The Spinal Cord and Spinal Nerves

  1. What are coverings of the spinal cord?
    –Spinal column


    •Dura mater

    •Arachnid mater

    •Pia mater

    –Blood vessels

    –Denticulate ligaments
  2. Name the differnt types of spaces?
    •Epidural space

    –Contains fat and connective tissue

    •Subdural space

    –Interstitial fluid

    •Subarchanoid space

  3. Anatomically describe the position of the spinal cavity (grooves, bulges etc)
    –Lies within the spinal cavity

    •Extends from the foramen magnum to the lower border of the first lumbar vertebra

    •Two bulges:

    –Cervical region

    –Lumbar region

    •Two deep grooves

    –Anterior median fissure

    –Posterior median sulcus
  4. Function of Spinal Cord
    –Conduction routes to and from the brain

    •Ascending tracts

    –Conduct sensory impulses up the spinal cord to the brain

    •Descending tracts

    –Conduct motor impulses down the spinal cord from the brain

    •Tracts are both structural and functional organization of nerve fibers

    –Reflex centre for spinal reflexes
  5. Spinal Nerves
    •31 pairs of spinal nerves

    •Connect the CNS to sensory receptors, muscles, and glands

    –Cervical (C1-C8)

    –Thoracic (T1-T12)

    –Lumbar (L1-L5)

    –Sacral (S1-S5)

    –One coccygeal nerve pair

    •All spinal nerves are mixed nerves

    –Contain sensory and motor fibers

    •Posterior (dorsal) root

    –Sensory axons

    •Anterior (ventral) root

    –Motor axons
  6. Connective Tissue Covering the Spinal Nerves

    –Outermost layer

    •Around the entire nerve


    –Middle layer

    •Around a bundle of nerves (fascicle)


    –Innermost layer

    •Around each nerve axon
  7. Branches (rami)
    –Posterior (dorsal) ramus

    –Anterior (ventral) ramus

    –Meningeal branch

    •Supplies the vertebrae, vertebral ligaments, blood vessels of the spinal cord and meninges

    –Rami communicantes

  8. Plexuses
    –Network of axons formed by the ventral rami of most spinal nerves (not T2-T12)

    •Cervical plexus

    •Brachial plexus

    •Lumbar plexus

    •Sacral plexus

    •Coccyegal plexus
  9. Intercostal Nerves
    –Thoracic nerves

    –The anterior rami of spinal nerves T2-T12

    –Directly innervate the structures they supply
  10. Cervical Plexus
    •Located deep within the neck

    •Consist of ventral rami C1-C4 and branch of ventral ramus of C5

    •Innervate the muscles and skin of the neck, part of the head, superior portion of the shoulder and chest and diaphragm
  11. Brachial Plexus
    •Located deep in the shoulder

    –Extends inferiorly and laterally on either side of the

    –Consists of ventral rami C5- C8 and T1

    •Innervates the lower part of the shoulder and entire arm

    –Axillary nerve

    –Musculocutaneous nerve

    –Median nerve

    –Radial nerve

    –Ulnar nerve
  12. Lumbar Plexus
    •Located in the lumbar region of the back

    –Adjacent to proximal Psoas muscle attachments

    •Consist of fibers of spinal nerves L1-L4

    •Supplies the anteriolateral abdominal wall, external genitals and part of the lower limbs




    –Lateral cutaneous nerve of the thigh

    –Femoral nerve

    Obturator nerve
  13. Sacral Plexus
    •Located in the pelvic cavity

    –Anterior to the sacrum

    •Consist of fibers from L4-S4

    •Tibial, common peroneal and sciatic nerves exit sacral plexus

    •Supply buttock, perineum and lower limb

    –Sciatic nerve

    –Gluteal nerve

    –Saphenous nerve
  14. Dermatomes
    •Defined as area of the skin supplied by somatic sensory (afferent) fibers of a given spinal nerve
  15. White Matter
    –Surrounds gray matter

    –Consists of large bundles of axons divided into tracts
  16. Gray Matter
    –Extend the length of spinal cord

    –Consists mostly of cell bodies of interneurons and motor neurons

    •Transverse section – H shaped

    •Anterior, posterior and lateral horns of gray matter
  17. Important sensory (ascending) tracts:
    –Lateral spinothalamic tract

    •Pain, coolness, itching, deep pressure, crude touch

    –Posterior column

    •Touch, light pressure, vibration, proprioception

    •Anterior spinothalamic tract

    –Sensory information from thoracic and cervical body areas

    •Fasciculi gracilis and cuneatus

    –Sensory information from sacral and lumbar body areas
  18. Spinocerebellar tracts and Spinotectal tract
    –Spinocerebellar tracts

    –Proprioception (limb and joint position)

    –Spinotectal tract

    –Coordinate head and eye movement in response to visual and auditory stimuli
  19. Important motor (descending) tracts
    –Lateral corticospinal tracts

    •Controls movement of ipsilateral limbs

    –Anterior corticospinal tracts

    –Reticulospinal tracts

    –Tectospinal tracts

    –Vestibulospinal tract
  20. A Reflex
    –Fast, involuntary response to a stimulus

    •Spinal reflex

    •Cranial reflex

    •Somatic reflex

    •Autonomic reflex

    –Integrate in spinal cord and lower brain

    –Coordinate with pacemakers and hormones
  21. Reflex Arc
    –Components of the reflex arc:


    •Sensory receptor

    •Sensory (afferent) neuron

    •Integrating centre (CNS)

    •Motor (efferent) neuron

    •Effector (target tissue)
  22. The Stretch Reflex
    –A muscle contraction in response to stretching of the muscle

    –Involve monosynaptic reflex arc

    –Example: patellar (knee jerk) reflex
  23. The Tendon Reflex
    –A feedback mechanism that controls increasing muscle tension by causing muscle relaxation before tension force becomes so great it may damage the muscle.

    • •Tendon reflex is less sensitive than stretch
    • reflex , but it can override the stretch reflex

    • Example: making you drop a very heavy weight, so
    • the tendons are not torn.
  24. The Flexor and Cross Extensor Reflex
    • –Flexor (withdrawal) reflex- excitation of flexor motor
    • neurons to withdraw from painful or noxious stimulus

    –Cross extensor reflex- maintaining the balance

    •Extensors stimulated

    •Flexors inhibited

    •Polysynaptic arc
Card Set
The Spinal Cord and Spinal Nerves
HUMAN ANantomy and organ system