BRAINSTEM

Structural Overview of Brainstem Midbrain, pons, medulla functions

BRAINSTEM DORSAL SURFACE VENTRAL SURFACE

medulla Connects pons superiorly with spinal cord inferiorly Conical in shape The Central canal continues upward into the lower half of medulla, in the upper half of medulla it expands as the cavity of fourth ventricle

two parts: open and closed an open part (close to the pons) a closed part (further down towards the spinal cord).

Gross Anatomy Review Medulla - ventral Anterior median fissure Pyramids Pyramidal decussation Olive Inferior cerebellar peduncle

Gross Anatomy Review Dorsal medulla Posterior median sulcus Gracile tubercle Cuneate tubercle.

Brainstem X-sections Caudal medulla Rostral medulla Caudal pons Rostral pons Caudal midbrain Rostral midbrain

medulla 3 sections inside the medulla: Pyramidal decussation Sensory decussation Level of olive

Caudal medulla pyramidal decussation

CAUDAL MEDULLA (LEVEL OF PYRAMIDAL DECUSSATION) FG DMS FC GN ST5 Central grey matter CN SN5 Central canal DSC PD VSC P VMF

CAUDAL MEDULLA (LEVEL OF PYRAMIDAL DECUSSATION) DMS: Dorsal median sulcus FG: fasciculus gracilis GN: Gracile nucleus FC: Fasciculus cuneatus CN: Cuneate nucleus SN5: Spinal nucleus of trigeminal nerve ST5: Spinal tract of trigeminal nerve P: Pyramid PD: Pyramidal decussation DSC: Dorsal spinocerebellar tract VSC: Ventral spinocerebellar tract VMF: Ventral median fissure

CAUDAL MEDULLA (LEVEL OF PYRAMIDAL DECUSSATION) GREY MATTER: Sensory nuclei: Gracile, cuneate, spinal nucleus of trigeminal WHITE MATTER: Ascending tracts: Gracile, cuneate, spinal tract of trigeminal, dorsal & ventral spinocerebellar, spinal leminiscus Descending tracts: Pyramidal & extrapyramidal tracts

CAUDAL MEDULLA (LEVEL OF PYRAMIDAL DECUSSATION) Pyramidal decussation: Most of the fibers of pyramid decussate then pass laterally & dorsally to form the lateral corticospinal tract that descend in the lateral white column of spinal & terminate in ventral horn cells of opposite side Spinal nucleus of trigeminal: It lies in the lower part of pons, the whole medulla & extends to the 2nd cervical segment of spinal cord where it is continuous with substantia gelatinosa. It receives pain & temperature sensations from the face along trigeminal nerve

CAUDAL MEDULLA (LEVEL OF PYRAMIDAL DECUSSATION) Dorsal & ventral spinocerebellar tracts: They carry proprioceptive fibers to the cerebellum through inferior cerebellar peduncle (dorsal) & superior cerebellar peduncle (ventral) Gracile &Cuneate tracts: They carry proprioceptive sensations & end in Gracile & Cuneate nuclei (2nd order neurones in dorsal column tract)

MID MEDULLA (LEVEL OF SENSORY DECUSSATION) DMS FG Central grey matter FC GN CN Central canal ST5 SN5 Internal Arcuate Fibers DSC M L VSC Sensory Decussation P VMF

MID MEDULLA (LEVEL OF SENSORY DECUSSATION) Gracile & cuneate nuclei: They are more prominent. Axons of cells of gracile & cuneate nuclei curve around the central canal as internal arcuate fibers then decussate forming the sensory decussation & ascend in the brain stem as medial leminiscus that end in the ventral posterolateral nucleus of thalamus Pyramid: They are more prominent

MID MEDULLA (LEVEL OF SENSORY DECUSSATION) GREY MATTER: Sensory nuclei: Gracile, cuneate, spinal nucleus of trigeminal WHITE MATTER: Ascending tracts: gracile, cuneate, spinal tract of trigeminal, dorsal & ventral spinocerebellar, spinal leminiscus Descending tracts: Pyramidal & extrapyramidal tracts

