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Brainstem Overview Medulla Pons Midbrain January 12, 2009 Ventral – Lateral View Corticospinal tract descends throughout movement Midbrain Cerebral peduncles Reticular formation descends throughout movement Pons Basis pontis ascends throughout arousal Medulla Pyramid Olive Ventral – Dorsal Organization (anterior - posterior) Basis Large anterior fiber tracts: cerebral peduncles, crossing pontine fibers, pyramids Ventral – Dorsal Organization Tegmentum Anterior cell body-rich areas, floor of brainstem: red nuclei, substantia nigra, reticular formation Ventral – Dorsal Organization Tectum Roof of the brainstem: superior colliculi, inferior colliculi: corpus quadrigemina Cerebellum Cuneatus, gracilis (medulla) Ventral – Dorsal Organization Tectum Basis Tegmentum Vertical Columns of Cranial Nerves Internal Columns of Nuclei III, IV, VI, XII V, VII, N. ambiguus, XII EW, Salivatory, DMN X V, VII, IX, X N. Solitary tract VIII Subdivisions of Vertical Columns • Motor nuclei – Somatic motor • closest to midline • eyes, tongue • CN III, IV, VI, XII – Branchial motor • Lateral position • Branchial arches: chewing, expression, middle ear, pharynx, larynx, sternomastoic, trapezius • CN V, VII, XI • N. ambiguus (IX, X) – Visceral motor • ventral / ventrolateral • Parasympathetic: glands, smooth muscle, heart, lungs, GI above splenic flexure • Edinger-Westfall (III) • Sup. & Inf. salivatory (VII) • Dorsal motor nucleus of X • Sensory nuclei – General sensory • • • • • lateral to branchial motor Face, sinuses, meninges All modalities CN V mainly Also CN VII, IX, X – Visceral sensory • lateral to visceral motor • Taste; cardiorespiratory, GI info • N. of the solitary tract (CN VII, IX, X) – Special sensory • • • • furthest lateral Balance; hearing CN VIII (vestibular) CN VIII (cochlear) Brainstem Overview Medulla Pons Midbrain . Internal Structure of Medulla Cross section at three levels • Level of pyramidal decussation • Level of lemniscal decussation • Level of inferior olivary nuclei Level of Pyramidal Decussation Lateral corticospinal tract 75 – 90% Gracile nucleus Spinal nucleus of V From pons to C4 Contralateral movement Pyramidal tract Anterior corticospinal tract -- fibers to innervate muscles of trunk Internal Structure of Medulla Cross section at three levels • Level of pyramidal decussation • Level of lemniscal decussation • Level of inferior olivary nuclei Level of Lemniscal Decussation Gracile nucleus MLF Cuneate nucleus Position & vibration sense Pyramids Internal arcuate fibers Medial lemniscus Carries 2nd order sensory neurons to VPL thalamus Internal Structure of Medulla Cross section at three levels • Level of pyramidal decussation • Level of lemniscal decussation • Level of inferior olivary nuclei Level of Inferior Olives Hypoglossal nucleus CN XII Inferior cerebellar peduncle = Restiform body Vestibular nuclei Medial Inferior MLF Inferior olivary nuclei Relay between cortex, vestibular nuclei, cerebellum, basal ganglia, and dorsal column nuclei Arcuate nuclei pontine nuclei Cranial Nerves of the Medulla Vestibular nuclei CN XII Cranial Nuclei of the Medulla N. solitarious Sensory nucleus for CN VII, IX, X Cranial Nuclei of the Medulla N. solitarious Sensory nucleus for CN VII, IX, X Spinal trigeminal tract CN V, VII, IX, X Cranial Nuclei of the Medulla N. solitarious Sensory nucleus for CN VII, IX, X Spinal trigeminal tract N. ambiguus CN V, VII, IX, X Motor nucleus for CN IX, X & XI Cranial Nuclei of the Medulla N. solitarious Dorsal motor nucleus of X Sensory nucleus for CN VII, IX, X Spinal trigeminal tract N. ambiguus CN V, VII, IX, X Motor nucleus for CN IX, X & XI CN IX: Glossopharyngeal Nerve N. solitarious Sensory nucleus for CN VII, IX, X Spinal trigeminal tract N. ambiguus CN V, VII, IX, X Motor nucleus for CN IX, X & XI CN IX: Glossopharyngeal Nerve N. solitarious Sensory nucleus for CN VII, IX, X Posterior 1/3 of the tongue Spinal trigeminal tract N. ambiguus CN V, VII, IX, X Motor nucleus for CN IX, X & XI CN IX: Glossopharyngeal Nerve N. solitarious