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Neuro Big Ideas > Week 3 - Neuro Big Ideas > Flashcards

Week 3 - Neuro Big Ideas Flashcards

1
Q

superior rectus

A

moves eye upward, anular ring to superior anterior eye, elevates the eye

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2
Q

lateral rectus

A

moves eye laterally, abducts eye, anular ring to anterior lateral eye

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3
Q

inferior oblique

A

moves eye up and laterally, medial orbit (maxilla) to inferior posterolateral eye, elevates eye, extorts the eye

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4
Q

inferior rectus

A

moves eye downward, anular ring to anterior inferior eye, depresses the eye

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5
Q

medial rectus

A

moves eye medially, adducts eye, anular ring to anterior medial eye

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6
Q

superior oblique

A

moves eye down and laterally, anular ring to medial tendon (trochlea) to superior posterolateral eye, depresses eye, intorts the eye

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7
Q

tendinous ring of Zinn (anular ring)

A

origin of all but one of the extraocular muscles, surrounds optic nerve and attaches to apex of bony orbit

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8
Q

CT of eye orbits

A

medial wall of orbit are parallel to each other, lateral walls of orbits for a 90 degree angel with each other

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9
Q

adduction

A

movement in horizontal plane, movement toward midline

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10
Q

abduction

A

movement in horizontal plane, movement away from midline

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11
Q

elevation

A

movement in vertical plane, movement upward

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12
Q

depression

A

movement in vertical plane, movement downward

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13
Q

conjugate eye movements

A

symmetrical, yoking of muscle pairs by reciprocal excitatory and inhibitory stimulation

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14
Q

yoking of eye muscles

A

in conjugate eye movement, reciprocal excitatory and inhibitory stimulation of eye muscles, ex: right eye adbucts while left eye adducts

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15
Q

intorsion

A

movement of eyes clockwise

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16
Q

extorsion

A

movement of eyes counterclockwise

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17
Q

convergence

A

both corneas adducted toward the midline

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18
Q

divergence

A

eyes return to primary frontal position from convergence

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19
Q

when eye is abducted

A

superior rectus elevates, inferior rectus depresses

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20
Q

when eye is adducted

A

inferior oblique elevates, superior oblique depresses

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21
Q

abducens nerve CN VI

A

supplies lateral rectus that abducts the eye, passes through superior orbital fissure

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22
Q

trochlear nerve CN IV

A

supplies superior oblique that depresses eye laterally, passes through superior orbital fissure, passes superior to tendinous ring

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23
Q

oculomotor nerve CN III

A

supplies superior rectus, medial rectus, inferior rectus, inferior oblique, levator palpebrae superioris, passes through superior orbital fissure, originates from medial to midbrain, runs in lateral wall cavernous sinus

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24
Q

pass superior to common tendinous ring

A

lacrimal nerve, trochlear nerve, frontal nerve

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25
Q

pass through common tendinous ring

A

optic nerve, oculomotor nerve, nasociliary nerve, abducences nerve

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26
Q

levator pelpebrae muscle

A

elevates eyelid involuntaryily, voluntarily, in concert with superior rectus, supplied by generval visceral efferent fibers from CN III and sypmathetic fibers

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27
Q

inferior branch oculomotor nerve

A

goes laterally in the orbit, contains oculomotor motor fibers to inferior rectus, medial rectus, and inferior oblique and parasympathetic fibers to ciliary muscles and pupillae constrictor muscle (via cilliary ganglion and short ciliary nerves)

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28
Q

superior branch oculomotor nerve

A

goes medially in the orbit, contains oculomotor nerve motor fibers to superior rectus and levator palpebrae superior

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29
Q

oculomotor nerve motor nucleus

A

motor nucleus is in the posterior midbrain, superior division to superior rectus and levator palpebrae superioris muscle, part of inferior division to medial rectus, inferior rectus, and inferior oblique

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30
Q

oculomotor nerve parasympathetic preganlionic nucleus

A

Edinger-Westphal nucleus in the midbrain, part of inferior division to ciliary muscles and pupillae constrictor muscles via ciliary ganglion and short ciliary nerves

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31
Q

trochlear nerve motor nucleus

A

general visceral efferent, nucleus in midbrain, nerves cross to contralateral when leaving the nucleus, emerge from dorsal brainstem, traverses cavernous sinus and passes through superior orbital fissure

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32
Q

abducens nerve motor nucleus

A

general somatic efferents, nucleus in pontine tegmentum, on floor of fourth ventricle, nerve runs along inferior edge of basilar pons and exits at pontine medullary junction, tranverses canvernous sinus, enters superior orbital fissure

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33
Q

aneurysms

A

compress adjacent nerves with deficit in eye movements

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34
Q

location of oculomotor nerve in relation to cerebral arteries

A

between posterior cerebral and superior cerebellar

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35
Q

location of abducens nerve in relation to cerebral arteries

A

surrounded by the labynthine (internal acoustic) and anterior inferior cerebellar arteries

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36
Q

eye movements

A

mostly reflexive - controlled by involuntary systems

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37
Q

slow eye movements

A

smooth pursuit

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38
Q

fast / jerky eye movements

A

saccadic movements

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39
Q

conjugate eye movement

A

eyes moving together

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40
Q

vergent eye movement

A

eyes moving in opposite directions

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41
Q

ocular gaze systems

A

part of a sensory system in which where eyes are pointing in space matters

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42
Q

saccadic movements

A

part of ocular gaze system, rapid, jerky movements that bring new objects onto fovea, allow quick scanning of points in image to capture salient features (like a new face)

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43
Q

smooth pursuit

A

ocular gaze systems, keep am moving image on centered fovea, tracking, keeps eye on the ball

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44
Q

vestibulo-ocular gaze

A

ocular gaze system, keeps image steady on fovea during head movement

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45
Q

vergence

A

ocular gaze system, keeps image on fovea when object moves nearer or farther away

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46
Q

medial longitudinal fasciculus MLF

A

distributes sensory input to motor nuclei on both sides of brain, crossed tracts with ascending and descending, from floor of fourth ventricle in medulla to midbrain, coordinates eye and head movement by yoking motor nuclei of CN III / IV / VI, integrates movements directed by frontal eye fields (gaze centers) and vestibulocochlear nerve information

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47
Q

saccadic gaze system

A

fast, voluntary, brings new image onto fovea, ex: patterns for inspecting human faces, higher centers signal gaze centers which signal inpsilateral and contralateral muscles via the medial longitudinal fasciculus, leads to conjugate movements

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48
Q

smooth pursuit system

A

lock conjugate gaze on moving object, spot object in motion and follow it, eye-hand coordination, must first see moving object -> optic nerve -> primary visual cortex -> middle temporal cortex + pontine nuclei + superior colliculus (speed and direction of pursuit) -> extraocular muscle activation via medial longitudinal fasciculus

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49
Q

vestibulo-ocular reflex

A

maintains visual fixation when head moves, compensatory eye movement is opposite head movement, vestibular apparatus -> CN VIII -> nuclei of CN III/IV/VI + gaze centers -> fibers ascend and descend in MLF to motor nuclei -> extraocular muscles

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50
Q

convergence

A

interpupilary distance decreases as object is brought closer and eyes adduct, contraction of medial recti and relaxation of lateral recti stimulated by input from visual cortex to motor nuclei

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51
Q

divergence

A

voluntary abduction of converged eyes back to primary position

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52
Q

sphincter pupillae

A

immediately around pupil, smooth muscle, constricts pupils, derived from neuroectoderm of optic cup, parasympathetic control

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53
Q

dilator pupillae

A

broader and radial outer iris, smooth muscle, dilate pupils, derived from neuroectoderm of optic cup, sympathetic control

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54
Q

parasympathetic control of pupils

A

pregaglionic cells in Edinger-Westphal nucleus -> axons in CN III -> ciliary ganglion + synapse -> postganglionic fibers in short ciliary nerve -> back of eye ball -> between choroid and sclera -> sphincter pupillae -> pupil constricts

