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neuroscience > Peripheral and Cranial Nerves > Flashcards

Peripheral and Cranial Nerves Flashcards

1
Q

Where is the line of division between the CNS and PNS

A
  • once the nerve exits the vertebrae that is the line of demarcation
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2
Q

How many spinal nerves are there total, what region, and where does the spinal cord end

A
  • total nerves = 31
  • 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccyx
  • Spinal cord ends at L1
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3
Q

Layers of a peripheral nerve

A
  • Peripheral nerve is covered by epineurium contains fascicles which are covered by perineurium
  • Fascicles contain axon bundles which are covered by endoneurium
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4
Q

Describe how nerve tissue allows for body movements

A
  • at rest axons & connective tissue are wrinkled
  • Increase stretch on nerve –> viscoelastic tubes stretch –> axons unfold –> fascicles glide on each other –> entire nerve glides relative to surrounding structures
  • process is reversed during shortening
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5
Q

What does the cervical plexus innervate

A
  • Motor: scalenes, anterior neck muscles, and diaphragm
  • Sensory: skin area from posterior scalp to clavicle
  • provides proprioceptive information from muscles, tendons, and joints it supplies
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6
Q

Clinical correlations of phrenic nerve

A
  • irritation from hiccups
  • referred pain to clavicle area and shoulder
  • paralysis from thoracic surgery, chest tubes, or SCI
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7
Q

Where does the brachial plexus emerge from

A
  • emerges from between anterior & middle scalene
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8
Q

Muscle innervations

A
  • Long Thoracic = serratus anterior, protraction of scapula
  • Dorsal scapular nerve = levator scapaula & rhomboids
  • Suprascapular nerve = supraspinatus & infraspinatus
  • Nerve to subclavius = subclavius
  • Musculocutaneous = all elbow flexors, biceps, brachialis, and brachioradialis
  • Axillary nerve = deltoid and teres minor
  • Median nerve = most of wrist flexors & pronator teres, thenar eminence, and lateral half of interossi
    Thoracodorsal = latissimus
  • Radial nerve = anconeous and triceps
  • Unlar nerve = unlar side wrist flexors, hypo-thenar, and medial half of interossi
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9
Q

Erb’s palsy

A
  • upper roots = C1-C7
  • affects shoulder flexion, extension, & abduction along with elbow flexors and supinator
  • presents with waiters tip position
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10
Q

Klumpke’s paralysis

A
  • lower roots = C8-T1
  • affects distal muscles of the upper extremity/most muscles of the hand
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11
Q

Lumbar plexus

A
  • from anterior rami of L1-L4
  • forms in the psoas major muscle
  • innervates skin and muscles of anterior and medial thigh
  • continuous with sacral plexus
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12
Q

Sacral plexus

A
  • from anterior rami of S1-S4
  • located anterior to piriformis
  • innervates posterior thigh and most of leg/foot
  • Sciatic comes out of the sacral plexus not the lumbar plexus
  • only plexus to contain parasympathetic axons while all others contain sympathetic axons
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13
Q

Diagnosis of peripheral nerve dysfunctions

A
  • Based on modality: motor, sensory, and/or autonomic changes
  • Based on severity of nerve damage: neurapraxia (temporary loss/compression), axonotmesis (injury to nerve/severe compression), or neurotmesis (nerve is cut)
  • Based on underlying disease process: carpal tunnel syndrome, neuropathies, Gullian-Barre syndrome
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14
Q

Cranial nerves

A
  • 12 pairs
  • considered peripheral nerves expect for CN I and CN II
  • myelin formed by Schwann cells expect CN I and CN II by oligos
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15
Q

Mnemonics to remember CNs and modalities of each

A
  • On Occasion Our Trusty Truck Acts Funny, Very Good Vehicle Any How (Olfactory, Optic, Oculomotor, Trochlear, Trigeminal, Abducens, Facial, Vestibulocochlear, Glossopharyngeal, Vagus, Spinal Accessory, Hypoglossal
  • Some Say Marry Money But My Brother Says Big Brains Matter More
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16
Q

Four functions of cranial nerves

A
  • Motor (somatic efferent): muscles of face, eyes, tongue, and 2 neck muscles
  • Somatosensory (somatic afferent): information from skin & muscles of face and TMJ
  • Special sensory (afferent): olfactory, visual, auditory, vestibular, and gustatory
  • Autonomic (visceral): regulation of pupil, lens curvature, HR, BP, breathing, and digestion (3, 7, 9, 10 CNs)
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17
Q

What CNs can be viewed from an inferior view of the brain

A
  • all CN brainstem connections are visible from the inferior view except CN 4
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18
Q

CN I Olfactory nerve

A
  • info from nasal chemoreceptors –> olfactory bulb –> olfactory tract –> olfactory cortex
  • only sensory nerve to reach cortex without first synapsing in thalamus
  • cells are replaced every 30-90 days and replacement declines with age
  • Amygdala = emotions, Hypothalamus = hunger, Parahippocampal Gyrus = memory
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19
Q

Visual fields and pathways

A
  • info from right visual field activates left half of retina
  • axons from temporal half of retina project ipsilateral LGB and axons from nasal half cross midline
20
Q

Visual field cuts due to lesions at various locations

A
  • Cut close to eye = one eye blindness on ipsilateral side
  • Cut at optic chasm = tunnel vision/bitemporal hemianopia
  • Cut before optic chasm = homonymous hemianopia/left or right sided blindness
  • Cut way before optic chasm = superior/inferior quandrantanopia
21
Q

Pupillary light reflex

A
  • shinning bright light causes constriction of pupil
  • parasympathetic control of iris sphincter muscle
22
Q

