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Cranial Nerves Neuro lab: 10 part1 (the first hour of the lab) Wednesday 11-5-2011 Last lecture we talked about the some of cranial nerves: oculomotor nerve, optic nerve & abducent nerve & today we r going to continue talking about Trigeminal nerve, facial & vestibulocochlear nerve We previously mentioned the oculomotor nerve supplies all muscles of the eye except (lateral rectus by abducent) & (superior oblique by troclear nerve) Each nerve has its own nucleus it might be motor or sensory & the largest cranial nerve is the Trigeminal nerve First: Trigeminal nerve Which is mixed nerve sensory & motor both of them originate from its own nucleus (sensory part-medial-from sensory nucleus) & (motor partlateral-from motor nucleus) both of them can be seen at the level of medulla oblongata. Sensory part of the trigeminal nerve enter inside the sensory ganglia (trigeminal ganglia) contains pseudounipolar cells the fibers that exit from it will divide into ascending & descending fibers. Ascending (sensory) fibers: they are fibers comes from the periphery, most of its fibers will go to the main sensory nucleus carry information of touch & pressure. Descending (sensory) fibers : most of its fibers go to the spinal nucleus & carry information of pain & temperature Some of the fibers go to the (Mesencephlon) which receive proprioception information ** All these fibers ((ascending, descending & proprioception)) will group together & go to specific nucleus in the thalamus ** I think it’ll go to the tectal station but I m not sure about it ** then to the cortex ((S1: postcentral gyrus)) so the sensory fibers have different modalities ** All sensations will go to the thalamus except olfaction. The motor part of the trigeminal nerve (which is located at the level of pons) will descend to motor nucleus that supplies muscles of mastication also o we have to know that it doesn’t make any synapse in the trigeminal ganglia The neurons of proprioception only pass beside the ganglia & make no synapse. All theses fibers will pass to the contra lateral side then through medial leminscus to the thalamus then to the cortex Motor part of trigeminal: The fibers will descend to the motor nucleus-at the level of pons medial to the sensory nucleus- through trigeminal nerve then go to the muscles of mastication We have previously mentioned that the trigeminal ganglia is a sensory ganglia & it will be divided into 3 parts 1-ophthalmic V1: from the superior orbital fissure 2-Maxillary V2: Foramen Rotundum 3-Mandibular V3: foramen ovale So the trigeminal nerve is sensory for the face SVE special visceral efferent for muscles like tensor palatini ,tensor tympani & ant belly of digastric …etc GSA general somatic afferent from the skin of the face to trigeminal ganglia to spinal or sensory ganglia Sensory branches of the trigeminal nerve 1. The ophthalmic nerve (V1) carries sensory information from the scalp and forehead, the upper eyelid, the conjunctiva and cornea of the eye, the nose (including the tip of the nose, except alae nasi), the nasal mucosa, the frontal sinuses, and parts of the meninges 2. The maxillary nerve (V2) carries sensory information from the lower eyelid and cheek, the nares and upper lip, the upper teeth and gums, the nasal mucosa, the palate and roof of the pharynx, the maxillary, ethmoid and sphenoid sinuses, and parts of the meninges. 3. The mandibular nerve (V3) carries sensory information from the lower lip, the lower teeth and gums, the chin and jaw (except the angle of the jaw, which is supplied by C2-C3), parts of the external ear, and parts of the meninges. The mandibular nerve carries touch/position and pain/temperature sensation from the mouth. It does not carry taste sensation (chorda tympani is responsible for taste), but one of its branches, the lingual nerve carries multiple types of nerve fibers that do not originate in the mandibular nerve. So to sum up the trigeminal nerve has 4 nuclei 1- Spinal nucleus 2- Sensory nucleus 3- Motor nucleus 4- Mesencphalic nucleus Also we knew that trigeminal ganglia is sensory ganglia group the sensation to the nucleus in the brain stem whatever it was sensory motor spinal then to the contralateral thalamus then to the primary sensory cortex &it may so to the secondary sensory gyrus for the memory also we mentioned that it is divided into 3 parts ophthalmic, maxillary & mandibular, we also notices that there is minimal overlapping opposite to the dermatomes where the overlapping is noticed. Second: Facial Nerve (7th cranial nerve) It’s mixed nerve has 3 main nuclei: Main motor nucleus Parasympathetic nucleus Sensory nucleus The facial colliculus is an elevated area located on the dorsal pons. It is formed by motor fibers of the facial nerve as they loop over the abducens nucleus. Thus a lesion to the facial colliculus would result in facial muscle paralysis. Motor Nucleus of facial nerve: Responsible for the motor of the muscles of the face we can notice that the motor fibers originate from it loop around the abducent nerve forming (facial colliculus) to descend to facial muscles * We have to know that the supplement of the face by the facial nerve is divided into Upper part & Lower part *The upper part receive corticonuclear fibers : which are fibers from the cortex –previously mentioned the cranial nerves control the spinal nerves by corticonuclear ((also called corticobulber)) which control the upper part of the facial