1. David A. Morton, Ph.D. Jan 10th, 2013
Brainstem
Midbrain and Pons
David A. Morton, Ph.D.
Jan 10th, 2013

2. Objectives Explain how spinal nerves differ from cranial nerves
Name all the cranial nerves and know their components and functions
Identify and locate the CN’s associated with the medulla, pons and midbrain
Recognize the major internal and external landmarks on the dorsal and ventral surface of the brain stem, so that you can determine if a gross or stained cross section is medulla, pons or midbrain.
Identify on a typical cross section all the brain stem nuclei containing motor neurons that end on striated muscle.
List the cranial nerves that contain parasympathetic fibers, the location of their nuclei, and their function
Explain why cranial nerves are so important in localizing lesions.
Name reflexes that test these nerves and brain stem levels.
Relate branches of the vertebrobasilar blood supply to the medulla and pons explaining the deficits that would occur with vascular occlusion.

3. Directional terms with Brain

4. Cranial nerve overview
CN I – Olfactory nerve

5. Cranial nerve overview
CN II – Optic nerve

6. Cranial nerve overview
CN III – Oculomotor nerve

7. Cranial nerve overview
CN IV – Trochlear nerve

8. Cranial nerve overview
CN V – Trigeminal nerve

9. Cranial nerve overview
CN VI – Abducens nerve

10. Cranial nerve overview
CN VII – Facial nerve

11. Cranial nerve overview
CN VIII – Vestibulocochlear nerve

12. Cranial nerve overview
CN IX – Glossopharyngeal nerve

13. Cranial nerve overview
CN X – Vagus nerve

14. Cranial nerve overview
CN XI – Spinal accessory nerve

15. Cranial nerve overview
CN XII – Hypoglossal nerve

16. Brain Overview
Brainstem
Midbrain
Pons
Medulla
Midbrain
Pons
Medulla

17. Brain Overview Diencephalon Thalamus Hypothalamus Pineal gland Th P
HTh P

18. Brain Overview Corpus callosum Lateral ventricle 3rd ventricle
Cerebral aqueduct
4th ventricle
Corpus callosum LV 3 aq 4

19. Spinal Cord and Spinal Nerve Review
Spinal nerve anatomy
Dorsal root
Somatic sensory neurons
Visceral sensory neurons
Ventral root
Visceral motor neurons
Somatic motor neurons
Alar
Basal
Sulcus limitans
Spinal cord
Som S VS VM SM

20. Internal anatomy of brainstem
Alar
Basal
Sulcus limitans
Spinal cord
Som S VS VM SM
The fate of the alar and basal laminae
Why are brain stem sensory nuclei lateral to motor nuclei in brainstem?
Alar
Basal
Sulcus limitans
Medulla
Som S VS VM SM BM

21. Midbrain (mesencephalon)
External anatomy:
Quadrigeminal plate
Superior colliculus
Inferior colliculus
Cerebral peduncles
CN IV SC CP IC IV
Dorsal view of brainstem

22. Midbrain (mesencephalon)
External anatomy:
Quadrigeminal plate
Superior colliculus
Inferior colliculus
Cerebral peduncles
CN III (arrows) SC CP
Ventral
Rostral midbrain IC CP CP
Dorsal view of midbrain
Ventral
Caudal midbrain

23. Midbrain Cranial nerve nuclei Rostral midbrain Oculomotor nucleus
Edinger-Westphal nucleus
Caudal midbrain
Trochlear nucleus
Oculomotor nucleus
Edinger-Westphal nucleus
Trochlear nucleus
Motor
Sensory

24. Midbrain (Rostral) Internal anatomy Tectum Tegmentum
Central gray matter
Red nucleus
Substantia nigra
Cerebral peduncles
Tectum Aq
Tegmentum Rn
Substantia nigra
Cerebral peduncle
Rostral midbrain

25. Midbrain (Rostral) Internal anatomy Oculomotor nucleus
Edinger-Westphal nucleus Aq
Substantia nigra
Cerebral peduncle
Rostral midbrain

26. Midbrain (Caudal) Internal anatomy Trochlear nucleus Caudal midbrain
Red nucleus
Substantia nigra
Caudal midbrain
Horizontal section

27. Midbrain Functional significance of midbrain:
Visual and auditory reflexes
Coordinates eye movements
Pupillary reflex
Consciousness and arousal (RAS)

28. Midbrain Arterial supply. Branches off the: Posterior cerebral artery
Basilar artery

29. Pupillary and Accommodation Reflexes
Bilateral contraction of sphincter pupillae and ciliary muscles
CN II
CN III
Pupillary and Accommodation Reflexes

32. Pons External anatomy: Basilar pons (pons proper)
Middle cerebellar peduncle (MC)
Basilar artery
4th ventricle
CNN V, VI, VII, VIII
4th
Pons
4th vent.
Horizontal section MC V MC VI
VII
4th
VIII

33. Pons Cranial nerve nuclei Rostral Pons Trigeminal nucleus Caudal Pons
Abducens nucleus
Facial nucleus
Sup salivatory nucleus
Trigeminal nucleus
Abducens nucleus
Facial nucleus
Sup salivatory nucleus
Motor
Sensory

34. Axons of the sensory part of V
Pons (Rostral/Mid)
Internal anatomy
Trigeminal motor nucleus
Functional significance
4th Ventricle
Axons of the sensory part of V
Motor nucleus of V
Tegmentum
R.F.
Pons Proper
Axons of the motor
part of V

35. Pons (caudal) Facial nucleus Branchial motor nucleus
Innervate muscles of face

36. Pons (caudal) Superior salivatory nucleus Visceral motor (Para)
Origin of preganglionic parasympathetic neurons

37. Pons (caudal) Abducens nucleus Origin of Abducens n. (CN VI)
Homolog to ventral horn

38. Pons (caudal) Internal anatomy Facial nucleus
Superior salivatory nucleus
Abducens nucleus

39. Corneal reflex Consensual reflex
Sensory: CN V-1 to spinal trigeminal nucleus
Motor: Facial nucleus out to the temporal branch of CN VII
Spinal trigem.
Nucleus & Tract

40. Corneal Reflex Touch the cornea L R Semilunar ganglion of CN V
Spinal trigeminal nucleus
CN V-1 L R
Facial motor nucleus
Temporal branch of CN VII
Blink
(Orbicularis occuli muscle)
Helpful tutorial:

41. Pons Arterial supply. Branches off the: Basilar artery
Median and Circumferential branches

42. Match the following reflexes with their associated brainstem level:
a. corneal reflex testing?
b. Gag reflex testing?
c. pupillary light reflex testing? II
III I

43. Match the following reflexes with their associated brainstem level:
corneal reflex testing?
b. Gag reflex testing?
c. pupillary light reflex testing? I
III II

44. You have a patient who cannot look to the right with the right eye or smile or wrinkle the right side of their face. Characterize the lesion as to level, side, structure(s) involved.

45. You have a patient who cannot look to the right with the right eye or smile or wrinkle the right side of their face. Characterize the lesion as to level, side, structure(s) involved.

46. What reflex would be abnormal in a patient with a lesion that included the circled area?

47. What reflex would be abnormal in a patient with a lesion that included the circled area?
Abducens nucleus
Facial nucleus