Anatomy of brainstem
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Anatomy of brainstem






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    Anatomy of brainstem Anatomy of brainstem Presentation Transcript

    • Brainstem
      Dr Manah Chandra Changmai
    • Brainstem
      • Located between the cerebrum and the spinal cord Provides a pathway for tracts running between higher and lower neural centers.
      • Consists of the midbrain, pons, andmedulla oblongata.
      • Each region is about an inch in length.
      Microscopically, it consists of deep gray matter surrounded by white matter fiber tracts.
      • Produce automatic behaviors necessary for survival.
    • Ventral surface of brain stem
    • Ventral – Lateral View
      Cerebral peduncles
      Basis pontis
    • Vertical Columns of Cranial Nerves
    • Internal Columns of Nuclei
    • 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
      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)
    • Midbrain
    • Midbrain
      Connects pons and cerebrum with forebrain
      • Shortest brain stem,not more than
      2cm in length,lies in the posterior cranial
      • For descriptive purpose,divided into
      Dorsal tectum and right and left cerebral
      • Each cerebral peduncles divide further
      into ventral cruscerebri and a dorsal
      Tegmentum by a pigmented lamina
      “ Substantianigra”
      • Cerebral peduncles contains:
      -Descending fibers that go to the cerebellum via the pons
      -Descending pyramidal tracts
      • Running through the midbrain is the hollow cerebral aqueduct which connects the 3rd and 4th ventricles of the brain.
    • Ventral – Dorsal Organization
    • Patterning of the Midbrain
    • Superior colliculi
      The roof of the aqueduct ( the tectum) contains the corpora quadrigemina
      2 superior colliculithat control reflex movements of the eyes, head and neck in response to visual stimuli
      2 inferior colliculithat control reflex movements of the head, neck, and trunk in response to auditory stimuli
      Inferior colliculi
      Corpora quadregemina
      Superior and inferior colliculiseperated by cruciform sulcus
      Superior colliculi larger and darker
      than inferior colliculi,the difference
      In colour due to superficial neurons in
      Superior colliculi
    • Internal Structure of Midbrain
      Cross section at two levels
      • Level of inferior colliculus
      • Level of superior colliculus
    • Internal structure
      Transverse section of midbrain
      Common to both at inferior and superior colliculus:
      • Cruscerebri (or basis pedunculi):
      - Consists of fibres descending from cerebral cortex.
      - Its medial one-sixth is occupied by coticopontine
      fibres from frontal lobe,lateral one-sixth fibres
      from temporal,occipital and parietal lobes,the
      intermediate two third by corticospinal and cortico-
      nuclear fibres.
      • Substantianigra:
      - Present immediately behind and medial to basis
      - It appears dark as neuron within it contain pigment.
      ( neuromelanin )
    • Substantianigra
    • Cerebral aqueduct
      Basis pedunculi
      (cerebral peduncle)
    • Internal Structure of Midbrain
      Cross section at inferior colliculus
    • Section at the level of inferior colliculus
      Inferior colliculus
      • Inferior colliculus
      - large mass of grey matter lying in the tectum
      - Forms cell station in auditory pathway.
      • Trochlear nucleus:
      - Lies in the ventral part of central grey matter
      • Mesencephalic nucleus of trigeminal nerve:
      - Lies in lateral part of the central grey matter
      • Medial leminiscus:
      - Fibres of ventral spinothalamic tract
      • Spinal leminiscus:
      - Fibres of lateral spinothalamic and spinotectal
      • Trigeminal leminiscus
    • Inferior colliculus
      Trochlear nerve(N)
      Mesencephalic nucleus of V cranial nerve
      Medial longitudinal fasciculus
    • Cross section at
      • Level of superior colliculus
    • Section at the level of superior colliculus
      Two large masses of grey matter seen at this level
      • Superior colliculus in the tectum
      – Receives visual input from retina and frontal
      and occipital eye fields
      – Receives auditor input from inferior colliculus
      – Mediates audiovisual refflexes
      • Commissure of superior colliculus
      – Connects two superior colliculus
      • Brachium of superior colliculus
      – Pathway for fibres from superior colliculus to
    • Section at the level of superior colliculus……contd.
      • Cerebral aqueduct and periaqueductal
      gray matter
      • Red nucleus in the tegmentum
      - Lies in the anterior part of the tegmentum,
      dorsomedial to the substantianigra
      - It is called because of reddish colour which is
      due to the presence of iron pigment in its
      • Oculomotor nucleus
      - Related to the ventral part of central grey matter
      • Medial longitundinal fasciculus
      – Vestibular fibres that coordinate eye
      – Interconnects ocular motor CN 3, 4, 6
      • Central tegmental tract
    • Section at the level of superior colliculus……contd.
