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The Central Nervous System

Delve into the intricate process of brain development from embryonic stages to birth, exploring key structures, regions, and functions. Learn about the organization of the brain, ventricular system, and the crucial role of the brain stem.

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The Central Nervous System

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  1. PART 2 The CentralNervous System

  2. The Brain • Performs the most complex neural functions • Intelligence • Consciousness • Memory • Sensory-motor integration • Involved in innervation of the head

  3. Embryonic Development of the Brain • Brain arises from rostral part of the neural tube • Three primary brain vesicles in four-week old embryo • Prosencephalon – the forebrain • Mesencephalon – the midbrain • Rhombencephalon – the hindbrain

  4. Embryonic Development of the Brain • Secondary brain vesicles • Prosencephalon • Divides into telencephalon and diencephalon • Mesencephalon – remains undivided • Rhombencephalon • Divides into metencephalon and myelencephalon

  5. Embryonic Development of the Brain • Structures of the adult brain • Develop from secondary brain vesicles • Telencephalonthe cerebral hemispheres • Diencephalonthalamus, hypothalamus, and epithalamus • Metencephalonpons and cerebellum • Myelencephalonmedulla oblongata

  6. Embryonic Development of the Brain • Brain stem includes • The midbrain, pons, and medulla oblongata • Ventricles • Central cavity of the neural tube enlarges

  7. Embryonic Development of the Brain Figure 13.7a–e

  8. Embryonic Development of the Brain • Brain grows rapidly, and changes occur in the relative position of its parts • Cerebral hemispheres envelop the diencephalon and midbrain • Wrinkling of the cerebral hemispheres • More neurons fit within limitedspace

  9. Brain Development from Week 5 to Birth Figure 13.8a–d

  10. Basic Parts and Organization of the Brain • Divided into four regions • Cerebral hemispheres • Diencephalon • Brain stem • Midbrain, pons, and medulla • Cerebellum

  11. Basic Parts and Organization of the Brain Figure 13.9

  12. Basic Parts and Organization of the Brain • Organization • Centrally located gray matter • Externally located white matter • Additional layer of gray matter external to white matter • Due to groups of neurons migrating externally • Cortex – outer layer of gray matter • Formed from neuronal cell bodies • Located in cerebrum and cerebellum

  13. Basic Parts and Organization of the Brain Figure 13.10

  14. Ventricles of the Brain • Expansions of the brain’s central cavity • Filled with cerebrospinal fluid • Lined with ependymal cells • Continuous with each other • Continuous with the central canal of the spinal cord

  15. Ventricles of the Brain • Lateral ventricles – located in cerebral hemispheres • Horseshoe-shaped from bending of the cerebral hemispheres • Third ventricle – lies in diencephalon • Connected with lateral ventricles by interventricular foramen

  16. Ventricles of the Brain • Cerebral aqueduct – connects 3rd and 4th ventricles • Fourth ventricle – lies in hindbrain • Connects to the central canal of the spinal cord

  17. Ventricles of the Brain Figure 13.11a, b

  18. The Brain Stem • Includes the • Midbrain • Pons • Medulla oblongata

  19. The Brain Stem • Several general functions • Produces automatic behaviors necessary for survival • Passageway for all fiber tracts running between the cerebrum and spinal cord • Heavily involved with the innervation of the face and head • 10 of the 12 pairs of cranial nerves attach to it • Which CN do NOT attach to brain stem?

