Brainstem Overview Medulla Pons Midbrain January 12 2009

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 C 4 Anterior corticospinal tract Contralateral movement Pyramidal 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 2 nd 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 4 th ventricle Cerebellum and Middle cerebellar peduncle Cranial Nerves V, 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

4 th Ventricle Pons Connection of pons to cerebellum Restiform body (inf. cerebellar peduncle) Middle cerebellar peduncle Medial lemniscus Ascending 2 nd 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 4 th Ventricle Middle cerebellar peduncle Corticospinal tract, Descending fibers corticobulbar tract, corticopontine fibers

Mid Pons 4 th 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 CN V Motor trigeminal nucleus 4 th Ventricle

Cranial Nerve of the Mid Pons 4 th Ventricle CN V Motor trigeminal nucleus Principal trigeminal sensory nucleus

Cranial Nerve of the Mid Pons 4 th 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 4 th ventricle cerebral aqueduct Superior cerebellar peduncle decussation

Upper Pons 4 th ventricle cerebral aqueduct Superior cerebellar peduncle Transverse ponto-cerebellar fibers Descending upper motor neurons

Upper Pons Periaqueductal gray matter 4 th ventricle cerebral aqueduct MLF

Upper Pons 4 th ventricle cerebral aqueduct Locus ceruleus Primary source of noradrenergic innervation to the brain Neurons contain melanin MLF

Upper Pons 4 th ventricle cerebral aqueduct Parabrachial Nucleus Also release catecholamines Neurons also contain melanin MLF

Upper Pons 4 th ventricle cerebral aqueduct 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