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Anatomy of the Central Nervous System: Spinal Cord and Brain

Learn about the structure and function of the spinal cord and brain, including the segments of the spinal cord, white and gray matter, and the protection provided by the meninges. Explore the organization and basic parts of the brain, as well as its important functions.

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Anatomy of the Central Nervous System: Spinal Cord and Brain

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  1. 13 PART 1 The CentralNervous System Pages 377-394, 396-412

  2. 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

  3. The Spinal Cord • Functions of the spinal cord • Spinal nerves attach to it • Provides two-way conduction pathway • Major center for reflexes • Location of the spinal cord • Runs through the vertebral canal • Extends from the foramen magnum to the level of the vertebra L1 or L2

  4. The Spinal Cord • Conus medullaris • The inferior end of the spinal cord • Filum terminale • Long filament of connective tissue • Attaches to the coccyx inferiorly • Cervical and lumbar enlargements • Where nerves for upper and lower limbs arise • Cauda equina • Collection of spinal nerve roots

  5. Cervical spinal nerves Cervical enlargement Dura and arachnoid mater Thoracic spinal nerves Lumbar enlargement Conus medullaris Lumbar spinal nerves Cauda equina Filum terminale (a) The spinal cord and its nerve roots, with the bony vertebral arches removed. The dura mater and arachnoid mater are cut open and reflected laterally. Sacral spinal nerves The Spinal Cord Figure 13.24

  6. The Spinal Cord • Spinal cord segments • Indicate the region of the spinal cord from which spinal nerves emerge • Designated by the spinal nerve that issues from it • T1 is the region where the first thoracic nerve emerges

  7. Dorsal (posterior) Ventral (anterior) Spinal cord segment C1 Spinal nerve C1 Spinal cord segment T1 Spinal nerve C8 Spinous process T1 Spinal nerve T1 Spinal cord segment T5 Spinal nerve T5 Spinal cord segment L1 Spinal nerve L1 Spinal nerve S1 Spinal Cord Segments Figure 13.25

  8. White Matter of the Spinal Cord • White matter • Outer region of the spinal cord • Composed of myelinated and unmyelinated axons • Allow communication between spinal cord and brain • Fibers classified by type • Ascending fibers • Descending fibers • Commisural fibers

  9. Gray Matter of the Spinal Cord and Spinal Roots • Shaped like the letter “H” • Gray commissure—contains the central canal • Dorsal horns • Consist of interneurons • Ventral and lateral horns • Contain cell bodies of motor neurons

  10. Dorsal median sulcus Gray commissure Dorsal funiculus Dorsal horn Gray matter Ventral funiculus White matter Ventral horn Lateral horn Lateral funiculus Dorsal root ganglion Spinal nerve Central canal Dorsal root (fans out into dorsal rootlets) Ventral median fissure Ventral root (derived from several ventral rootlets) Pia mater Arachnoid mater Spinal dura mater (b) The spinal cord and its meningeal coverings Anatomy of the Spinal Cord Figure 13.26

  11. Organization of the Gray Matter of the Spinal Cord • Gray matter • Divided according to somatic and visceral regions • SS—somatic sensory • VS—visceral sensory • VM—visceral motor • SM—somatic motor

  12. Dorsal root (sensory) Dorsal horn (interneurons) Dorsal root ganglion SS Somatic sensory neuron VS VM Visceral sensory neuron SM Visceral motor neuron Ventral horn (motor neurons) Somatic motor neuron Spinal nerve Ventral root (motor) Interneurons receiving input from somatic sensory neurons Interneurons receiving input from visceral sensory neurons Visceral motor (autonomic) neurons Somatic motor neurons Gray Matter of the Spinal Cord and Spinal Roots Figure 13.27

  13. Protection of the Spinal Cord • Protected by vertebrae, meninges, and CSF • Meninges • Dura mater—a single layer surrounding spinal cord • Arachnoid mater—lies deep to the dura mater • Pia mater—innermost layer • Delicate layer of connective tissue • Extends to the coccyx • Denticulate ligaments—lateral extensions of pia mater

  14. Figure 13.26a Anatomy of the spinal cord. Pia mater Epidural space(contains fat) Arachnoid mater Spinalmeninges Dura mater Subdural space Subarachnoidspace(contains CSF) Dorsal rootganglion Body ofvertebra Cross section of spinal cord andvertebra, cervical region

  15. Figure 13.26b Anatomy of the spinal cord. Dura mater Dorsal funiculus Dorsal mediansulcus Dorsal rootganglion Dorsal hornof gray matter Gray commissure Lateral funiculus Ventral hornof gray matter Central canal Ventral medianfissure Ventral funiculus Light micrograph of cross section through spinal cord, cervical region (8)