muscles & it is controlled by both hemispheres BUT The lower part is controlled by the contralateral side of the cortex Sensory Nucleus of facial nerve: It’s going to bring sensation from the face “ant 2/3 of the tongue” to geniculate ganglia ((like the sensory trigeminal ganglia it contains pseudounipolar cells to the sensory nucleus of facial nerve So From peripheral muscle like ant 2/3 of the tongue to geniculate ganglia to the sensory ganglia of facial nerve ((we have to know that it’s not separated it’s part of nucleus Solitaris—upper part of solitaris in the medulla)) where it synapses to the thalamus then to the cortex (postcentral gyrus) this is special sensation but general sensation of the tongue by lingual nerve. SoNucleus solitaris is a sensory nucleus that receive only sensory information from sensory part of cranial nerves or sensory cranial nerves & its upper part receive from facial nucleus **Imp note: 1) There is no synapse in the geniculate ganglia of facial nerves only there is cell bodies. 2) Ganglia: group of cell bodies outside CNS 3) nucleus solitaris in the medulla oblongata Parasympathetic nucleus of facial nerve It’s very near to the motor nucleus in the brain stem & it has 2 nuclei 1) superior salivatory nucleus 2) lacrimal nucleus both of them send preganglionic fibers to geniculate ganglia (No synapse) then go to the parasympathetic to synapse then postsynaptic fibers to the glands & smooth muscles **If all the fibers (parasyp, sensory&motor)) gather they will form facial nerve **sensory for the ant 2/3 of the tongue by chorda tympani to geiculate then contralateral thalamus **Motor for muscles like mylohyoid & digastric... Etc **parasymp originate of 2 nuclei which are called sup salivatory nucleus & lacrimal nucleus their fibers are preganglionic parasymp to pterygopalatine ganglion ((to the lacrimal gland)) &submandibular ganglion ((to submandibular gland & sublingual gland)) The passage of facial nerve outside the cranial cavity through the internal auditory meatus then outside the skull through stylomastoid foramen through the parotid gland it’ll divide into 5 branches. Types of its fibers: a. b. c. d. SVE: special visceral efferent (for muscles of facial expression) SVA: special visceral afferent GSA: general somatic afferent ((I didn’t hear it well)) sorry please anyone know it write it on the facebook group sorry again According to dr alia she said that most of the questions in the exam are about trigeminal & facial nerves also we have to know all the anatomical info because they are included. Third:Vestibulocochlear Nerve: It’s the 8th cranial nerve, responsible for hearing & equilibrium , it’s purely sensory The information about hearing & equilibrium are carried through it which enter to the internal auditory meatus with the facial nerve to the brain stem at the junction between pons & medulla oblongata It’s divided into 2 parts cochlear part responsible for hearing & vestibular part for balance & equilibrium (A) Vestibular ganglia is sensory ganglia contain cell bodies of vestibular nerve & it’s in the periphery contain group of cell bodies but vestibular nuclei it’s centrally located in the central nervous system specifically in the brain stem. Axons of the vestibular nerve synapse in the vestibular nucleus on the lateral floor and wall of the fourth ventricle in the pons and medulla. It arises from bipolar cells in the vestibular ganglion, ganglion of Scarpa, which is situated in the upper part of the outer end of the internal auditory meatus. So vestibular nerve starts from periphery to the cell bodies in vestibular ganglia ((which is in the internal auditory meatus)) to centrally toward brain ((brain stem)) then to the cortex but before it’ll pass through the thalamus. **vestibular nerve make synapse in the vestibular complex send efferent fibers for balance to cerebellum, spinal cord through vestibulospinal tract then through MLF but the other fibers go to the vestibulospinal tract (epsilateral). We have to know that both cerebellum & vestibular nerve are responsible for the balance NOW the question the must come to our minds “why does it send its fibers to cerebellum & spinal cord???!!!! ANS: for controlling; this means cerebellum control it by the spinal cord &part of it will be bound with the muscle of the eyes for movement during running …etc Vestibular canal sends fibers to vestibular ganglia (sensory ganglia) NO synapse to vestibular complex that sends some fibers to the MLF, cerebellum & spinal cord to the thalamus finally to the cortex (B) Cochlear Nerve: Conduction from organ of corti inside cochlea to cochlear nucleus in the brain stem then synapse ant & posterior ((ventral & dorsal)) to inferior peduncle through hearing pathway synapse in the trapezoid body which has nuclei of cochlear nerve –after synapse it must go to cortex but this doesn’t occur- to the lateral leminscus to inf colliculus where it synapse then to the tectum in the mid brain responsible for hearing. NOTES: Superior colliculus for vision Inferior colliculus for hearing to the medial genicualte body MGB to the cortex ( temporal lobe 41 & 42 ) by radiation like what occurs in the optic nerve Cochlear nerve pass at the junction between pons & medulla & enter its nucleus (cochlear nucleus)…etc –previous pathway- ………to be continued Done By: Dareen Matarweh :D (Never give up on something if you think you can fight for it. REMEMBER: "It’s difficult to wait but it's more difficult when you regret.")