Brainstem

1. The Brain stem and Cranial Nerves
Dr Mwachaka
Dept. Human Anatomy,
University of Nairobi-Kenya

2. Objectives
• Name the components of brainstem
• State the external features of brainstem
• Describe the internal features of brainstem
• State the functional components of cranial nerves
• Applied anatomy of the brainstem

3. Qn 1: Open medulla
Name structures 1, 6, 8, 9

4. Qn 2: Caudal closed medulla
Name structures
B,C,D, J

5. Qn 3: Name structures A-C found
in the caudal mid brain

6. Qn 4
Name the cranial nerve nuclei that contain GSE
(General somatic Efferent) component in
a) Medulla
b) Mid brain

7. Qn 5
• Name the brain stem nuclei associated with
1. Vagus nerve
2. Facial nerve

8. Brain stem – Components

9. Functions of brainstem
• conduit for the tracts - ascending and descending
• control of respiration and cardiovascular systems
• contains the nuclei of cranial nerves III through XII.

10. Brain stem – external features

12. Internal features

13. Names of cranial nerves
• Ⅰ Olfactory nerve
• Ⅱ Optic nerve
• Ⅲ Oculomotor nerve
• Ⅳ Trochlear nerve
• Ⅴ Trigeminal nerve
• Ⅵ Abducent nerve
• Ⅶ Facial nerve
• Ⅷ Vestibulocochlear nerve
• Ⅸ Glossopharyngeal nerve
• Ⅹ Vagus nerve
• Ⅺ Accessory nerve
• Ⅻ Hypoglossal nerve

15. Classification of cranial nerves
• Sensory cranial nerves: contain only afferent (sensory) fibers
– ⅠOlfactory nerve
– ⅡOptic nerve
– Ⅷ Vestibulocochlear nerve
• Motor cranial nerves: contain only efferent (motor) fibers
– Ⅲ Oculomotor nerve
– Ⅳ Trochlear nerve
– ⅥAbducent nerve
– Ⅺ Accessory nerv
– Ⅻ Hypoglossal nerve
• Mixed nerves: contain both sensory and motor fibers---
– ⅤTrigeminal nerve,
– Ⅶ Facial nerve,
– ⅨGlossopharyngeal nerve
– ⅩVagus nerve

17. Functional components
• Motor (Efferent):
– GSE (somatomotor)– muscles of the tongue and eye
– SVE (branchiomotor) – pharyngeal apparatus muscles
– GVE (visceromotor) – parasympathetic
• Sensory (Afferent)
– GSA – General sensations from head
– GVE – General sensations from the viscera
– SVA – Special sensations – Olfaction, Taste
– SSA – Special sensations – Vision, Hearing and balance

18. Cranial nerve nuclei arrangement

19. Sensory cranial nerves
N. Location of cell
body and axon
categories
Cranial Entry Terminal nuclei Main action
Ⅰ Olfactory cells (SVA) Cribrifom
foramina
Olfactory bulb Smell
Ⅱ Ganglion cells (SSA) Optic canal Lateral
geniculate body
Vision
Ⅷ Vestibular
ganglion(SSA)
Internal
acoustic
meatus
Vestibular
nuclei
Equilibrium
Cochlear ganglion
(SSA)
Cochlear nuclei Hearing

20. Olfactory nerve - SVA

21. Olfactory pathway

22. Optic pathway - SSA

23. Vestibulocochlear nerve
Vestibular ganglion(SSA) ↘ ↗ Vestibular nuclei
Internal acoustic meatus
Cochlear ganglion (SSA) ↗ ↘ Cochlear nuclei

24. Vestibular division

25. Cochlear division

26. Motor cranial nerves
N. Nucleus of origin and
axon categories
Cranial exit Main action
Ⅲ Nucleus of oculomotor
(GSE)
Superior orbital
fissure
Motor to superior, inferior
and medial recti; inferior
obliquus; levator
palpebrae superioris
Accessory nucleus of
oculomotor (GVE)
Parasympathetic to
sphincter pupillea and
ciliary muscl
Ⅳ Nucleus of trochlear
nerve (GSE)
Superior orbital
fissure
Motor to superior obliquus
Ⅵ Nucleus of abducens
nerve (GSE)
Superior orbital
fissure
Motor to lateral rectus
Ⅺ Nucleus of accessory
nerve (SVE)
Jugular foramen Motor to
sternocleidomastoid and
trapezius
Ⅻ Nucleus of hypoglossal
nerve( GSE)
Hypoglossal canal Motot to muscles of
tongue

28. Oculomotor (III): GSE, GVE
• GSE: Superior, inferior and medial recti; inferior
obliquus; levator palpebrae superioris
• GVE: Sphincter pupillae and ciliary muscle

