1. Brainstem
Overview
Medulla
Pons
Midbrain
January 12, 2009

2. Ventral – Lateral View Midbrain Pons Medulla
Corticospinal tract descends throughout  movement
Reticular formation descends throughout  movement
ascends throughout  arousal
Midbrain
Cerebral peduncles
Pons
Basis pontis
Medulla
Pyramid Olive

3. Ventral – Dorsal Organization (anterior - posterior)
Basis
Large anterior fiber tracts: cerebral peduncles, crossing pontine fibers, pyramids

4. Ventral – Dorsal Organization
Tegmentum
Anterior cell body-rich areas, floor of brainstem: red nuclei, substantia nigra, reticular formation

5. Ventral – Dorsal Organization
Tectum
Roof of the brainstem: superior colliculi, inferior colliculi: corpus quadrigemina
Cerebellum
Cuneatus, gracilis (medulla)

6. Ventral – Dorsal Organization
Tectum
Tegmentum
Basis

7. Vertical Columns of Cranial Nerves

8. 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

9. 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)

10. Brainstem
Overview
Medulla
Pons
Midbrain .

11. Internal Structure of Medulla
Cross section at three levels
Level of pyramidal decussation
Level of lemniscal decussation
Level of inferior olivary nuclei

12. Level of Pyramidal Decussation
Lateral corticospinal tract
75 – 90%
Gracile nucleus
Spinal nucleus of V
From pons to C4
Contralateral movement
Pyramidal tract
Anterior corticospinal tract fibers to innervate muscles of trunk

13. Internal Structure of Medulla
Cross section at three levels
Level of pyramidal decussation
Level of lemniscal decussation
Level of inferior olivary nuclei

14. Level of Lemniscal Decussation
Gracile nucleus
Cuneate nucleus
MLF
Position & vibration sense
Pyramids
Medial lemniscus
Carries 2nd order sensory neurons to VPL thalamus
Internal arcuate fibers

15. Internal Structure of Medulla
Cross section at three levels
Level of pyramidal decussation
Level of lemniscal decussation
Level of inferior olivary nuclei

16. Level of Inferior Olives
Vestibular nuclei
Medial Inferior
Hypoglossal nucleus CN XII
Inferior cerebellar peduncle = Restiform body
Inferior olivary nuclei
MLF
Relay between cortex, vestibular nuclei, cerebellum, basal ganglia, and dorsal column nuclei
Arcuate nuclei  pontine nuclei

17. Cranial Nerves of the Medulla
Vestibular nuclei
CN XII

18. Cranial Nuclei of the Medulla
N. solitarious
Sensory nucleus for CN VII, IX, X

19. Cranial Nuclei of the Medulla
N. solitarious
Sensory nucleus for CN VII, IX, X
Spinal trigeminal tract
CN V, VII, IX, X

20. Cranial Nuclei of the Medulla
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

21. 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

22. 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

23. 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

24. 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

25. 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)

26. 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)

27. CN X: Vagus Nerve “Wanderer” 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

28. CN X: Vagus Nerve “Wanderer” 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

29. CN X: Vagus Nerve “Wanderer” 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

30. CN X: Vagus Nerve “Wanderer” 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

31. CN X: Vagus Nerve “Wanderer” 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

32. CN X: Vagus Nerve “Wanderer” 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

33. Brainstem
Overview
Medulla
Pons
Midbrain

34. Basis pontis 4th ventricle Cerebellum and Middle cerebellar peduncle
Pons
Landmarks
Basis pontis th ventricle Cerebellum and Middle cerebellar peduncle
Cranial Nerves
V, VI, VII, VIII

35. Pontine Nuclei Input (ipsilateral) Output (contralateral) 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)

36. 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

37. Pons 4th Ventricle Connection of pons to cerebellum
Restiform body (inf. cerebellar peduncle)
Middle cerebellar peduncle
Medial lemniscus Ascending 2nd order sensory neurons
Descending upper motor neurons

38. Cranial Nerves of Lower Pons
Posterior view:
Cerebullum cut away
CN VIII – Vestibular Nuclei Pure sensory  lateral location Balance

