1. Spinal Cord Location and Structure
    • •Provides a two-way conduction pathway to and from the brain
    • •Begins at the foramen magnum
    • •Ends as conus medullaris at L1 or L2 vertebral level in most adults
  2. Filum Terminale
    • -fibrous extension from conus medullaris that anchors the spinal cord to the coccyx
    • •31pairs of spinal nerves (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccyx)
  3. Features of the spinal cord
    The cauda equina is a collection of spinal nerves at the inferior end of the spinal cord, below the conus medularis

    Cervical and lumbar enlargements the nerves serving the upper and lower limbs emerge here
  4. The Bony Skeleton
    • •The spinal cord sits in the vertebral canal
    • •The spinal nerves exit from the intervertebral foramen with the exception of C1spinal nerve which exits between the skull and the C1 vertebra
  5. Spinal Cord Anatomy
    • •Internal gray matter is mostly cell bodies
    • •Gray matter surrounds the central canal
    • •Central canal is filled with cerebrospinal fluid
    • •Exterior white mater
    • •conduction tracts
  6. Gray Matter
    • Dorsal horns (pointed)
    • •interneurons that receive somatic and visceral sensory input

    • Ventral horns (rounded)
    • •somatic motor neurons whose axons exit the cord via ventral roots

    • Lateral horns (only in thoracic and lumbar regions)
    • •Visceral output via sympathetic neurons visceral motor

    • Dorsal root (spinal) ganglia
    • •contain cell bodies of sensory neurons one for each spinal level
  7. White Matter (Tracts)
    • •Consists mostly of ascending (sensory) and descending (motor) tracts
    • •Transverse tracts (commissural fibers) cross from one side to the other

    • Tracts are located in three white columns
    • 1.dorsal (posterior)
    • 2.lateral
    • 3.ventral (anterior)

    •Each spinal tract is composed of axons with similar functions
  8. Spinal Cord Anatomy
    •Spinal nerves leave at the level of each vertebrae

    •Spinal nerve consists of:

    • Dorsal root
    • •Axons carry somatic and visceral sensoryinformation
    • •Associated with the dorsal root ganglionat each spinal level of the cord
    • •Ganglia are collections of cell bodies ofunipolar neurons outside the central nervous system

    • Ventral root
    • •Axons that carry motor output
  9. Pathway Generalizations
    • •Pathways decussate (cross over) 10% go straight down and cross at the spinal cord
    • •Most consist of two or three neurons (a relay)
    • •Pathways are paired symmetrically (one on each side of the spinal cord or brain)
  10. Descending Pathways and Tracts
    •Involve two neurons:

    • 1.Upper motor neurons (brain)
    • •Pyramidal cells in primary motor cortex, can't recieve info

    • 2.Lower motor neurons (spinal cord)
    • •Ventral horn motor neurons
    • •Innervate skeletal muscles, can't carry info to muscles
  11. The Pyramidal System
    • •Impulses from pyramidal neurons in the precentral gyri pass through the pyramidal (also called corticospinal) tracts then to appropriate muscle
    • •Axons synapse with ventral horn motor neurons
    • •The pyramidal system controls fast and fine (skilled) movements
  12. Peripheral Nervous System (PNS) Nerve Structure
    • Endoneurium (inside)
    • • surrounds each fiber

    • Perineurium (around)
    • •Binds groups of fibers into fascicles

    • Epineurium (outside)
    • •Binds fascicles together
  13. PNS:Classification of Nerves
    • Mixed nerves
    • •Both sensory and motor fibers

    • Sensory(afferent) nerves (dorsal)
    • •Carry impulses toward the CNS

    • Motor (efferent) nerves (ventral)
    • •Carryimpulses away from the CNS
  14. PNS Spinal Nerves
    • •31 pairs of spinal nerves
    • •Formed by the combination of the ventral and dorsal roots of the spinal cord
    • •Named for the region from which they arise
    • •C8 comes out between C7/T1, T1 comes out between T1/T2 (named for the vertebrae above it)
  15. PNS: Anatomy of Spinal Nerves
    •Spinal nerves divide soon after leaving the spinal cord into a dorsal ramus and a ventral ramus

