Week 3 - Neuro Big Ideas Flashcards
(392 cards)
1
Q
superior rectus
A
moves eye upward, anular ring to superior anterior eye, elevates the eye
2
Q
lateral rectus
A
moves eye laterally, abducts eye, anular ring to anterior lateral eye
3
Q
inferior oblique
A
moves eye up and laterally, medial orbit (maxilla) to inferior posterolateral eye, elevates eye, extorts the eye
4
Q
inferior rectus
A
moves eye downward, anular ring to anterior inferior eye, depresses the eye
5
Q
medial rectus
A
moves eye medially, adducts eye, anular ring to anterior medial eye
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
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
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
9
Q
adduction
A
movement in horizontal plane, movement toward midline
10
Q
abduction
A
movement in horizontal plane, movement away from midline
11
Q
elevation
A
movement in vertical plane, movement upward
12
Q
depression
A
movement in vertical plane, movement downward
13
Q
conjugate eye movements
A
symmetrical, yoking of muscle pairs by reciprocal excitatory and inhibitory stimulation
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
15
Q
intorsion
A
movement of eyes clockwise
16
Q
extorsion
A
movement of eyes counterclockwise
17
Q
convergence
A
both corneas adducted toward the midline
18
Q
divergence
A
eyes return to primary frontal position from convergence
19
Q
when eye is abducted
A
superior rectus elevates, inferior rectus depresses
20
Q
when eye is adducted
A
inferior oblique elevates, superior oblique depresses
21
Q
abducens nerve CN VI
A
supplies lateral rectus that abducts the eye, passes through superior orbital fissure
22
Q
trochlear nerve CN IV
A
supplies superior oblique that depresses eye laterally, passes through superior orbital fissure, passes superior to tendinous ring
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
24
Q
pass superior to common tendinous ring
A
lacrimal nerve, trochlear nerve, frontal nerve
25
pass through common tendinous ring
optic nerve, oculomotor nerve, nasociliary nerve, abducences nerve
26
levator pelpebrae muscle
elevates eyelid involuntaryily, voluntarily, in concert with superior rectus, supplied by generval visceral efferent fibers from CN III and sypmathetic fibers
27
inferior branch oculomotor nerve
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)
28
superior branch oculomotor nerve
goes medially in the orbit, contains oculomotor nerve motor fibers to superior rectus and levator palpebrae superior
29
oculomotor nerve motor nucleus
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
30
oculomotor nerve parasympathetic preganlionic nucleus
Edinger-Westphal nucleus in the midbrain, part of inferior division to ciliary muscles and pupillae constrictor muscles via ciliary ganglion and short ciliary nerves
31
trochlear nerve motor nucleus
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
32
abducens nerve motor nucleus
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
33
aneurysms
compress adjacent nerves with deficit in eye movements
34
location of oculomotor nerve in relation to cerebral arteries
between posterior cerebral and superior cerebellar
35
location of abducens nerve in relation to cerebral arteries
surrounded by the labynthine (internal acoustic) and anterior inferior cerebellar arteries
36
eye movements
mostly reflexive - controlled by involuntary systems
37
slow eye movements
smooth pursuit
38
fast / jerky eye movements
saccadic movements
39
conjugate eye movement
eyes moving together
40
vergent eye movement
eyes moving in opposite directions
41
ocular gaze systems
part of a sensory system in which where eyes are pointing in space matters
42
saccadic movements
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)
43
smooth pursuit
ocular gaze systems, keep am moving image on centered fovea, tracking, keeps eye on the ball
44
vestibulo-ocular gaze
ocular gaze system, keeps image steady on fovea during head movement
45
vergence
ocular gaze system, keeps image on fovea when object moves nearer or farther away
46
medial longitudinal fasciculus MLF
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
47
saccadic gaze system
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
48
smooth pursuit system
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
49
vestibulo-ocular reflex
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
50
convergence
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
51
divergence
voluntary abduction of converged eyes back to primary position
52
sphincter pupillae
immediately around pupil, smooth muscle, constricts pupils, derived from neuroectoderm of optic cup, parasympathetic control
53
dilator pupillae
broader and radial outer iris, smooth muscle, dilate pupils, derived from neuroectoderm of optic cup, sympathetic control
54
parasympathetic control of pupils
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
55
parasympathetic control of pupils
