Central Nervous System PDF Notes

(003) CENTRAL NERVOUS SYSTEM DR. ARELLANO| 10/07/2020 OUTLINE II. CENTRAL NERVOUS SYSTEM I. INTRODUCTION II. CENTRAL NERVOUS SYSTEM  Parts of the CNS:...

(003) CENTRAL NERVOUS SYSTEM DR. ARELLANO| 10/07/2020 OUTLINE II. CENTRAL NERVOUS SYSTEM I. INTRODUCTION II. CENTRAL NERVOUS SYSTEM  Parts of the CNS: III. BRAIN 1. Cerebral Hemisphere A. DIVISIONS OF THE BRAIN 2. Cerebellum 3. Brain stem IV. MEDULLA OBLONGATA a) Midbrain V. PONS b) Pons VI. CEREBELLUM c) Medulla oblongata A. CEREBELLAR CONNECTIONS 4. Spinal Cord B. LOBES OF CEREBELLUM Brain and Spinal Cord C. CEREBELLAR CORTEX  - main centers where correlation and integration of D. FOUR INTRA-CEREBELLAR NUCLEI nervous information occur VII. 4TH VENTRICLE - covered with membranes (MENINGES) A. DIVISIONS OF THE MIDBRAIN - suspended in the CSF B. CHARACTERISTIC LEVELS - further protected by bones of the skull and the VIII. MIDBRAIN vertebral column C. DIVISIONS OF THE MIDBRAIN D. CHARACTERISTIC LEVELS IX. FOREBRAIN A. DIENCEPHALON X. CEREBRUM A. CEREBRAL CORTEX B. BASAL GANGLIA / NUCLEI C. CORONA RADIATA XI. SPINAL CORD A. GRAY MATTER B. NERVE CELL GROUS OF THE ANTERIOR GRAY COLUMNS C. NERVE CELL GROUS OF THE POSTERIOR GRAY COLUMNS D. NERVE CELL GROUS OF THE LATERAL GRAY COLUMNS E. CENTRAL CANAL F. WHITE MATTER G. CORTICOSPINAL TRACT I. INTRODUCTION The nervous system includes: 1. Central Nervous System a. Brain b. Spinal Cord 2. Peripheral Nervous System a. Cranial and Spinal nerves b. Autonomic Nervous system Figure 2.  The CNS is composed of: 1. Neurons- large numbers of excitable nerve cells a. Axons/Nerve Fibers- long processes of nerve cell 2. Neuroglia- specialized tissue that supports the neuron - non-excitable Figure 1. The Central Nervous System. Prepared and Edited by: Padolina, J.  (003) CENTRAL NERVOUS SYSTEM DR. ARELLANO| 10/07/2020  The CNS is organized internally into: 1. Gray Matter- nerve cells embedded in neuroglia -contains a meshwork of neural tissues such as axonal, dendritic, and glial processes that are very tightly packed together and fill interneural spaces (Neuropil) 2. White Matter- nerve fibers embedded in neuroglia -white color is due to the presence of lipid material in the myelin sheath -is devoid of neuronal cell bodies and consists primarily of myelinated axons, some unmyelinated axons, the supportive neuroglial oligodendrocytes, and blood vessels. Figure 4. The Medulla oblongata V. PONS -”Bridge” -derived from the large number of transverse fibers on its anterior aspect, connecting the two cerebellar hemispheres -contains many nuclei as well as ascending & descending nerve fibers Boundaries: -Posterior: anterior surface of cerebellum -Superior: Midbrain -Inferior: Medulla oblongata Figure 3. Axial cut of Brain and Spinal Cord showing the Gray and White Matter III. BRAIN -lies in the cranial cavity -continuous with SC through the Foramen Magnum -surrounded by 3 meninges: 1. Dura Mater 2. Arachnoid Mater 3. Pia Mater -meninges are continuous with the corresponding meninges of the SC -CSF surrounds the brain in the SA space Figure 5. The Medulla oblongata with labels. A. Divisions of the Brain (Ascending order from the SC) 1. Hindbrain/Brain stem VI. CEREBELLUM a) Medulla Oblongata b) Pons c) Cerebellum -lies within the posterior cranial fossa 2. Midbrain -posterior to the pons and medulla oblongata 3. Forebrain -consists of two hemispheres connected by a median a) Diencephalon (between brain) portion called Vermis b) Cerebrum -not part of the brain stem but is rather considered a suprasegmental structure because it is located superior to brainstem IV. MEDULLA OBLONGATA A. CEREBELLAR CONNECTIONS -aka Myencephalon A. Superior Cerebellar Peduncle -most caudal segment of the brainstem -Brachium conjunctivum -conical in shape -connects cerebellum to the midbrain -connects the pons superiorly to the SC inferiorly -contains Nuclei- collections of neurons B. Middle Cerebellar Peduncle -conduit for ascending and descending nerve fibers -Brachium Pontis -Connects cerebellum to the pons Prepared and Edited by: Padolina, J.  (003) CENTRAL NERVOUS SYSTEM DR. ARELLANO| 10/07/2020 C. Inferior Cerebellar Peduncle -Restiform body -connects cerebellum to the medulla oblongata Figure 7. Layers of the Cerebellar cortex D. FOUR INTRA-CEREBELLAR NUCLEI -They receive input from Purkinje cell axons and from collaterals of cerebellar afferent fibers. Figure 6. Cerebellum with cerebellar connections -4 masses of gray -lateral to medial order: B. LOBES OF THE CEREBELLUM A. Anterior Lobe -superior surface of the cerebellum Dentate Emboliform Globose Fastigial -Primary Fissure- separates the anterior lobe from the middle lobe 1. Dentate Nucleus B. Middle Lobe -largest among the nuclei -largest part of the cerebellum -”crumpled bag” shape -between the primary and uvulonodular fissures 2. Emboliform Nucleus C. Floculonodular Lobe -ovoid shape -posterior to the uvulonodular fissure -meidal to the dentate nucleus -no morphological or funtional significance 3. Globose Nucleus C. CEREBELLAR CORTEX -one or more rounded cell groups that lie medial to the emboliform nucleus -surface layer of each cerebellar hemispheres -composed of gray matter 4. Fastigial Nucleus -thrown into fold or Folia, separated of -lies near the midline in the vermis, close to the roof of the 4 th Transverse fissures ventricle  Layers of the Cerebellar cortex A. Molecular Layer -2 types of cells: 1. Stellate Cells (outer) 2. Basket Cells (inner) B.Purkinje Cell Layer -large Golgi type I neurons -flask-shaped -collateral branches makes synaptic contacts with the dendrites of the basket and stellate cells C. Granular Layer -small cells with densely staining nuclei and scanty cytoplasm Figure 8.1. The four intra-cerebellar nuclei and the cerebellar lobes -synaptic contacts with mossy fiber inputs -Parallel Fibers run at right angle to the dendritic processes of the Purkinje Cells -contains granule cells, Golgi cells, and mossy fibers Prepared and Edited by: Padolina, J.  (003) CENTRAL NERVOUS SYSTEM DR. ARELLANO| 10/07/2020 A. 3 DIVISIONS OF THE MIDBRAIN 1. Tectum (Quadrigeminal plate) -dorsal to the cerebral aqueduct -roof-like structure -includes the superior and inferior colliculi (Characteristic structure of the area) 2. Tegmentum (central part) -main portion of the mesencephalon -lies inferior to the cetral gray matter -contains ascending and descending tracts, reticular nuclei and nuclear masses 3. Basis pedunculi (ventral part) -substantia nigra + crus cerebri *Crus cerebri- composed primarily of descending Figure 8.2. The four intra-cerebellar nuclei and the cerebellar lobes fibers -contains descending cortical projections VII. 4TH VENTRICLE -includes cerebral peduncles and corticofugal fibers Substantia nigra- pigmented nuclear mass in -cavity filled with CSF between the dorsal surface pf the cerebral -surrounded by the cerebellum, medulla oblongata, and the peduncle and tegmentum pons -connected superiorly to the 3rd ventricle via the cerebral Note: The term cerebral peduncle is sometimes used for the crus aqueduct cerebri, but it actually represents the entire midbrain below the -continuous inferiorly to the central canal of the SC tectum (tegmentum and basis pedunculi). -communicates with the SA space through 3 openings: A. Foramen of Luschka (2) - lateral B. Foramen of Magendie (1) - median B. 2 CHARACTERISTIC LEVELS: 1. Inferior colliculus -characterized by: a. Decusation of the superior cerebellar peduncle b. Trochlear nucleus 2. Superior colliculus -characterized by: a. Red nucleus b. Oculomotor nucleus c. Posterior commisure Figure 9. 4th Ventricle VIII. MIDBRAIN -aka the Mesenchephalon -represents the smallest and least differentiated segment of the infratentorial brainstem Figure 9. The Midbrain -lies rostral to the pons. -narrow part of the brain that connects the forebrain to the hindbrain *Cerebral Aqueduct- narrow cavity of the midbrain *Periaqueductal gray (central gray)- sleeve of neuron cell bodies that completely surround the cerebral aqueduct Prepared and Edited by: Padolina, J.  (003) CENTRAL NERVOUS SYSTEM DR. ARELLANO| 10/07/2020 IX. FOREBRAIN A. DIENCEPHALON -completely hidden from the surface of the brain -consists of: a. Thalamus (dorsal) - eggshaped mass of gray matter that lies on either side of the 3rd ventricle -anterior end form the poterior boundary of the Interventricular Foramen -mediates the conscious sensation and some aspects of motor control as well as somatosensory, visual, or auditory inputs b. Hypothalamus (ventral) Figure 10.Thalamus and Hypothalamus -forms the lower part of the lateral wall and floor of the 3rd ventricle X. CEREBRUM -regulates functions that are “automatically” adjusted (such as blood pressure and body temperature) -aka the Telencephalon without our being aware of the change. -The largest part of the brain -2 hemispheres that is connected by a mass of white matter called Corpus Callosum -separated by a deep cleft, the Longitudinal Fissure, into which projects the Falx Cerebri Boundaries: -each extends from the frontal to occipital bones -superior to the anterior and middle cranial fossae -posteriorly, lies above the Tentorium Cerebelli Figure 11. Cerebrum A. CEREBRAL CORTEX -composed of Gray Matter -has folds or Gyri -separated by fissures or Sulci -large sulci are used to subdivide the surface of each hemisphere into Lobes -lobes are named according to the bones of the cranium under which they lie -4 lobes: a. Frontal lobe b. Parietal lobe c. Temporal lobe d. Occipital lobe Prepared and Edited by: Padolina, J.  (003) CENTRAL NERVOUS SYSTEM DR. ARELLANO| 10/07/2020 Figure 13. Corona Radiata  Caudate nucleus -tailed nucleus situated on the medial side of the internal capsule  Lentiform nucleus -len-shaped nucleus on the lateral side of the IC  Lateral ventricle -cavity present w/in each cerebral hemisphere -communicates with the 3rd ventricle via the interventricular foramen Figure 12. Cerebrum lobes and Cranium B. BASAL GANGLIA / NUCLEI -large masses of gray matter within the hemisphere inside the white matter -term basal ganglia is a misnomer -consist of : 1. Caudate and Lenticular nuclei (dorsal basal nuclei) 2. Nucleus accumbens and parts of the Adjacent olfactory tubercle (the ventral striatum) 3. Substantia innominata (ventral pallidum) Figure 14. Axial cute of the Cerebrum C. CORONA RADIATA -fan-shaped collection of nerve fibers XI. SPINAL CORD -passes in the white matter to and from the cerebral cortex to the brainstem -converges on the basal nuclei, and passes between them -roughly cylidnrical in shape as the Internal Capsule -begins superiorly at the foramen magnum -continuous with medulla oblongata in the brain -terminate inferiorly: a. Level of the lower border of L1 (adult) b. Level of the upper border of L3 (pedia) -occupies the upper two-thirds (2/3) of the vertebral canal of the vertebral column -3 meninges: a. Dura b. Arachnoid c. Pia Mater -further protection is provided by the CSF Prepared and Edited by: Padolina, J.  (003) CENTRAL NERVOUS SYSTEM DR. ARELLANO| 10/07/2020 -gives origin to the Brachial Plexus (cervical region) -give origin to the Lumbosacral Plexus (lower thoracic and lumbar region) -fusiformly enlarged as the: a. Cervical enlargement b. Lumbar enlargement -31 pairs of spinal nerves attahced to the SC by the Anterior/Motor Roots and Posterior/Sensory Roots -Each posterior root possess Posterior Root Ganglion  Conus Medullaris -tapering end of the spinal cord  Filum Terminale -extension of the pia mater at the apex of the conus medullaris of the spinal cord -descends to be attached to the posterior surface of the coccyx  Anterior Median Fissure -deep longitudinal fissure  Posterior Median Sulcus -shallow furrow Figure 15.1. Spinal Cord A. GRAY MATTER B. NERVE CELL GROUPS IN THE ANTERIOR GRAY COLUMNS -H-shaped pillar with anterior and posterior gray columns or horns 1.Medial Group -united by a thin gray commisure, containing the -innervates skeletal muscles of the neck and small central canal trunk, the intercostal and abdominal muscles -amount of gray matter present at any given level of the Spinal cord is related to the amount of muscle 2.Central Group innervated at that level -smallest (C3,C4,C5) -divided into: -innervates Diaphragm (Phrenic Nucleus) a. Anterior (ventral) horn -(C1 to C6) innervates sternocleidomastoid and b. Posterior (dorsal) horn trapezius muscle (Accessory Nucleus) Note: Size of the spinal cord is greatest within the cervical and -axons form the spinal part of the accessory nerve (CN XI) lumbosacral enlargementa of the cord (innervate the muscles -(L2 to S1) Lumbosacral Nucleus axons have an of the UE and LE) unknown distribution Large Multipolar nerve cells 3. Lateral Group -axons pass out