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55
Q

parasympathetic control of pupils

A

pregaglionic cells in Edinger-Westphal nucleus -> axons in CN III -> ciliary ganglion + synapse -> postganglionic fibers in short ciliary nerve -> back of eye ball -> between choroid and sclera -> ciliary muscles constrict -> less tension on suspensory fibers -> lens rounds up (can focus on near)

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56
Q

accommodation

A

pupillary constriction, ciliary muscle contraction, convergence of eyes (medial rectus muscles - all involves CN III

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57
Q

sympathetic control of pupils

A

fibers from 1st and 2nd thoracic spinal nerves -> preganglionic fibers -> sympathetic trunk -> superior cervical ganglion ->postganglionic fibers in carotid plexus -> long ciliary nerve (nasociliary nerve, V1) -> ciliary ganglion -> dilator pupillae -> pupils dilate

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58
Q

pupilary light reflex

A

controls the diameter of the pupil in response to light, direct response is ipsilateral, consensual response is contralateral, light -> retina -> optic nerve -> superior brachium -> midbrain -> pretectal olivery nucleus -> Ednger-Westphal nucleus preganglionic parasympathetic -> oculomotor nerve -> ciliary ganglion -> postganglionic -> sphincter pupillae; crossing at optic chiasma; crossing from pretectal olivary nucleus to Ednger-Westphal nucleus

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59
Q

unilateral lesion of oculomotor nerve

A

compressed oculomotor nerve by posterior communicating artery aneurysm, prevents signal from reaching sphincter pupillae

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60
Q

right lesion on oculomotor nerve

A

light shown on right eye causes consensual response in left eye but not direct response in right eye – when light is shown on left eye the left eye will have direct response and the right eye will have absent consensual response - no pupilar response on side of lesion

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61
Q

left lesion on oculomotor nerve

A

light shown on right eye causes direct but not consensual response, light shown on left eye causes consensual response but not direct response - no pupilary response on side of lesion

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62
Q

case - double vision when checking left blind spot, left eye fully abducts

A

left eye abduction and left abducens must be fine, that leaves right medial rectus lesion and oculomotor nerve

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63
Q

case - difficulty seeing in dim light, no sweating on right side, right droopy eyelid

A

Horner syndrome, sympathetic nerve deficit, affected postganglionic cell bodies are in superior cervical ganglion

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64
Q

case - double vision following stroke when head is turned left, right is abducted at rest but can follow your finger

A

lesions on right medial longitudinal fasciculus

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65
Q

case - left nystagmus, staggers to right when walking

A

lesion is in right vestibulocochlear nerve because nystagmus is to the left

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66
Q

case - double vision when reading, head tilted to the right, left eye deviates upward when looking medially

A

lesion on trochlear nerve, which exits brain on dorsal midbrain

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67
Q

visual pathways

A

30%+ of cortex, 50-60% of brain in visual processing, 1,000,000 optic nerve fibers, 90% of all information coming in to brain is visual, more people are visual learners

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68
Q

two focusing surfaces of eye

A

cornea (3/4 of focusing) and lens (1/4 of focusing, upside down image on retina

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69
Q

emmetropia

A

image naturally focuses on retina, good vision without correction

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70
Q

myopia

A

nearsighted, image focuses in front of retina, longer eye, steeper cornea - corrected with concave lens pushes image back

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71
Q

hyperopia

A

farsighted, image focuses behind retina, shorter eye, flatter cornea - convex lens brings image forward

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72
Q

presbyopia

A

loss of focusing power with age, 40+

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73
Q

astigmatism

A

distorted cornea, images focuses on several spots on retina, blurred image

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74
Q

power of eye

A

diopters, 1 diopter will focus an object at one meter, eye = 60 diopters (cornea ~ 45 diopters, lens ~ 15 diopters)

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75
Q

lens power

A

inversely related to focal point, two diopter lens focuses at 0.5 meters, 3 diopter lens focuses at 1/3 meter

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76
Q

eye prescriptions

A

+ = farsighted; - = nearsighted, ex: -4.0 diopter = near sighted, focus point 1/4 meter away (25 cm)

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77
Q

laser vision correction

A

reshapes the cornea to change the power of the eye - often get glare at edge of treatment zone because image is distorted where flat meets curved, can also change the power of the eye with intraocular lens replacement

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78
Q

intraocular lens replacement

A

for cataracts

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79
Q

optical Hx

A

age, onset, pain, vision loss, medications, systemic illness, fevers, rashes

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80
Q

vision check

A

eye individually, with glasses, distance and near, equal or unequal vision, intensity with penlight or red color, 20/20?

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81
Q

20/20

A

can see at 20 feet what should be seen at 20 feet, 20/40 see at 20 feet what should be seen at 40 feet, newspaper print is 20/50

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82
Q

pupil check

A

look into distance (pupils should get smaller), note pupil size (1mm difference normal - normal pupillary size 5-8mm), roundness, symmetric, react equally to light, swinging flashlight (marcus gunn) for relative afferent pupil defect

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83
Q

PERL

A

pupils are equal and reactive to light

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84
Q

RAPD - relative afferent pupil defect

A

lesion on afferent portion of optic nerve before optic chiasm, on effected side - missing direct and consensual reaction to light because enter afferent pathway is blocked, opposite effected side - normal direction and consensual reaction to light because parasympathetic pathway via CN III is intact, vision should be worse in affected eye

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85
Q

things that may cause relative afferent pupil defect / marcus gunn pupil

A

optic neuritis (inflammed optic nerve), ischemic optic neuropathy, retinal detachment, asymmetric glaucoma

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86
Q

things not associated with relative afferent pupil defect / marcus gunn pupil

A

amblyopia (lazy eye), cataracts, vitreous hemorrhage

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87
Q

aniscocoria (unequal sized pupils)

A

mydriatic (dilated) = parasympathetic problem, miotic (constricted) = sympathetic problem

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88
Q

mydriatic pupil

A

dilated, parasympathetic problem

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89
Q

miotic pupil

A

constricted, sympathetic problem

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90
Q

pupillary light reflex

A

parasympathetic, optic nerve (afferent) -> midbrain -> oculomotor nerve -> pupil constrictor (efferent)

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91
Q

sympathetic pupil control

A

brainstem -> cervical ganglion synapses -> iris

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92
Q

pupil constriction

A

basic reflex, light directly affects pupil size

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93
Q

pupil dilation

A

non-light stimulus, mood, concentration, flight / fight, dopamine / serotonin

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94
Q

blinking

A

protective, striated muscle with ACh on nicotinic receptors and smooth with NE on alpha1 receptors

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95
Q

tears

A

protective, spontaneous (basal), reflexively, emotional, parasympathetic ACh on muscarinic receptors

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96
Q

epiphora

A

overflow of tears, due to overproduction or blocked drainage

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97
Q

cornea

A

greater refractive power

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98
Q

lens

A

less refractive power, but adjusted to accomodate near vision

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99
Q

pupillary light reflex

A

regulates light intensity, miosis (constriction), parasympathetic to sphincter pupillae with muscarinic receptors

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100
Q

mydriasis

A

dilated pupils, sympathetic via alpha1 receptors activates dilator pupillae

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101
Q

miosis

A

constricted pupils

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102
Q

increased intraocular pressure

A

loss of vision

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103
Q

cones

A

photopic vision - blue (short), green (medium), red (long), temporal and spatial resolution, discrimination of surfaces and movement in bright light

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104
Q

visual acuity

A

ability to discriminate detail, types - spatial, temporal, spectral, primarily cone system

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105
Q

phototransduction

A

4 steps that use 2nd messenger cascade to amplify signal

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106
Q

phototransduction in rods

A

activation of rhodopsin -> closure of cyclic nucleotide gated Na+ channel -> hyperpolerizes photoreceptor

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107
Q

visual cycle

A

bleaching and recycling of 11-cis-retinol between photoreceptor and retinal pigment epithelium, process is key to dark adaptation and is disrupted by vit A deficiency and macular degeneration

