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The Central Nervous System

The Central Nervous System. Central nervous system – the brain and spinal cord Directional terms unique to the CNS Rostral – toward the nose Caudal – toward the tail. Embryonic Development of the Brain. Figure 13.2a-e. Embryonic Development of the Brain. Figure 13.2a-e.

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The Central Nervous System

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  1. The Central Nervous System • Central nervous system – the brain and spinal cord • Directional terms unique to the CNS • Rostral – toward the nose • Caudal – toward the tail

  2. Embryonic Development of the Brain Figure 13.2a-e

  3. Embryonic Development of the Brain Figure 13.2a-e

  4. Embryonic Development of the Brain Figure 13.2a-e

  5. Embryonic Development of the Brain Figure 13.2a-e

  6. Embryonic Development of the Brain • Brain arises from the rostral part of the neural tube • Three primary brain vesicles in 4-week embryo • Prosencephalon – the forebrain • Mesencephalon – the midbrain • Rhombencephalon – the hindbrain

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

  8. 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

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

  10. 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 limited space

  11. Brain Development from Week 5 to Birth Figure 13.3a-d

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

  13. Basic Parts and Organization of the Brain Figure 13.4

  14. 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

  15. Basic Parts and Organization of the Brain Figure 13.5

  16. 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

  17. 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

  18. 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

  19. Ventricles of the Brain Figure 13.6a, b

  20. Protection of the Brain – Cerebrospinal Fluid (CSF) • Provides a liquid cushion for the brain and spinal cord • The brain “floats” in CSF • Formed in choroid plexuses in the brain ventricles

  21. Protection of the Brain – Cerebrospinal Fluid (CSF) Figure 13.27a

  22. Protection of the Brain – Cerebrospinal Fluid (CSF) Figure 13.27b

  23. Protection of the Brain – Blood-Brain Barrier • Prevents most blood-borne toxins from entering the brain • Impermeable capillaries • Not an absolute barrier • Nutrients such as oxygen pass through • Allows alcohol, nicotine, and anesthetics through

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