Week 13 Part A: Cranial Nerves Part B: Spinal Nerves Part C: Physiology Lab: Nerve Conduction Velocity

CN I Olfactory nerve

Sensory for smell; located in nasal cavity; fibers pass through cribriform foramina to olfactory bulb

Filaments of olfactory nerve

Fibers passing from nasal mucosa through cribriform foramina

Cribriform foramina

Tiny holes in ethmoid bone for CN I filaments

Olfactory bulb

Structure in frontal lobe receiving CN I signals

CN II Optic nerve

Sensory for vision; passes through optic canal to optic chiasm

Optic canal

Opening in sphenoid bone for CN II

Optic chiasma/chiasm

Crossing of optic nerves anterior to pituitary gland

CN V Trigeminal nerve

Mixed nerve of the face; emerges from pons

Ophthalmic division (V1)

Sensory; passes through superior orbital fissure

Superior orbital fissure

Opening for CN III, IV, V1, VI

Maxillary division (V2)

Sensory; passes through foramen rotundum

Foramen rotundum

Passageway for CN V2

Mandibular division (V3)

Mixed; passes through foramen ovale

Foramen ovale

Opening for CN V3

CN VIII Vestibulocochlear nerve

Sensory for hearing and balance; enters skull through internal acoustic meatus

Vestibular nerve

Balance branch of CN VIII

Cochlear nerve

Hearing branch of CN VIII

Internal acoustic meatus

Passage for CN VII and VIII

CN X Vagus nerve

Mixed; sensory & motor to viscera; exits skull via jugular foramen

Jugular foramen

Opening for CN IX, X, XI

Sensory and motor for viscera

Function of CN X

CN XI Accessory nerve

Motor to sternocleidomastoid & trapezius; root enters via foramen magnum

Foramen magnum

Entry point for spinal root of CN XI

Sternocleidomastoid

Innervated by CN XI

Trapezius

Innervated by CN XI

Olfactory nerve

I

Optic nerve

II

Trigeminal nerve

V

Ophthalmic division of trigeminal nerve

V1

Maxillary division of trigeminal nerve

V2

Mandibular division of trigeminal nerve

V3

Vestibulocochlear nerve

VIII

Vestibular branch of vestibulocochlear nerve

VIII (Balance)

Cochlear branch of vestibulocochlear nerve

VIII (Auditory)

Vagus nerve

X

Accessory nerve

XI

Epineurium

Outer connective tissue covering of a nerve

Perineurium

Surrounds each fascicle

Fascicle

Bundle of axons within a nerve

Endoneurium

Connective tissue surrounding each axon

Axon

Nerve fiber that carries impulses

Myelin sheath

Fatty insulation increasing conduction speed

Cervical nerves (C1-C8)

First spinal nerve group

Thoracic nerves (T1-T12)

Twelve spinal nerves

Lumbar nerves (L1-L5)

Five spinal nerves

Sacral nerves (S1-S5)

Five spinal nerves

Coccygeal nerve (Co1)

Single nerve

Cervical plexus

Formed by C1-C5

Phrenic nerve

From C3-C5; innervates diaphragm

Brachial plexus

Formed by C5-T1

Musculocutaneous nerve

Flexor muscles of brachium

Median nerve

Flexors of antebrachium; carpal tunnel nerve

Ulnar nerve

Flexors of antebrachium & hand

Radial nerve

Extensors of brachium & antebrachium

Axillary nerve

Deltoid and teres minor

Lumbar plexus

Formed by L1-L4

Femoral nerve

Quadriceps, sartorius, pectineus, iliacus

Obturator nerve

Adductors of thigh, gracilis

Sacral plexus

Formed by L4-S4

Sciatic nerve

Largest nerve: divides into tibial + common fibular

Tibial nerve

Posterior thigh (except short head of biceps femoris), leg, foot muscles

Common fibular nerve

Short head of biceps femoris, tibialis anterior, fibularis group, toe extensors

Power Lab

Device that records nerve activity and EMG signals

Stimulating bar electrode

Delivers electrical stimulus to nerve

2 electrode cables (positive and negative)

Carry electrical signals for recording

Foam electrodes

Stick-on electrodes used to record EMG

Electrode paste

Improves electrical conductivity

Abductor pollicis brevis

Muscle that contracts during the NCV experiment

Nerve conduction velocity (NCV)

Speed of action potential along a nerve

How NCV is calculated

Distance between stimulation points / (latency elbow - latency wrist)

Purpose of NCV

To measure conduction speed of the median nerve

Why elbow latency is longer

Greater distance for impulse to travel from elbow to muscle

Structure stimulated during lab

Axon of somatic motor neuron to abductor pollicis brevis

How a shock triggers an AP

Electrical stimulus depolarizes axon membrane directly

What EMG graph shows (x-axis)

Time in milliseconds

What EMG graph shows (y-axis)

Voltage in millivolts