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108
Q

muscles of blinking

A

orbicularis oculi, levator palpebrae superioris, superior tarsal muscle

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109
Q

orbicularis oculi

A

striated, ACh on nicotinic receptors, eyelid position

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110
Q

levator palpebrae superioris

A

striated, ACh on nicotinic receptors, eyelid position

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111
Q

superior tarsal muscle

A

smooth, sympathetic on alpha1 receptors

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112
Q

maintaining ocular opening

A

tonic activation of levator palpebrae superioris and superior tarsal muscle, inactivation of orbicularis oculi

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113
Q

gentle opening/closing, adjusts to moving eye

A

activation / inactivation of levator palpebrae superioris, inactivation of orbicularis oculi

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114
Q

blinking with firm closure

A

activation of orbicularis oculi, inactivation of levator palpebrae superioris

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115
Q

functions of blinking

A

corneal lubrication, eye protection, visual information processing (temporal information processing)

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116
Q

spontaneous blinking

A

conjugate, periodic, symmetric, absence of external / internal stimuli, 10-20/min, starts in premotor brainstem and affected by dopaminergic activity - decreased with Parkinson’s and increased with schizophrenia and Huntington’s

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117
Q

blink reflex

A

touch cornea to afferents to trigeminal nerve - or - bright light / rapid moving object to afferents to optic nerve; faster than spontaneous blinking

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118
Q

3 layers of tear film

A
  1. lipid from eyelid oil gland (blockage = sty), 2. aqueous lacrimal gland solution with lysozyme, 3. mucous from conjunctiva
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119
Q

composition of tears

A

varies with age and stimulus, emotional = more hormones (prolactin, ACTH, enkephalin), basal tears decrease with age (dry eye)

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120
Q

tear flow

A

evaporation, drainage through nasolacrimal duct into nasal cavity

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121
Q

epiphora

A

overflow of tears, parasympathetic, increased tears from lacrimal gland and decreased outflow due to closure of lacrimal duct

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122
Q

induces epiphora

A
  1. corneal stimulation of CN V -> reflex tears, 2. emotional, parasympathetic, mediated by limbic system and hypothalamus, psychic tears, red face, convulsive breathing
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123
Q

image on retina

A

inverted and reversed by eye, brain considers normal and learned to interpret

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124
Q

refraction

A

focuses light, greatest at air/tissue junction (cornea)

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125
Q

diopter

A

= 1 / focal length, cornea +44D, lens +15-29D, +59-75D total

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126
Q

accomodation

A

lens adjustment for near vision, far vision = lens flat with tight zonule fibers and relaxed ciliary muscle, near vision = lens rounded, zonule fibers relaxes and ciliary muscles contracted, brings image that would be behind eye onto retina

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127
Q

distance curve of lens

A

sympathetic action at beta2 receptors, flat lens, relaxes ciliary muscles, tight zonule fibers

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128
Q

near curve of lens

A

parasympathetic action on muscarinic receptors, constricted ciliary muscles, relaxed zonule fibers, rounder lens

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129
Q

Tx of system deficit

A

treat system deficit, do not treat by affecting opposite system with antagonist

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130
Q

production of aqueous humor

A
  1. sympathetic -> cAMP -> stimulation of beta2 receptor increases and alpha2 decreases, 2. carbonic anhydrase forms bicarbonate (HCO3-) increasing Cl- secretion which increases water secretion
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131
Q

elimination of aqueous humor

A
  1. parasympathetic constriction of sphincter pupillae increases outflow, 2. uveal scleral flow - reabsorbed by relaxed ciliary muscle (increased by prostaglandins)
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132
Q

flow of aqueous humor

A

ciliary epithelium -> over lens -> through pupil -> canal of schlemm and ciliary muscle

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133
Q

aqueous humor

A

~125mL

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134
Q

intraocular pressure

A

20mmHg

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135
Q

transduction

A

conversion of energy into electrical graded potential

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136
Q

special sense

A

graded potential in receptor cell passes causes action potential in another cell (excludes smell)

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137
Q

photoreceptors

A

rods / cones, receptor cell graded potential, NT synapse with bipolar cells

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138
Q

bipolar cells

A

NT synapse with ganglion cells with action potential

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139
Q

horizontal cells

A

lateral inhibition at photoreceptor / bipolar cell synapse

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140
Q

amacrine cells

A

lateral inhibition at synapse of bipolar and ganglion cells

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141
Q

visible light

A

electromagnetic, frequency (wavelength) and intensity (brightness), perceived light is reflected off objects to the eye

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142
Q

each photoreceptor

A

encodes intensity of one wavelength at one point in space

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143
Q

photopigements

A

determine wavelength seen

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144
Q

range of wavelength overlap (black/white, red, green)

A

ensures that will not be missed if certain rods / cones missing

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145
Q

upper wavelength of green and red

A

does not overlap with black/white, used to preserve night vision with red light and a few activated cones

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146
Q

optic disc

A

no rods / cones

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147
Q

fovea centralis

A

peak cones, decreasing to periphery

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148
Q

periphery rods

A

peak immediately beyond fovea cone peak, decrease peripherally, but more in periphery than cones

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149
Q

rods

A

more photopigment, rhodopsin, high sensitivity to photons (saturated in daylight, small dynamic range), low temporal resolution / slow / more integrated, poor spatial resolution (large receptive field for scattered light, large convergence onto bipolar cells)

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150
Q

cones

A

less photopigment, 3 overlapping pigments, low sensitivity to photons (saturated in bright light with large dynamic range), high temporal resolution (fast, less integration), good spatial resolution for points of light and little convergence onto bipolar cells

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151
Q

spatial acuity

A

2 point discrimination, function of location on retina (fovea vs periphery) and brightness (brighter = more cones), test with Snellen Eye Chart

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152
Q

temporal acuity

A

distinguish two visual stimuli over time, “blinking”

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153
Q

critical fusion frequency

A

point at which flashing light is perceived at continuous, old movies called “flicks” did not reach this point

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154
Q

spectral acuity

A

distinguish between different wavelengths of light

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155
Q

phototransduction steps

A
  1. light activates rhodopsin, 2. rhodopsin binds to transducin g-protein that converts GTP to GDP which activates phosphodiesterase, 3. phosphdiesterase breaks cGMP down to GMP, 4. closing of cGMP depedent nonspecific ligand gated cation channel prevents Na+ from going into cell and hyperpolarizes cell
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156
Q

photoreceptor - receptor potential

A

hyperpolerization from -40mV down to -80mV due to closing of Na+ channels and continued outflow of K+, happens in rods

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157
Q

dark accommodation

A

pumping of more 11-cis-retinal into rods in low light, makes rods more sensitive

158
Q

other functions of retinal pigment epithelium

A

regeneration of rods / cones, forms blood-retina barrier

159
Q

steps of visual cycle (mostly for rods, cones less RPE depedent)

A
  1. rhodopsin hit by photon and split into opsin and all-trans-retinal, 2. bleaching - all rhodopsin broken into two, 3. all-trans-retinal pumped out of rod into RPE (opsin stays in rod), 4. turned back into 11-cis-retinal and sent back to rod
160
Q

parasympathetic

A

preganglionic - ACh to nicotinic receptors, postganglionic - ACh to muscarinic receptors

161
Q

sympathetic

A

preganglionic - ACh to nicotinic receptors, postganglionic - NE to alpha1 receptors

162
Q

actions of sympathetic NS

A

mydriasis - contraction of pupillary dilator (alpha1 receptors), open eyelids - contraction of superior tarsal (alpha1 receptor), relax ciliary muscles for distant vision (beta2 receptor), inhibit aqueous humor formation (alpha2 receptor)

163
Q

actions of parasympathetic NS

A

focus eye via pupilary muscle contraction, miosis - pupillary sphincter contraction, enhanced drainage of aqueous humor via trabecular meshwork and canal of Schlemm - all muscarinic receptors

164
Q

inner ear receptors

A

two types, both convert mechanical energy into receptor potential

165
Q

Type I inner hair cells

A

true sensory receptors that convey information of the brainstem, in cochlea, flask-shaped, mechanoreceptors -> stretch activated channel that allows depolarizing K+ in, receive afferent and efferent (adjusts displacement) innervation

