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
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
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
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
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
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
7
Q
Where does the brachial plexus emerge from
A
- emerges from between anterior & middle scalene
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
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
10
Q
Klumpke’s paralysis
A
- lower roots = C8-T1
- affects distal muscles of the upper extremity/most muscles of the hand
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
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
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
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
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
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)
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
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
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
Conjugate eye movements
- 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
Tropia
- 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
Phoria
- more subtle deviation
- not always present
- double vision when fatigued and when binocular vision is broken
- can be tested with cross-cover test
28
Directing gaze to visual targets
- Saccades = looking left to right
- Smooth pursuit = following an object
- Vergence = focusing on something that is far coming closer
29
Vestibulo-ocular reflex (VOR)
- 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
Optokinetic nystagmus
- 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
Saccades
- 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
Smooth pursuit
- purpose is to follow a moving object
- Structures involved: eye fields, cerebellum, vestibular nuclei, reticular formation
33
Nystagmus
- can be caused by damage to the vestibular system, cerebellum, or could be physiologic
- abnormal oscillating movements of the eyes
34
Deficient VOR
- tested by head impulse test
- due to weak vestibular system or changes in VOR gain by cerebellar lesion
35
Deficient smooth pursuit
- compensatory saccades and cogwheeling
36
CN V Trigeminal nerve
- 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
CN VII Facial nerve
- 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
Differential diagnosis between stroke & facial/Bell's palsy
- 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
CN VIII Vestibulocochlear nerve
- 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
Conversation of sound waves to neural signals
- 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
CN IX Glossopharyngeal nerve
- 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
CN X Vagus nerve
- touch and motor from pharynx and larynx
- taste from epiglottis/root of tongue
- efferent arm for gag reflex and swallowing reflex
43
Process of swallowing
- 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
CN XI Spinal Accessory nerve
- innervates SCM and trapezius
- cranial component innervates soft palate, larynx, & pharynx muscles
45
CN XII Hypoglossal nerve
- innervates intrinsic and extrinsic ipsilateral tongue muscles
- if damaged we will see a "lick your lesion" (tongue deviates toward side of lesion)