39. Cranial Nerves of Lower Pons
CN VIII –
Vestibular Nuclei
(Cochlear Nuclei)

40. 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

41. Cranial Nerves of Lower Pons
CN VII nucleus Facial nerve
Muscles of face

42. Cranial Nerves of Lower Pons
CN VI nucleus – Abducens nerve
Abduction of eye

43. 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

44. Mid Pons
4th Ventricle
Middle cerebellar peduncle
Corticospinal tract, corticobulbar tract, corticopontine fibers
Descending fibers

45. Mid Pons Pontine nuclei in basis 4th Ventricle
Middle cerebellar peduncle
Pontine nuclei in basis

46. Trapezoid body – transverse fibers in pontine tegmentum
Mid Pons
Lateral lemniscus
from cochlear nucleus
hearing
Pontine nuclei
Trapezoid body – transverse fibers in pontine tegmentum

47. Mid 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

48. Cranial Nerve of the Mid Pons
4th Ventricle
CN V
Motor trigeminal nucleus

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

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

51. 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

52. Upper Pons 4th ventricle  cerebral aqueduct
Superior cerebellar peduncle
decussation

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

54. Upper Pons MLF 4th ventricle  cerebral aqueduct
Periaqueductal gray matter
MLF

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

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

57. Upper Pons MLF 4th ventricle  cerebral aqueduct
Pediculopontine Nucleus
MLF
Some neurons release acetylcholine
Other neurons release glutamate
They assist in learning and voluntary motor control, e.g. locomotion, saccadic eye

58. Brainstem
Overview
Medulla
Pons
Midbrain

59. Midbrain Landmarks Cranial Nerves
Cerebral peduncles Optic chiasm Interpeduncular fossa (Superior colliculi) (Inferior colliculi) (Superior cerebellar peduncle)
Cranial Nerves
III, IV

60. Patterning of the Midbrain

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

62. External Structure of Midbrain
Quadrigeminal Plate
Superior colliculus
Inferior colliculus
CN IV
Trochlear nerve
Dorsal surface
Cerebellum removed

63. Cranial Nerves of the Midbrain
Anterior exit
CN III (1)
CN VI (5)
Posterior exit
CN IV (2)
MLF - Medial longitudinal fasciculus (7)
Vestibular nuclei (6)
Pons (3)

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

65. Lower Midbrain Inferior colliculus hearing cerebral aqueduct DORSAL
VENTRAL
cerebral peduncles

66. Lower Midbrain Inferior colliculus Substantia nigra
Melanin-containing cells that produce dopamine Project to the basal ganglia

67. Lower Midbrain Inferior colliculus Substantia nigra Crus cerebri
(cerebral peduncle)
Basis peduncularis

68. Lower Midbrain
Inferior colliculus
CN IV Trochlear nerve

69. Lower Midbrain
Inferior colliculus
CN IV Trochlear nerve
MLF

70. Lower Midbrain Inferior colliculus CN IV MLF
Dorsal raphe nucleus – projects serotonergic fibers to basal ganglia and throughout cortex

71. Lower Midbrain Inferior colliculus hearing Mesencephalic nucleus of V
analogous to dorsal root ganglion but within CNS

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

73. Substantia nigra Crus cerebri
Upper Midbrain
Superior colliculus
vision
Substantia nigra Crus cerebri
(cerebral peduncle)

74. Medial geniculate body
Upper Midbrain
Superior colliculus
vision
Medial geniculate body
hearing

75. Upper Midbrain Vision Hearing
Superior colliculus  Lateral geniculate body
Hearing
Inferior colliculus  Medial geniculate body

76. Upper Midbrain Superior colliculus vision
Red nucleus – relay from cortex and cerebellum to spinal cord, inferior olive, reticular formation, cerebellum
Controls arm movement

77. 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

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

79. Innervation of Eye Muscles
Dorsal view
Cerebellum removed

80. Innervation of Eyes & Muscles
Lacrimal gland (CN VII)
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

81. Tuesday
Diencephalon
Thalamus
Hypothalamus