      • Medial lemniscus
      – Spinal afferent tract
      • Spinal lemniscus
      – Spinal afferent tract
      • Substantianigra
      – Receives GAGAergic input from caudate putamen
      – Projects dopaminergicfibres to caudate putamen
      – Projects nondopminergicfibres to thalamus
      • Cruscerebri
      Superior colliculus
    • Superior colliculus
      Occulomotor nucleus
      Red nucleus
      – relay from cortex and cerebellum to spinal cord, inferior olive, reticular formation, cerebellum
      Controls arm movement
      • Corticobulbar Fibers
      – Arise from precentral and postcentral
      – May synapse directly on motor neurons
      or indirectly via interneurons
      (corticoreticular fibers)
      – Innervate sensory relay nuclei
      – Innervate cranial nerve motor nuclei
      bilaterally, with the exception of upper
      face division of the facial nucleus
      – Innervates the ipsilateral spinal nucleus
      of CN 11, which supplies the
      sternocleidomastoid muscle and the
      contralateral spinal nucleus of CN 11,
      which innervates the trapezius muscle
    • Pons
    • Pons
      • The pons shows a convex anterior surface
      with prominent transversely running fibres.
      These fibres collect to form bundles,the
      middle cerebellar peduncles.
      • Trigeminal nerve emerges from the anterior
      surface,at the junction between pons and
      middle cerebellar peduncle.
      • The anterior surface of pons is marked in the
      midline by a shallow groove,thesulcusbasilariswhich lodges the basilar artery.
    • Subdivided into ventral and dorsal part
      Ventral part of the pons contains
      • Pontine nuclei:
      • Recievescorticopontinefibres from frontal,
      temporal,parietal and occipital lobes of cerebrum
      • The efferent fibres form the transverse fibres
      of pons.
      • It has been estimated that there are about twenty
      million neurons in pontinenuclei.Most of them
      are glutaminergic.
      • Vertically running corticospinal and corticopontine
      • Transversely running fibres arising in pontine nuclei
      Pontine nuclei
    • Dorsal part of pons
      • The dorsal part of the pons may be regarded as continuation
      of the part of the medulla behind the pyramids.
      • Superiorly continous with the tegmentum of the midbrain.
      • Occupied predominately by reticular formation
      • Posterior surface help to form floor of fourth ventricle
      • The dorsal part is bounded laterally by inferior cerebellar
      peduncle in the lower part of the pons and superior cerebellar
      peduncle in upper part.
      Upper pons
    • Dorsal surface of pons
      Six ascending tract
      1 Dorsal and ventral cochlear nuclei
      – Receives auditory input from the cochlea
      through CN 8
      2 Trapezoid body
      – Formed by decussating fibres of the
      ventral cochlear nuclei
      3 Superior olivary nucleus
      – Auditory relay nucleus that receives input
      from the cochlear nuclei and contributes
      to lateral lemniscus
      4 Lateral lemniscus
      » Auditory pathway that conducts most
      contralateral cochlear input
      5 Medial lemniscus
      » Spinal afferent pathway
      6 Spinal lemniscus
      » Spinal afferent pathway
    • 4th Ventricle
      Connection of pons to cerebellum
      Restiform body (inf. cerebellar peduncle)
      Middle cerebellar peduncle
      Medial lemniscusAscending 2nd order sensory neurons
      Descending upper motor neurons
    • Section through lower part of the pons
      • Abducent nucleus of CN 6
      • Lateral gaze
      • Dorsal and ventral cochlear nuclei of CN8
      • Medial, lateral and superior vestibular
      nuclei of CN 8
      • Receive proprioceptive input from vestibular
      systems and cerebellum
      • Projects to cerebellum and medial longitudinal
      • Spinal trigeminal tract of CN 5
      • Facial nucleus of CN 7 • Gives rise to fibres that innervate the muscles of
      facial expression
      • Superior olivary nucleus
      – Auditory relay nucleus that receives input
      from the cochlear nuclei and contributes
      to lateral lemniscus
    • Cranial Nerves of Lower Pons
      Vestibular Nuclei
      Pure sensory  lateral location
    • Cranial Nerves of Lower Pons
      At a slightly higher level
      Abducens N. nucleus
      Abduction of eye
      Longest, most vulnerable CN
      Facial N. nucleus
      Muscles of face
    • Mid Pons
      4th Ventricle
      Middle cerebellar peduncle
      Corticospinal tract,corticobulbar tract,
      corticopontine fibers
      Descending fibers
    • Mid Pons
      Lateral lemniscus
      Trapezoid body
      fibers from dorsal column (position and vibration)
      Medial leminiscus
      fibers from dorsal column (position and vibration)
      Pontine nuclei
      Trapezoid body :
      transverse fibers in pontinetegmentum
    • Mid Pons
      Medial lemniscusfibers from dorsal column (position and vibration)
      Motor trigeminal nucleus
      Trigeminal tractpain, temperature, touch from contralateral face
      Principal trigeminal sensory nucleus
      Cranial nerve nuclei and Lemniscal sensory system – in tegmentum of the pons
    • Section through upper part of pons
      • Superior cerebellar peduncle
      • Principal sensory nucleus of CN 5
      – Receives discriminative tactile and pressure
      sensation from face, terminates in thalamus
      • Lateral lemniscus
      » Auditory pathway that conducts most
      contralateral cochlear input
      • Trapezoid body
      – Formed by decussating fibres of the
      ventral cochlear nuclei
    • Upper Pons
      Periaqueductal gray matter
      Medial longitudinal fasciculus
      Superior cerebellar peduncle
      Transverse ponto-cerebellar fibers
    • Upper Pons
      Pediculopontine Nucleus
      Locus ceruleus
      Parabrachial Nucleus
      Some neurons release acetylcholine
      Other neurons release glutamate
      They assist in learning and voluntary motor control, e.g. locomotion, saccadic e
    • External structure of medulla
      • Most inferior region of the brain stem.