Sensory nucleus for CN VII, IX, X Posterior 1/3 of the tongue Spinal trigeminal tract N. ambiguus CN V, VII, IX, X Motor nucleus for Sensation behind ear CN IX, X & XI CN IX: Glossopharyngeal Nerve N. solitarious Sensory nucleus for CN VII, IX, X Posterior 1/3 of the tongue Spinal trigeminal tract N. ambiguus CN V, VII, IX, X Motor nucleus for Sensation behind ear CN IX, X & XI Stylopharyngeus (lifts pharynx) CN IX: Glossopharyngeal Nerve N. solitarious Inf. salivatory nucleus Parotid gland, parasympathetic Sensory nucleus for CN VII, IX, X Posterior 1/3 of the tongue Spinal trigeminal tract N. ambiguus CN V, VII, IX, X Motor nucleus for Sensation behind ear CN IX, X & XI Stylopharyngeus (lifts pharynx) CN X: Vagus Nerve “Wanderer” N. solitarious Sensory nucleus for CN VII, IX, X Spinal trigeminal tract N. ambiguus CN V, VII, IX, X Motor nucleus for CN IX, X & XI CN X: Vagus Nerve “Wanderer” N. solitarious Sensory nucleus for CN VII, IX, X Taste, epiglottis Cardiorespiratory Spinal trigeminal tract N. ambiguus CN V, VII, IX, X Motor nucleus for CN IX, X & XI CN X: Vagus Nerve “Wanderer” N. solitarious Sensory nucleus for CN VII, IX, X Taste, epiglottis Cardiorespiratory Spinal trigeminal tract N. ambiguus CN V, VII, IX, X Motor nucleus for Ear CN IX, X & XI CN X: Vagus Nerve “Wanderer” N. solitarious Sensory nucleus for CN VII, IX, X Taste, epiglottis Cardiorespiratory Spinal trigeminal tract N. ambiguus CN V, VII, IX, X Motor nucleus for Ear CN IX, X & XI Pharynx Larynx CN X: Vagus Nerve “Wanderer” N. solitarious Dorsal motor nucleus of X Sensory nucleus for CN VII, IX, X Taste, epiglottis Cardiorespiratory Spinal trigeminal tract N. ambiguus CN V, VII, IX, X Motor nucleus for Ear CN IX, X & XI Pharynx Larynx CN X: Vagus Nerve “Wanderer” N. solitarious Dorsal motor nucleus of X Parasympathetic, preganglionic Sensory nucleus for CN VII, IX, X Taste, epiglottis Cardiorespiratory Spinal trigeminal tract N. ambiguus CN V, VII, IX, X Motor nucleus for Ear CN IX, X & XI Pharynx Larynx Brainstem Overview Medulla Pons Midbrain Pons Landmarks Basis pontis 4th ventricle Cerebellum and Middle cerebellar peduncle Cranial Nerves V, VI, VII, VIII Pontine Nuclei Input (ipsilateral) Motor cortex Sensory cortex Association cortex Cingulate cortex Output (contralateral) Transverse crossing via middle cerebellar peduncle to cerebellum Pontine nuclei Project to cerebellum Continuation of arcuate nuclei (over pyramids) Internal Structure of the Pons Cross section at three levels • Level of facial nucleus (CN VII) • Level of middle cerebellar peduncle • Level of locus ceruleus 4th Ventricle Pons Connection of pons to cerebellum Restiform body (inf. cerebellar peduncle) Middle cerebellar peduncle Medial lemniscus Ascending 2nd order sensory neurons Descending upper motor neurons Cranial Nerves of Lower Pons Posterior view: Cerebullum cut away CN VIII – Vestibular Nuclei Pure sensory lateral location Balance Cranial Nerves of Lower Pons CN VIII – Vestibular Nuclei (Cochlear Nuclei) Cranial Nerves of Lower Pons At a slightly higher level CN VI nucleus – Abducens nerve Abduction of eye Longest, most vulnerable CN CN VII nucleus – Facial nerve Muscles of face Cranial Nerves of Lower Pons CN VII nucleus - Facial nerve Muscles of face Cranial Nerves of Lower Pons CN VI nucleus – Abducens nerve Abduction of eye Internal Structure of the Pons Cross section at three levels • Level of facial nucleus (CN VII) • Level of middle cerebellar peduncle • Level of locus ceruleus Anterior view Mid Pons 4th Ventricle Middle cerebellar peduncle Corticospinal tract, Descending fibers corticobulbar tract, corticopontine fibers Mid Pons 4th Ventricle Middle cerebellar peduncle Pontine nuclei in basis Mid Pons Lateral lemniscus from cochlear nucleus hearing Pontine nuclei Trapezoid body – transverse fibers in pontine tegmentum Mid Pons Lateral lemniscus Medial lemniscus fibers from dorsal column (position and vibration) Trigeminal tract pain, temperature, touch from contralateral face Pontine nuclei Lemniscal sensory system – in tegmentum of the pons