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Anatomy of brainstem

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Anatomy of brainstem

  1. 1. Brainstem<br />By<br />Dr Manah Chandra Changmai<br /> IMS<br />
  2. 2. Brainstem<br /><ul><li>Located between the cerebrum and the spinal cord Provides a pathway for tracts running between higher and lower neural centers.
  3. 3. Consists of the midbrain, pons, andmedulla oblongata.
  4. 4. Each region is about an inch in length.</li></ul>Microscopically, it consists of deep gray matter surrounded by white matter fiber tracts.<br /><ul><li>Produce automatic behaviors necessary for survival.</li></ul>Midbrain <br />Pons<br />Medulla<br />obongata<br />
  5. 5. Ventral surface of brain stem<br />Midbrain<br />Pons <br />Medulla<br />oblongata<br />
  6. 6. Ventral – Lateral View<br />Midbrain<br />Cerebral peduncles<br />Pons<br />Basis pontis<br />Medulla<br />
  7. 7.
  8. 8. Vertical Columns of Cranial Nerves<br />
  9. 9. Internal Columns of Nuclei<br />
  10. 10. Subdivisions of Vertical Columns<br />Motor nuclei<br />Somatic motor<br />closest to midline<br />eyes, tongue<br />CN III, IV, VI, XII<br />Branchial motor<br />Lateral position<br />Branchial arches: chewing, expression, middle ear, pharynx, larynx, sternomastoic, trapezius<br />CN V, VII, XI<br />N. ambiguus (IX, X)<br />Visceral motor<br />ventral / ventrolateral<br />Parasympathetic: glands, smooth muscle, heart, lungs, GI above splenic flexure<br />Edinger-Westfall (III)<br />Sup. & Inf. salivatory<br />Sensory nuclei<br />General sensory<br />lateral to branchial motor<br />Face, sinuses, meninges<br />All modalities<br />CN V mainly<br />Also CN VII, IX, X<br />Visceral sensory<br />lateral to visceral motor<br />Taste; cardiorespiratory, GI info<br />N. of the solitary tract (CN VII, IX, X)<br />Special sensory<br />furthest lateral<br />Balance; hearing<br />CN VIII (vestibular)<br />CN VIII (cochlear)<br />
  11. 11. Midbrain <br />
  12. 12. Midbrain<br />Connects pons and cerebrum with forebrain<br />Cruscerebri<br /><ul><li>Shortest brain stem,not more than</li></ul>2cm in length,lies in the posterior cranial <br />Fossa.<br /><ul><li>For descriptive purpose,divided into</li></ul>Dorsal tectum and right and left cerebral<br />Peduncles.<br /><ul><li>Each cerebral peduncles divide further</li></ul>into ventral cruscerebri and a dorsal<br />Tegmentum by a pigmented lamina<br />“ Substantianigra”<br /><ul><li>Cerebral peduncles contains:</li></ul>-Descending fibers that go to the cerebellum via the pons<br />-Descending pyramidal tracts<br /><ul><li>Running through the midbrain is the hollow cerebral aqueduct which connects the 3rd and 4th ventricles of the brain.</li></li></ul><li>Ventral – Dorsal Organization<br />Tectum<br />Basis<br />Tegmentum<br />
  13. 13. Patterning of the Midbrain<br />
  14. 14.