  20. Ventral View of the Brain Figure 13.12

  21. The Brain Stem – The Medulla Oblongata • Most caudal level of the brain stem • Is continuous with the spinal cord • Choroid plexus lies in the roof of the fourth ventricle • External landmarks of medulla • Pyramids of the medulla • Lie on its ventral surface • Decussation of the pyramids • Crossing over of motor tracts

  22. The Brain Stem – The Medulla Oblongata • External landmarks of medulla (continued) • Inferior cerebellar peduncles • Fiber tracts connecting medulla and cerebellum • Olive (olive of the medulla) • Contains inferior olivary nucleus

  23. The Brain Stem – The Medulla Oblongata • Cranial nerves VIII–XII attach to the medulla • VIII – Vestibulocochlear • IX – Glossopharyngeal nerve • X – Vagus nerve • XI – Accessory • (Spinal Accessory – a branch of the vagus nerve) • XII – Hypoglossal nerve

  24. The Brain Stem – Medulla Oblongata Figure 13.13a

  25. The Brain Stem – Medulla Oblongata Figure 13.13b

  26. The Brain Stem – The Medulla Oblongata • The core of the medulla contains • Much of the reticular formation • Nuclei influence autonomic functions • Visceral centers of the reticular formation include • Cardiac center • Vasomotor center • The medullary respiratory center • Centers for hiccupping, sneezing, swallowing, and coughing

  27. The Brain Stem – The Medulla Oblongata Table 13.1 (1 of 3)

  28. The Brain Stem – The Medulla Oblongata Figure 13.13c

  29. The Brain Stem – The Pons • A “bridge” between the midbrain and medulla oblongata • Pons contains the nuclei of cranial nerves • V – Trigeminal nerve • VI – Abducens nerve • VII – Facial nerve

  30. The Brain Stem – The Pons • The pons contains • Motor tracts coming from the cerebral cortex • Pontine nuclei • Connect portions of the cerebral cortex and cerebellum • Send axons to cerebellum through the middle cerebellar peduncles

  31. The Brain Stem – The Pons Figure 13.14b

  32. The Brain Stem – The Pons Table 13.1 (2 of 3)

  33. The Brain Stem – The Midbrain • Lies between the diencephalon and the pons • Cerebral aqueduct • The central cavity of the midbrain • Cerebral peduncles located on the ventral surface of the brain • Contain pyramidal (corticospinal) tracts • Superior cerebellar peduncles • Connect midbrain to the cerebellum

  34. The Brain Stem and Diencephalon Figure 13.13a

  35. The Brain Stem and Diencephalon Figure 13.13b

  36. The Brain Stem – The Midbrain • Periaqueductal gray matter surrounds the cerebral aqueduct • Involved in two related functions • Fright-and-flight reaction • Mediates response to visceral pain Figure 13.21

  37. The Brain Stem – The Midbrain • Corpora quadrigemina (quad-ri-gemina) • The largest nuclei • Divided into the superior and inferior colliculi • Superior colliculi – nuclei that act in visual reflexes • Inferior colliculi – nuclei that act in reflexive response to sound

  38. The Brain Stem – Dorsal View Figure 13.13c

  39. The Brain Stem – The Midbrain • Imbedded in the white matter of the midbrain • Two pigmented nuclei • Substantia nigra – neuronal cell bodies contain melanin • Functionally linked to the basal nuclei • Red nucleus – lies deep to the substantia nigra • Largest nucleus of the reticular formation

  40. The Cerebellum • Located dorsal to the pons and medulla • Smoothes and coordinates body movements • Helps maintain equilibrium

  41. The Cerebellum • Consists of two cerebellar hemispheres • Surface folded into ridges called folia • Separated by fissures • Hemispheres each subdivided into • Anterior lobe • Posterior lobe • Flocculonodular lobe (tiny)

  42. The Cerebellum Figure 13.15a

  43. The Cerebellum • Composed of three regions • Cortex – gray matter • Arbor vitae • Internal white matter • Deep cerebellar nuclei – deeply situated gray matter

  44. The Cerebellum • Cerebellum receives information from the cerebral cortex • On equilibrium • On current movements of • Limbs, neck, and trunk

  45. The Cerebellum – Cerebellar Peduncles • Thick tracts connecting the cerebellum to the brain stem are • Superior cerebellar peduncles • Middle cerebellar peduncles • Inferior cerebellar peduncles • Fibers to and from the cerebellum are ipsilateral • Run to and from the same side of the body

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