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The Central Nervous System

PART 2. The Central Nervous System. The Brain. Performs the most complex neural functions Intelligence Consciousness Memory Sensory-motor integration Involved in innervation of the head. Embryonic Development of the Brain. Brain arises from rostral part of the neural tube

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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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