PNS Terminology Ganglia neuron cell bodies dendrites Nerves

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

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”

Optic Chiasma I II V VI VII IX VIII X XI

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

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

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

• 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 Motor Cranial Nerves • The abducens nerve (VI) –Innervates lateral rectus muscle of eye

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

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

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

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

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

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

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

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

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

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

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

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

Nerve Plexuses • Four major plexuses – Cervical plexus – Brachial plexus – Lumbar plexus – Sacral plexus • 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

External Anatomy of Spinal Cord

Cervical Plexus • C 1 -C 4 ventral rami • Some fibers from C 5 • Innervates muscles of the neck and diaphragm – major nerve from plexus = Phrenic nerve Diaphragm

Brachial Plexus • Ventral rami of C 5 -T 1 • Innervates pectoral girdle and upper limbs

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

Lumbar Plexus • • ventral rami of T 12–L 4 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

Sacral Plexus • ventral rami of L 4–S 4 • innervates pelvic girdle and lower limbs • sciatic nerve becomes the tibial nerve, sural nerves & common fibular nerve in the leg