166
Q

Type II outer hair cells

A

biological amplifiers like a motor unit, in cochlea, cylindrical shape, mechanoreceptors -> stretch activated channel that allows depolarizing K+ in, receive afferent and efferent (adjusts displacement) innervation, lateral cisternae (ER)

167
Q

Type I inner hair cell innervation

A

90% afferent innervation, an afferent fiber goes to 1 hair cell, each hair cell received multiple afferents (redundant = specific), efferent to dendrite or primary afferent (not hair cell itself), true sensory receptors

168
Q

Type II outer hair cell innervation

A

10% of afferent innervation, less organized - an afferent goes to many hair cells, each hair cell gets one afferent fiber (less specific), large / secure synapse with direct efferent, act more like contractile motor unit (modulating)

169
Q

inner ear transduction is directional

A

displacement toward tallest stereocilia depolarizes (when basilar membrane moves toward scala vestibuli), negative deflection (basal membrane toward scala tympani) causes hyperpolarization

170
Q

negative displacement

A

tallest to shortest, basal membrane upward, relaxing tip link closes channel -> hyperpolarization, happens at trough in sin wave of sound

171
Q

positive displacement

A

shortest to tallest, basal membrane downward, stretching tip link opens channel -> depolarization because K+ enters, happens at crest in sin wave of sound

172
Q

adaptation to prolonged stimuli in hearing

A

decrease in response of receptor to a sustained stimulus at a constant level, maintenance of tip link tension so some are open and some are closed (tip link set point), means there is always a way to generate hypolarization, done by motor complex in stereocilia with actin structure and myosin VIIa motor (mutation of which can cause a form of deafness)

173
Q

semicircular canals

A

detect head rotation / angular acceleration, six canals that work in pairs (when one is depolarized the other is hyperpolarized)

174
Q

otolith organs (utricle and saccule)

A

detect gravity / linear acceleration, position relative to ground

175
Q

vestibular system

A

balance, posture, coordination of head and body movement, fixation of image on fovea - integrated with input from other systems (eyes, joint proprioceptors), when inputs disagree brain believes vestibular input but brain will singal to get you to stop (vertigo, nausea, vomiting, nystagmus)

176
Q

semicircular canals

A

ampulla with cupula to bone, dynamic - no output at rest or in constant motion, hair cells stimulated by: 1. head rotation (haircells move, fluid doesn’t, deflects stereocillia - receptor potential), 2. head reaches constant velocity (cupula has caught up to hair cells, no deflection, no receptor potential), 3. head stops rotating (haircells stop, fluid keeps moving, opposite of previous receptor potential)

177
Q

horizontal canals

A

depolarization in same direction as head rotation, tallest stereocilia to lateral, ex: if turn head left fluid pushes stereocillia right causing depolarization on left (increased firing) and hyperpolarization on right (decreased firing)

178
Q

anterior / posterior canals

A

depolarize in opposite direction as head tilt, paired left ant / right post and vice versa, tip head and forward acts on one pair, ex: tip head left and forward - depolarizes left anterior and hyperpolarizes right posterior, tip head right and forward - depolarize right anterior and hyperpolarize left posterior, nod forward depolarizes both anterior canals and hyperpolarizes posterior canals, nod backwards depolarizes both posterior canals and hyperpolarizes anterior canals

179
Q

otolith organ

A

detects gravity, calcium carbonate crystals on top of hair cells cause stereocilia deflection in response to gravity, two otolith organs at 90 degree to eachother with stereocilia in different directions, saccule oriented horizontally, utricle oriented vertically, both respond in all orientations

180
Q

utricle otolith organ

A

tallest stereocilia toward striola line

181
Q

saccule otolith organ

A

tallest stereocilia away from striola line

182
Q

sound transduction

A

encodes

183
Q

sound stimulus

A

sin wave (pure tone), has two parts: 1. frequency (pitch) dependent on wavelength, 2. intensity (loudness) dependent on amplitude

184
Q

sound intensity

A

loudness, depends on wave amplitude, measured in decibels (dB)

185
Q

formula for decibels

A

dB = 20 log (P1 / P0), P = pressure, log scale means large dynamic range that ear encodes (10x10 to the 6th), relative measurement, relative to normal = dBSL, absolute reference = dBSPL

186
Q

complex sound

A

ear takes complex sounds and breaks it into component parts (frequencies) - deconstructs sound (noise contains all frequencies)

187
Q

linear system

A

same frequency goes in and same frequency comes out - no the ear - the cochlea is nonlinear

188
Q

non-linear system

A

energy is added into the process, cochlea

189
Q

middle ear function

A

stops loss of energy that would otherwise happen at interface between air / water interface which would reduce hearing and reflect 99.9% of energy, without middle ear amplification would have 40-55 dB hearing loss

190
Q

aucoustic impedance matching

A

middle ear amplifies force, normally air conduction is better then bone conduction, 3 mechanisms: 1. tympanic membrane bigger than oval window (areal ratio), 2. handle of the malleus is larger than handle of incus (lever ratio), 3. buckling of TM at edges concentrates force in middle of TM - affecting any of these three things will affect conduction

191
Q

conductive hearing loss

A

anything that affects 1. tympanic membrane bigger than oval window (areal ratio), 2. handle of the malleus is larger than handle of incus (lever ratio), 3. buckling of TM at edges concentrates force in middle of TM

192
Q

acoustic impedance

A

can’t get perfect match at all frequencies, middle ear is better / worse at minimizing loss of different frequencies, depends on resonance

193
Q

resonance

A

two properties - 1. mass (heavy things resonate at low frequencies), 2. stiffness (elasticity, increased stiffness gives resonance at higher frequency)

194
Q

affects resonance in the ear

A
  1. mass of ossicles, 2. size of middle ear space determines stiffness - there are conditions that affect one or the other
195
Q

otosclerosis

A

bone builds up on the stapes, mass is increased and high frequency resonance decreases

196
Q

otitis media

A

middle ear infection, increases stiffness first losing low frequency, then increased mass around ear bones decreases high frequency

197
Q

absolute audiograms

A

map of hearing at various frequencies, measured in terms of threshold / intensity, determined by middle ear - if middle ear can get vibration through the cochlea will pick it up, absolute sound level dB vs frequency, we hear best (lowest threshold) between 500Hz and 5KHz, pain dB level is just before saturation point

198
Q

audiogram relative to normal (clinically used)

A

sets normal threshold point equal to zero for each frequency, define relative intensity, zero readings are good, as you move away from zero have hearing loss, only goes to 8kHz but can hear up to 20 kHz at birth

199
Q

normal range of speech

A

250-4kHz, 40-60 dB

200
Q

middle ear function

A

transfer determines absolute threshold of hearing at each frequency - cochlea is so sensitive it can transduce and signal - thus, middle ear determines what you can hear

201
Q

sound in cochlea

A

sound waves pass through cochlea instantly, traveling wave pattern of basilar membrane established gradually independent whether the sound came through bone or oval window, traveling wave has frequency vs. place relationship - high frequency at base and low frequency at apex

202
Q

basilar membrane

A

resonates differently at different places in cochlea creating traveling wave with frequency vs place relationship - high frequency at base and low frequency at apex

203
Q

air vs bone

A

in normal hearing air conduction should be greater than bone conduction due to amplification that occurs in the middle ear

204
Q

traveling wave in cochlea

A

always starts at base and builds towards max at apex with a peak in a specific place for a given frequency, high frequencies peak at the base and low frequencies peak at the apex

205
Q

tonotopic map in cochlea

A

primary afferents connect to individual points that only respond to specific frequencies, base = high frequency, apex = low frequency

206
Q

basilar membrane response to different frequencies

A

combination of mass (number of cells) an stiffness, apex mass > base mass, base stiffness > apex stiffness, each point on basal membrane resonates differently

207
Q

outer hair cell amplification

A

receptor potential exerts force on basilar membrane -> positive feedback that amplifies vibration of membrane in nonlinear, frequency specific manner - receptor potential changed into a contraction that increases vibration of basal membrane which increases inner hair cell signaling, allowing for smaller amplitude detection, ex: swing leg pumping analogy

