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Anatomy of brainstem


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  • 1. Brainstem
    Dr Manah Chandra Changmai
  • 2. Brainstem
    • Located between the cerebrum and the spinal cord Provides a pathway for tracts running between higher and lower neural centers.
    • 3. Consists of the midbrain, pons, andmedulla oblongata.
    • 4. 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.
  • 5. Ventral surface of brain stem
  • 6. Ventral – Lateral View
    Cerebral peduncles
    Basis pontis
  • 7.
  • 8. Vertical Columns of Cranial Nerves
  • 9. Internal Columns of Nuclei
  • 10. Subdivisions of Vertical Columns
    Motor nuclei
    Somatic motor
    closest to midline
    eyes, tongue
    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)
  • 11. Midbrain
  • 12. 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
  • 13. Patterning of the Midbrain
  • 14.
  • 15. 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
  • 16. Internal Structure of Midbrain
    Cross section at two levels
    • Level of inferior colliculus
    • 17. 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 )
  • 18. Substantianigra
  • 19. Cerebral aqueduct
    Basis pedunculi
    (cerebral peduncle)
  • 20. Internal Structure of Midbrain
    Cross section at inferior colliculus
  • 21. 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
  • 22. 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
  • 23. 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
  • 24. Superior colliculus
    Occulomotor nucleus
    Red nucleus
    – relay from cortex and cerebellum to spinal cord, inferior olive, reticular formation, cerebellum
    Controls arm movement
  • 25.
    • 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
  • 26. Pons
  • 27. 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.
  • 28. Subdivided into ventral and dorsal part
    Ventral part of the pons contains
    • Pontine nuclei:
    • 29. 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
  • 30. 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.
    • 31. Occupied predominately by reticular formation
    • 32. Posterior surface help to form floor of fourth ventricle
    • 33. 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
  • 34. 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
  • 35. 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
  • 36. Section through lower part of the pons
    • Abducent nucleus of CN 6
    • Lateral gaze
    • Dorsal and ventral cochlear nuclei of CN8
    • 37. 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
    • 38. 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
  • 39. Cranial Nerves of Lower Pons
    Vestibular Nuclei
    Pure sensory  lateral location
  • 40. 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
  • 41. Mid Pons
    4th Ventricle
    Middle cerebellar peduncle
    Corticospinal tract,corticobulbar tract,
    corticopontine fibers
    Descending fibers
  • 42. 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
  • 43. 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
  • 44. Section through upper part of pons
    • Superior cerebellar peduncle
    • 45. 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
  • 46. Upper Pons
    Periaqueductal gray matter
    Medial longitudinal fasciculus
    Superior cerebellar peduncle
    Transverse ponto-cerebellar fibers
  • 47. 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
  • 49. External structure of medulla
    • Most inferior region of the brain stem.
    • 50. Becomes the spinal cord at the level of the foramen magnum.
    • 51. 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
    • 52. Anterior median fissure
    • 53. Posterior median fissure
    Medulla oblongata
    Spinal cord
  • 54. External surface of medulla
    Ventral surface of medulla oblongata contains
    • Pyramid
    • 55. elevation between anterior median
    and anterolateralsulcus
    • Formed due to decussation of corticospinal
    • Olive
    • 56. Oval swelling between anterolateral
    posterolateralsulcus,half an inch
    • Produced by large mass of gray
    matter called inferior olivary
  • 57. Pyramid
    Anterolateral fissure
    Anterior median fissure
  • 58. 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
  • 60. Internal Structure of Medulla
    Cross section at three levels
    Level of pyramidal decussation
  • 61. 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
  • 62. Internal Structure of Medulla
    Cross section at level of lemniscaldecussation
  • 63. Level of LemniscalDecussation
    Gracile nucleus
    Medial longitudinal fasciculus
    Cuneate nucleus
    Medial lemniscus
    Carries 2nd order sensory neurons to VPL thalamus
    Internal arcuate fibers
  • 64. Cross section at level of
    Level ofinferior olivary nuclei
  • 65. 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
  • 66. 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
  • 67. 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
  • 68. 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
  • 69. Mnemonic
    Out On Our Table Top Are Fruits, Very Green Veggies And Hamburgers
  • 70. The End