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Peripheral Nervous System Structures Purpose: To identify cranial nerves and their targets To identify selected nerves of the cervical, brachial, lumbar, and sacral plexus. To identify the target muscles (or other organs) of the selected nerves To identify selected autonomic nerves and ganglia. Each student will locate the following nerves and ganglia of the peripheral nervous system (PNS). Nerves are bundles of many axons supported by several layers of connective tissue (analogous to the arrangement of muscle fascicles in muscles) and will appear as long tough fibrous strands. Each axon in a nerve may be either sensory, carrying information to the CNS (brain and spinal cord), or motor, carrying commands from the CNS to a target organ (muscle or a gland). Follow each nerve as much as possible from the trunk to its peripheral attachment. The central nervous system (CNS) attachment of each nerve will probably not be visible, but the student can find the information about the attachment of the nerves to the CNS (brain and spinal cord) in the available dissector and anatomy atlas. Ganglia are groups of many neuron cell bodies protected in a tough connective tissue pouch located in the PNS. The major locations for ganglia are: the posterior (sensory) root near the spinal cord where the cell bodies of sensory neurons are located, a paravertebral chain of ganglia of the sympathetic (fight or flight) branch of the autonomic nervous system, collateral ganglion, as part of complex plexuses of nerves in the trunk (also sympathetic), terminal ganglia of the parasympathetic (rest and digest) system. If these are visible they will be seen as part of an internal organ. 38 Cranial Nerve Cranial Nerves Origin or Peripheral Insertion attachment (attachment site in brain) Visible Location Olfactory (I) Optic (II) Oculomotor (III) Trochlear (IV) Trigeminal (V) (ophthalmic branch) Trigeminal (maxillary branch) Trigeminal (mandibular branch) Abducens (VI) Facial (VII) Vestibulocochlear (VIII) Glossopharyngeal (IX) Vagus (X) Accessory (XI) Hypoglossal (XII) Selected Nerves of the Cervical Plexus Cervical Nerve Rami Ansa cervicalis Target Phrenic 39 Selected Nerves of the Brachial Plexus Brachial Nerve Rami Musculocutaneous Target Axillary Radial Median Ulnar Long Thoracic Selected Nerves of the Lumbar Plexus Lumbar Nerve Rami Iliohypgastric Target Ilioinguinal Lateral femoral cutaneous Genitofemoral Obturator Femoral 40 Sacral Plexus Rami Target Autonomic Ganglia Specific Location Incoming Nerve Sacral Nerve Superior gluteal Inferior gluteal Sciatic *Tibial *Fibular Posterior femoral cutaneous Pudendal *branches of the sciatic nerve. Ganglion Celiac Superior mesenteric Inferior mesenteric NOTES: 1. Describe the pathway of the sympathetic trunk: 2. Describe the greater and lesser splanchnic nerves: 3. Describe the branches of the vagus nerve: 41