1. Pages 255-264

2.  A PNS nerve is a bundle of neuron fibers ◦ each bundle has connective tissue coverings:  Nerve connective tissue layers (from deep to superficial) ◦ Endoneurium: wraps each nerve fiber ◦ Perineurium: wraps groups of fibers  These bundles of fibers are called fascicles ◦ Epineurium: wraps groups of fascicles to form the larger nerve

3. Endoneurium Perineurium Epineurium Axon Myelin sheath Fascicle Blood vessels

4.  Spinal nerves exit at each vertebral level ◦ Dorsal and ventral roots fuse to form spinal nerves  Specific nerves coincide with specific sections of the vertebral column ◦ Cervical = C1-C8 ◦ Thoracic = T1-T12 ◦ Lumbar = L1-L5 ◦ Sacral = S1-S4

5. C1C1 T1T1 L1L1 S1S1 2 3 4 5 6 7 8 2 3 4 5 6 7 8 2 3 4 5 2 3 4 9 10 11 12 Cervical nerves Thoracic nerves Lumbar nerves Sacral nerves Ventral rami form cervical plexus (C 1 – C 5 ) Ventral rami form brachial plexus (C 5 – C 8 ; T 1 ) No plexus formed (intercostal nerves) (T 1 – T 12 ) Ventral rami form lumbar plexus (L 1 – L 4 ) Ventral rami form sacral plexus (L 4 – L 5 ; S 1 – S 4 ) (a)

6.  12 pairs of nerves serve the head and neck ◦ One exception: the vagus nerves innervate the thoracic and abdominal cavities ◦ All but three are sensory and motor pathways;  the three exceptions (which are purely sensory) are: 1.Optic 2.Olfactory 3.Vestibulocochlear © 2015 Pearson Education, Inc.

7. I Olfactory II Optic III Oculomotor IV Trochlear VI Abducens V Trigeminal VII Facial Vestibular branch Cochlear branch VIII Vestibulocochlear IX Glossopharyngeal X Vagus XI Accessory XII Hypoglossal

8.  Plexus–networks of nerves serving motor and sensory needs of the limbs  Form from ventral rami (branches)of spinal nerves  Four plexuses: 1.Cervical 2.Brachial 3.Lumbar 4.Sacral © 2015 Pearson Education, Inc.