      • Becomes the spinal cord at the level of the foramen magnum.
      • Medulla is broad above ,joins with pons
      narrow below, continous with spinal cord
      • Length is about 3cm, width is about 2cm
      at its upper end
      • Surfaces shows series of fissures
      • Anterior median fissure
      • Posterior median fissure
      Medulla oblongata
      Spinal cord
    • External surface of medulla
      Ventral surface of medulla oblongata contains
      • Pyramid
      • elevation between anterior median
      and anterolateralsulcus
      • Formed due to decussation of corticospinal
      • Olive
      • Oval swelling between anterolateral
      posterolateralsulcus,half an inch
      • Produced by large mass of gray
      matter called inferior olivary
    • Pyramid
      Anterolateral fissure
      Anterior median fissure
    • Posterior part of medulla oblongata
      The posterior part of medulla contains
      • Fasciculus gracilis medially ending in rounded
      elevation ,called nucleus gracilis
      • Fasciculus cuneatus laterally ending in rounded
      elevation,callednucleus cuneatus
      • Posterior part of the medulla forms
      the floor of the fourth ventricle
      • Tuberculumcinereum, longitudinal
      elevation in the lower part of medulla
      lateral to fasciculus cuneatus.
      Floor of fourth
      Gracile tubercle
      Posterior median sulcus
      Posterior median fissure
      Cuneate tubercle
    • Internal Structure of Medulla
      Cross section at three levels
      Level of pyramidal decussation
    • Level of Pyramidal Decussation
      Lateral corticospinal tract
      75 – 90%
      Gracile nucleus
      spinal nucleus of V
      From pons to C4
      Pyramidal tract
      Anterior corticospinal tract -- fibers to innervate muscles of trunk
    • Internal Structure of Medulla
      Cross section at level of lemniscaldecussation
    • Level of LemniscalDecussation
      Gracile nucleus
      Medial longitudinal fasciculus
      Cuneate nucleus
      Medial lemniscus
      Carries 2nd order sensory neurons to VPL thalamus
      Internal arcuate fibers
    • Cross section at level of
      Level ofinferior olivary nuclei
    • Level of Inferior Olives
      Vestibular nuclei Medial Inferior
      Hypoglossal nucleus CN XII
      Inferior cerebellar peduncle= Restiform body
      Inferior olivary nuclei
      Relay between cortex, vestibular nuclei, cerebellum, basal ganglia, and dorsal column nuclei
    • Cranial Nerves of the Medulla
      N. solitarious
      Sensory nucleus for CN VII, IX, X
      Vestibular nuclei
      Posterior 1/3 of the tongue
      Dorsal motor nucleus of X
      N. ambiguus
      Motor nucleus for CN IX, X & XI
      Spinal trigeminal tract
      CN V, VII, IX, X
      Stylopharyngeus (lifts pharynx)
      Sensation behind ear
    • 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
      N. ambiguus
      Motor nucleus for CN IX, X & XI
      Stylopharyngeus (lifts pharynx)
      Spinal trigeminal tract
      CN V, VII, IX, X
      Sensation behind ear
    • CN X: Vagus Nerve
      Dorsal motor nucleus of X
      Parasympathetic, preganglionic
      N. solitarious
      Sensory nucleus for CN VII, IX, X
      Taste, epiglottis Cardiorespiratory
      N. ambiguus
      Motor nucleus for CN IX, X & XI
      Pharynx Larynx
      Spinal trigeminal tract
      CN V, VII, IX, X
    • Mnemonic
      Out On Our Table Top Are Fruits, Very Green Veggies And Hamburgers
    • The End