  15. 15. Superior colliculi<br />The roof of the aqueduct ( the tectum) contains the corpora quadrigemina<br />2 superior colliculithat control reflex movements of the eyes, head and neck in response to visual stimuli<br />2 inferior colliculithat control reflex movements of the head, neck, and trunk in response to auditory stimuli<br />Inferior colliculi<br />Corpora quadregemina<br />Superior and inferior colliculiseperated by cruciform sulcus<br />Superior colliculi larger and darker <br />than inferior colliculi,the difference <br />In colour due to superficial neurons in<br />Superior colliculi<br />
  16. 16. Internal Structure of Midbrain<br />Cross section at two levels<br /><ul><li>Level of inferior colliculus
  17. 17. Level of superior colliculus</li></li></ul><li>Internal structure <br />Transverse section of midbrain<br />Common to both at inferior and superior colliculus:<br /><ul><li>Cruscerebri (or basis pedunculi):</li></ul>- Consists of fibres descending from cerebral cortex.<br /> - Its medial one-sixth is occupied by coticopontine<br />fibres from frontal lobe,lateral one-sixth fibres<br /> from temporal,occipital and parietal lobes,the<br /> intermediate two third by corticospinal and cortico-<br /> nuclear fibres.<br /><ul><li>Substantianigra:</li></ul>- Present immediately behind and medial to basis<br />pedunculi.<br /> - It appears dark as neuron within it contain pigment.<br /> ( neuromelanin )<br />
  18. 18. Substantianigra<br />Cruscerebri<br />
  19. 19. Cerebral aqueduct<br />Basis pedunculi<br />Substantianigra<br />Cruscerebri<br />(cerebral peduncle)<br />
  20. 20. Internal Structure of Midbrain<br />Cross section at inferior colliculus<br />
  21. 21. Section at the level of inferior colliculus<br />Inferior colliculus<br /><ul><li>Inferior colliculus</li></ul> - large mass of grey matter lying in the tectum<br /> - Forms cell station in auditory pathway.<br /><ul><li>Trochlear nucleus:</li></ul> - Lies in the ventral part of central grey matter<br /><ul><li>Mesencephalic nucleus of trigeminal nerve:</li></ul> - Lies in lateral part of the central grey matter<br /><ul><li>Medial leminiscus:</li></ul> - Fibres of ventral spinothalamic tract<br /><ul><li>Spinal leminiscus:</li></ul> - Fibres of lateral spinothalamic and spinotectal<br /> tract.<br /><ul><li>Trigeminal leminiscus</li></li></ul><li>Inferior colliculus<br />Trochlear nerve(N)<br />Mesencephalic nucleus of V cranial nerve<br />Medial longitudinal fasciculus<br />
  22. 22. Cross section at<br /><ul><li>Level of superior colliculus</li></li></ul><li>Section at the level of superior colliculus<br />Two large masses of grey matter seen at this level<br /><ul><li>Superior colliculus in the tectum</li></ul>– Receives visual input from retina and frontal<br />and occipital eye fields<br />– Receives auditor input from inferior colliculus<br />– Mediates audiovisual refflexes<br /><ul><li>Commissure of superior colliculus</li></ul>– Connects two superior colliculus<br /><ul><li>Brachium of superior colliculus</li></ul>– Pathway for fibres from superior colliculus to<br />Cortex<br />