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)
56
accommodation
pupillary constriction, ciliary muscle contraction, convergence of eyes (medial rectus muscles - all involves CN III
57
sympathetic control of pupils
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
58
pupilary light reflex
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
59
unilateral lesion of oculomotor nerve
compressed oculomotor nerve by posterior communicating artery aneurysm, prevents signal from reaching sphincter pupillae
60
right lesion on oculomotor nerve
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
61
left lesion on oculomotor nerve
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
62
case - double vision when checking left blind spot, left eye fully abducts
left eye abduction and left abducens must be fine, that leaves right medial rectus lesion and oculomotor nerve
63
case - difficulty seeing in dim light, no sweating on right side, right droopy eyelid
Horner syndrome, sympathetic nerve deficit, affected postganglionic cell bodies are in superior cervical ganglion
64
case - double vision following stroke when head is turned left, right is abducted at rest but can follow your finger
lesions on right medial longitudinal fasciculus
65
case - left nystagmus, staggers to right when walking
lesion is in right vestibulocochlear nerve because nystagmus is to the left
66
case - double vision when reading, head tilted to the right, left eye deviates upward when looking medially
lesion on trochlear nerve, which exits brain on dorsal midbrain
67
visual pathways
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
68
two focusing surfaces of eye
cornea (3/4 of focusing) and lens (1/4 of focusing, upside down image on retina
69
emmetropia
image naturally focuses on retina, good vision without correction
70
myopia
nearsighted, image focuses in front of retina, longer eye, steeper cornea - corrected with concave lens pushes image back
71
hyperopia
farsighted, image focuses behind retina, shorter eye, flatter cornea - convex lens brings image forward
72
presbyopia
loss of focusing power with age, 40+
73
astigmatism
distorted cornea, images focuses on several spots on retina, blurred image
74
power of eye
diopters, 1 diopter will focus an object at one meter, eye = 60 diopters (cornea ~ 45 diopters, lens ~ 15 diopters)
75
lens power
inversely related to focal point, two diopter lens focuses at 0.5 meters, 3 diopter lens focuses at 1/3 meter
76
eye prescriptions
+ = farsighted; - = nearsighted, ex: -4.0 diopter = near sighted, focus point 1/4 meter away (25 cm)
77
laser vision correction
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
78
intraocular lens replacement
for cataracts
79
optical Hx
age, onset, pain, vision loss, medications, systemic illness, fevers, rashes
80
vision check
eye individually, with glasses, distance and near, equal or unequal vision, intensity with penlight or red color, 20/20?
81
20/20
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
82
pupil check
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
83
PERL
pupils are equal and reactive to light
84
RAPD - relative afferent pupil defect
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
85
things that may cause relative afferent pupil defect / marcus gunn pupil
optic neuritis (inflammed optic nerve), ischemic optic neuropathy, retinal detachment, asymmetric glaucoma
86
things not associated with relative afferent pupil defect / marcus gunn pupil
amblyopia (lazy eye), cataracts, vitreous hemorrhage
87
aniscocoria (unequal sized pupils)
mydriatic (dilated) = parasympathetic problem, miotic (constricted) = sympathetic problem
88
mydriatic pupil
dilated, parasympathetic problem
89
miotic pupil
constricted, sympathetic problem
90
pupillary light reflex
parasympathetic, optic nerve (afferent) -> midbrain -> oculomotor nerve -> pupil constrictor (efferent)
91
sympathetic pupil control
brainstem -> cervical ganglion synapses -> iris
92
pupil constriction
basic reflex, light directly affects pupil size
93
pupil dilation
non-light stimulus, mood, concentration, flight / fight, dopamine / serotonin
94
blinking
protective, striated muscle with ACh on nicotinic receptors and smooth with NE on alpha1 receptors
95
tears
protective, spontaneous (basal), reflexively, emotional, parasympathetic ACh on muscarinic receptors
96
epiphora
overflow of tears, due to overproduction or blocked drainage
97
cornea
greater refractive power
98
lens
less refractive power, but adjusted to accomodate near vision
99
pupillary light reflex
regulates light intensity, miosis (constriction), parasympathetic to sphincter pupillae with muscarinic receptors
100
mydriasis
dilated pupils, sympathetic via alpha1 receptors activates dilator pupillae
101
miosis
constricted pupils
102
increased intraocular pressure
loss of vision
103
cones
photopic vision - blue (short), green (medium), red (long), temporal and spatial resolution, discrimination of surfaces and movement in bright light
