1. The Spinal Cord & Spinal Nerves Together with brain forms the CNS Functions –spinal cord reflexes –integration (summation of inhibitory and excitatory) nerve impulses –highway for upward and downward travel of sensory and motor information

2. Spinal Cord Protection By the vertebral column, meninges, cerebrospinal fluid, and vertebral ligaments.

3. Structures Covering the Spinal Cord Vertebrae Epidural space filled with fat Dura mater –dense irregular CT tube Subdural space filled with interstitial fluid Arachnoid = spider web of collagen fibers Subarachnoid space = CSF Pia mater

4. External Anatomy of Spinal Cord Flattened cylinder 16-18 Inches long & 3/4 inch diameter In adult ends at L2 In newborn ends at L4 Growth of cord stops at age 5 Cervical enlargement –upper limbs Lumbar enlargement –lower limbs

5. Inferior End of Spinal Cord Conus medullaris –cone-shaped end of spinal cord Caudae equinae (horse’s tail) –dorsal & ventral roots of lowest spinal nerves

6. Spinal Cord & Spinal Nerves Spinal nerves begin as roots Dorsal or posterior root is incoming sensory fibers –dorsal root ganglion (swelling) = cell bodies of sensory nerves Ventral or anterior root is outgoing motor fibers

7. Spinal tap or Lumbar Puncture Technique –long needle into subarachnoid space –safe from L3 to L5 Purpose –sampling CSF for diagnosis –injection of antibiotics, anesthetics or chemotherapy –measurement of CSF pressure

8. Gray Matter of the Spinal Cord Gray matter is shaped like the letter H or a butterfly –contains neuron cell bodies, unmyelinated axons & dendrites –paired dorsal and ventral gray horns –gray commissure crosses the midline Central canal continuous with 4th ventricle of brain Note: colors in reverse due to staining of tissue

9. White Matter of the Spinal Cord White matter covers gray matter Contains axons that form ascending & descending tracts

10. Tracts of the Spinal Cord Function of tracts –highway for sensory & motor information –sensory tracts ascend –motor tracts descend Naming of tracts –indicates position & direction of signal –example = anterior spinothalamic tract impulses travel from spinal cord towards brain (thalamus) found in anterior part of spinal cord

11. Spinal Nerves 31 Pairs of spinal nerves Named & numbered by the cord level of their origin –8 pairs of cervical nerves (C1 to C8) –12 pairs of thoracic nerves (T1 to T12) –5 pairs of lumbar nerves (L1 to L5) –5 pairs of sacral nerves (S1 to S5) –1 pair of coccygeal nerves Mixed sensory & motor nerves

12. Connective Tissue Coverings Endoneurium = wrapping of each nerve fibers Perineurium = surrounds group of nerve fibers forming a fascicle Epineurium = covering of entire nerve

13. Endoneurium Perineurium Epineurium

14. Dermatomes & Myotomes Each spinal nerve contains both sensory & motor nerve fibers Dermatome – area of skin supplied by one spinal nerve –overlap prevents loss of sensation if one damaged –sensory anesthesia requires 3 spinal nerves to be blocked Skin on face supplied by Cranial Nerve V

15. Dermatomes Damaged regions of the spinal cord can be distinguished by patterns of numbness over a dermatome region Spinal cord transection –injury that severs the cord loss of sensation & motor control below the injury

16. Disorders Neuritis –inflammation of nerves –caused by injury, vitamin deficiency or poison Shingles –infection of peripheral nerve by chicken pox virus –causes pain, skin discoloration, line of skin blisters Poliomyelitis –viral infection causing motor neuron death and possible death from cardiac failure or respiratory arrest