  23. 23. Section at the level of superior colliculus……contd.<br /><ul><li>Cerebral aqueduct and periaqueductal</li></ul>gray matter<br /><ul><li>Red nucleus in the tegmentum</li></ul> - Lies in the anterior part of the tegmentum,<br />dorsomedial to the substantianigra<br />- It is called because of reddish colour which is <br /> due to the presence of iron pigment in its <br /> neurons.<br /><ul><li>Oculomotor nucleus</li></ul> - Related to the ventral part of central grey matter<br /><ul><li>Medial longitundinal fasciculus</li></ul>– Vestibular fibres that coordinate eye<br />movements<br />– Interconnects ocular motor CN 3, 4, 6<br /><ul><li>Central tegmental tract</li></li></ul><li>Section at the level of superior colliculus……contd.<br /><ul><li>Medial lemniscus</li></ul>– Spinal afferent tract<br /><ul><li>Spinal lemniscus</li></ul>– Spinal afferent tract<br /><ul><li>Substantianigra</li></ul>– Receives GAGAergic input from caudate putamen<br />– Projects dopaminergicfibres to caudate putamen<br />– Projects nondopminergicfibres to thalamus<br /><ul><li>Cruscerebri</li></ul>Superior colliculus<br />
  24. 24. Superior colliculus<br />Edingerwestfal<br />nucleus<br />Occulomotor nucleus<br />Red nucleus<br />– relay from cortex and cerebellum to spinal cord, inferior olive, reticular formation, cerebellum<br />Controls arm movement <br />
  25. 25. <ul><li>Corticobulbar Fibers</li></ul>– Arise from precentral and postcentral<br />Gyri<br />– May synapse directly on motor neurons<br />or indirectly via interneurons<br />(corticoreticular fibers)<br />– Innervate sensory relay nuclei<br />– Innervate cranial nerve motor nuclei<br />bilaterally, with the exception of upper<br />face division of the facial nucleus<br />– Innervates the ipsilateral spinal nucleus<br />of CN 11, which supplies the<br />sternocleidomastoid muscle and the<br />contralateral spinal nucleus of CN 11,<br />which innervates the trapezius muscle<br />
  26. 26. Pons<br />
  27. 27. Pons<br /><ul><li>The pons shows a convex anterior surface</li></ul> with prominent transversely running fibres.<br /> These fibres collect to form bundles,the<br /> middle cerebellar peduncles.<br /><ul><li>Trigeminal nerve emerges from the anterior </li></ul>surface,at the junction between pons and <br /> middle cerebellar peduncle.<br /><ul><li>The anterior surface of pons is marked in the </li></ul> midline by a shallow groove,thesulcusbasilariswhich lodges the basilar artery.<br />Pons<br />s<br />Sulcusbasilaris<br />
  28. 28. Subdivided into ventral and dorsal part<br />Ventral part of the pons contains<br /><ul><li>Pontine nuclei:
  29. 29. Recievescorticopontinefibres from frontal,</li></ul>temporal,parietal and occipital lobes of cerebrum<br /><ul><li>The efferent fibres form the transverse fibres</li></ul> of pons.<br /><ul><li>It has been estimated that there are about twenty</li></ul> million neurons in pontinenuclei.Most of them <br /> are glutaminergic.<br /><ul><li>Vertically running corticospinal and corticopontine</li></ul>fibres.<br /><ul><li>Transversely running fibres arising in pontine nuclei</li></ul>Pontine nuclei<br />
  30. 30. Dorsal part of pons<br />Midpons<br /><ul><li>The dorsal part of the pons may be regarded as continuation</li></ul> of the part of the medulla behind the pyramids.<br /><ul><li>Superiorly continous with the tegmentum of the midbrain.
  31. 31. Occupied predominately by reticular formation
  32. 32. Posterior surface help to form floor of fourth ventricle
  33. 33. The dorsal part is bounded laterally by inferior cerebellar</li></ul> peduncle in the lower part of the pons and superior cerebellar<br /> peduncle in upper part.<br />DORSAL PART<br />Upper pons<br />