104
visual acuity
ability to discriminate detail, types - spatial, temporal, spectral, primarily cone system
105
phototransduction
4 steps that use 2nd messenger cascade to amplify signal
106
phototransduction in rods
activation of rhodopsin -> closure of cyclic nucleotide gated Na+ channel -> hyperpolerizes photoreceptor
107
visual cycle
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
108
muscles of blinking
orbicularis oculi, levator palpebrae superioris, superior tarsal muscle
109
orbicularis oculi
striated, ACh on nicotinic receptors, eyelid position
110
levator palpebrae superioris
striated, ACh on nicotinic receptors, eyelid position
111
superior tarsal muscle
smooth, sympathetic on alpha1 receptors
112
maintaining ocular opening
tonic activation of levator palpebrae superioris and superior tarsal muscle, inactivation of orbicularis oculi
113
gentle opening/closing, adjusts to moving eye
activation / inactivation of levator palpebrae superioris, inactivation of orbicularis oculi
114
blinking with firm closure
activation of orbicularis oculi, inactivation of levator palpebrae superioris
115
functions of blinking
corneal lubrication, eye protection, visual information processing (temporal information processing)
116
spontaneous blinking
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
117
blink reflex
touch cornea to afferents to trigeminal nerve - or - bright light / rapid moving object to afferents to optic nerve; faster than spontaneous blinking
118
3 layers of tear film
1. lipid from eyelid oil gland (blockage = sty), 2. aqueous lacrimal gland solution with lysozyme, 3. mucous from conjunctiva
119
composition of tears
varies with age and stimulus, emotional = more hormones (prolactin, ACTH, enkephalin), basal tears decrease with age (dry eye)
120
tear flow
evaporation, drainage through nasolacrimal duct into nasal cavity
121
epiphora
overflow of tears, parasympathetic, increased tears from lacrimal gland and decreased outflow due to closure of lacrimal duct
122
induces epiphora
1. corneal stimulation of CN V -> reflex tears, 2. emotional, parasympathetic, mediated by limbic system and hypothalamus, psychic tears, red face, convulsive breathing
123
image on retina
inverted and reversed by eye, brain considers normal and learned to interpret
124
refraction
focuses light, greatest at air/tissue junction (cornea)
125
diopter
= 1 / focal length, cornea +44D, lens +15-29D, +59-75D total
126
accomodation
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
127
distance curve of lens
sympathetic action at beta2 receptors, flat lens, relaxes ciliary muscles, tight zonule fibers
128
near curve of lens
parasympathetic action on muscarinic receptors, constricted ciliary muscles, relaxed zonule fibers, rounder lens
129
Tx of system deficit
treat system deficit, do not treat by affecting opposite system with antagonist
130
production of aqueous humor
1. sympathetic -> cAMP -> stimulation of beta2 receptor increases and alpha2 decreases, 2. carbonic anhydrase forms bicarbonate (HCO3-) increasing Cl- secretion which increases water secretion
131
elimination of aqueous humor
1. parasympathetic constriction of sphincter pupillae increases outflow, 2. uveal scleral flow - reabsorbed by relaxed ciliary muscle (increased by prostaglandins)
132
flow of aqueous humor
ciliary epithelium -> over lens -> through pupil -> canal of schlemm and ciliary muscle
133
aqueous humor
~125mL
134
intraocular pressure
20mmHg
135
transduction
conversion of energy into electrical graded potential
136
special sense
graded potential in receptor cell passes causes action potential in another cell (excludes smell)
137
photoreceptors
rods / cones, receptor cell graded potential, NT synapse with bipolar cells
138
bipolar cells
NT synapse with ganglion cells with action potential
139
horizontal cells
lateral inhibition at photoreceptor / bipolar cell synapse
140
amacrine cells
lateral inhibition at synapse of bipolar and ganglion cells
141
visible light
electromagnetic, frequency (wavelength) and intensity (brightness), perceived light is reflected off objects to the eye
142
each photoreceptor
encodes intensity of one wavelength at one point in space
143
photopigements
determine wavelength seen
144
range of wavelength overlap (black/white, red, green)
ensures that will not be missed if certain rods / cones missing
145
upper wavelength of green and red
does not overlap with black/white, used to preserve night vision with red light and a few activated cones
146
optic disc
no rods / cones
147
fovea centralis
peak cones, decreasing to periphery
148
periphery rods
peak immediately beyond fovea cone peak, decrease peripherally, but more in periphery than cones
149
rods
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)
150
cones
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
151
spatial acuity
