Neuroanatomy #4. Cranial nerves VIII, IX, XI and XII Aygul Shafigullina Department of Morphology and General Pathology CN VIII – Vestibular cochlear nerve – Nervus vestibulocochlearis CN VIII – Vestibulocochlear nerve – Nature and nuclei Nature Nucleus Ganglion and Function receptors Sensory (specific Vestibular: Vestibular ganglion Equilibrium sensitivity) - Superior (Bekhterev) (g.Scarpae) - Lateral (Deiters) - Medial (Schwalbe) Receptor – hair cells - Inferior (Roller) of internal ear vestibulum Sensory (specific Cochlear: Spiral ganglion Hearing sensitivity) - Ventral - Dorsal Hair cells of cochlea CN VIII – Vestibulocochlear nerve – Cochlear part • malleus (hammer) • incus (anvil) • stapes (stirrup) The INNER EAR consists of a maze of fluid-filled tubes, running through the temporal bone of the skull. The bony tubes, the bony labyrinth, are filled with a fluid called perilymph. There are three major sections of the bony labyrinth: 1. The front portion, the snail-shaped cochlea, functions in hearing. 2. The rear part, the semicircular canals, helps maintain balance. 3. Interconnecting the cochlea and the semicircular canals is the vestibule, containing the sense organs responsible for balance, the utricle and saccule. Within this bony labyrinth is a second series of delicate cellular tubes, called the membranous labyrinth, filled with the fluid called endolymph. The membranous labyrinth within the cochlea houses the Organ of Corti, containing the inner and outer hair cells that generate the nerve impulses required for hearing. Epithelial cells of the bony labyrinth produce perilymph: Scala tympani and scala vestibuli contain perilymph Sensory cells – hair cells (Organ of Corti) 1st neuron cell bodies – in spiral ganglion Sound waves External acoustic meatus Tympanic membrane (its vibration) Middle ear ossicles (malleus-incus- stapes) – intensify the vibrations and transmit it to oval window of cochlear Vibration of perilymph in cochlear Vibration of endolymph Irritation of hair cells (organ of Corti) – transform irritation to nerve impulse Primary sensory neurons (spiral ganglion) Diagram of relationship of nerves in the internal acoustic meatus: VII = facial nerve NI = nervus intermedius VIIIc = cochlear nerve VIIIvs = superior division of vestibular nerve VIIIvi = inferior division of vestibular nerve 2nd neuron – Cochlear nuclei of CN VIII: - Ventral - Dorsal Cortical auditory center (Heschl gyrus) •4th neuron Inferior colliculus of midbrain, medial geniculate bodies, nucleus of thalamus – subcortical auditory center Superior olivary nucleus 2nd neuron (ipsi- and contralateral sides, 3rd neuron axons arise with lateral 2nd neuron lemniscus) – determine sound localization 1st neuron Conductor (external air pathway) and neurosensory (cochlear) components of the CNVIII Sing a sound and, while singing, close one of the ears. Normally, the sound`s volume in closed ear increases. Ludwig van Beethoven (1770-1827) CN VIII – Vestibulocochlear nerve – Vestibular part Vestibular apparatus – sensory hair cells in 5 structures: utricle, saccule, 3 semicircular canals 1st neuron cell bodies – in vestibular (Scarpa`s) ganglion 2nd neuron Vestibular nuclei of CN VIII: - Superior (Bekhterev) - Lateral (Deiters) - Medial (Schwalbe) - Inferior (Roller) 3rd neuron 2nd neuron 1st neuron Ascending medial longitudinal fascicule (reticular formation) - to nuclei of CN III, CN IV, CN VI Descending medial longitudinal fascicule (reticular formation) and vestibulospinal tract Otolith organs react to gravity! Sea sickness Romberg's test, Romberg's sign, or the Romberg maneuver is a test used in an exam of neurological function for balance, and also as a test for drunken driving. Membranous labyrinth • there are more compartments and ducts within the membranous labyrinth than there are regions of the bony labyrinth • it is important to recognize that the membranous labyrinth is completely enclosed, therefore there are no connections between the spaces containing endolymph and those containing perilymph • beginning at the oval and round windows, the first part of the membranous labyrinth is the cochlear duct (= scala media); it extends anteriorly before coiling around the modiolus Membranous labyrinth • branching off the cochlear duct is the narrow ductus reuniens that connects to the saccule, the most anterior and inferior of the vestibular system components • the saccule