11.8.Overview of the nervous system.txt

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11.8.Overview of the nervous system.txt
2010-11-08 20:35:05

11.8.Overview of the nervous system
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  1. 11.8.Overview of the nervous system
    • Understand the general divisions of the NA and their functions
    • Understand anatomical direction, planes of section, and appearance of stained and unstained tissue of the CNS; describe the distribution of cranial nerves.
    • Understand the general features of the nervous system including: gray/white matter, nuclei, ganglia, nerves, fasciculi (tracts), distribution of gray and white matter in brain vs. spinal cord, function and location of meninge and ventricles, and major blood vessels.
  2. Peripheral nervous system (PNS)
    • All spinal nerves and cranial nerves
    • All autonomic nerves: sympathetic, parasympathetic, enteric
    • All ganglia associated with spinal, cranial, and autonomic nerves: .
    • Dorsal Root Ganglia (sensory): contain the cell bodies of sensory spinal nerves
    • Cranial nerve Ganglia (sensory): trigeminal, geniculate, spiral, vestibular, superior/inferior ganglia of CN IX, superior/inferior ganglia of CN X
    • Autonomic Ganglia (motor): sympathetics and parasympathetics
  3. Sympathetics:
    • chain ganglia
    • prevertebral ganglia: (celiac, aorticorenal, superior/inferior mesenterics)
  4. parasympathetics:
    • cilliary
    • pterygopalatine
    • submandibular
    • otic
    • terminal
  5. Central Nervous System (CNS)
    • Composed of Brain and Spinal cord
    • Transmit, integrate and process sensory and motor information
  6. Brain =
    • Brain = cerebral hemispheres + brainstem + cerebellum
    • Cerebral hemispheres: = telencephalon + diencephalon
  7. Telencephalon
    • Cortex
    • White matter
    • Deep nuclei
  8. Diencephalon
    • Thalamus
    • Subthalamus
    • Epithalamus
    • Hypothalamus
  9. Brainstem =
    Medulla, pons, midbrain
  10. Each component of the CNS has unique features and specific functions
    • 2 hemispheres each with a lateral and medial surface
    • lobes
    • gyrus
    • fissures
    • sulcus
    • Major components: cortex, deep white matter, and the diencephalon
  11. Lobes:
    • Frontal
    • Parietal
    • Occipital
    • Temporal
    • Large areas separated by landmarks that correspond to specific functions
  12. Gyrus
    a folded, raised portion of surface; convolution
  13. Fissures
    Deep spaces or depressions in the surface
  14. Sulcus
    Shallow depression between gyri
  15. Functions of cerebral hemispheres
    • Sensory perception
    • Cognition (thinking, reasoning, planning, etc)
    • Emotion and memory
    • Language ( both comprehension and speech)
    • Voluntary movement
  16. Brainstem composed of
    • Midbrain, pons, medulla
    • Cranial nerves II-XII located rostral to caudal, their positions essential for case solving
  17. Brainstem Functions
    • Origin of cranial nerves: sensory, motor, and autonomic information for the head; autonomic information for the body
    • A highway between cerebral hemispheres and spinal cord for sensory and motor pathways: …
    • Contains vital autonomic centers controlling: consciousness, heartbeat, blood pressure, respiratory rhythm
  18. Cerebellum: important in coordination of movement, learning movements, and (cognition).
  19. Spinal Cord
    • Located within the vertebral canal; it extends to vertebral level L1-L2: …
    • Segments: cervical (8), thoracic (12), lumbar (5), sacral (5)
    • Cervical and lumbosacral enlargements correspond to innervation of limbs
  20. Functions of spinal cord:
    • Incoming sensory info and outgoing motor info for entire body
    • Sympathetic and sacral parasympathetic innervation of viscera
  21. The CNS is Covered by 3 connective tissue layers, the meninges, that protect it
    • Dura, arachnoid, pia matters
    • These 3 also create spaces for blood vessels and nerves to travel
    • The spaces are potential sites for hematomas due to head trauma and vascular defects.
    • Bacteria and viruses that invade the nervous system can infect the meninges, causing meningitis, which can secondarily affect the underlying nervous tissue.