2 point discrimination, function of location on retina (fovea vs periphery) and brightness (brighter = more cones), test with Snellen Eye Chart
152
temporal acuity
distinguish two visual stimuli over time, "blinking"
153
critical fusion frequency
point at which flashing light is perceived at continuous, old movies called "flicks" did not reach this point
154
spectral acuity
distinguish between different wavelengths of light
155
phototransduction steps
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
156
photoreceptor - receptor potential
hyperpolerization from -40mV down to -80mV due to closing of Na+ channels and continued outflow of K+, happens in rods
157
dark accommodation
pumping of more 11-cis-retinal into rods in low light, makes rods more sensitive
158
other functions of retinal pigment epithelium
regeneration of rods / cones, forms blood-retina barrier
159
steps of visual cycle (mostly for rods, cones less RPE depedent)
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
parasympathetic
preganglionic - ACh to nicotinic receptors, postganglionic - ACh to muscarinic receptors
161
sympathetic
preganglionic - ACh to nicotinic receptors, postganglionic - NE to alpha1 receptors
162
actions of sympathetic NS
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
actions of parasympathetic NS
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
inner ear receptors
two types, both convert mechanical energy into receptor potential
165
Type I inner hair cells
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
Type II outer hair cells
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
Type I inner hair cell innervation
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
Type II outer hair cell innervation
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
inner ear transduction is directional
displacement toward tallest stereocilia depolarizes (when basilar membrane moves toward scala vestibuli), negative deflection (basal membrane toward scala tympani) causes hyperpolarization
170
negative displacement
tallest to shortest, basal membrane upward, relaxing tip link closes channel -> hyperpolarization, happens at trough in sin wave of sound
171
positive displacement
shortest to tallest, basal membrane downward, stretching tip link opens channel -> depolarization because K+ enters, happens at crest in sin wave of sound
172
adaptation to prolonged stimuli in hearing
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
semicircular canals
detect head rotation / angular acceleration, six canals that work in pairs (when one is depolarized the other is hyperpolarized)
174
otolith organs (utricle and saccule)
detect gravity / linear acceleration, position relative to ground
175
vestibular system
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
semicircular canals
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
horizontal canals
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
anterior / posterior canals
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
otolith organ
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
utricle otolith organ
tallest stereocilia toward striola line
181
saccule otolith organ
tallest stereocilia away from striola line
182
sound transduction
encodes
183
sound stimulus
sin wave (pure tone), has two parts: 1. frequency (pitch) dependent on wavelength, 2. intensity (loudness) dependent on amplitude
184
sound intensity
loudness, depends on wave amplitude, measured in decibels (dB)
185
formula for decibels
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
complex sound
ear takes complex sounds and breaks it into component parts (frequencies) - deconstructs sound (noise contains all frequencies)
187
linear system
same frequency goes in and same frequency comes out - no the ear - the cochlea is nonlinear
188
non-linear system
energy is added into the process, cochlea
189
middle ear function
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
aucoustic impedance matching
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
conductive hearing loss
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
acoustic impedance
can't get perfect match at all frequencies, middle ear is better / worse at minimizing loss of different frequencies, depends on resonance
193
resonance
two properties - 1. mass (heavy things resonate at low frequencies), 2. stiffness (elasticity, increased stiffness gives resonance at higher frequency)
194
affects resonance in the ear
1. mass of ossicles, 2. size of middle ear space determines stiffness - there are conditions that affect one or the other
195
otosclerosis
bone builds up on the stapes, mass is increased and high frequency resonance decreases
196
otitis media
middle ear infection, increases stiffness first losing low frequency, then increased mass around ear bones decreases high frequency
197
absolute audiograms
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
audiogram relative to normal (clinically used)
