PNS Terminology

1. PNS Terminology • Ganglia – neuron cell bodies & dendrites • Nerves – bundles of myelinated axons • PNS neuroglia • Satellite cells • Enclose neuron cell bodies in ganglia • Schwann cells • Cover peripheral axons

2. I - Olfactory II - Optic III - Oculomotor IV-Trochlear V - Trigeminal VI - Abducens VII - Facial VIII – Acoustic/Vestibulocochlear IX - Glossopharyngeal X - Vagus XI – Accessory/Spinal Accessory XII - Hypoglossal -cranial nerves – 12 pairs -olfactory, optic & acoustic contain only sensory axons = sensory nerves - oculomotor, trochlear, abducens, accessory & hypoglossal carry only motor information = motor nerves -remaining are mixed nerves – both motor and sensory axons “some say my mother bought my brother some bitter beer – my, my”

3. Optic Chiasma I III II V VI VII IX VIII X XI

4. The Olfactory Nerve (I) • Sensory Nerve • Carries sensory information • Sense of smell • Synapse within olfactory bulbs

5. Sensory Nerve • The optic nerve (II) • carries visual information to occipital lobe

6. The Vestibulocochlear Nerve (VIII) • Sensory Nerve • also called the Acoustic nerve • Vestibular nerve • Monitors sense of balance, position and movement • Cochlear nerve • Monitors hearing

7. Motor Cranial Nerves • The oculomotor nerve (III) • Primary source of innervation for extra-ocular muscles • Move the eyeball • The trochlear nerve (IV) • Smallest cranial nerve • Innervates superior oblique eye muscle • The abducens nerve (VI) • Innervates lateral rectus muscle of eye

8. Motor Cranial Nerves • The accessory nerve (XI) – Motor nerve • innervates swallowing muscles & controls sternocleidomastoid and trapezius muscles and other muscles of pectoral girdle • two branches: cranial part (internal branch) & spinal part (external branch) • The hypoglossal nerve (XII) – motor nerve • voluntary motor control over tongue movements

9. The Trigeminal Nerve (V) • Largest cranial nerve • Mixed nerve • Ophthalmic branch • sensory – upper eyelid, eyeball lacrimal glands, side of nose, forehead and scalp • Maxillary branch • sensory – nose, palate, part of pharynx, upper teeth, upper lip and lower eyelid • Mandibular branch • sensory – tongue, cheek, lower teeth, skin over mandible and side of head anterior to ear -motor – muscles of chewing

10. The Facial Nerve (VII) • Mixed nerve • controls muscles of scalp and facial expression • transmits pressure sensations from face & taste sensations from tongue • major branches: • Temporal • Zygomatic • Buccal • Mandibular • Cervical

11. The Glossopharyngeal Nerve (IX) • Mixed nerve • Innervates the tongue & controls swallowing

12. The Vagus Nerve (NX) • Mixed nerve • vital to autonomic control of visceral function • major nerve of the ANS/parasympathetic system

13. 31 Pairs of Spinal Nerves • Ensheathed by three connective tissue layers • Outermost epineurium • dense network of collagen fibers around the peripheral nerve • Middle perineurium • partitions nerve into fascicles • Inner endoneurium • delicate connective tissue fibers surrounding each axon Neurilemma Schwann cell

14. 31 Pairs of Spinal Nerves • under the endoneurium is the myelin sheath • outer layer of the myelin sheath is called the neurilemma • neurilemma covers the myelin sheath and Schwann cells • myelin sheath covers the axon

15. Spinal Nerves • connected to the spinal cord via roots (bundles of axons) • Posterior root= sensory axons into the posterior gray horn • Anterior root= motor axons from the anterior gray horn

16. Spinal Nerves • before the posterior root is the dorsal root ganglion= cell bodies of incoming sensory neurons (axons continue on to form the root)

17. Spinal Nerve • spinal nerves emerge from intervertebral foramina as mixed nerves • after passing through intervertebral foramina the spinal nerve branches into three rami • Dorsal ramus • Ventral ramus • Rami communicantes

18. Dorsal ramus -sensory/motor innervation to and from skin and muscles of back Spinal Nerve Epidural space Dura and Arachnoid maters • Ventral ramus - sensory/motor innervation to and from skin and structures of ventral and lateral body wall, muscles of the upper and lower limbs Dorsal Ramus Dorsal Root Ventral Ramus Dorsal Root Ganglion • rami communicantes -carries axons of the sympathetic ANS Ventral Root Rami Communicantes

19. Dorsal Root of SN Ventral Root of SN SPINAL NERVE Dorsal Ramus Ventral Ramus Rami Communicantes Sensory – IN Motor – OUT SKIN BACK MUSCLES Sensory – IN Motor – OUT TRUNK LIMBS Signals to and from the ANS VISCERA – cardiac and Smooth muscle

20. Nerve Plexuses • nerve networks formed by the ventral rami of spinal nerves • found in neck, arm, low back & sacral regions • no plexus in thoracic region • intercostal nerves this region • Four major plexuses • Cervical plexus • Brachial plexus • Lumbar plexus • Sacral plexus

21. External Anatomy of Spinal Cord

22. Cervical Plexus • C1-C4 ventral rami • Some fibers from C5 • Innervates muscles of the neck and diaphragm • major nerve from plexus = Phrenic nerve  Diaphragm

23. Brachial Plexus • Ventral rami of C5-T1 • Innervates pectoral girdle and upper limbs

24. Brachial Plexus • nerves arise from cords & trunks • Superior, middle and inferior trunks • Lateral, medial and posterior cords • musculocutaneous, radial, median and ulnar nerves arise from these cords • Lateral cord: musculocutaneous, median nerves • Medial cord: ulnar, median nerves • Posterior cord: radial, axillary nerves

25. Lumbar Plexus • ventral rami of T12–L4 • Innervate pelvic girdle and lower limbs • femoral nerve gives off many muscular branches • posterior segment gives off branches to the quads and branches to the knee + large saphenous nerve

26. Sacral Plexus • ventral rami of L4–S4 • innervates pelvic girdle and lower limbs • sciatic nerve becomes the tibial nerve, sural nerves & common fibular nerve in the leg