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Brainstem

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

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Brainstem

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  1. Midbrain and Pons Brainstem 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

  18. Brain Overview • Corpus callosum • Lateral ventricle • 3rdventricle • 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 Som S Alar VS Sulcus limitans VM SM Basal Spinal cord

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

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

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

  31. 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

  32. 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

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

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

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

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

  37. 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

  38. Corneal Reflex Touch the cornea 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)

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

  40. 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

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

  42. 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.

  43. 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.

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

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

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