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
normal range of speech
250-4kHz, 40-60 dB
200
middle ear function
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
sound in cochlea
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
basilar membrane
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
air vs bone
in normal hearing air conduction should be greater than bone conduction due to amplification that occurs in the middle ear
204
traveling wave in cochlea
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
tonotopic map in cochlea
primary afferents connect to individual points that only respond to specific frequencies, base = high frequency, apex = low frequency
206
basilar membrane response to different frequencies
combination of mass (number of cells) an stiffness, apex mass > base mass, base stiffness > apex stiffness, each point on basal membrane resonates differently
207
outer hair cell amplification
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
otoacoustic emissions
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
measuring otoacoustic emissions
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
stria vascularis
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
haircell ion concentrations
K+ 120mM, -40mV resting potential
212
K+ channel in hair cells
150mM out, 120mM in, +80mV out, -40mV in, makes K+ go into hair cell and depolarize
213
gap junction system
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
high K+ in stria vascularis
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
visual pathway
rod / cone -> bipolar cell -> ganglion cell -> optic nerve -> optic chiasm -> optic tract -> geniculate nucleus -> geniculocalcarine tract (optic radiation) -> calcarine cortex (area 17)
216
retinal quadrants
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
monocular visual fields
from within eye looking out, upper temporal field, lower temporal field, upper nasal field, lower nasal field - tested with confrontation
218
blind spot
15 degree to temporal side on horizontal meridian in visual field, correspond with location of optic nerve
219
binocular visual fields
combined monocular visual fields, binocular in middle with monocular crescents laterally, upper left, upper right, lower left, lower right
220
image on retina
is reversed and upside down
221
retinotopic organization
xxx
222
Meyer's loop
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
calcarine cortex
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
lesion in area 17
blindness in contralateral visual field
225
visual association cortex (area 18 and 19)
input from area 17, Brodman's, complex aspects of vision
226
lesion in area 18 / 19
failure to recognize something
227
most temporal vision
ends up on nasal retina in same side eye
228
medial binocular vision
ends up on temporal retina in opposite side eye
229
optic nerve
both nasal and temporal field fibers
230
left visual fields
lateral portion ends up in nasal left eye and medial portion ends up in temporal right eye - flipped upside down
231
right visual fields
lateral portion ends up in nasal right eye and medial portion ends up in temporal left eye - flipped upside down
232
optic chiasm
nasal fibers (containing what was originally in lateral temporal fields) cross
233
optic tract
fibers from left temporal eye (medial right visual field) and right nasal eye (lateral right visual field)
234
geniculate nucleus
fibers from left temporal eye (medial right visual field) and right nasal eye (lateral right visual field)
235
geniculocalcarine tract (optic radiation)
fibers from left temporal eye (medial right visual field) and right nasal eye (lateral right visual field)
236
geniculate nucleus organization
upper visual field is lateral and upper visual field if medial, with large central portion for fovea centralis
237
calcarine cortex (area 17) organization
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
calcarine cortex
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
pupillary light reflex (miosis)
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
afferent lesion of pupillary light reflex
in optic nerve, effected side has consensual reflex but not direct reflex
241
efferent lesion of pupillary light reflex
in CN III, affected side has neither direct or consensual reflex
242
accommodation (near) reflex
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
afferent limb of accommodation reflex
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
efferent limb of accommodation reflex
GSE and GVE in CN III
245
correct use of ophthalmoscope
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
visual exam
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
oropharyngeal exam
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
auditory pathway - basic audition / afferent system
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
auditory - efferent system