Caudal medulla int arcuate fibers gracile & cuneate nuc & fasc Int arcuate fibers – ML MLF Nucleus of spinal tract of trigeminal nerve Inferior olivary nuc Pyramids Hypoglossal nuclei

Rostral medulla inf olivary nuc olivary nuclear complex Vestibulocochlear nuclei Nucleus ambiguus Hypoglossal nerve, dorsal nucleus of vagus, vestibulocochlear, glossopharyngeal and accessory nuclei

ROSTRAL MEDULLA DCN 4TH V ICP VCN Vagus Nerve I.O. ML Hypoglossal MV LV V H S ICP VCN M L F A D Vagus Nerve I.O. ML M Hypoglossal Nerve P VMF

ROSTRAL MEDULLA H: Hypoglossal nucleus V: Dorsal vagal nucleus S: Nucleus solitarius A: nucleus ambiguus MV: Medial vestibular nucleus LV: Lateral vestibular nucleus DCN: Dorsal cochlear nucleus VCN: Ventral cochlear nucleus ICP: Inferior cerebellar peduncle I.O.: Inferior olive D: Dorsal accessory olive M: Medial accessory olive MLF: Medial longitudinal fascisulus ML: Medial leminiscus P: Pyramid VMF: Ventral median fissure

ROSTRAL MEDULLA GREY MATTER: Motor nuclei: Hypoglossal, dorsal vagal, nucleus ambiguus Sensory nuclei: Nucleus solitarius, medial & lateral vestibular nuclei, dorsal & ventral cochlear nuclei, spinal nucleus of trigeminal Extrapyramidal nuclei: Inferior olive, medial & dorsal accessory olive

ROSTRAL MEDULLA WHITE MATTER: Ascending tracts: Medial leminiscus, spinal leminiscus, spinal tract of trigeminal, ventral spinocerebellar tract Descending tracts: Pyramidal & extrapyramidal tracts Both ascending & descending tract: Medial longitudinal fasciculus Inferior cerebellar peduncle: fibers connecting medulla to cerebellum

ROSTRAL MEDULLA Hypoglossal nucleus: It lies in the medial part of floor of 4th ventricle. It contains motor neurones innervating muscles of tongue (except palatoglossus) through hypoglossal nerve Dorsal vagal nucleus: It lies in the floor of 4th ventricle , lateral to hypoglossal nucleus. It contains preganglionic parasympathetic neurones running in the vagus nerve Nucleus Solitarius: It lies ventrolateral to dorsal vagal nucleus. It receive taste fibers from facial, glossopharyngeal & vagus nerves

ROSTRAL MEDULLA Nucleus ambiguus: It lies dorsal to inferior olivary nucleus. It contains motor neurones innervating muscles of pharynx, palate & larynx through glossopharyngeal, vagus & cranial part of accessory nerves Medial & lateral vestibular nuclei: They lie in the floor of 4th ventricle, lateral to dorsal vagal nucleus. They receive afferent fibers from vestibular nerve Dorsal & ventral cochlear nuclei: They lie dorsal (dorsal nucleus) & lateral (ventral nucleus) to ICP. They receive afferent fibers from cochlear nerve

ROSTRAL MEDULLA Olivary nuclear complex: It is formed of a large nucleus (inferior olive) & 2 smaller nuclei (medial & dorsal accessory olive). Afferents: From cerebral and cerebellar cortex & spinal cord Efferents: To cerebellum through ICP Function: They are concerned with control of movement

ROSTRAL MEDULLA Medial longitudinal fasciculus: It consists of both ascending & descending fibers: Ascending fibers: connect vestibular nuclei to nuclei supplying extraoccular muscles (occulomotor, trochlear & abducent nuclei). It coordinates movements of head & eyes Descending fibers: connect vestibular nuclei to nuclei of ventral horn of spinal cord (medial vestibulospinal tract). It control body posture & balance