29. 3rd nerve palsy

30. Trochlear nerve (IV) - GSE

31. Abducens nerve (VI) - GSE
Abducens palsy

32. Accessory nerve (XI) - SVE

33. Hypoglossal nerve (XII) - GSE

34. Oculamotor paralysis
Abducent nerve injury

35. Mixed cranial nerves
• V - Trigeminal nerve
• VII - Facial nerve
• IX - Glossopharyngeal nerve
• X - Vagus nerve

36. Trigeminal nerve (V)
• GSA – sensory to the face
• GVE –muscles of 1st pharyngeal arch (mastication)

37. Facial nerve (VII)
• SVE – muscles of facial expression (2nd pharyngeal arch)
• GVE – secretomotor to lacrimal, submandibular and sublingual glands
• SVA - taste buds of anterior 2/3 of tongue (nucleus of solitary tract)
• GSA - fibers from skin of external ear

38. Facial nerve (Ⅶ)
• SVE – muscles of facial expression (2nd
pharyngeal arch)
• GVE – secretomotor to lacrimal,
submandibular and sublingual glands
• SVA - taste buds of anterior 2/3 of
tongue (nucleus of solitary tract)
• GSA - fibers from skin of external ear

39. Injury to the facial nerve

40. Glossopharyngeal (IX)
• SVE - from nucleus ambiguus, and supply
stylopharygeus
• GVE - from inferior salivatory nucleus to
parotid gland
• SVA - taste posterior 1/3 of tongue >
nucleus of solitary tract
• GVA – general sensation posterior 1/3
tongue, pharynx, auditory tube and
tympanic cavity, carotid sinus and
glomus>nucleus of solitary tract
• GSA fibers: sensation from skin of
posterior surface of auricle and

41. Vagus nerve (X)
• SVE : from n. ambiguus, to muscles of
pharynx and larynx
• GVE : from dorsal nucleus of vagus
nerve to cardiac muscles, smooth
muscles and glands of viscera
• GVA: general sensations from viscera
in neck, thoracic and abdominal cavity
to nucleus of solitary tract
• GSA: sensation from auricle, external
acoustic meatus and cerebral dura
mater

45. Qn 1: Open medulla
Name structures 1, 6, 8, 9

46. Open medulla
1. Inferior cerebellar peduncle
2. Floor of fourth ventricle
3. Hypoglossal nucleus
4. Medial longitudinal fasciculus
5. Reticular formation
6. Medial lemniscus
7. Arcuate nuclei
8. Inferior olivary nucleus
9. Pyramids

47. Central medulla

48. Upper medulla

49. Qn 9: Caudal closed medulla
Name structures
B,C,D, J

50. Caudal closed medulla
A. Posterior median sulcus
B. Nucleus Gracilis
C. Nucleus Cuneatus
D. Spinal Trigeminal Nucleus
E. Central Gray (N. of C.N. XII, X and N. solitary)
F. Fasciculus Gracilis
G. Fasciculus Cuneatus
H. Spinal Trigeminal tract
I. Reticular Formation (Location of N. Ambiguus)
J. Pyramid
K. Anterior Median Fissure
L. Pyramidal decussation
M. Reticular Formation (Internal Arcuate Fibers)
N. Posterior Spinocerebellar Tract
O. Anterior spinocerebellar Tract
P. Inferior Olivary Nucleus
Q. Anterior/Lateral Spinothalamic Tract
(Anteriolateral Pathway)

51. Qn 3: Name structures A-C found
in the caudal mid brain

52. Midbrain caudal

53. Pons

54. Brainstem vascular territories

55. Medulla

56. Medial medullary syndrome
(occlusion of vertebral artery)
A. Ipsilateral 12th nerve palsy
B. Paralysis of arm and leg, sparing
face
C. impaired proprioceptive & tactile
sense over half the body

57. Lateral medullary syndrome
(PICA occlusion)
A. Hemianaesthesia over half the face:
B. Loss of taste: Nucleus and tractus solitarius
C. Ataxia of limbs, falling to side of lesion:
D. Dysphagia, paralysis of palate & vocal cord
E. Nystagmus, vertigo, nausea, vomiting:

58. Pontine syndromes

59. Medial Pontine syndrome
(occlusion of paramedian branches of basilar artery)
Ipsilateral
A. Ataxia of limbs and gait
B. Abduscens nerve palsy
Contralateral
C. Paralysis of face, arm, and leg
D. Impaired tactile and proprioceptive sense
over half of the body

60. Lateral pontine syndrome
(occlusion of anterior inferior cerebellar artery)
• Ipsilateral
A. nystagmus, vertigo
B. Facial paralysis
C. Deafness, tinnitus:
D. Impaired sensation over face
E. Ataxia:
• Contralateral
– Impaired pain and thermal sense

61. MID BRAIN

62. Qn 4
Name the cranial nerve nuclei that contain GSE
(General somatic Efferent) component in
a) Medulla
b) Mid brain

63. Cranial nerve nuclei arrangement

65. Qn 5
• Name the brain stem
nuclei associated with
1. Vagus nerve
2. Facial nerve

67. Thank you