hair cells -> spiral ganglion / auditory nerve -> cochlear nuclei (brainstem) -> trapezoid body -> superior olivary complex -> auditory nerve -> hair cells (motor part)
250
auditory reflex pathway - efferent system
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
acoustic pathway cells
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
acoustic pathway
starts with sensation at hair cells, ends with perception at cortex
253
ipsilateral/unilateral hearing loss
single lesion in periphery, including hair cells, cochlea, auditory nerve, cochlear nulceus
254
bilateral hearing loss
extensive bilateral connection, single lesion central after cochlear nucleus
255
noise exposure, ototoxic drugs, malformations - bilateral hearing loss
considered multiple lesion
256
vestibular pathway
more related to motor / reflexes, has four parts
257
afferent vestibular pathway
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
efferent - vestibulospinal reflex
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
efferent - vestibulo-ocular reflex
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
efferent - vestibulocerebellar reflex
related to motor control, hair cells -> vestibular nerve / ganglion -> vestibular nuclei (inferior) -> inferior cerebellar peduncle -> vestibulo-cerebellum (flocculonodular lobe)
261
path of sound
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
acoustic neuroma
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
two sesnory nuclei of auditory / vestibular pathways
cochlear nucleus (more lateral) and vestibular nucleus (more medial) below middle cerebellar peduncle, posterior and lateral near medulla and pons boundary
264
motor nuclei of auditory / vestibular pathways
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
vestibulospinal tracts
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
mid-medulla
know because giant inferior olivary nucleus (not part of auditory pathway, but superior olivary nucleus is)
267
solitary tract and nucleus
dark small spot. lateral floor of fourth ventrical in mid-medulla
268
vestibular nucleus
immediately posterior to solitary tract of lateral edge of fourth ventricle in mid-medulla
269
medial vestibular nucleus
more medial and no dark spots, mid-medulla
270
interior vestibular nucleus
more lateral and dark spots, mid-medulla
271
median longitudinal fesiculus
median floor of fourth ventricle, dark area, mid-medulla
272
rostral medulla
smaller inferior olivary nusclei and flarring of cerebellar peduncles, widening of fourth ventricle
273
cochlear nucleus
rostral medulla, most lateral floor of fourth ventricle
274
vestibular nucleus
rostral medulla, medial to cochlear nucleus in floor of fourth ventricle
275
mid-pons
large middle cerebellar peducles and basal pons (corticospinal tracts), smaller fourth ventricle
276
superior olivary nucleus
pons, small what patch between basiliar pons and abducens nucleus
277
superior vestibular nucleus
pons, light area in most lateral corner of floor of fourth ventricle
278
facial nerve
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
abducens nucleus
pons, medial to superior vestibular in floor of fourth ventricle, facial nerve wraps around it
280
rostral pons
huge basal pons (corticospinal tracts), small superior point of fourth ventricle narrowing to aqueduct
281
median longitudinal fasiculus
small, dark spots most medial floor of fourth ventricle
282
lateral lemniscus
curved lateral anterior edge of pons touching basil pons, runs between superior olivary nucleus and interior colliculus
283
caudal midbrain
cerebral aqueduct (round) surrounded by periaqueductal grey, huge basil pons gone
284
medial longitudinal fasiculus
midbrain, small dark spots, medial and touching anterior edge of periaqueductal gray
285
decussation of superior cerebellar peduncles
midbrain, large dark circle between periaquaductal gray and cerebellar peduncles, looks like it has small holes in it
286
inferior colliculus
midbrain, dark oval lateral to periaqueductal gray
287
brachium of inferior colliculus
midbrain, dark curved edge lateral to periaquedeuctal gray and ventral to inferior colliculus, fibers going to thalamus
288
rostral midbrain
looks like a butterfly, large thalamus lateral and posterior, third ventricle in middle with a little periaqueductal gray, midbrain darker and anterior
289
medial geniculate body
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
lateral geniculate body
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
primary auditory cortex
temporal lobe, gets there by passing through medial geniculate nucleus through ventral internal capsule to temporal lobe
292
vestibular system
in cortex around area of insula
293
auditory brainstem response
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
peak I in auditory brainstem response
auditory nerve response
295
peak II in auditory brainstem reponse
output from cochlear nucleus with trapezoid body response
296