208
Q

otoacoustic emissions

A

fluid wave in cochlea conducted back through perilymph, vibrates middle ear, generates sound from ear, comes from the fact that outer hair cells are adding energy to the system through amplification - this makes the ear a nonlinear system, can be detected in normal working ear

209
Q

measuring otoacoustic emissions

A

would get frequency put into ear back out, but would also get a number of other frequencies produced by the ear itself, can use to test hearing in people who can’t respond behaviorally (babies)

210
Q

stria vascularis

A

produces endolymph (high K+) and endocochlear potential (+80mV), ion transporters similar to the kidney (thus drugs affecting renal function are often ototoxic - esp loop diuretics that affect Na+/K+/Cl- transporters, on lateral wall of cochlea, pump K+ into endolymph (150mM)

211
Q

haircell ion concentrations

A

K+ 120mM, -40mV resting potential

212
Q

K+ channel in hair cells

A

150mM out, 120mM in, +80mV out, -40mV in, makes K+ go into hair cell and depolarize

213
Q

gap junction system

A

shunts K+ back to stria vascularis, 40% of hearing loss is genetic and is often related to this shunt defect (gap junction protein defect)

214
Q

high K+ in stria vascularis

A

K+ channels, ATPases, Na/K/2Cl transporter pump, target of loop diuretics, in both kidney and ear - loop diuretics can cause pharmacological hearing loss

215
Q

visual pathway

A

rod / cone -> bipolar cell -> ganglion cell -> optic nerve -> optic chiasm -> optic tract -> geniculate nucleus -> geniculocalcarine tract (optic radiation) -> calcarine cortex (area 17)

216
Q

retinal quadrants

A

as looking at pt through scope, upper temporal quadrant, lower temporal quadrant, upper nasal quadrant, lower nasal quadrant - divided by vertical and horizontal meridians

217
Q

monocular visual fields

A

from within eye looking out, upper temporal field, lower temporal field, upper nasal field, lower nasal field - tested with confrontation

218
Q

blind spot

A

15 degree to temporal side on horizontal meridian in visual field, correspond with location of optic nerve

219
Q

binocular visual fields

A

combined monocular visual fields, binocular in middle with monocular crescents laterally, upper left, upper right, lower left, lower right

220
Q

image on retina

A

is reversed and upside down

221
Q

retinotopic organization

A

xxx

222
Q

Meyer’s loop

A

axons from lateral geniculate nucleus with upper visual field information loop into temporal lobe lateral to temporal horn of ventricles on way to visual cortex

223
Q

calcarine cortex

A

around calcarine fissure, upper vision fields to lower lingual gyrus, lower vision fields to upper cuneus gyrus, macula is most caudal in area 17, peripheral field is rostral area 17

224
Q

lesion in area 17

A

blindness in contralateral visual field

225
Q

visual association cortex (area 18 and 19)

A

input from area 17, Brodman’s, complex aspects of vision

226
Q

lesion in area 18 / 19

A

failure to recognize something

227
Q

most temporal vision

A

ends up on nasal retina in same side eye

228
Q

medial binocular vision

A

ends up on temporal retina in opposite side eye

229
Q

optic nerve

A

both nasal and temporal field fibers

230
Q

left visual fields

A

lateral portion ends up in nasal left eye and medial portion ends up in temporal right eye - flipped upside down

231
Q

right visual fields

A

lateral portion ends up in nasal right eye and medial portion ends up in temporal left eye - flipped upside down

232
Q

optic chiasm

A

nasal fibers (containing what was originally in lateral temporal fields) cross

233
Q

optic tract

A

fibers from left temporal eye (medial right visual field) and right nasal eye (lateral right visual field)

234
Q

geniculate nucleus

A

fibers from left temporal eye (medial right visual field) and right nasal eye (lateral right visual field)

235
Q

geniculocalcarine tract (optic radiation)

A

fibers from left temporal eye (medial right visual field) and right nasal eye (lateral right visual field)

236
Q

geniculate nucleus organization

A

upper visual field is lateral and upper visual field if medial, with large central portion for fovea centralis

237
Q

calcarine cortex (area 17) organization

A

fovea centralis most dorsal, medial visual field more ventral, lateral visual field most ventral, upper visual field in lingual gyrus, lower visual field in cuneus gyrus

238
Q

calcarine cortex

A

left side contains lateral right visual field from nasal right eye and medial right visual field from temporal left eye; right side contains lateral left visual field from nasal left eye and medial left visual field from temporal right eye

239
Q

pupillary light reflex (miosis)

A

light in right eye -> nasal and temporal fibers -> optic nerve -> afferent temporal fibers to ipsilateral and nasal fibers cross to contralateral -> lateral geniculate nucleus + brachium of superior colliculus -> synapses in pretectal area -> synapses with preganglionic efferents in nucleus of edinger-westphal -> CN III -> ciliary ganglion -> postganglionic parasympathetic efferent -> short ciliary nerves -> sphincter pupillae muscle

240
Q

afferent lesion of pupillary light reflex

A

in optic nerve, effected side has consensual reflex but not direct reflex

241
Q

efferent lesion of pupillary light reflex

A

in CN III, affected side has neither direct or consensual reflex

242
Q

accommodation (near) reflex

A

shift of gaze from far to near -> 1. ocular convergence (medial recti, GSE CN III), 2. pupillary constriction (sphincter pupillae, GVE CN III), 3. lens thickening (ciliary muscle contraction and zonule fiber relaxation, GVE CN III)

243
Q

afferent limb of accommodation reflex

A

optic nerve -> optic tract -> lateral geniculate nucleus -> optic radiation -> visual cortex -> visual association cortex -> optic radiation -> brachium superior colliculus -> superior colliculus -> oculomotor nuclei -> oculomotor nerve

244
Q

efferent limb of accommodation reflex

A

GSE and GVE in CN III

245
Q

correct use of ophthalmoscope

A

chose spot size to match pupil size, focus as move in, dimmer light better for pt, right eye to right eye, left eye to left eye, dim room, pt looks up and distant, pt slightly below, work in at 15 degrees off medial, look in all directions in eye

246
Q

visual exam

A

conjuctiva, H extraoculars (look for nystagmus on lateral H = CN VIII), acuity, fields, pupillary reflex, convergence, PERL, anisocoria, conjugate gaze, eye orbital, red reflex

247
Q

oropharyngeal exam

A

light, tongue blade, can see epiglotis in kids, look at teeth, take teeth out if dentures, look under tongue, look up nasopharynx with light and mirror (watch gag reflex), look down larynx with light and mirror (watch gag reflex)

248
Q

auditory pathway - basic audition / afferent system

A

hair cells -> spiral ganglion / auditory nerve -> cochlear nuclei (brainstem) -> trapezoid body -> superior olivary complex -> lateral lemniscus -> inferior colliculus -> brachium of inferior colliculus -> medial geniculate nucleus (thalamus) -> internal capsule -> primary auditory cortex (transverse temporal gyrus) + auditory association cortex (superior temporal gyrus)

249
Q

auditory - efferent system

A

hair cells -> spiral ganglion / auditory nerve -> cochlear nuclei (brainstem) -> trapezoid body -> superior olivary complex -> auditory nerve -> hair cells (motor part)

250
Q

auditory reflex pathway - efferent system

A

hair cells -> spiral ganglion / auditory nerve -> cochlear nuclei (brainstem) -> trapezoid body -> superior olivary complex -> auditory nerve -> trigeminal motor nucleus + facial motor nucleus -> CN V3 to tensor tympani and CN VII to stapedius muscle, decreases sound transmission in middle ear, slow to protect from sudden sounds

251
Q

acoustic pathway cells

A

1st order - spiral gaglion cells, 2nd order in cochlear nucleus, 3rd order in superior olivary complex, 4th order - inferior colliculus, 5th order - medial geniculate nucleus, 6th order - primary auditory cortex

