neuroanatomy #4. cranial nerves viii, ix, xi and xii...the glossopharyngeal fibers travel just...
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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 receptors
Function
Sensory (specific sensitivity)
Vestibular: - Superior (Bekhterev) - Lateral (Deiters) - Medial (Schwalbe) - Inferior (Roller)
Vestibular ganglion (g.Scarpae) Receptor – hair cells of internal ear vestibulum
Equilibrium
Sensory (specific sensitivity)
Cochlear: - Ventral - Dorsal
Spiral ganglion Hair cells of cochlea
Hearing
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
Irritation of hair cells (organ of Corti) – transform irritation to nerve impulse
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
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
Superior olivary nucleus (ipsi- and contralateral sides, axons arise with lateral lemniscus) – determine sound localization
1st neuron
2nd neuron
2nd neuron 3rd neuron
•4th neuron Inferior colliculus of midbrain, medial geniculate bodies, nucleus of thalamus – subcortical auditory center
Cortical auditory center (Heschl gyrus)
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)
1st neuron
2nd neuron
3rd 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.
• 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
Membranous labyrinth
CN IX – Glossopharyngeal nerve – Nervus glossopharyngeus
Nature Nucleus Ganglia and receptor cells
Area of innervation
Somatic motor Nucleus ambiguus - - m.stylopharyngeus
Parasympathetic (visceral motor)
Nucleus salivatorius inferior
Ganglion oticum - Secretory innervation of parotid salivary gland
Visceral sensory Nucleus (tractus) solitarius
Ganglion inferior - Sensitivity from carotid glomus (chemoreceptors) and carotid sinus (baroreceptors)
General somatic sensory Nucleus (tractus) solitarius
Ganglion inferior
- skin of the external ear, internal surface of the tympanic membrane, upper pharynx, tonsils, soft palate, and the posterior 1/3 of the tongue.
Special sensory Nucleus (tractus) solitarius
Ganglion inferior
- Taste sensitivity of the 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
CN IX – Glossopharyngeal nerve – Nervus glossopharyngeus
The glossopharyngeal fibers travel just anterior to the cranial nerves X and XI which also exit the skull via the jugular foramen.
1st neuron cell bodies – in superior and inferior (petrosal)
ganglia
1st sensory nucleus – superior/inferior ganglia
Otic ganglion: - parasympathetic - 2nd parasympathetic
neuron cell bodies - Secretory innervation of
ipsilateral parotid salivary gland
- Postganglionic fibers from the otic ganglion travel with the auriculotemporal branch of CN V3 to enter the substance of the parotid gland.
CN IX
SM - Somatic motor PS – Parasympathetic S - Sensory
S, PS
PS
SM
S
S
S - taste
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
Nature Nucleus Ganglia and receptor cells
Area of innervation
Somatic motor Nucleus spinalis nervi accessorius
- - m. sternocleidomastoideus - m. trapezius
CN XI – Accessory nerve – Nervus accessorius
CN XI – Accessory nerve – Nervus accessorius
CN XI – Accessory nerve
CN XII – Hypoglossal nerve – Nervus hypoglossus
Nature Nucleus Ganglia and receptor cells
Area of innervation
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
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 masticatory muscles
Test skin sensitivity
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
Uvula turned to healthy side
Descent of left side of soft palate
CN XI – Accessory nerve
Test m. sternocleidomastoideus Test m. trapezoideus
CN XII – Hypoglossal nerve