  16. Cerebrospinal Fluid • Fills the hollow cavities of the brain and spinal cord • Provides a liquid cushion for the spinal cord and brain • Other functions: • Nourishes brain and spinal cord • Removes wastes • Carries chemical signals between parts of the CNS

  17. The Brain • Performs the most complex neural functions • Intelligence • Consciousness • Memory • Sensory-motor integration • Involved in innervation of the head • Brain also controls: • Heart rate, respiratory rate, blood pressure • Autonomic nervous system • Endocrine system

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

  19. 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 • Cortex—outer layer of gray matter • Formed from neuronal cell bodies • Located in cerebrum and cerebellum

  20. Cortex of gray matter Central cavity Migratory pattern of neurons Inner gray matter Outer white matter Cerebrum Cerebellum Gray matter Region of cerebellum Central cavity Inner gray matter Outer white matter Gray matter Brain stem Central cavity Outer white matter Inner gray matter Spinal cord Basic Parts and Organization of the Brain Figure 13.3

  21. 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

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

  23. Lateral ventricle Septum pellucidum Anterior horn Posterior horn Interventricular foramen Inferior horn Third ventricle Inferior horn Cerebral aqueduct Lateral aperture Median aperture Fourth ventricle Lateral aperture Central canal (a) Anterior view (b) Left lateral view Ventricles of the Brain Figure 13.4

  24. The Brain Stem • Medulla oblongata, pons & midbrain • 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

  25. Frontal lobe Olfactory bulb (synapse point of cranial nerve I) Optic chiasma Optic nerve (II) Optic tract Mammillary body Midbrain Pons Temporal lobe Medulla oblongata Cerebellum Spinal cord Ventral View of the Brain Figure 13.5

  26. 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 • Inferior cerebellar peduncles • Fiber tracts connecting medulla and cerebellum Cranial nerves VIII–XII attach to the medulla

  27. View (a) View (c) Diencephalon Optic chiasma View (b) Thalamus Optic nerve (II) Hypothalamus Optic tract Mammillary body Oculomotor nerve (III) Crus cerebri of cerebral peduncles (midbrain) Trochlear nerve (IV) Trigeminal nerve (V) Middle cerebellar peduncle Pons Facial nerve (VII) Abducens nerve (VI) Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Hypoglossal nerve (XII) Pyramid Vagus nerve (X) Ventral root of first cervical nerve Thalamus Accessory nerve (XI) Diencephalon Hypothalamus Decussation of pyramids Midbrain Pons Spinal cord Brainstem Medulla oblongata (a) Ventral view The Brain Stem—Medulla Oblongata Figure 13.6

  28. View (a) View (c) Thalamus Optic tract View (b) Infundibulum Superior colliculus Pituitary gland Inferior colliculus Crus cerebri of cerebral peduncles (midbrain) Trochlear nerve (IV) Superior cerebellar peduncle Trigeminal nerve (V) Pons Middle cerebellar peduncle Facial nerve (VII) Inferior cerebellar peduncle Abducens nerve (VI) Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Olive Hypoglossal nerve (XII) Vagus nerve (X) Accessory nerve (XI) Thalamus Diencephalon Hypothalamus Midbrain Pons Brainstem Medulla oblongata (b) Left lateral view The Brain Stem—Medulla Oblongata Figure 13.6

  29. 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

  30. View (a) View (c) Thalamus Midbrain Diencephalon Superior colliculus Corpora quadrigemina of tectum View (b) Inferior colliculus Trochlear nerve (IV) Superior cerebellar peduncle Pineal gland Pons Middle cerebellar peduncle Medulla oblongata Inferior cerebellar peduncle Anterior wall of fourth ventricle Facial nerve (VII) Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Choroid plexus (fourth ventricle) Vagus nerve (X) Accessory nerve (XI) Dorsal median sulcus Thalamus Diencephalon Hypothalamus Dorsal root of first cervical nerve Midbrain Pons Brainstem Medulla oblongata (c) Dorsal view The Brain Stem—The Medulla Oblongata Figure 13.6

  31. Solitary nucleus Hypoglossal nucleus (XII) Fourth ventricle Dorsal motor nucleus of vagus (X) Vestibular nuclear complex (VIII) Choroid plexus Inferior cerebellar peduncle Cochlear nuclei (VIII) Lateral nuclear group Medial nuclear group Nucleus ambiguus Reticular formation Raphe nucleus Inferior olivary nucleus Medial lemniscus Pyramid (c) Medulla oblongata

  32. The Brain Stem—The Medulla Oblongata

  33. 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

  34. Superior cerebellar peduncle Fourth ventricle Reticular formation Trigeminal main sensory nucleus Trigeminal motor nucleus Middle cerebellar peduncle Pontine nuclei Trigeminal nerve (V) Fibers of pyramidal tract Medial lemniscus (b) Pons The Brain Stem—The Pons Figure 13.7