peak III in auditory brainstem response
from brachium of inferior colliculus
297
peak IV in auditory brainstem response
response of primary auditory cortex
298
peak V in auditory brainstem response
response of primary auditory cortex
299
Weber test
tests sound localization
300
sound localization
done by differences in timing and intensity between two ears, done by lateral and medial superior olive, local a sound in space
301
lateral superior olive
localizes high frequency stimuli by comparing interaural intensity differences (IID) - louder in closer ear
302
medial superior olive
localizes low frequency sound using interaural timing differences (ITD) - arrives faster in closer ear
303
vestibulospinal reflexes
cooordinate head / trunk / body position to keep head upright, evident during decerebrate rigidity (removal of descending alpha motor neuron cortex control)
304
lateral vestibulospinal tract
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
medial vestibulospinal tract
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
vestibulo-ocular reflex
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
path of vestibulo-ocular reflex
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
lesion on one side of horizontal canals pair
brain interprets as depolarization on the other side
309
nystagmus
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
vestibular function assessment
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
caloric test for vestibular function
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
three types of hearing loss
conductive, sensorineural, and central auditory processing disorder
313
conductive hearing loss
damage to external or middle ear so that sound vibrations in air are never conducted to the inner ear
314
sensorineural hearing loss
damage to hair cells, auditory nerve, cochlear nucleus (all result in unilateral same side hearing loss)
315
central processing hearing disorder
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
absolute audiogram
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
relative audiogram
uses 0 reference point from absolute audiogram as normal, worse hearing as threshold goes down on graph
318
human speech
250-4000Hz, 30-70dB
319
profound hearing loss =
can't hear noises below 80dB
320
normal hearing =
able to hearing anything at or below 25dB, air thresholds < bone thresholds
321
air conduction through middle ear
should give lower hearing thresholds than bone conduction
322
audiogram symbols
O = right with air conduction, X = left with air conduction, < = right with bone conduction, > = left with bone conduction
323
conductive hearing loss
audiogram shows bone threshold < air threshold
324
sensorineural hearing loss
ex: hair cell problem, equally high air and bone thresholds, basis for RINNE test
325
Rinne test
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
Weber test
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
tympanometry
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
acoustic reflex test
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
Rinne test
tuning fork to mastoid then beside ear, for air vs bone conduction, evaluates conductive hearing loss
330
Weber test
tuning fork on center of head, determines whether sound latealizes, evaluates conductive vs sensorineural hearing loss
331
behavioral test
booth, headphones, raise hand when noise is hear, evaluates cochlear function, auditory pathway and CNS / motor response to pathway
332
otoacoustic emmission test
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
auditory brainstem response
EEG electrodes to scalp, earphones, varied sounds, measure amplitude and latency of waves evoked, evaluates middle ear, inner ear, auditory nerve, auditory pathway
334
lateral vestibulospinal tract
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
medial vestibulospinal tract
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
vestibulo-ocular reflex
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
path of vestibulo-ocular reflex
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
lesion on one side of horizontal canals pair
brain interprets as depolarization on the other side
339
nystagmus
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
vestibular function assessment
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
caloric test for vestibular function
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
three types of hearing loss
conductive, sensorineural, and central auditory processing disorder
343
conductive hearing loss
damage to external or middle ear so that sound vibrations in air are never conducted to the inner ear
344
sensorineural hearing loss
damage to hair cells, auditory nerve, cochlear nucleus (all result in unilateral same side hearing loss)
345
central processing hearing disorder
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
absolute audiogram
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
