Spinal Cord Organization

1. Spinal Cord Organization January 9, 2008

2. Spinal Cord 31 segments terminates at L1-L2 special components - conus medularis - cauda equina no input from the face

3. Spinal Cord, Roots & Nerves Dorsal root Ventral root Spinal nerve

4. Dorsal Root Ganglion Cell bodies of 1st order sensory neurons Afferent

5. Spinal Cord Cross Section Dorsal root sensory afferent motor efferent Ventral root

6. Cross Section of Spinal Cord White matter peripheral Gray matter central Central canal

7. Volume of Gray & White Matter Gray matter enlarges at cervical and lumbar regions. White matter increases at higher levels of the cord.

8. Central Gray Matter Motor neurons 2nd order sensory neurons Interneurons Glial cells Motor neuron = lower motor neuron = anterior horn cell = second order motor neuron

9. Organization of Gray Matter Pain Temperature

10. Organization of Gray Matter Position sense Vibration Pressure Touch

11. Organization of Gray Matter Position sense from legs Between T1 and L2 enlarged Dorsal nucleus of Clarke 2nd order sensory neuron going to cerebellum Neck & base of Posterior Horn

12. Organization of Gray Matter Interomedio-lateral horn Between T1 and L2 enlarged Sympathetic neurons (preganglionic) Intermediolateral Horn

13. Sympathetic Innervation

14. Organization of Gray Matter . At S2, S3, and S4 Parasympathetic neurons (preganglionic) Intermediolateral Horn

15. Parasympathetic Innervation

16. Organization of Gray Matter Modulates motor activity via gamma motor neurons Adjusts briskness of deep tendon reflexes

17. Organization of Gray Matter Nuclei of alpha and gamma motor neurons Innervates muscle spindles and muscles

18. Lower Motor Neurons Alpha motor neurons originate from Rexed lamina IX ventral – dorsal organization ventral  extensor muscles dorsal  flexor muscles medial – lateral organization medial  proximal muscles lateral  distal muscles

19. Somatotopic Organization

20. Coordinating Role of Interneurons

21. Breathing Nuclei of alpha and gamma motor neurons LMNs from spinal levels C3, C4 & C5 innervate the phrenic nerve Controls diaphragm

22. Control Functions Nuclei of alpha and gamma motor neurons At levels S1 - S4 LMNs form Onuf’s nucleus Innervates anal and urethral spincters; needed for sexual function

23. Sacral cord

24. Configuration of Gray Matter Abundant white matter high in the spinal cord Enlargement of gray matter at the cervical level Innervates arm muscles

25. Configuration of Gray Matter Enlargement in thoracic region for sympathetic neurons Enlargement in lumbar region for motor neurons to the legs Minimal white matter at the lower cord

26. Descending Motor Pathway Upper motor neuron 1st order neuron synapses on LMN Crossed pathway Lateral corticospinal Uncrossed pathway Anterior corticospinal

27. Somatotopic Organization

28. Spinal Cord Tracts Unconscious position sense movement feedback

29. ↑ Sensory Gracile tract Leg position & vibration Cuneate tract Arm position & vibration Dorsal spinocerebellar tract Strength & muscle speed Ventral spinocerebellar tract Modulation; interneurons Lateral spinothalamic tract Pain & temperature Anterior spinothalamic tract Light touch Spinocervical thalamic tract Kinesthetic movement & discriminative touch ↓Motor Corticospinal tract Speed & agility Reticulospinal tract Differential facilitation of motor neurons Rubrospinal tract Fix movement errors Lateral vestibulospinal tract Extensor & posture Medial vestibulospinal tract Flexor & head position Tectospinal tract Head turning Ascending & Descending Tracts

30. Ascending Tracts Sensory Position Vibration Sensory Pain Temperature

31. Spinal Cord Injury Position Pain Brown – Sequard Syndrome

32. Transverse vs Hemi Cord Syndrome

33. Anterior vs Posterior Cord Syndromes

34. Blood Supply to Spinal Cord

35. Traumatic Spinal Cord Injury DUI: $100 addt’l fine South Carolina Spinal Cord Injury Research Board

36. Monday Brainstem