  34. 34. Dorsal surface of pons<br />Six ascending tract<br />1 Dorsal and ventral cochlear nuclei<br /> – Receives auditory input from the cochlea<br /> through CN 8<br />2 Trapezoid body<br /> – Formed by decussating fibres of the<br /> ventral cochlear nuclei<br />3 Superior olivary nucleus<br /> – Auditory relay nucleus that receives input<br /> from the cochlear nuclei and contributes<br /> to lateral lemniscus<br /> 4 Lateral lemniscus<br />» Auditory pathway that conducts most<br />contralateral cochlear input<br /> 5 Medial lemniscus<br />» Spinal afferent pathway<br /> 6 Spinal lemniscus<br />» Spinal afferent pathway<br />
  35. 35. 4th Ventricle<br />Connection of pons to cerebellum<br />Restiform body (inf. cerebellar peduncle)<br />Middle cerebellar peduncle<br />Medial lemniscusAscending 2nd order sensory neurons<br />Descending upper motor neurons<br />
  36. 36. Section through lower part of the pons<br /><ul><li>Abducent nucleus of CN 6</li></ul>• Lateral gaze<br /><ul><li>Dorsal and ventral cochlear nuclei of CN8
  37. 37. Medial, lateral and superior vestibular</li></ul>nuclei of CN 8<br />• Receive proprioceptive input from vestibular<br />systems and cerebellum<br />• Projects to cerebellum and medial longitudinal<br />fasciculus<br /><ul><li>Spinal trigeminal tract of CN 5
  38. 38. Facial nucleus of CN 7 • Gives rise to fibres that innervate the muscles of</li></ul>facial expression<br /><ul><li>Superior olivary nucleus</li></ul>– Auditory relay nucleus that receives input<br />from the cochlear nuclei and contributes<br />to lateral lemniscus<br />
  39. 39. Cranial Nerves of Lower Pons<br />Vestibular Nuclei <br />Pure sensory  lateral location <br />Balance<br />
  40. 40. Cranial Nerves of Lower Pons<br />At a slightly higher level<br />Abducens N. nucleus<br />Abduction of eye<br />Longest, most vulnerable CN<br />Facial N. nucleus<br />Muscles of face<br />
  41. 41. Mid Pons<br />4th Ventricle<br />Middle cerebellar peduncle<br />Corticospinal tract,corticobulbar tract, <br />corticopontine fibers<br />Descending fibers<br />
  42. 42. Mid Pons<br />Lateral lemniscus<br />Trapezoid body<br />fibers from dorsal column (position and vibration)<br />Medial leminiscus<br />fibers from dorsal column (position and vibration)<br />Pontine nuclei<br />Trapezoid body :<br />transverse fibers in pontinetegmentum<br />
  43. 43. Mid Pons<br />Medial lemniscusfibers from dorsal column (position and vibration)<br />Motor trigeminal nucleus<br />Trigeminal tractpain, temperature, touch from contralateral face<br />Principal trigeminal sensory nucleus<br />Cranial nerve nuclei and Lemniscal sensory system – in tegmentum of the pons<br />
  44. 44. Section through upper part of pons<br /><ul><li>Superior cerebellar peduncle
  45. 45. Principal sensory nucleus of CN 5</li></ul>– Receives discriminative tactile and pressure<br />sensation from face, terminates in thalamus<br /><ul><li>Lateral lemniscus</li></ul>» Auditory pathway that conducts most<br />contralateral cochlear input<br /><ul><li>Trapezoid body</li></ul>– Formed by decussating fibres of the<br />ventral cochlear nuclei<br />
  46. 46. Upper Pons<br />Periaqueductal gray matter<br />Medial longitudinal fasciculus<br />Superior cerebellar peduncle<br />decussation<br />Transverse ponto-cerebellar fibers<br />
  47. 47. Upper Pons<br />Pediculopontine Nucleus<br />Locus ceruleus<br />Parabrachial Nucleus<br />Some neurons release acetylcholine <br />Other neurons release glutamate<br />They assist in learning and voluntary motor control, e.g. locomotion, saccadic e<br />
  48. 48. MEDULLA OBLONGATA<br />
  49. 49. External structure of medulla<br /><ul><li>Most inferior region of the brain stem.
  50. 50. Becomes the spinal cord at the level of the foramen magnum.