Pupillary reflex test

A
  • can detect problems with CN II and/or CN III
  • can also detect relative afferent problems in pupillary pathway (RAPD) using swinging flashlight test
  • Direct response is present and consensual response is absent = Oculomotor damage
  • Direct absent and consensual present = Optic damage
23
Q

Accommodation reflex (near triad)

A
  • to move from viewing a far object to a near object
  • pupils constrict - sphincter pupillae
  • lens gets more convex - ciliary muscle contract
  • eyes converge (adduct) - medial rectus
24
Q

Eyes muscles and CN innervations

A
  • CN III: Superior rectus, Inferior rectus, Medial rectus, Inferior oblique (up and in), Levator palpabrae superioris (lifting upper eye lid), and controls pupil/lens
  • CN IV: superior oblique (down and adducted/towards nose)
  • CN VI: Lateral rectus
  • LR6SO4
25
Q

Conjugate eye movements

A
  • coordination of eye movements via medial longitudinal fasciculus
  • MLF connects the nuclei of the different CNs involved with eye movements (CN III, IV, VI, VIII, XI)/3, 4, 6, 8, 11
26
Q

Tropia

A
  • deviation of one eye from forward gaze when both eyes are open
  • deviation always present
  • large deviations detected with H-test
  • small deviations detected with cover-uncover test
  • Eso = medially deviated, Exo = laterally deviated, Hyper = goes down from up level, Hypo = goes up from down level
27
Q

Phoria

A
  • more subtle deviation
  • not always present
  • double vision when fatigued and when binocular vision is broken
  • can be tested with cross-cover test
28
Q

Directing gaze to visual targets

A
  • Saccades = looking left to right
  • Smooth pursuit = following an object
  • Vergence = focusing on something that is far coming closer
29
Q

Vestibulo-ocular reflex (VOR)

A
  • stabilize the visual world & prevents it from appearing to bounce/jump during head movements
  • initiated by vestibular receptors in the 3 fluid filled semicircular canals in inner ears
30
Q

Optokinetic nystagmus

A
  • normal
  • Optokinetic = initiated by moving visual stimuli
  • Nystagmus = involuntary oscillating movements of the eyes
  • purpose is to adjust eye position to keep image stable on retina during slow sustained head movements
31
Q

Saccades

A
  • fast eye movements to switch gaze from one object to another
  • Structures involved in reflexive saccades: superior colliculus and cranial nerve nuclei
  • Structures involved in voluntary saccades: visual cortex, perception/action streams, frontal eye fields, basal ganglia ocular loop pathways, superior colliculus, reticular formation, and cranial nerve nuclei
32
Q

Smooth pursuit

A
  • purpose is to follow a moving object
  • Structures involved: eye fields, cerebellum, vestibular nuclei, reticular formation
33
Q

Nystagmus

A
  • can be caused by damage to the vestibular system, cerebellum, or could be physiologic
  • abnormal oscillating movements of the eyes
34
Q

Deficient VOR

A
  • tested by head impulse test
  • due to weak vestibular system or changes in VOR gain by cerebellar lesion
35
Q

Deficient smooth pursuit

A
  • compensatory saccades and cogwheeling
36
Q

CN V Trigeminal nerve

A
  • 3 branches: ophthalmic, maxillary, mandibular
  • Biggest CN
  • light touch from all branches, proprioceptive information from TMJ, and nociceptive/temperature information
  • touch, nociceptive, pressure info from anterior 2/3 of tongue
  • mandibular branch is motor for muscles of mastication
  • afferent limb of corneal blink reflex
37
Q

CN VII Facial nerve

A
  • motor for facial expression
  • taste from anterior 2/3 of tongue
  • parasympathetic for lacrimal, nasal, and salivary glands
  • efferent arm of corneal blink reflex
38
Q

Differential diagnosis between stroke & facial/Bell’s palsy

A
  • Facial/Bell’s palsy will impair one whole half of the face
  • Stroke will typically only impair the lower half of one side of the face
39
Q

CN VIII Vestibulocochlear nerve

A
  • 2 branches: vestibular = info about head position/movement with respect to gravity and cochlear = hearing
  • receptors for both functions in labyrinth
  • sensory organs for vestibular: crista ampullaris in semicircular canals and otolithic organs in utricle & saccule
  • sensory organ for hearing: organ of Corti in middle compartment of fluid filled tube containing basilar membrane
40
Q

Conversation of sound waves to neural signals

A
  • sound waves hit eardrum
  • ossicles move causing vibration of membrane at opening of upper chamber
  • movement of fluid in upper chamber
  • vibration of basilar membrane & attached hair cells
  • hairs bend and hair cells depolarize
  • cochlear nerve endings activated
41
Q

CN IX Glossopharyngeal nerve

A
  • touch from soft palate and pharynx
  • taste from posterior 1/3 of tongue
  • stylopharyngess muscle to help with swallowing
  • afferent arm for gag reflex and swallowing reflex (efferent arm by vagus)
42
Q

CN X Vagus nerve

A
  • touch and motor from pharynx and larynx
  • taste from epiglottis/root of tongue
  • efferent arm for gag reflex and swallowing reflex
43
Q

Process of swallowing

A
  • Oral phase: larynx closes and food moves to pharynx
  • Pharyngeal/Laryngeal phase: soft palate & epiglottis stops food from moving to nasal cavity/lungs
  • Esophageal phase: peristalsis
44
Q

CN XI Spinal Accessory nerve

A
  • innervates SCM and trapezius
  • cranial component innervates soft palate, larynx, & pharynx muscles
45
Q

CN XII Hypoglossal nerve

A
  • innervates intrinsic and extrinsic ipsilateral tongue muscles
  • if damaged we will see a “lick your lesion” (tongue deviates toward side of lesion)

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