  22. Dura matter
    Outer, toughest layer
  23. Arachnoid matter
    Middle layer
  24. Pia
    Inner-most layer on the surface of the CNS
  25. Brian is Hollow. It contains a system of connected spaces, the ventricles, which are filled with CSF
    • Ventricles are located within the cerebral hemispheres and brainstem
    • The spinal cord contains a potential space
    • CSF is produces in the ventricles and flows into one of the meningeal spaces (subarachnoid space) to surround the brain and spinal cord to proide a protective cushion from surreounding bone.
    • CSF also collects brain metabolites, which cannot enter blood vessls due to the BBB
    • In lumbar puncture: CSF is sampled from a region around the spinal cord to assess CNS infections
    • Sometimes the flow of CSF in the ventricular system is blocked, causing hydrocephalus, which leads to a dangerous increase in intracranial pressure
  26. Nerve Cells are the functional units of the nervous system. Their function depends upon Glial cells
    • Because of their special role in communication, nerve cells have unique structural features: cell body, axon, dendrites, terminals
    • Glial cells are intimately associated with neuronal metabolism, signaling, protection, and repair
    • Nerve cells communicate at synapses, which allow them to connect to form pathways and to integrate information
    • Synaptic communication depends on release of NTs. Many neurological and psychiatric disorders result from abnormal NT release
    • Diseases such as multiple sclerosis attach glial cells that prodce myelin surrounding nerve axons, impairing conduction of electrical signals
    • Some neurological and psychiatric disorders (Parkinson’s Disease, schizophrenia, depression) result from abnormal release of NTs. Treatments for these disorders involve drugs that alter synaptic transmission
  27. The nervous system is highly organized
    • Axons are collected into bundles. Nerve cell bocies are collected into groups. Asons and nerve cell bodies are separated from one another – because their tasks are different
    • Cell body in PNS – ganglion
    • Cell body in CNS – nucleus/gray matter
    • Axon in PNS – Nerve
    • Axon in CNS – Tract or Fasciculus/White Matter
  28. Inside the CNS, axons appear different from nerve cell bodies
    • Unstained: axons (white matter) appear white due to the myelin that surrounds them. Cell bodies (gray matter) appear darker
    • In Weigert stain – myelinated axons are stained black, but cell bodies are not stained
    • The position of gray and white matter changes throughout the CNS from cerebral hemispheres to brainstem to spinal cord based on functional needs
  29. The CNS is studied anatomically, pathologically, radiologically, and clinically by comparison of different planes of section
    Disorders of the nervous system usually involve specific locations of injury. These locations overlap with pathways carrying information and result in loss of specific functions. To understand and even predict the deficits that injuries cause, we must understand the arrangement of pathways inside the CNS.
  30. Coronal, horizontal and sagittal sections show different views of the brain in MRIs and other imaging techniques
    Cerebral hemispheres, brainstem, and spinal cord have different 3-D shapes. Hemispheres are spherical, but the brainstem and spinal cord are cylindrical. Thus, coronal , horizontal, and sagittal section are used to study the hemispheres, but cross-sections (also transverse, axial, horizontal) primarily are used for the brainstem and spinal cord
  31. Anatomical directions and terminology
    • For the hemispheres: superior/dorsal; anterior, posterior, inferior/rostral
    • For brainstem and spinal cord: superior, caudal, anterior/ventral, posterior/dorsal
    • It is important to recognize the orientation of sections, which provides clues to the location in the CNS. Cross-sections of the brainstem and spinal cord differ in shape in different regions because their 3-D geometry changes over their length. As this module progresses, you will begin to recognize the shape of cross-sections.
  32. CNS requires a continuous supply of blood to maintain its high metabolic activity
    • Arterial supply to CNS fro 2 major sources:
    • Internal carotid arteries – 2
    • Vertebral arteries – 2
  33. Internal Carotid Arteries
    • Form the anterior circulation
    • Give rise to the anterior and middle cerebral arteries
    • Supply most of the cerebral hemispheres (frontal, parietal, and superior temporal lobes and deep structures)
  34. Vertebral Arteries
    • Form the posterior circulation; form basilar artery then 1 posterior cerebral arteries
    • Numerous branches of these arteries supply: spinal cord, brainstem, cerebellum, occipital lobe, and inferior temporal lobe
    • Anterior and posterior circulation anastomose in Circle of Willis
  35. Stroke
    Caused by a loss of blood supply to a region of the brain. It causes specific sensory/motor deficits that are related directly to structures in the damaged region.