    • Ramus
    • •branch of a spinal nerve
    • •contains both motor and sensory fibers

    • Dorsal ramus
    • •serve the skin and muscles of the posterior trunk
    • (feed paravertebral region of muscles)

    • Ventral ramus
    • •form a complex of networks (plexus) for the anterior
    • (thoracic region follows the intercostal space)
  16. PNS: Spinal Nerve Plexuses
    • Plexus
    • •networks of nerves serving motor andsensory needs of the limbs
    • •Form from ventral rami of spinal nerves in the cervical, lumbar, and sacral regions

    • Four plexuses:
    • •Cervical
    • •Brachial
    • •Lumbar
    • •Sacral
  17. Cervical Plexus
    • •Originates from ventral rami of C1 – C5
    • •Serves anterior neck muscles known as the strap muscles

    • Important nerve:
    • •Phrenic nerve roots from C3,4,5 supplying the diaphragm
  18. Brachial Plexus
    •Originates from ventral rami in C5 – C8 andT1(posterior to clavicle and anterior to the 1st rib)

    • Important nerves:
    • •Radial nerve
    • •Terminal branch of radial nerve called the axillary nerve
    • •Median nerve
    • •Musculocutaneous nerve
    • •Ulnar nerve
    • Areas served:
    • shoulder, arm, forearm, and hand
  19. Lumbar Plexus
    • •Originates from ventral rami in L1 through L4
    • Important nerves:
    • •Femoral
    • •Obturator
    • •L2, L3, L4
    • Areas served:
    • •Lower abdomen L1 sensory
    • •Anterior and medial thighs L2, L3, L4
  20. Sacral Plexus (lumbosacral plexus)
    •Originates from ventral rami in L4-L5 and S1–S4

    • Important nerves:
    • •Sciatic (huge, a thumb width)
    • •Superior and inferior gluteal

    • Areas served:
    • •Lower trunk and posterior thigh
    • •Lateral and posterior leg and foot
    • •Gluteal muscles of hip area
  21. PNS: Cranial Nerves
    • •Twelv epairs of nerves that mostly serve the head and neck
    • •Only the pair of vagus nerves extend to thoracic and abdominal cavities
    • •Most are mixed nerves, but three are sensory only (CN I, II and VIII)
  22. PNS: Cranial Nerves Device
    • •I – Olfactory nerve, smell
    • •II – Optic nerve, sight
    • •III – Oculomotor nerve
    • •IV – Trochlear nerve
    • •V – Trigeminal nerve
    • •VI – Abducens nerve
    • •VII – Facial nerve
    • •VIII – Vestibulocochlear nerve, hearing
    • •IX – Glossopharyngeal nerve
    • •X – Vagus nerve(wanders from head to transverse colon)
    • •XI – Accessory nerve
    • •XII – Hypoglossal nerve
  23. What is a Dermatone?
    A patch of skin supplied by one spinal nerve segment.
  24. PNS: Cranial Nerves I-IV
    • •I Olfactory nerve: special sensory for smell
    • •II Optic nerve: special sensory for vision
    • •III Oculomotor nerve: motor fibers to most eye muscles(2 exceptions) rasies the eye lid
    • •IV Trochlear nerve: motor fiber to the superior oblique eye muscle
  25. PNS: Cranial Nerves V-VIII
    • •V Trigeminal nerve: all 3 divisions are sensory for the face; the 3rd division also has motor fibers to the muscles for chewing
    • •VI Abducens nerve: motor fibers to lateral rectuseye muscles
    • •VII Facial nerve: Special sensory for taste; motor fibers to the face; visceral motor fibres to glands of face except for parotidgland
    • •VIII Vestibulocochlear nerve: sensory for balance and hearing
  26. PNS: Cranial Nerves IX-XII
    • •IX Glossopharyngeal nerve: sensory for taste; motor fibers to the one muscle of the pharynx; visceral motor fibres to parotid gland
    • •X Vagus nerves: Visceral sensory and motor fibers for pharynx, larynx, and viscera
    • •XI Accessory nerve: motor fibers totrapezius and sternocleidomastoidmuscles
    • •XII Hypoglossal nerve: motor fibers to tongue
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