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U3 - Nerves
| Question | Answer |
|---|---|
| Nerves | cable-like organ of PNS; consists of a bundle of many nerve fibers/axons |
| Endoneurium | wrapping of connective tissue surrounding each axon/nerve fiber |
| Fascicles | groups of axons bound in small bundles, each wrapped in perineurium |
| Perineurium | connective tissue wrapping each fascicle |
| Epineurium | connective tissue sheath surrounding entire nerve |
| Cranial Nerves | 12 pairs; mainly supply head & neck; 1 pair extends to thoracic/abdominal cavities (vagus); most mixed; 3 pairs sensory (olfactory, optic, vestibulocochlear); 10/12 attached to brain stem; exit via various foramina; has verbal name and Roman numeral name |
| Names of Cranial Nerves | On Old Olympus Towering Tops A Flowering Vine Grew Vast And High/Olfactory Optic Oculomotor Trochlear Trigeminal Abducens Facial Vestibulocochlear Glossopharyngeal Vagus Accessory Hypoglossal |
| I. Olfactory Nerve | fibers arise from olfactory receptor cells in olfactory epithelium in nasal cavity; pass thru foramina in cribriform plate of ethmoid bone to synapse w/ neurons in olfactory bulb; signals only assoctd w/ smell |
| II. Optic nerve | vision; fibers run from retina; 2 nerves converge to form optic chiasma; partial crossover of visual fibers occurs; then to synapse with neurons in thalamus to primary visual cortex of occipital lobe for visual interpretation. Entirely sensory |
| III. Oculomotor nerve | “eye mover,” innervate four of six extrinsic eye muscles-superior, medial, inferior rectus and inferior oblique. Autonomic fibers innervate iris for constriction and ciliary muscle for lens altering for focus on nearby objects |
| IV. Trochlear nerve | innervates one of six extrinsic eye muscles, superior oblique |
| V. Trigeminal nerve | 3 divisions-opthalmic, maxillary, mandibular; all carry sensory impulses from skin of face |
| VI. Abducens nerve | somatic motor fibers supply one extrinsic eye muscle—lateral rectus—which abducts eye |
| VII. Facial nerve | somatic motor fibers supply muscles of facial expression; inflammation of nerve or damage can cause Bell’s palsy |
| VIII. Vestibulocochlear Nerve | purely sensory; vestibular division carries impuleses assoctd w/ equilibrium; arises from receptors in vestibule and semicircular canals of inner ear; cochlear division sends impuleses assoctd w/ hearing from cochlea of inner ear. |
| IX. Glossopharyngeal nerve | some fibers supply part of the tongue, some innervate swallowing muscles of pharynx/throat |
| X. Vagus nerve | autonomic/visceral motor fibers extend to organs in thoracic & abdominal cavities; important part of parasympathetic nervous system, so fibers promote digestive activity, yet slow heart rate |
| XI. Accessory nerve | innervates sternocleidomastoid and trapezius muscles |
| XII. Hypoglossal nerve | somatic motor fibers supply skeletal muscle of tongue (bottom) |
| Spinal nerves | 31 pairs; named for region of spinal cord from which they arise, connected w/ dorsal and ventral root; mixed nerve; branches into dorsal and ventral ramus |
| Rami (plural Ramus) | spinal nerve branches; contain both sensory and motor fibers |
| Dorsal rami of spinal nerves | innervate posterior trunk and neck |
| Ventral rami of spinal nerves | larger; contain more fibers needed for innervation of lateral and anterior trunk and upper and lower limbs |
| Breakdown of spinal nerves | all in pairs – 8 cervical, 12 thoracic, 5 lumbar, 5 sacral spine, 1 coccygeal |
| Nerve plexuses | ventral rami of cervical, lumbar, and sacral spinal nerves are arranged in complex networks; four kinds—cervical, brachial, lumbar, sacral |
| Cervical plexus | deep in neck; rise to phrenic nerve (diaphragm) |
| Brachial plexus | most important aspects are in axilla (armpit); serves sensory & motor needs of upper limb by giving rise to musculocutaneous, radial, medial, ulnar nerves |
| Median nerve | innervates most of anterior forearm; supplied musculature that’s responsible for movement of thumb; often severed in wrist-slashing; carpal tunnel syndrome |
| Ulnar nerve | funny bone sensation |
| Radial nerve | posterior forearm innervation; wristdrop injuries |
| Lumbar plexus | gives rise to femoral nerve (quadriceps femoris group) |
| Sacral plexus | serves sensory and motor needs of posterior aspect of lower limb; sciatic nerve which splits near popliteal region into tibial and common peroneal/fibular nerve. |
| Dermatomes | patch of skin innervated by cutaneous sensory fibers of a single spinal nerve; clinical significance relative to pinpointing level of spinal cord injuries and examining shingle flareups |
| Shingles | herpes zoster; viral infection of sensory neurons serving skin; rash of scaly, painful blisters usually confined to narrow strip of skin on 1 side of trunk corresponding to part. Dermatome; stems from chickenpox. |
| Migraine headaches | relate to sensory innervation of brains arteries by trigeminal nerve; associated w/ dilation of cerebral arteries and subsequent compression and irritation of sensory nerve endings of trigeminal nerve, thus causing pain |
Created by:
mbtrimm
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