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CNS – The Spinal Cord, Spinal Nerves & Spinal Reflexes

CNS – The Spinal Cord, Spinal Nerves & Spinal Reflexes. Spinal Cord & Spinal Nerves. Spinal cord Truly the pathway between body and mind Conducts impulses to and from the brain Carries out spinal reflexes Spinal nerves 31 pairs All are mixed nerves. Mixed Nerves?. Dorsal roots

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CNS – The Spinal Cord, Spinal Nerves & Spinal Reflexes

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  1. CNS – The Spinal Cord, Spinal Nerves & Spinal Reflexes

  2. Spinal Cord & Spinal Nerves • Spinal cord • Truly the pathway between body and mind • Conducts impulses to and from the brain • Carries out spinal reflexes • Spinal nerves • 31 pairs • All are mixed nerves

  3. Mixed Nerves? • Dorsal roots • Ganglion containing axons of sensory neurons (afferent) • Ventral roots • All motor fibers (axons) leave the cord by the ventral roots (efferent)

  4. General Organization • Highly organized, very efficient

  5. Spinal Reflexes • Rapid, automatic nerve responses triggered by specific stimuli • Controlled by spinal cord alone; not the brain

  6. Gross Anatomy of the Spinal Cord

  7. The Adult Spinal Cord • About 18 inches (45 cm) long • 1/2 inch (14 mm) wide • Ends between vertebrae L1 and L2

  8. Bilateral Symmetry • Grooves divide the spinal cord into left and right • Posterior median sulcus: • Shallow • Anterior median fissure: • deeper groove on anterior side

  9. Enlargements of the Spinal Cord • Caused by: • amount of gray matter in segment • involvement with sensory and motor nerves of limbs • Cervical enlargement: • nerves of shoulders and upper limbs • Lumbar enlargement: • nerves of pelvis and lower limbs

  10. The Distal End • Conus medullaris: • thin, conical spinal cord below lumbar enlargement • Filum terminale: • thin thread of fibrous tissue at end of conus medullaris • attaches to coccygeal ligament

  11. Meninges of the Spinal Cord

  12. The Meninges • Specialized membranes isolate spinal cord from surroundings • Spinal meninges: • protect spinal cord • carry blood supply • continuous with cranial meninges • Meningitis: • viral or bacterial infection of meninges

  13. The 3 Meningeal Layers • Dura mater: • outer layer of spinal cord • Arachnoid mater: • middle meningeal layer • Pia mater: • inner meningeal layer

  14. Spinal Dura Mater • Are tough and fibrous • Cranially: • fuses with periosteum of occipital bone • is continuous with cranial dura mater • Caudally: • tapers to dense cord of collagen fibers • joins filum terminale in coccygeal ligament

  15. The Epidural Space • Between spinal dura mater and walls of vertebral canal • Contains loose connective and adipose tissue • Anesthetic injection site

  16. Arachnoid Mater • Middle meningeal layer • Arachnoid membrane: • simple squamous epithelia • covers arachnoid mater

  17. Inter-Layer Spaces • filled with cerebrospinal fluid(CSF)

  18. Cerebrospinal Fluid (CSF) • Is found in subarachnoid space • Carries dissolved gases, nutrients, and wastes • Spinal tap: • withdraws CSF

  19. Pia Mater • Is the innermost meningeal layer • Is a mesh of collagen and elastic fibers • Is bound to underlying neural tissue

  20. Spinal Cord Meninges

  21. Sectional Anatomy of the Spinal Cord

  22. Consists of…. • White matter • Gray matter • Gray horns • Posterior gray horns • contain somatic and visceral sensory nuclei • Anterior gray horns • contain somatic motor nuclei • Lateral gray horns • are in thoracic and lumbar segments • contain visceral motor nuclei

  23. Spinal cord is so highly organized: • it is possible to predict results of injuries to specific areas

  24. Spinal Nerves • The roots unite into the spinal nerve • Spinal nervesexit through intervertebral foramen • Splitintobranches, or rami.

  25. Dermatomes Specific bilateral region of the skin surface monitored by a single pair of spinal nerves

  26. Nerve Plexuses • Plexus = “braid” • Nerves supplying the limbs form plexuses when they leave the spinal cord • Cervical plexus • Brachial plexus • Lumbar plexus • Sacral plexus

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