ROSTRAL MEDULLA Spinal leminiscus: It carries pain, temperature & touch sensations from the opposite side of body to ventral posterolateral nucleus of thalamus Inferior cerebellar peduncle: It is formed of fibers connecting medulla to cerebellum

Level of Inferior Olives Vestibular nuclei Medial Inferior Hypoglossal nucleus CN XII Inferior cerebellar peduncle = Restiform body Inferior olivary nuclei MLF Arcuate nuclei  pontine nuclei

Rostral medulla N. solitarious Dorsal motor nucleus of X Sensory nucleus for CN VII, IX, X Dorsal motor nucleus of X Spinal trigeminal tract CN V, VII, IX, X N. ambiguus Motor nucleus for CN IX, X & XI

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

Cranial Nuclei of the Medulla N. solitarious Sensory nucleus for CN VII, IX, X Spinal trigeminal tract N. ambiguus Motor nucleus for CN IX, X & XI

Cranial Nuclei of the Medulla N. solitarious Sensory nucleus for CN VII, IX, X Dorsal motor nucleus of X Spinal trigeminal tract CN V, VII, IX, X N. ambiguus Motor nucleus for CN IX, X & XI

CN IX: Glossopharyngeal Nerve N. solitarious Sensory nucleus for CN VII, IX, X Spinal trigeminal tract CN V, VII, IX, X N. ambiguus 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 CN V, VII, IX, X N. ambiguus 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 CN V, VII, IX, X Sensation behind ear N. ambiguus 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 CN V, VII, IX, X Sensation behind ear N. ambiguus Motor nucleus for CN IX, X & XI Stylopharyngeus (lifts pharynx)

CN IX: Glossopharyngeal Nerve N. solitarious Sensory nucleus for CN VII, IX, X Posterior 1/3 of the tongue Inf. salivatory nucleus Parotid gland, parasympathetic Spinal trigeminal tract CN V, VII, IX, X Sensation behind ear N. ambiguus Motor nucleus for CN IX, X & XI Stylopharyngeus (lifts pharynx)

CN X: Vagus Nerve N. solitarious Spinal trigeminal tract Sensory nucleus for CN VII, IX, X Spinal trigeminal tract CN V, VII, IX, X N. ambiguus Motor nucleus for CN IX, X & XI

CN X: Vagus Nerve N. solitarious Spinal trigeminal tract Sensory nucleus for CN VII, IX, X Taste, epiglottis Cardiorespiratory Spinal trigeminal tract CN V, VII, IX, X N. ambiguus Motor nucleus for CN IX, X & XI

CN X: Vagus Nerve N. solitarious Spinal trigeminal tract Sensory nucleus for CN VII, IX, X Taste, epiglottis Cardiorespiratory Spinal trigeminal tract CN V, VII, IX, X Ear N. ambiguus Motor nucleus for CN IX, X & XI

CN X: Vagus Nerve N. solitarious Spinal trigeminal tract Sensory nucleus for CN VII, IX, X Taste, epiglottis Cardiorespiratory Spinal trigeminal tract CN V, VII, IX, X Ear N. ambiguus Motor nucleus for CN IX, X & XI Pharynx Larynx

CN X: Vagus Nerve N. solitarious Dorsal motor nucleus of X Sensory nucleus for CN VII, IX, X Taste, epiglottis Cardiorespiratory Dorsal motor nucleus of X Spinal trigeminal tract CN V, VII, IX, X Ear N. ambiguus Motor nucleus for CN IX, X & XI Pharynx Larynx

CN X: Vagus Nerve N. solitarious Dorsal motor nucleus of X Sensory nucleus for CN VII, IX, X Taste, epiglottis Cardiorespiratory Dorsal motor nucleus of X Parasympathetic, preganglionic Spinal trigeminal tract CN V, VII, IX, X Ear N. ambiguus Motor nucleus for CN IX, X & XI Pharynx Larynx