252
Q

acoustic pathway

A

starts with sensation at hair cells, ends with perception at cortex

253
Q

ipsilateral/unilateral hearing loss

A

single lesion in periphery, including hair cells, cochlea, auditory nerve, cochlear nulceus

254
Q

bilateral hearing loss

A

extensive bilateral connection, single lesion central after cochlear nucleus

255
Q

noise exposure, ototoxic drugs, malformations - bilateral hearing loss

A

considered multiple lesion

256
Q

vestibular pathway

A

more related to motor / reflexes, has four parts

257
Q

afferent vestibular pathway

A

hair cells -> vestibular nerve / ganglion -> vestibular nuclei (superior) -> medial lemniscus -> ventroposterior nucleus -> internal capsule -> vestibular cortex (superior temporal gyrus, posterior to primary somatosensory cortex)

258
Q

efferent - vestibulospinal reflex

A

control head / neck / upper limb position in response to head movement; hair cells -> vestibular nerve / ganglion -> vestibular nuclei (lateral/medial) -> lateral vestibulospinal tract (LVST) to limbs/trunk and medial vestibulospinal tract (MVST) to upper back/neck

259
Q

efferent - vestibulo-ocular reflex

A

controls eye position, hair cells -> vestibular nerve / ganglion -> vestibular nuclei (medial) -> medial longitudinal fasciculus (MLF) -> oculomotor nucleus (CN III - superior/medial/inferior rectus) and abducens nucleus (CN VI - lateral rectus) and trochlear nucleus (CN IV superior oblique)

260
Q

efferent - vestibulocerebellar reflex

A

related to motor control, hair cells -> vestibular nerve / ganglion -> vestibular nuclei (inferior) -> inferior cerebellar peduncle -> vestibulo-cerebellum (flocculonodular lobe)

261
Q

path of sound

A

external auditory meatus -> cochlea (in temporal bone) -> vestibulocochlear nerve fibers -> internal auditory meatus (w/ facial nerve and labyrinthine artery) -> brainstem -> vestibulocochlear nucleus (border between medulla and pons) near infererior cerebellar pendulce -> inferior colliculus -> brachium of inferior colliculus -> median ganiculate body of thalamus

262
Q

acoustic neuroma

A

will impact facial nerve and labyrinthine artery that travel with the vestibulococlear nerve in the skull, ex: loss of blood supply can kill hair cells affecting hearing and balance

263
Q

two sesnory nuclei of auditory / vestibular pathways

A

cochlear nucleus (more lateral) and vestibular nucleus (more medial) below middle cerebellar peduncle, posterior and lateral near medulla and pons boundary

264
Q

motor nuclei of auditory / vestibular pathways

A

oculomotor nucleus (deep to superior colliculus in midbrain), trochlear nucleus (deep to inferior colliculus in midbrain), tigeminal nucleus (below superior cerebellar peduncle), abducens nucleus (medial to middle cerebrellar peduncle), facial nucleus (medial to middle cerebellar peduncle - lateral to abducens)

265
Q

vestibulospinal tracts

A

upper motor neuron tracts that goes from vestibular nuclei to ventral horn of spinal cord, located medial to spinothalamic tract and immediatly lateral to ventral median fissure on spinal cord

266
Q

mid-medulla

A

know because giant inferior olivary nucleus (not part of auditory pathway, but superior olivary nucleus is)

267
Q

solitary tract and nucleus

A

dark small spot. lateral floor of fourth ventrical in mid-medulla

268
Q

vestibular nucleus

A

immediately posterior to solitary tract of lateral edge of fourth ventricle in mid-medulla

269
Q

medial vestibular nucleus

A

more medial and no dark spots, mid-medulla

270
Q

interior vestibular nucleus

A

more lateral and dark spots, mid-medulla

271
Q

median longitudinal fesiculus

A

median floor of fourth ventricle, dark area, mid-medulla

272
Q

rostral medulla

A

smaller inferior olivary nusclei and flarring of cerebellar peduncles, widening of fourth ventricle

273
Q

cochlear nucleus

A

rostral medulla, most lateral floor of fourth ventricle

274
Q

vestibular nucleus

A

rostral medulla, medial to cochlear nucleus in floor of fourth ventricle

275
Q

mid-pons

A

large middle cerebellar peducles and basal pons (corticospinal tracts), smaller fourth ventricle

276
Q

superior olivary nucleus

A

pons, small what patch between basiliar pons and abducens nucleus

277
Q

superior vestibular nucleus

A

pons, light area in most lateral corner of floor of fourth ventricle

278
Q

facial nerve

A

pons, dark line that runs medial to superior vestibular nucleus, hooks around posterior edge of abducens nucleus in floor of fourth ventricles and dives back into pons medial to abducens nucleus

279
Q

abducens nucleus

A

pons, medial to superior vestibular in floor of fourth ventricle, facial nerve wraps around it

280
Q

rostral pons

A

huge basal pons (corticospinal tracts), small superior point of fourth ventricle narrowing to aqueduct

281
Q

median longitudinal fasiculus

A

small, dark spots most medial floor of fourth ventricle

282
Q

lateral lemniscus

A

curved lateral anterior edge of pons touching basil pons, runs between superior olivary nucleus and interior colliculus

283
Q

caudal midbrain

A

cerebral aqueduct (round) surrounded by periaqueductal grey, huge basil pons gone

284
Q

medial longitudinal fasiculus

A

midbrain, small dark spots, medial and touching anterior edge of periaqueductal gray

285
Q

decussation of superior cerebellar peduncles

A

midbrain, large dark circle between periaquaductal gray and cerebellar peduncles, looks like it has small holes in it

286
Q

inferior colliculus

A

midbrain, dark oval lateral to periaqueductal gray

287
Q

brachium of inferior colliculus

A

midbrain, dark curved edge lateral to periaquedeuctal gray and ventral to inferior colliculus, fibers going to thalamus

288
Q

rostral midbrain

A

looks like a butterfly, large thalamus lateral and posterior, third ventricle in middle with a little periaqueductal gray, midbrain darker and anterior

289
Q

medial geniculate body

A

relay nucleus for the auditory system, in thalamus portion of midbrain, along anterior edge of thalamus that touches midbrain, medial to lateral geniculate body

290
Q

lateral geniculate body

A

relay nucleus for the visual system, in thalamus portion of midbrain, along anterior edge of thalamus that touches midbrain, lateral to medial geniculate nucleus

291
Q

primary auditory cortex

A

temporal lobe, gets there by passing through medial geniculate nucleus through ventral internal capsule to temporal lobe

292
Q

vestibular system

A

in cortex around area of insula

293
Q

auditory brainstem response

A

ABR, brainstem auditory evoked response, repetitions of short sound stimulus, get synchronization in auditory pathway because pathway is heavily myelinated and specialized to detect differences in timing, peaks and valley that match repsonses of nuclei as they are reached (peaks I-V), give estimate of functioning along entire pathway

294
Q

peak I in auditory brainstem response

A

auditory nerve response

295
Q

peak II in auditory brainstem reponse

A

output from cochlear nucleus with trapezoid body response

296
Q

peak III in auditory brainstem response

A

from brachium of inferior colliculus

297
Q

peak IV in auditory brainstem response

A

response of primary auditory cortex

298
Q

peak V in auditory brainstem response

A

response of primary auditory cortex

299
Q

Weber test

A

tests sound localization

300
Q

sound localization

A

done by differences in timing and intensity between two ears, done by lateral and medial superior olive, local a sound in space

301
Q

lateral superior olive

A

localizes high frequency stimuli by comparing interaural intensity differences (IID) - louder in closer ear

302
Q

medial superior olive

A

localizes low frequency sound using interaural timing differences (ITD) - arrives faster in closer ear

303
Q

vestibulospinal reflexes

A

cooordinate head / trunk / body position to keep head upright, evident during decerebrate rigidity (removal of descending alpha motor neuron cortex control)

304
Q

lateral vestibulospinal tract

A

afferent from entire vestibular labyrinth (motion and gravity), lateral vestibular nucleus, posture changes to compensate for body tilting / movement, efferents are ipsilateral, excitatory, adjusts limbs and trunk by contracting extensors and relaxation of flexors

