Peripheral Nervous System

1. Peripheral Nervous System Spinal Nerves And Plexuses

2. 2 Components of PNS • 12 pr. of cranial nerves • 31 pr. of spinal nerves • What is a spinal nerve?

3. What is a spinal nerve? • There are 31 pair of spinal nerves. • They enter and leave the spinal cord through the intervertebral foramen.

4. Spinal Nerve

5. What is a spinal nerve? • A spinal nerve has two components: • Sensory fibers (axons) going into the spinal cord • Motor fibers (axons) leaving the spinal cord • These two components split from each other once the spinal nerve is inside the vertebral foramen • Posterior root – sensory axons entering spinal cord • Anterior root – motor axons leaving spinal cord

6. Spinal Nerve

7. Spinal Nerve

8. Spinal Nerve Roots • Posterior root – enters spinal cord with sensory information • Anterior root – leaves spinal cord with motor information

9. Spinal Nerve Reflex • Simple reflex is a 2 neuron circuit

10. Spinal Nerve 3 1 7 2 5 4 6

11. Spinal Nerve • Cell body of sensory neuron • Posterior (sensory) root • Posterior root ganglion • Anterior (motor) root • Cell body of motor neuron • Axon of motor neuron • Spinal nerve

12. Dermatome An area of skin supplied by a single spinal nerve Shingles Inflammation of a dermatome caused by chickenpox virus….rash, blisters and pain…chance of secondary infection by bacteria

13. Nerve Plexuses • A plexus is a network of spinal nerves on both L&R sides of the spinal cord. • A plexus will ultimately produce peripheral or “named” nerves. • There are four plexuses: • Cervical • Brachial • Lumbar • Sacral

14. Study Hint for Plexuses • Table with 5 columns • Plexus name • Spinal nerves in that plexus • Peripheral “named” nerves generated from that plexus • Compartment innervated by each peripheral nerve • Muscle function of each peripheral nerve

15. 1. Cervical Plexus

16. 1. Cervical Plexus • C1 – C4 • Phrenic n. • Innervates the diaphragm • Comprised of contributions from C3, C4 & C5 • Paralysis of diaphragm and death

17. 2. Brachial Plexus

18. 2. Brachial Plexus • C5 – T1 (How many spinal nerves in this plexus?) • This plexus generates peripheral (“named”) nerves that supply sensory and motor innervation to the upper extremities • Five major peripheral nerves are generated from this plexus.

19. 2. Brachial Plexus • Axillary • Radial • Musculocutaneous • Median • Ulnar

20. Axillary n.

21. Radial n.

22. Musculocutaneous n.

23. Median n.

24. Ulnar n.

25. 3. Lumbar Plexus

26. 3. Lumbar Plexus • L1 – L4 • This plexus generates peripheral nerves that provide sensory and motor innervation to portions of the lower extremies • Two major peripheral nerves are generated from this plexus

27. 3. Lumbar Plexus • Femoral • Obturator

28. Femoral n.

29. Obturator n.

30. 4. Sacral Plexus

31. 4. Sacral Plexus • L4 – S4 • This plexus generates peripheral nerves that provide sensory and motor innervation to portions of the lower extremies • Three peripheral nerves are generated from this plexus

32. 4. Sacral Plexus • Sciatic • Tibial • Common fibular

33. Sciatic n. • Composed of tibial and common fibular divisions wrapped in a common sheath

34. Tibial n.

35. Common Fibular n.