in the anterior roots of the spinal nerves as alpha efferents (innervates the skeletal muscle) -cervical and lumbosacral segments of the SC -innervating skeletal muscles of the limbs Small multipolar nerve cells -axons pass out as gamma efferents (innervates intrafusal C. NERVE CELL GROUPS IN THE POSTERIOR GRAY COLUMNS muscle fibers) of neuromuscular spindles 1. Substantia Gelatinosa Group -located apex of the posterior gray column -Golgi Type II neurons -recieves afferent fobers from the posterior root (pain, temperature, and touch) -recieves descending fiber inputs from supraspinal level 2. Nucleus Proprius Group -located anterior to the substantia gelatinosa -main bulk of cells present in the posterior gray column -recieves fibers from posterior white column -senses: a. Position & movement (Proprioception) b. Two-point discrimination c. Vibration Prepared and Edited by: Padolina, J.  (003) CENTRAL NERVOUS SYSTEM DR. ARELLANO| 10/07/2020 3. Nucelus Dorsalis (Clark’s Column) -base of the posterior gray column -C8-L3 or L4 segment only -cells are large -associated with proprioceptive endings (neuromuscular spindles & tendon spindles) 4. Visceral Afferent Nucleus (T1-L3) -medium sized nerve cells (lateral to the nucleus dorsalis of Clark) -recieving visceral afferent information D. NERVE CELL GROUP IN THE LATERAL GRAY COLUMNS 1.Intermediolateral group of cells (T1-L2 or L3) -give rise to pre-ganglionic sympathetic fibers -similar group found in the S2 to S4 segments of SC Figure 15.3. Spinal Cord E. CENTRAL CANAL -Present throughout the SC G. CORTICOSPINAL TRACT -filled with CSF -fibers arise as axons of Pyramidal Cells in the 5th layer of -lined with ciliated columnar epithelium (ependyma) the cerebral cortex -closed inferiorly, and opens superiorly into the 4 th -fibers are myelinated and relatively slow conducting small ventricle fibers -CST Fibers: F. WHITE MATTER a. 2/3 from pre-central gyrus -composed of: b. 1/3 from the post central gyrus a. Nerve fibers b. Neuroglia Or: c. Blood vessels -surrounds the gray matter a. 1/3 from the primary motor cortex (area 4) -white in color b. 1/3 from the secondary motor cortex (area 6) -Division: c. 1/3 from the parietal lobe (area 3,1,2) a. Anterior white column or funiculi b. Lateral white column or funiculi *insert CST pic c. Posterior white column or funiculi Figure 15.2. Spinal cord Figure 16. Corticospinal cord Prepared and Edited by: Padolina, J.  (003) CENTRAL NERVOUS SYSTEM DR. ARELLANO| 10/07/2020 TEST YOUR KNOWLEDGE REFERENCES 1. These are all nerve cell groups of the posterior gray columns Dr. Arellano’s Lecture except Haines D.E., Mihailhoff G.A. (2018) Fundamental Neuroscience for Basic and Clinical A. Nucleus Proprius Applications (5th ed) Elsevier Inc., Philadephia Waxman S.G. (2013) Clinical Neuroanatomy (25th Ed) McGraw-Hill Education, New York B. Nucleus Dorsalis C. Globose Nucleus D. Substantia Gelatinosa 2. The inferior colliculus is characterized by A. Decussation of the superior cerebellar peduncle B. Red nucleus C. Oculomotor nucleus D. Posterior commisure 3. Fan-shaped collection of nerve fibers: A. Basal Nuclei B. Conus Medullaris C. Foramen Magnum D. Corona Radiata 4. The white color in white matter is due to the presence of lipid material in the myelin sheath? A. True B. False 5. Nerve cell groups that give rise to pre-ganglionic sympathetic fibers. A. Intermediolateral group B. Substantia Gelatinosa group C. Medial group D. Lateral group 6. Mass of white matter that connects the 2 hemispheres of the Cerebrum A. Corpus Callosum B. Longitudinal Fissure C. Falx Cerebri D. Subtantia Nigra 7. The amount of gray matter present at any given level of the Spinal cord is related to the amount of muscle innervated at that level. A. True B. False 8. Median portion that connects the 2 hemispheres of the Cerebellum A. Corona Radiata B. Corpus Callosum C. Vermis D. Folia 9. All of these are the layers of the Cerebellar cortex except A. Molecular Layer B. Pyramidal Layer C. Purkinje Cell Layer D. Granular Layer 10. Extension of the pia mater at the apex of the conus medullaris of the spinal cord A. Corticospinal tract B. Cerebral Aqueduct C. Vermis D. Filum Terminale Ans: C, A, D, A, A, A, A, C, B, D Prepared and Edited by: Padolina, J.