305
Q

medial vestibulospinal tract

A

afferent from semicircular canals (motion), medial and descending vestibular nuclei, stabilize head during walking, efferents are bilateral, excitatory and inhibitory, relaxes muscles of upper back and neck

306
Q

vestibulo-ocular reflex

A

assessing brain death, eyes don’t turn with head = brain death, move head in one directio causes eyes to move in opposite direction, purpose - adjusts eye position to compensate for head motion, to see it cortical control must be gone, this reflex is slower than cortex

307
Q

path of vestibulo-ocular reflex

A

turn head in horizontal plane -> causes depolarization on side in direction of turn and hyperpolarization of side opposite direction of turn -> depolarizing / excitation in vestibular nuclei on side in direction of head turn and hyperpolarization / inhibition on side opposite direction of head turn -> excited nuclei feeds forward to CN that will keep eye in place and inhibitory nuclei feeds forward to inhibit muscle that would move eye out place (eye move opposite direction of horizontal head movement)

308
Q

lesion on one side of horizontal canals pair

A

brain interprets as depolarization on the other side

309
Q

nystagmus

A

slow drift of eyes in direction opposite head movement (pursuit) followed by rapid recovery movement in with direction of movement (saccade), named for direction of fast recovery movement, pursuit is a vestibulo-ocular reflex, saccade is controlled by higher cortex centers, can evoke by stimulating the vestibular system (spinning), if happens spontaneously = underlying pathology

310
Q

vestibular function assessment

A

a lesion that cuts off the cortex will leave the pursuit but eliminate the saccade of nystagmus, up brainstem lesion both pursuit and saccade will be eliminated in nystagmus

311
Q

caloric test for vestibular function

A

cool water in one canal will an opposite direction (side) nystagmus, warm water in ear will produce a same direction (side) nystagmus, brain dead = all nystagmus absent, coma = saccade absent, pursuit present - done with head tilted to isolate horizontal canals

312
Q

three types of hearing loss

A

conductive, sensorineural, and central auditory processing disorder

313
Q

conductive hearing loss

A

damage to external or middle ear so that sound vibrations in air are never conducted to the inner ear

314
Q

sensorineural hearing loss

A

damage to hair cells, auditory nerve, cochlear nucleus (all result in unilateral same side hearing loss)

315
Q

central processing hearing disorder

A

any damage / lesion beyond cochlear nucleus, results in bilateral hearing loss, ex: cocktail party effect - can hear fine but inferior colliculus defect can’t distinguish a sound signal from noise (with age processing problem)

316
Q

absolute audiogram

A

0-140 dB, same reference point for all frequencies, can hear 50-20,000Hz at birth, worse hearing as threshold goes up on graph

317
Q

relative audiogram

A

uses 0 reference point from absolute audiogram as normal, worse hearing as threshold goes down on graph

318
Q

human speech

A

250-4000Hz, 30-70dB

319
Q

profound hearing loss =

A

can’t hear noises below 80dB

320
Q

normal hearing =

A

able to hearing anything at or below 25dB, air thresholds < bone thresholds

321
Q

air conduction through middle ear

A

should give lower hearing thresholds than bone conduction

322
Q

audiogram symbols

A

O = right with air conduction, X = left with air conduction, < = right with bone conduction, > = left with bone conduction

323
Q

conductive hearing loss

A

audiogram shows bone threshold < air threshold

324
Q

sensorineural hearing loss

A

ex: hair cell problem, equally high air and bone thresholds, basis for RINNE test

325
Q

Rinne test

A

tells whether a person has conductive or sensorineuronal hearing loss, air conduction should be louder than bone conduction, profound hearing loss on one side may cause patient to report noise heard in other good ear giving false results

326
Q

Weber test

A

normal = sound localization to center due to equal hearing/hearing loss on both sides, no lateralizing, if unilateral sensorineuronal loss - pt will reporter louder in normal ear, if you have unilateral conductive loss - pt reports localization to effected side

327
Q

tympanometry

A

sealed ear canal, apply sound, reapply sound with varied pressure in canal, measures middle ear compliance, evaluates fluid filled middle ear, negative middle ear pressure, TM performation, ossicular chain disruption, patency of ventilation tube

328
Q

acoustic reflex test

A

apply loud sound, conduct tympanometry, hearling loss required to evoke acoustic reflex, evaluates middle ear function, inner ear/auditory nerve/brainstem function, facial nerve/trigeminal nerve function

329
Q

Rinne test

A

tuning fork to mastoid then beside ear, for air vs bone conduction, evaluates conductive hearing loss

330
Q

Weber test

A

tuning fork on center of head, determines whether sound latealizes, evaluates conductive vs sensorineural hearing loss

331
Q

behavioral test

A

booth, headphones, raise hand when noise is hear, evaluates cochlear function, auditory pathway and CNS / motor response to pathway

332
Q

otoacoustic emmission test

A

mic and speaker in ear canal, play varied clicks, messure emissions that comes off TM in response, evaluates middle ear function and cochlear outer hair cell function

333
Q

auditory brainstem response

A

EEG electrodes to scalp, earphones, varied sounds, measure amplitude and latency of waves evoked, evaluates middle ear, inner ear, auditory nerve, auditory pathway

334
Q

lateral vestibulospinal tract

A

afferent from entire vestibular labyrinth (motion and gravity), lateral vestibular nucleus, posture changes to compensate for body tilting / movement, efferents are ipsilateral, excitatory, adjusts limbs and trunk by contracting extensors and relaxation of flexors

335
Q

medial vestibulospinal tract

A

afferent from semicircular canals (motion), medial and descending vestibular nuclei, stabilize head during walking, efferents are bilateral, excitatory and inhibitory, relaxes muscles of upper back and neck

336
Q

vestibulo-ocular reflex

A

assessing brain death, eyes don’t turn with head = brain death, move head in one directio causes eyes to move in opposite direction, purpose - adjusts eye position to compensate for head motion, to see it cortical control must be gone, this reflex is slower than cortex

337
Q

path of vestibulo-ocular reflex

A

turn head in horizontal plane -> causes depolarization on side in direction of turn and hyperpolarization of side opposite direction of turn -> depolarizing / excitation in vestibular nuclei on side in direction of head turn and hyperpolarization / inhibition on side opposite direction of head turn -> excited nuclei feeds forward to CN that will keep eye in place and inhibitory nuclei feeds forward to inhibit muscle that would move eye out place (eye move opposite direction of horizontal head movement)

338
Q

lesion on one side of horizontal canals pair

A

brain interprets as depolarization on the other side

339
Q

nystagmus

A

slow drift of eyes in direction opposite head movement (pursuit) followed by rapid recovery movement in with direction of movement (saccade), named for direction of fast recovery movement, pursuit is a vestibulo-ocular reflex, saccade is controlled by higher cortex centers, can evoke by stimulating the vestibular system (spinning), if happens spontaneously = underlying pathology

340
Q

vestibular function assessment

A

a lesion that cuts off the cortex will leave the pursuit but eliminate the saccade of nystagmus, up brainstem lesion both pursuit and saccade will be eliminated in nystagmus

341
Q

caloric test for vestibular function

A

cool water in one canal will an opposite direction (side) nystagmus, warm water in ear will produce a same direction (side) nystagmus, brain dead = all nystagmus absent, coma = saccade absent, pursuit present - done with head tilted to isolate horizontal canals

342
Q

three types of hearing loss

A

conductive, sensorineural, and central auditory processing disorder

343
Q

conductive hearing loss

A

damage to external or middle ear so that sound vibrations in air are never conducted to the inner ear

344
Q

sensorineural hearing loss

A

damage to hair cells, auditory nerve, cochlear nucleus (all result in unilateral same side hearing loss)

345
Q

central processing hearing disorder

A

any damage / lesion beyond cochlear nucleus, results in bilateral hearing loss, ex: cocktail party effect - can hear fine but inferior colliculus defect can’t distinguish a sound signal from noise (with age processing problem)

346
Q

absolute audiogram

A

0-140 dB, same reference point for all frequencies, can hear 50-20,000Hz at birth, worse hearing as threshold goes up on graph