  51. 51. Medulla is broad above ,joins with pons</li></ul> narrow below, continous with spinal cord<br /><ul><li>Length is about 3cm, width is about 2cm</li></ul> at its upper end<br /><ul><li>Surfaces shows series of fissures
  52. 52. Anterior median fissure
  53. 53. Posterior median fissure</li></ul>Medulla oblongata<br />Spinal cord<br />
  54. 54. External surface of medulla<br />Ventral surface of medulla oblongata contains<br /><ul><li>Pyramid
  55. 55. elevation between anterior median </li></ul> and anterolateralsulcus<br /><ul><li>Formed due to decussation of corticospinal</li></ul>fibres.<br /><ul><li>Olive
  56. 56. Oval swelling between anterolateral</li></ul>posterolateralsulcus,half an inch<br /> long<br /><ul><li>Produced by large mass of gray</li></ul> matter called inferior olivary<br /> nucleus<br />Olive<br />Pyramid<br />
  57. 57. Pyramid<br />Olive <br />Anterolateral fissure<br />Anterior median fissure<br />
  58. 58. Posterior part of medulla oblongata<br />The posterior part of medulla contains<br /><ul><li>Fasciculus gracilis medially ending in rounded</li></ul> elevation ,called nucleus gracilis<br /><ul><li>Fasciculus cuneatus laterally ending in rounded</li></ul>elevation,callednucleus cuneatus<br /><ul><li>Posterior part of the medulla forms</li></ul> the floor of the fourth ventricle<br /><ul><li>Tuberculumcinereum, longitudinal</li></ul> elevation in the lower part of medulla<br /> lateral to fasciculus cuneatus.<br />
  59. 59. DORSAL SURFACE OF MEDULLA OBLONGATA<br />Floor of fourth <br />ventricle<br />Obex<br />Gracile tubercle<br />Posterior median sulcus<br />Posterior median fissure<br />Cuneate tubercle<br />
  60. 60. Internal Structure of Medulla<br />Cross section at three levels<br />Level of pyramidal decussation<br />
  61. 61. Level of Pyramidal Decussation<br />Lateral corticospinal tract<br /> 75 – 90%<br />Gracile nucleus<br />spinal nucleus of V<br />From pons to C4<br />Pyramidal tract<br />Anterior corticospinal tract -- fibers to innervate muscles of trunk <br />
  62. 62. Internal Structure of Medulla<br />Cross section at level of lemniscaldecussation<br />
  63. 63. Level of LemniscalDecussation<br />Gracile nucleus<br />Medial longitudinal fasciculus<br />Cuneate nucleus<br />Medial lemniscus<br />Carries 2nd order sensory neurons to VPL thalamus<br />Internal arcuate fibers<br />
  64. 64. Cross section at level of <br />Level ofinferior olivary nuclei<br />
  65. 65. Level of Inferior Olives<br />Vestibular nuclei Medial Inferior<br />Hypoglossal nucleus CN XII<br />Inferior cerebellar peduncle= Restiform body<br />Inferior olivary nuclei<br />Relay between cortex, vestibular nuclei, cerebellum, basal ganglia, and dorsal column nuclei<br />
  66. 66. Cranial Nerves of the Medulla<br />N. solitarious<br />Sensory nucleus for CN VII, IX, X<br />Vestibular nuclei<br />Posterior 1/3 of the tongue<br />Dorsal motor nucleus of X<br />N. ambiguus<br />Motor nucleus for CN IX, X & XI<br />Spinal trigeminal tract<br />CN V, VII, IX, X<br />Stylopharyngeus (lifts pharynx)<br />Sensation behind ear<br />
  67. 67. CN IX: Glossopharyngeal Nerve<br />N. solitarious<br />Sensory nucleus for CN VII, IX, X<br />Posterior 1/3 of the tongue<br />Inf. salivatory nucleus<br />Parotid gland, parasympathetic<br />N. ambiguus<br />Motor nucleus for CN IX, X & XI<br />Stylopharyngeus (lifts pharynx)<br />Spinal trigeminal tract<br />CN V, VII, IX, X<br />Sensation behind ear<br />
  68. 68. CN X: Vagus Nerve<br />Dorsal motor nucleus of X<br />Parasympathetic, preganglionic<br />N. solitarious<br />Sensory nucleus for CN VII, IX, X<br />Taste, epiglottis Cardiorespiratory<br />N. ambiguus<br />Motor nucleus for CN IX, X & XI<br />Pharynx Larynx<br />Spinal trigeminal tract<br />CN V, VII, IX, X<br />Ear<br />
  69. 69. Mnemonic<br />Out On Our Table Top Are Fruits, Very Green Veggies And Hamburgers<br />
  70. 70. The End<br />