The Peripheral Nervous System Pages 255 264 Peripheral

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The Peripheral Nervous System Pages 255 -264

The Peripheral Nervous System Pages 255 -264

Peripheral Nervous System �A PNS nerve is a bundle of neuron fibers ◦ each

Peripheral Nervous System �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

Figure 7. 23 Structure of a nerve. Axon Myelin sheath Endoneurium Perineurium Epineurium Fascicle

Figure 7. 23 Structure of a nerve. Axon Myelin sheath Endoneurium Perineurium Epineurium Fascicle Blood vessels

PNS: Spinal Nerves � Spinal nerves exit at each vertebral level ◦ Dorsal and

PNS: Spinal Nerves � 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 = C 1 -C 8 Thoracic = T 1 -T 12 Lumbar = L 1 -L 5 Sacral = S 1 -S 4

Figure 7. 25 a Spinal nerves. Cervical nerves C 1 2 3 4 5

Figure 7. 25 a Spinal nerves. Cervical nerves C 1 2 3 4 5 6 7 8 T 1 2 3 Ventral rami form cervical plexus (C 1 – C 5) Ventral rami form brachial plexus (C 5 – C 8; T 1) 4 Thoracic nerves 5 6 7 8 9 10 Lumbar nerves Sacral nerves 11 12 L 1 2 3 4 5 S 1 2 (a) No plexus formed (intercostal nerves) (T 1 – T 12) 3 4 Ventral rami form lumbar plexus (L 1 – L 4) Ventral rami form sacral plexus (L 4 – L 5; S 1 – S 4)

PNS: Cranial Nerves � 12 pairs of nerves serve the head and neck ◦

PNS: Cranial Nerves � 12 pairs of nerves serve the head and neck ◦ One exception: the vagus nerves innervate 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.

Figure 7. 24 Distribution of cranial nerves. III Oculomotor IV Trochlear VI Abducens I

Figure 7. 24 Distribution of cranial nerves. III Oculomotor IV Trochlear VI Abducens I Olfactory V Trigeminal II Optic VII Facial Vestibular branch Cochlear branch VIII Vestibulocochlear X Vagus XII Hypoglossal XI Accessory IX Glossopharyngeal

PNS: Spinal Nerve Plexuses � Plexus–networks of nerves serving motor and sensory needs of

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