1. Brain Stem I Basic Neuroscience James H. Baños, Ph.D.

2. Overview • Major external features • Transverse sections • Pathways: The big Four • Neurotransmitter nuclei

3. Major Brain Stem Activities • Conduit • Ascending and descending pathways • Integrative functions • Complex motor patterns • Respiratory and cardiovascular activity • Regulation of arousal and level of consciousness • Cranial Nerve functions

4. Major External Features

5. Midbrain Pons Medulla Brain Stem

6. Midbrain • Cerebral Peduncles • Interpeduncular cistern • Origin of CN III -- Oculomotor Nerve • Corpora Quadrigemina • Superior Colliculi • Inferior Colliculi

7. Midbrain Corpora quadrigemina CN III Cerebral peduncles Interpeduncular cistern

8. Pons • Cerebellar Peduncles • Superior (Dives under the colliculi) • Middle (Bridge of the pons) • Inferior (inferior/medial to middle) • Floor of the 4th Ventricle

9. Pons

10. Pons Middle cerebellar peduncle

11. Pons Superior cerebellar peduncles Middle cerebellar peduncle Inferior cerebellar peduncles

12. Pons • 4th Ventricle • Inflow from aqueduct of Sylvius • Sulcus limitans

13. Medulla • Pyramids • Pyramidal decussation • Inferior olive • Obex (inferiormost point of the 4th ventricle)

14. Medulla Obex Pyramids Inferior olive

15. Medulla Inferior Olive Pyramids

16. Transverse Sections

17. Transverse Sections • But first…a word about orientation… Anatomical Clinical

18. Midbrain • Cerebral peduncles • Substantia nigra • Red nucleus Midbrain = Mickey

19. Midbrain Myelin Stained Cerebral peduncles

20. Midbrain Substantia nigra

21. Midbrain Red Nucleus

22. Midbrain Colliculi

23. Midbrain Substantia nigra

24. Midbrain Red nucles Substantia nigra

25. Pons • 4th ventricle • Pontine nuclei • Locus ceruleus

26. Pons Pontine nuclei 4th vent Locus ceruleus

27. Pons Locus ceruleus

28. Pons • 4th ventricle • Pontine nuclei • Locus ceruleus

29. Pons 4th ventricle Sulcus Limitans Middle cerebellar peduncle

30. Pons

31. Rostral Medulla • Pyramids • Inferior Olive

32. Rostral Medulla Pyramids Inferior olive

33. Caudal Medulla • Sensory nuclei • Nucleus Gracilis • Nuclues Cuneatus • Pyramidal decussation

34. Caudal Medulla Nucleus cuneatus Nucleus gracilis

35. Tectum and Tegmentum

36. Tectum and Tegmentum • Tectum • Area posterior to the ventricular space • Only prominent in the midbrain • Superior and inferior colliculi (“tectal plate”)

37. Tectum and Tegmentum Tectal Plate

38. Tectum and Tegmentum • Tegmentum • Area anterior to the ventricular space (but not everything anterior) • This is the embryologically oldest areas of the brainstem • Area anterior to the tegmentum “added on” during development

39. Big Four Pathways

40. Remember the Big Four? Corticospinal tract Dorsal Columns Spinothalamic tract Spinocerebellar tracts

41. Big Four Pathways • Corticospinal tract • Descending motor • Spinothalamic tract • Ascending pain/temperature • Dorsal columns/Medial lemniscus • Ascending somatosensory and conscious proprioception • Spinocerebellar tracts • Ascending unconscious proprioception

42. The Big Four -- Caudal Medulla Lateral Cuneate Nucleus Corticospinal tract Medial Lemniscus Spinothalamic tract Spinocerebellar tracts

43. The Big Four -- Rostral Medulla Corticospinal tract Medial Lemniscus Spinothalamic tract Spinocerebellar tracts

44. The Big Four…err…three -- Pons Corticospinal tract Medial Lemniscus Spinothalamic tract

45. The Big Three -- Midbrain Corticospinal tract Medial Lemniscus Spinothalamic tract

46. Brain Stem Nuclei

47. Brain Stem Nuclei • Major neurotransmitter nuclei • Reticular formation (not really a “nucleus” but acts like a group of nuclei) • Nuclei associated with cranial nerves

48. Raphe Nuclei • Ridge of cells along the midline in the center of the brainstem • Multiple nuclei • Caudal • projections to the spinal cord and other parts of the brainstem • Rostral • projections to multiple cortical areas

49. Raphe Nuclei • Major serotonin nuclei • Technically part of the reticular formation • Complex reciprocal relationships with multiple areas • Ascending pathways involved in many neurobehavioral phenomena • Mood • Sleep • Feeding/satiety • Descending pathways modulate spinal cord function • Pain

50. Locus Ceruleus • Major norepinephrine nucleus • Dorsal wall of the rostral pons • Projects to • Spinal cord • Brain Stem • Cortex