Pons Lies anterior to cerebellum Connects medulla to midbrain 1 inch long

Pons Landmarks Cranial Nerves 4th ventricle Cerebellum and Middle cerebellar peduncle Basilar groove Cranial Nerves Abducent, facial, vestibulocochlear, Trigeminal nerves

Ventral – Lateral View Midbrain Pons Medulla Cerebral peduncles Basis pontis Medulla Pyramid Olive

Pons Posterior view Median sulcus Medial eminence Sulcus limitans Facial colliculus Area vestibuli

Pons It is commonly divided into anterior part(basal part) and posterior part (tegmentum) by transversely running fibers of trapezoid body

Internal Structure of the Pons Cross section at two levels Level of facial nucleus (CN VII) Level of trigeminal nuclei

Level of facial colliculus

Pons 4th Ventricle Connection of pons to cerebellum (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

level of Upper Pons

Upper Pons 4th Ventricle Middle cerebellar peduncle Corticospinal tract, corticobulbar tract, corticopontine fibers Descending fibers

Upper Pons Pontine nuclei in basis 4th Ventricle Middle cerebellar peduncle Pontine nuclei in basis

Upper Pons Pontine nuclei Lateral lemniscus Pontine nuclei Trapezoid body – transverse fibers in pontine tegmentum

Lower Pons Pontine nuclei Medial lemniscus fibers from dorsal column (position and vibration) Lateral lemniscus Trigeminal tract pain, temperature, touch from contralateral face Pontine nuclei Lemniscal sensory system – in tegmentum of the pons

Cranial Nerve of the upper Pons 4th Ventricle CN V Motor trigeminal nucleus

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

Cranial Nerve of the upper Pons 4th Ventricle CN V Motor trigeminal nucleus Trigeminal fascicles Trigeminal nerve Principal trigeminal sensory nucleus

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

Upper Pons 4th ventricle  cerebral aqueduct MLF

Midbrain 0.8 inch in length Connects Pons and cerebellum with the forebrain

cerebral aqueduct

EXTERNAL MORPHOLOGY superior colliculus

EXTERNAL MORPHOLOGY inferior colliculus

EXTERNAL MORPHOLOGY CN.IV

EXTERNAL MORPHOLOGY crus cerebri

interpeduncular fossa EXTERNAL MORPHOLOGY interpeduncular fossa

EXTERNAL MORPHOLOGY CN.III

INTERNAL MORPHOLOGY-slide 16 cerebral aqueduct

External Structure of Midbrain Optic chiasm Interpeduncular fossa Oculomotor nerve (CN III) Trochlear nerve (CN IV) Pons crus cerebri Ventral surface (anterior)

Posterior view

Patterning of the Midbrain

Internal Structure of Midbrain Cross section at two levels Level of inferior colliculus Level of superior colliculus

Lower Midbrain Inferior colliculus hearing cerebral aqueduct DORSAL VENTRAL Crus cerebri

Lower Midbrain Inferior colliculus Substantia nigra Melanin-containing cells that produce dopamine Project to the basal ganglia, cerebral cortex, cerebellum, hypothalamus

Lower Midbrain Inferior colliculus Substantia nigra Crus cerebri

Lower Midbrain Inferior colliculus CN IV Trochlear nerve

Lower Midbrain Inferior colliculus CN IV Trochlear nerve MLF

Lower Midbrain Inferior colliculus CN IV MLF

Lower Midbrain Inferior colliculus hearing Mesencephalic nucleus of V

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

Upper Midbrain Vision Hearing 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, thalamus, reticular formation, substsantia nigra

Cranial Nerves of Upper Midbrain Superior colliculus vision Edinger Westfal nucleus MLF Red nucleus CN III Oculomotor nucleus