relative audiogram
uses 0 reference point from absolute audiogram as normal, worse hearing as threshold goes down on graph
348
human speech
250-4000Hz, 30-70dB
349
profound hearing loss =
can't hear noises below 80dB
350
normal hearing =
able to hearing anything at or below 25dB, air thresholds < bone thresholds
351
air conduction through middle ear
should give lower hearing thresholds than bone conduction
352
audiogram symbols
O = right with air conduction, X = left with air conduction, < = right with bone conduction, > = left with bone conduction
353
conductive hearing loss
audiogram shows bone threshold < air threshold
354
sensorineural hearing loss
ex: hair cell problem, equally high air and bone thresholds, basis for RINNE test
355
Rinne test
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
Weber test
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
tympanometry
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
acoustic reflex test
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
Rinne test
tuning fork to mastoid then beside ear, for air vs bone conduction, evaluates conductive hearing loss
360
Weber test
tuning fork on center of head, determines whether sound latealizes, evaluates conductive vs sensorineural hearing loss
361
behavioral test
booth, headphones, raise hand when noise is hear, evaluates cochlear function, auditory pathway and CNS / motor response to pathway
362
otoacoustic emmission test
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
auditory brainstem response
EEG electrodes to scalp, earphones, varied sounds, measure amplitude and latency of waves evoked, evaluates middle ear, inner ear, auditory nerve, auditory pathway
364
local nerve block
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
Tabes dorsalis
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
neurosyphilis
Argyll Robertson pupils, fail to constrict to light but do constrict for convergence
367
2SQ - epithelial lining of 2nd pharyngeal pounch forms
mesenchyme of the palatine tonsils and tonislar fossa
368
2SQ - brain is not like a computer
no set memory capacity, doesn't perform binary computations, modulations perception instead of passively processing input
369
2SQ - retinitis in case of HIV
mostly likely caused by cytomegalovirus CMV, which is a herpesvirus
370
2SQ - trachoma
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
2SQ - drug of choice for otitis media inchildren
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
testing sensory divisions of CN V - trigeminal
light touch and sharp to three division of the trigeminal - ophthalmic, maxillary, mandibular
373
ascending somatosensory branches that can be tested
spinothalamic tract and dorsal column medial leminiscus
374
spinothalamic tract
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
dorsal column medial leminsicus
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
trigeminal system - descending tract
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
levels of somatosensory crossing
spinothalamic - within 2 segment of entering spinal cord, dorsal column medial lemniscus - medulla
378
location of the somatosensory tracts
spinothalamic - ventrolateral in spinal cord, dorsal column medial lemniscus - dorsal and medial; rostral pons - the two tracts are close together
379
descending trigeminal crossing over
1st order descends ipsilateral, 2nd order ascend contralateral and cross at lower medulla / upper spinal cord level
380
sensory dissociation
one somato sensory system affected when the other is not, pain/temp vs prioprioception/vibration/touch
381
crossed sensory findings
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
testing spinothalamic tract
pain and temp
383
testing dorsal column medial lemniscus tract
vibration, position sense, tactile discrimination - direction / 2 point / graphesthesia / stereognosis / double stimulation
384
somatosensory test traps
light touch is in both spinothalamic and dorsal column systems - not specific, subjective responses
385
somatosensory test pearls
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
testing CN III, IV, VI
look for conjugate gaze in reflected light, look for ptosis, H test - eyes together and separately
387
malignant otitis externa
uncommon, caused by Pseudomonas, elderly diabetics and immunocompromised
388
conductive hearing loss
Weber test lateralizes toward it, Rinne test shows bone conduction > air conduction
389
Meniere disease
inner ear, increased endolymph, fluctuating hearing loss, episodic vertigo, tinnitus, aural fullness, 40-50s, salt/caffeine/nicotine restriction and diuretics
390
lower medulla
lateral vestibular nucleus (checkerboard pattern), part of vestibulospinal reflex
391
afferent pupillar defect (marcus gunn pupil)
may indicate optic nerve disease, but is associated with abnormal pupil reaction to direct light stimulation
392
superior oblique
depresses and intorts the eye