347
Q

relative audiogram

A

uses 0 reference point from absolute audiogram as normal, worse hearing as threshold goes down on graph

348
Q

human speech

A

250-4000Hz, 30-70dB

349
Q

profound hearing loss =

A

can’t hear noises below 80dB

350
Q

normal hearing =

A

able to hearing anything at or below 25dB, air thresholds < bone thresholds

351
Q

air conduction through middle ear

A

should give lower hearing thresholds than bone conduction

352
Q

audiogram symbols

A

O = right with air conduction, X = left with air conduction, < = right with bone conduction, > = left with bone conduction

353
Q

conductive hearing loss

A

audiogram shows bone threshold < air threshold

354
Q

sensorineural hearing loss

A

ex: hair cell problem, equally high air and bone thresholds, basis for RINNE test

355
Q

Rinne test

A

tells whether a person has conductive or sensorineuronal hearing loss, air conduction should be louder than bone conduction, profound hearing loss on one side may cause patient to report noise heard in other good ear giving false results

356
Q

Weber test

A

normal = sound localization to center due to equal hearing/hearing loss on both sides, no lateralizing, if unilateral sensorineuronal loss - pt will reporter louder in normal ear, if you have unilateral conductive loss - pt reports localization to effected side

357
Q

tympanometry

A

sealed ear canal, apply sound, reapply sound with varied pressure in canal, measures middle ear compliance, evaluates fluid filled middle ear, negative middle ear pressure, TM performation, ossicular chain disruption, patency of ventilation tube

358
Q

acoustic reflex test

A

apply loud sound, conduct tympanometry, hearling loss required to evoke acoustic reflex, evaluates middle ear function, inner ear/auditory nerve/brainstem function, facial nerve/trigeminal nerve function

359
Q

Rinne test

A

tuning fork to mastoid then beside ear, for air vs bone conduction, evaluates conductive hearing loss

360
Q

Weber test

A

tuning fork on center of head, determines whether sound latealizes, evaluates conductive vs sensorineural hearing loss

361
Q

behavioral test

A

booth, headphones, raise hand when noise is hear, evaluates cochlear function, auditory pathway and CNS / motor response to pathway

362
Q

otoacoustic emmission test

A

mic and speaker in ear canal, play varied clicks, messure emissions that comes off TM in response, evaluates middle ear function and cochlear outer hair cell function

363
Q

auditory brainstem response

A

EEG electrodes to scalp, earphones, varied sounds, measure amplitude and latency of waves evoked, evaluates middle ear, inner ear, auditory nerve, auditory pathway

364
Q

local nerve block

A

amide type local anesthetic, lidocaine used for circumcision, side effects - 1. neurotoxicity causing lightheadedness . tinnitus / vertigo / muscle fasciculation / convulsions / seizures and 2. cardiovascular toxicity - if injected into a vein, arrhythmia/ventricular tachycardia/cardiac arrest

365
Q

Tabes dorsalis

A

late, untreated manifestation of syphilis, light staining dorsal column and Lissauer’s tract, demyelination in dorsal column/dorsal roots/dorsal ganglia, loss of discriminitive touch/proprioception/vibration = dorsal column loss, areflexia = dorsal root loss, ataxia, difficulty walking, positive Romberg

366
Q

neurosyphilis

A

Argyll Robertson pupils, fail to constrict to light but do constrict for convergence

367
Q

2SQ - epithelial lining of 2nd pharyngeal pounch forms

A

mesenchyme of the palatine tonsils and tonislar fossa

368
Q

2SQ - brain is not like a computer

A

no set memory capacity, doesn’t perform binary computations, modulations perception instead of passively processing input

369
Q

2SQ - retinitis in case of HIV

A

mostly likely caused by cytomegalovirus CMV, which is a herpesvirus

370
Q

2SQ - trachoma

A

caused by serovars A, B, and C of chlamydia trachomatis, causing conjunctival and corneal infection that is spread in developing countries by eye seeking flies, starts with lymphoid follicles, then necrosis, granulation tissue, scar formation causes lacrimal duct obstruction and eyelid distortion , can also be transmitted to neonates during birth and in sexually active young adults

371
Q

2SQ - drug of choice for otitis media inchildren

A

amoxicillin, if not successful switch to 2nd gen cephalosporin like cefaclor, need to tx for strep p (gram + diplococci) and H inf (gram - rod)

372
Q

testing sensory divisions of CN V - trigeminal

A

light touch and sharp to three division of the trigeminal - ophthalmic, maxillary, mandibular

373
Q

ascending somatosensory branches that can be tested

A

spinothalamic tract and dorsal column medial leminiscus

374
Q

spinothalamic tract

A

somatosensory, pain and temp, part of anteriolateral system, 1st order synapses with 2nd order within a few segments of entering dorsal horn then crosses over in the ventral white commissure to the anteriolateral spinal cord, 2nd order synapse with 3rd order in the venteral posterior lateral thalamus - 3rd order axons go to postcentral gyrus

375
Q

dorsal column medial leminsicus

A

somatosensory, proiocpetion and discrinimatory sensation, part of the dorsal column, 1st order enter spinal cord and ascend ipsilateral in dorsal column to the 2nd order in medulla, 2nd order cross over in medial lemniscus to ventral posterior lateral thalamus, 3rd order to postcentral gyrus

376
Q

trigeminal system - descending tract

A

somatosensory for the face, 1st order descending tract of trigeminal nerve (pain and temp) from midpons to upper cervical spinal cord, 2nd order in nucleus of trigeminal nerve cross over and ascend to the ventral posterior medial thalamus (trigeminothalamic tract), 3rd to the postcentral gyrus

377
Q

levels of somatosensory crossing

A

spinothalamic - within 2 segment of entering spinal cord, dorsal column medial lemniscus - medulla

378
Q

location of the somatosensory tracts

A

spinothalamic - ventrolateral in spinal cord, dorsal column medial lemniscus - dorsal and medial; rostral pons - the two tracts are close together

379
Q

descending trigeminal crossing over

A

1st order descends ipsilateral, 2nd order ascend contralateral and cross at lower medulla / upper spinal cord level

380
Q

sensory dissociation

A

one somato sensory system affected when the other is not, pain/temp vs prioprioception/vibration/touch

381
Q

crossed sensory findings

A

brainstem lesions - can have one side of face and opposite side of body affected, spinal cord lesion - dorsal column findings on one side and spinothalamic findings on the opposite side

382
Q

testing spinothalamic tract

A

pain and temp

383
Q

testing dorsal column medial lemniscus tract

A

vibration, position sense, tactile discrimination - direction / 2 point / graphesthesia / stereognosis / double stimulation

384
Q

somatosensory test traps

A

light touch is in both spinothalamic and dorsal column systems - not specific, subjective responses

385
Q

somatosensory test pearls

A

sensory level determines spinal cord problem, sharp sensation used to determine level, usually defect 1-2 segments below lesion, spinal nerve lesion - dermatome, pheripheral nerve - in its distribution, polyneuropathy - stocking and gloves distribution (longest and first to be affected)

386
Q

testing CN III, IV, VI

A

look for conjugate gaze in reflected light, look for ptosis, H test - eyes together and separately

387
Q

malignant otitis externa

A

uncommon, caused by Pseudomonas, elderly diabetics and immunocompromised

388
Q

conductive hearing loss

A

Weber test lateralizes toward it, Rinne test shows bone conduction > air conduction

389
Q

Meniere disease

A

inner ear, increased endolymph, fluctuating hearing loss, episodic vertigo, tinnitus, aural fullness, 40-50s, salt/caffeine/nicotine restriction and diuretics

390
Q

lower medulla

A

lateral vestibular nucleus (checkerboard pattern), part of vestibulospinal reflex

391
Q

afferent pupillar defect (marcus gunn pupil)

A

may indicate optic nerve disease, but is associated with abnormal pupil reaction to direct light stimulation

392
Q

superior oblique

A

depresses and intorts the eye

Neuro Big Ideas (3 decks)

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