinical Info: Oculomotor Nerve (III) Ptosis - eyelid drop Ophthalmoplegia – problems in adjusting to light – deviation of eye movements – diplopia (double vision) Left Oculomotor (III) Nerve Paralysis Diplopia Left eye is deviated Does not move laterally laterally Diplopia 51  CN IV: Trochlear (Latin for pulley) Somatic Motor: Superior Oblique 52  General somatic efferent Superior oblique muscle for eye movement is only function Clinical – Difficulty looking downward and outward when Trochlear is injured – eye drifts upward relative to the normal eye 53 Trochlear Nucleus Trochlear Superior Nucleus Oblique Muscle Trochlear (IV) Nerve 54  Trochlear IV Only CN to exit brainstem dorsally Only CN that exits contralaterally Pierces dura at the angle between the free and attached borders of tentorium cerebelli At the lateral wall of cavernous sinus inferior to oculomotor nerve Passes through superior orbital fissure, above tendinous ring Runs above levator palpebrae superioris 55  Smallest of the cranial nerves Somatic motor component At the level of tegmentum of midbrain at the level of inferior colliculus innervate the opposite superior oblique muscle Superior Oblique Muscle Function Right Superior Oblique Muscle Eye ball directed down and out  CN VI: Abducens Abducens nucleus is located in the lower pons at the level of facial colliulus. Close to midline 2 groups of neurons – Neurons which form axons of abducens nerve – internuclear neurons whose axons ascend in MLF to project medial rectus lower motor neurons at the level of superior colliculus (important for coordination of the lateral gaze)  Abducens (VI) Abducens (VI) Nucleus Abducens (VI) Nerve Lateral Rectus Muscle 60  Course Emerge from ventral surface at pontomedullary junction Runs rostrally and laterally in subarachnoid space of posterior cranial fossa Pierce dura at a point lateral to dorsum sellae, continues forward between dura and apex of the petrous portion, makes a right sharp angled bend over apex and enters cavernous sinus Lateral to internal carotid artery Passes through superior orbital fissure in the tendinous ring Course of CN VI  Abducens (VI) General somatic efferent Left Abducens (VI) Innervates only a single muscle: Nerve Paralysis Left eye is deviated lateral rectus muscle which moves medially eye laterally Clinical Info: – When injured, medial rectus muscle is unopposed – eye shifts medially – Susceptible to disruption – Check for medial strabismus Turns in medially Double vision 64  CN V: Trigeminal – Motor nucleus at Pons – Three Sensory Nucleus of Trigeminal Mesencephalic nuc. (proprioceptive) Pontine (Primary Sensory) nuc. (touch&pressure) Spinal Trigeminal nuc. (pain&temperature)  Trigeminal nerve Components of fibers SVE fibers: originate from motor nucleus of trigeminal nerve, and supply masticatory muscles GSA fibers: transmit facial sensation to sensory nuclei of trigeminal nerve, the GSA fibers have their cell bodies in trigeminal ganglion, which lies on the apex of petrous part of temporal bone  Mesencephalic nucleus unique,first-order sensory neurons in the CNS Carry signals from muscle spindles of mastication and mechanoreceptors in gums, teeth and hard palate Central processes project to motor nuc. of CNV to provide reflex control of the bite.  Pontine- 2 parts Dorsomedial part from oral cavity, origin of dorsal trigeminothalamic tract (central pathways) Ventrolateral part from all trigeminal divisions, somatotopically organized  Spinal nuc.- from pontine trigeminal nucleus to C2 where merges with dorsal gray matter of spinal cord The central processes of spinal trigeminal ganglion form a tract called tract of spinal trigeminal nucleus  Discriminitive Touch pathway First order neuron – cell bodies in trigeminal ganglion, carry information from face and meninges to pontine trigeminal nucleus Second order neuron- cell bodies in pontine trigeminal nuc. 2 ascending tracts; – Dorsal trigeminothalamic tract (oral cavity) ; – Ventral trigeminothalamic tract-cross midline in medial leminiscus Third order neuron- – ipsilateral VP of thalamus-ipsilateral sensory cortex – contralateral VP of thalamus-contralateral sensory cortex  Pain & temperature Primary neuron- cell bodies in trigeminal ganglion, axons form tract of spinal trigeminal nucleus- synapse in spinal nucleus Secondary neurons- in spinal nucleus, axons cross midline in spinal lemniscus- Vmpo and MD of thalamus Collaterals to reticular formation- activate arousal and visceral response to pain Collaterals to periaqeueductal gray- activate descending, pain inhibiting pathways Third neuron- – Vmpo to sensory cortex and insular cortex (location and intensity of signals) – MD to cingulate cortex (distressing, emotional aspect of pain)  Motor nucleus Chewing is a reflex activity. Signals from sensory nuclei of CNV both directly and pontine reticular formation. Speech- cerebral hemispheres via corticobulbar tract  Trigeminal nerve; three major divisions Opthalmic Maxillary Mandibular Emerges from midlateral surface of the pons as a large sensory root and a small motor root Sensory ganglion in trigeminal cave near the apex of petrous portion of trigeminal nerve Motor branches are in mandibular division  Trigeminal (V) General somatic afferent Principal sensory nerve for head, face, orbit and oral cavity mediate sensations of pain, temperature, proprioception and fine discriminative touch Sensations from anterior 2/3 of tongue Three sensory branches – Ophthalmic – Maxillary – Mandibular 82  Trigeminal (V) Special visceral efferent Motor for mastication muscles for chewing and speaking – Lateral pterygoid – Temporalis – Masseter – Mylohyoid Anterior belly of digastric Nerve to mylohyoid – Medial pterygoid Tensor veli palatini Tensor tympani Reflex for jaw jerk reflex (mandibular) 85 Trigeminal (V) Opthalmic Maxillary Mandibular 86 Branches Ophthalmic nerve (Ⅴ1, sensory) leave the skull through the superior orbital fissure, to enter orbital cavity Branches – Frontal nerve: Supratrochlear nerve Supraorbital nerve – Lacrimal nerve – Nasociliary nerve Distribution: Sensation from cerebral duramater Visual organ Mucosa of nose Skin above the eye and back of nose Maxillary nerve (Ⅴ2, sensory) Leave skull through foramen rotundum Branches – Infraorbital nerve – Zygomatic nerve – Superior alveolar nerve – Palatine nerve Distribution: Sensation from cerebral duramater Maxillary teeth Mucosa of nose and mouth Skin between eye and mouth Mandibular nerve (Ⅴ3, mixed) Leave the skull through the foramen ovale to enter the infratemporal fossa Branches – Auriculotemporal nerve – Buccal nerve – Lingual nerve – Inferior alveolar nerve – Nerve of masticatory muscles Distribution: Sensation from cerebral dura mater Teeth and gum of lower jaw Mucosa of floor of mouth Anterior 2/3 of tongue Skin of auricular and temporal regions and below the mouth Motor to masticatory muscles, mylohyoid, and anterior belly of digastric  Clinical Info: Trigeminal (V) Sensory – Test for touch discrimination in different facial zones – Check for sneeze and corneal reflexes – Tic of douloureux (trigeminal neuralgia) which is excruciating pain Motor – Check for paralysis or paresis of ipsilateral muscles of mastication – Check for absent or exaggerated jaw reflex – Look for deviation of jaw toward side of injury – Unilateral lesion has mild effect on bite strength while bilateral has severe effect 98