  35. The Brain Stem—The Pons Table 13.2 (2 of 2)

  36. 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 tracts • Superior cerebellar peduncles • Connect midbrain to the cerebellum

  37. Dorsal Superior colliculus Tectum Periaqueductal gray matter Cerebral aqueduct Oculomotor nucleus (III) Reticular formation Medial lemniscus Red nucleus Substantia nigra Fibers of pyramidal tract Ventral Crus cerebri of cerebral peduncle (a) Midbrain

  38. View (a) View (c) Diencephalon Optic chiasma View (b) Thalamus Optic nerve (II) Hypothalamus Optic tract Mammillary body Oculomotor nerve (III) Crus cerebri of cerebral peduncles (midbrain) Trochlear nerve (IV) Trigeminal nerve (V) Middle cerebellar peduncle Pons Facial nerve (VII) Abducens nerve (VI) Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Hypoglossal nerve (XII) Pyramid Vagus nerve (X) Ventral root of first cervical nerve Thalamus Accessory nerve (XI) Diencephalon Hypothalamus Decussation of pyramids Midbrain Pons Spinal cord Brainstem Medulla oblongata (a) Ventral view The Brain Stem Figure 13.6

  39. The Brain Stem View (a) View (c) Thalamus Optic tract View (b) Infundibulum Superior colliculus Pituitary gland Inferior colliculus Crus cerebri of cerebral peduncles (midbrain) Trochlear nerve (IV) Superior cerebellar peduncle Trigeminal nerve (V) Pons Middle cerebellar peduncle Facial nerve (VII) Inferior cerebellar peduncle Abducens nerve (VI) Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Olive Hypoglossal nerve (XII) Vagus nerve (X) Accessory nerve (XI) Thalamus Diencephalon Hypothalamus Midbrain Pons Brainstem Medulla oblongata (b) Left lateral view Figure 13.6

  40. The Brain Stem—The Midbrain • Corpora quadrigemina • The largest nuclei • Divided into the superior and inferiorcolliculi • Superior colliculi—nuclei that act in visual reflexes • Inferior colliculi—nuclei that act in reflexive response to sound

  41. The Brain Stem—Dorsal View View (a) View (c) Thalamus Midbrain Diencephalon Superior colliculus Corpora quadrigemina of tectum View (b) Inferior colliculus Trochlear nerve (IV) Superior cerebellar peduncle Pineal gland Pons Middle cerebellar peduncle Medulla oblongata Inferior cerebellar peduncle Anterior wall of fourth ventricle Facial nerve (VII) Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Choroid plexus (fourth ventricle) Vagus nerve (X) Accessory nerve (XI) Dorsal median sulcus Thalamus Diencephalon Hypothalamus Dorsal root of first cervical nerve Midbrain Pons Brainstem Medulla oblongata (c) Dorsal view

  42. The Cerebellum • Located dorsal to the pons and medulla • Smoothes and coordinates body movements • Helps maintain equilibrium • Consists of two cerebellar hemispheres • Composed of three regions • Cortex—gray matter • Arbor vitae • Internal white matter • Deep cerebellar nuclei—deeply situated gray matter

  43. Anterior lobe Arbor vitae Cerebellar cortex Folia Anterior lobe Pons Cerebellar cortex Fourth ventricle Arbor vitae Posterior lobe Flocculonodular lobe Medulla oblongata Choroid plexus (a) Midsagittal section Cerebellar peduncles Posterior lobe Superior Middle Choroid plexus of fourth ventricle Inferior Medulla oblongata Flocculonodular lobe (b) Illustration of parasagittal section The Cerebellum Figure 13.8

  44. The Cerebellum—Cerebellar Peduncles • Thick tracts connecting the cerebellum to the brain stem are • Superior cerebellar peduncles • Middle cerebellar peduncles • Inferior cerebellar peduncles

  45. The Diencephalon • Forms the center core of the forebrain • Surrounded by the cerebral hemispheres • Composed of three paired structures • Thalamus • Hypothalamus • Epithalamus • Border the third ventricle • Primarily composed of gray matter

  46. Cerebral hemisphere Corpus callosum Septum pellucidum Fornix Interthalamic adhesion (intermediate mass of thalamus) Choroid plexus Thalamus (encloses third ventricle) Posterior commissure Interventricular foramen Pineal gland (part of epithalamus) Anterior commissure Corpora quadrigemina Hypothalamus Midbrain Cerebral aqueduct Optic chiasma Pituitary gland Arbor vitae (of cerebellum) Mammillary body Fourth ventricle Pons Choroid plexus Medulla oblongata Cerebellum Spinal cord (a) The Diencephalon and Brainstem Figure 13.9

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