connects to the utricle, which occupies the rest of the vestibule • the saccule and utricle have a Y-shaped connection with each other, and with the endolymphatic duct, which travels through the vestibular aqueduct to a blind end called the endolymphatic sac (not shown in the picture) • the semicircular canals are connected to the utricle; the anterior and posterior canals form a common duct at the end opposite their ampullae CN IX – Glossopharyngeal nerve – Nervus glossopharyngeus CN IX – Glossopharyngeal nerve – Nervus glossopharyngeus Nature Nucleus Ganglia and receptor Area of innervation cells Somatic motor Nucleus ambiguus - - m.stylopharyngeus Parasympathetic Nucleus salivatorius Ganglion oticum - Secretory innervation of (visceral motor) inferior parotid salivary gland Visceral sensory Nucleus (tractus) Ganglion inferior - Sensitivity from carotid solitarius glomus (chemoreceptors) and carotid sinus (baroreceptors) General somatic sensory Nucleus (tractus) Ganglion inferior - skin of the external ear, solitarius internal surface of the tympanic membrane, upper pharynx, tonsils, soft palate, and the posterior 1/3 of the tongue. Special sensory Nucleus (tractus) Ganglion inferior - Taste sensitivity of the solitarius posterior 1/3 (root) of the tongue CN IX – Glossopharyngeal nerve – Nervus glossopharyngeus CN IX – Glossopharyngeal nerve – Nervus glossopharyngeus Emerge from brain: sulcus dorsolateralis retroolivaris medullae oblongatae 1st neuron cell bodies – in superior and inferior (petrosal) ganglia The glossopharyngeal fibers travel just anterior to the cranial nerves X and XI which also exit the skull via the jugular foramen. CN IX Otic ganglion: - parasympathetic - 2nd parasympathetic PS neuron cell bodies - Secretory innervation of ipsilateral parotid S, PS salivary gland - Postganglionic fibers 1st sensory nucleus from the otic ganglion SM – superior/inferior travel with the ganglia auriculotemporal S branch of CN V3 to S enter the substance of the parotid gland. S - taste SM - Somatic motor PS – Parasympathetic S - Sensory S CN IX - central course - visceral sensory component • From the nucleus solitarius, connections are made with several areas in the reticular formation and hypothalamus to mediate cardiovascular and respiratory reflex responses to changes in blood pressure, and serum concentrations of CO2 and O2. CN IX - Clinical correlation • The general sensory fibers of CN IX mediate the afferent limb of the pharyngeal reflex in which touching the back of the pharynx stimulates the patient to gag (i.e. the gag reflex). The efferent signal to the musculature of the pharynx is carried by the branchial motor fibers of the vagus nerve. CN XI – Accessory nerve – Nervus accessorius CN XI – Accessory nerve – Nervus accessorius Nature Nucleus Ganglia and Area of innervation receptor cells Somatic motor Nucleus spinalis nervi - - m. sternocleidomastoideus accessorius - m. trapezius CN XI – Accessory nerve – Nervus accessorius CN XI – Accessory nerve CN XII – Hypoglossal nerve – Nervus hypoglossus CN XII – Hypoglossal nerve – Nervus hypoglossus Nature Nucleus Ganglia and Area of innervation receptor cells Somatic motor Nucleus nervi hypoglossi - - Skeletal muscles of the tongue - Infrahyoid group of muscles (together with branches of cervical plexus) CN XII – Hypoglossal nerve – Nervus hypoglossus Hypoglossal nerve (XII) – only contralateral side (total decussation) Normal Deviate to damaged side Cranial nerves: I – Olfactory II – Optic III – Oculomotor IV – Trochlear V – Trigeminal VI – Abducens VII – Facial VIII – Vestobulocochlear IX – Glossopharyngeal X – Vagus XI – Accessory XII – Hypoglossal Tests to check cranial nerves CN I – Olfactory nerve CN II – Optic nerve CN III – Oculomotor nerve CN IV – Trochlear nerve CN VI – Abducens nerve CN III – Oculomotor nerve, parasympathetic component CN V – Trigeminal nerve Corneal reflex Test skin sensitivity Test masticatory muscles CN VII – Facial nerve Test taste sensitivity Test mimic muscles Don’t forget! - Dry eye - Dry mucous of nasal and oral cavity CN VIII – Vestibulocochlear nerve Tests of Rinne Romberg's test Tests of Weber CN IX – Glossopharyngeal nerve The gag reflex Don’t forget! - Parotid salivary gland CN X – Vagus nerve Descent of left side of Uvula turned to soft palate healthy side CN XI – Accessory nerve Test m. sternocleidomastoideus Test m. trapezoideus CN XII – Hypoglossal nerve .