Cranial Nerve of the Mid Pons 4th Ventricle CN V Motor trigeminal nucleus Cranial Nerve of the Mid Pons 4th Ventricle CN V Motor trigeminal nucleus Principal trigeminal sensory nucleus Cranial Nerve of the Mid Pons 4th Ventricle CN V Motor trigeminal nucleus Trigeminal fascicles Trigeminal nerve Principal trigeminal sensory nucleus Internal Structure of the Pons Cross section at three levels • Level of facial nucleus (CN VII) • Level of middle cerebellar peduncle • Level of locus ceruleus Upper Pons 4th ventricle cerebral aqueduct Superior cerebellar peduncle decussation Upper Pons 4th ventricle cerebral aqueduc Superior cerebellar peduncle Transverse ponto-cerebellar fibers Descending upper motor neurons Upper Pons Periaqueductal gray matter 4th ventricle cerebral aqueduc MLF Upper Pons 4th ventricle cerebral aqueduc Locus ceruleus Primary source of noradrenergic innervation to the brain Neurons contain melanin MLF Upper Pons 4th ventricle cerebral aqueduc Parabrachial Nucleus Also release catecholamines Neurons also contain melanin MLF Upper Pons 4th ventricle cerebral aqueduc Pediculopontine Nucleus Some neurons release acetylcholine Other neurons release glutamate They assist in learning and voluntary motor control, e.g. locomotion, saccadic eye MLF Brainstem Overview Medulla Pons Midbrain Midbrain Landmarks Cerebral peduncles Optic chiasm Interpeduncular fossa (Superior colliculi) (Inferior colliculi) (Superior cerebellar peduncle) Cranial Nerves III, IV Patterning of the Midbrain External Structure of Midbrain 1. Optic chiasm 2. Interpeduncular fossa 3. Oculomotor nerve (CN III) 4. Trochlear nerve (CN IV) 5. Pons 6. Cerebral peduncles (crus cerebri) Ventral surface (anterior) External Structure of Midbrain Quadrigeminal Plate • Superior colliculus • Inferior colliculus CN IV Trochlear nerve Dorsal surface Cerebellum removed Cranial Nerves of the Midbrain Anterior exit Posterior exit CN III (1) CN IV (2) CN VI (5) MLF - Medial longitudinal fasciculus (7) Vestibular nuclei (6) Pons (3) Internal Structure of Midbrain Cross section at two levels • Level of inferior colliculus • Level of superior colliculus Lower Midbrain Inferior colliculus hearing DORSAL cerebral aqueduct cerebral peduncles VENTRAL Lower Midbrain Inferior colliculus Substantia nigra Melanin-containing cells that produce dopamine Project to the basal ganglia Lower Midbrain Inferior colliculus Substantia nigra Crus cerebri (cerebral peduncle) Basis peduncularis Lower Midbrain Inferior colliculus CN IV Trochlear nerve Lower Midbrain Inferior colliculus CN IV Trochlear nerve MLF Lower Midbrain Inferior colliculus CN IV MLF Dorsal raphe nucleus – projects serotonergic fibers to basal ganglia and throughout cortex Lower Midbrain Inferior colliculus hearing Mesencephalic nucleus of V analogous to dorsal root ganglion but within CNS Internal Structure of Midbrain Cross section at two levels • Level of inferior colliculus • Level of superior colliculus Upper Midbrain Superior colliculus vision Substantia nigra Crus cerebri (cerebral Upper Midbrain Superior colliculus vision Medial geniculate body hearing Upper Midbrain Vision Superior colliculus Lateral geniculate body Hearing Inferior colliculus Medial geniculate body Upper Midbrain Superior colliculus vision Red nucleus – relay from cortex and cerebellum to spinal cord, inferior olive, reticular formation, cerebellum Controls arm movement Cranial Nerves of Upper Midbrain Superior colliculus vision Edinger Westfal nucleus Parasympathetic to ciliary ganglion Pupillary sphincter ciliary muscles Red nucleus CN III Oculomotor nucleus Cranial Nerves of Upper Midbrain Superior colliculus vision Edinger Westfal nucleus MLF Red nucleus CN III Oculomotor nucleus Innervation of Eye Muscles Dorsal view Cerebellum removed Innervation of Eyes & Muscles Lacrimal gland VII) (CN Superior rectus Inferior rectus Medial rectus Inferior Oblique (CN III) Superior oblique (CN IV) Lateral rectus (CN VI) Parasympathetic: Edinger-Westfal (CN III) Sympathetic: Superior Cervical Ganglion Tuesday Diencephalon Thalamus Hypothalamus
