1. The Nervous System: Spinal Cord and Spinal Nerves

2. Introduction –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. Gross Anatomy of the Spinal Cord

4. Coverings of the Spinal Cord –3 layers called meninges –Dura mater  Outer layer  Dense irregular connective tissue –Arachnoid  Middle layer  Encloses cerebrospinal fluid –Pia mater  Adheres tightly to the surface of the spinal cord

5. Meninges of the Spinal Cord

6. Sectional Anatomy of the Spinal Cord –Inner part consists of gray matter –Outer part consists of white matter

7. Sectional Anatomy of the Spinal Cord

8. Example of Ascending Nerve Tracts

9. Spinal Nerves – Connect to the spinal cord via roots –The roots unite into the spinal nerve  Dorsal root  Ventral root –Spinal nerves exit through holes between the vertebrae –Split into branches  Supply muscles and skin

10. Spinal Nerves

11. Dermatomes

12. Nerve Plexuses –Plexus = “braid” –Nerves supplying the limbs form plexuses when they leave the spinal cord  Cervical –Innervates neck and shoulder  Brachial –Innervates shoulder and arm  Lumbosacral –Innervates abdomen, hip, thigh, leg, genital region –Sciatic nerve

13. Nerve Plexuses

14. Cervical Plexus

15. Brachial Plexus

17. Lumbar Plexus

18. Sacral Plexus

19. Spinal Reflexes –Reflexes are automatic responses to stimuli –Spinal reflexes result from the stimulation of a spinal reflex arc. –Basic elements of a reflex arc  Receptor  Afferent pathway (sensory)  Synapse in spinal cord (integrating center)  Efferent pathway (motor)  Response (effector)

20. A Reflex Arc

21. Stretch Reflex