Flashcards in Test 2 Deck (298)
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1
Definition of Cognition
-act or process of knowing, including awareness and judgement
- basic mental structures that include concentration, analysis, discrimination, organization, categorization, memory skills
- These skills allow us to process information
- provide basis for appropriate interaction with our surroundings
- necessary for learning, reasoning, and problem-solving and applying adequate judgement to situations
2
Luria model of Brain-Behavior relationships
Unit 1-RAS
Unit 2- Cerebral Cortex
Unit 3- Frontal lobes
3
Unit 1
Reticular activating system
Arousal
4
Impairment of unit 1
fluctuating responsiveness
decreased vigilance
becomes exhausted by minimal activity
fatigue
5
RAS comprises much of the brainstem
medulla includes the descending RAS systems
Pons and midbrain include the ascending RAS
6
Reticular formation
-provides specific sensory input and nonspecific activating impulses from the brainstem to the cerebral cortex
- maintains muscle tone of antigravity muscles
- Assists in regulation of respiration and HR
- Modulates the sense of pain
7
Reticular formation is the gatekeeper to what?
consciousness
spark of the mind
8
Reticular formation connects with what?
major nerves in the spinal column and brain
9
What does the reticular formation sort?
100 million impulses that assault the brain each second
- deflects the trivial and allowing the vital through to alert the mind
10
Damage to the catalytic bunch of cells that make up the reticular formation results in what?
Coma-loss of consciousness
11
Unit 2
cerebral cortex
information processing
12
unit 2 impairment
-initial processing of raw input in primary projection areas
- Associative processing in secondary projection zones
- integrational processing in tertiary zone
13
Unit 3
frontal lobe
executive functions
14
unit 3 impairments
deficient error detection/ correction
perseveration/ impersistence (keep coming back to same topic)
impaired sequencing
indifference
disinhibited behavior
impaired planning
15
Functions of 3 units in relation to eachother
Unit 1- provides necessary cortical tone
Unit 2- analyzes and synthesizes
Unit 3- interaction, regulation, verification
16
Basketball team metaphor for Luria's units
each player has a role and responsibility
if each player only attends to his specific function, the result is unsuccessful
effectiveness as a team only occurs if the parts work and function together
17
Association cortices divided into?
*majority of brain's surface
1) Unimodal- modality specific
2) heteromodal- higher order
18
Unimodal
formulates motor programs involving multiple joints
Somatosensory
visual
auditory
premotor
supplementary motor
19
Heteromodal
-bidirectional connections
-allows for higher order mental functions
-integration of information from various modalities
prefrontal
-Awareness of one's body and the extrapersonal space in which it moves (parietal lobe)
- Requires integrateion of vestibular, visual, and proprioceptive inputs
-parietal heteromodal association
-temporal heteromodal association
20
multimodal association cortex
lateral association cortex: posterior and anterior association cortices
Basomedial (limbic) association cortex
21
Lateral association cortex: posterior association areas
Spatial cognition
facial recognition
22
LAC: PAA- Spatial cognition
wide variety of behaviors mediating attention to intrapersonal and extrapersonal space
Unilateral hemispatial neglect most prominent deficit with damage
23
LAC:PAA- facial recognition
mediated by temporal association areas
damage can result in prosopagnosia
24
Lateral Association cortex: anterior association ares
-neural substrates for planning, foresight, insight, empathy, altruism, abstract reasoning, self-awareness, governing of emotion
- prefrontal cortex- dorsolateral prefrontal cortex, orbital frontal cortex
25
Executive function
-Called contingency planning
-nonsocial behaviors are mediated by the anterior association cortex
- social behaviors are mediated by limbic association cortex
- capacity to generate behaviors that are appropriate to the circumstances for which they unfold
26
Basomedial (limbic) association cortex
-includes anterior cingulate cortex (ACC)
-involved with emotional processing and performance evaluation and optimization
- roles in focused problem solving, error recognition, and anticipation
27
Assessing cognition: patient interview
alert and oriented x3 (person, place, time)
what is your name
where are you right now
what day is it
what time of day is it
28
Assessing cognition: ability to follow directions
please stand up for me
walk to the door and back
walk to the stairs and climb them (2 step commands)
pick up the towel from the table, fold it, and place it on the shelf (3 step commands)
29
Wernicke's Area
Responsible for language processing that enables series of sounds to bed comprehended as words
- located in posterior 2/3 of superior temporal gyrus
30
Wernicke's area has connections to what 2 lobes?
parietal
temporal
- function with wernicke's to assist with language comprehension
31
Broca's area
motor program that activates sequences of sounds to produce words and sentences formulated here
32
What area and what lobe does Broca's area communicate with?
Wernicke's area
frontal lobe
33
what regions of frontal lobe does Broca's area communicate with?
prefrontal cortex
premotor cortex
supplementary motor area
- function with Broca to formulate higher order motor aspects of speech
- correct syntax
34
Listening and replying to speech order of areas (6)
1) Primary auditory cortex
2) secondary auditory cortex
3) wernicke's area
4) subcortical connections
5) broca's area
6) oral and throat region of sensorimotor cortex
35
listening and replying to speech order of actions
1) auditory discrimination
2) classification of sounds (language vs. noise)
3) auditory comprehension, vocabulary
4) Link Wernicke's and Broca's areas
5) Instructions for language output
6) Cortical output to speech muscles
36
Language disorders
aphasia
dysarthria
dysphagia
echolalia
37
Aphasia
acquired impairment of the ability to communicate through speech, writing, or gestures
38
Aphasia examples
broca's
wernicke's
global
39
Broca's aphasia
- caused by lesions to Broca's area and adjacent structures
- Commonly left MCA
40
Symptoms Broca's aphasia
decreased fluency of spontaneous speech (extreme difficulty naming items)
phrase length <5 words
# content words exceeds # function words
prosody (rhythm, stress, intonation) lacking in speech production
comprehension intact
41
Wernicke's aphasia
lesions to wernicke's area and adjacent structures
commonly infarct to left MCA
42
Symptoms Wernicke's aphasia
markedly impaired comprehension
patients do not respond appropriately to questions
Can not follow most commands
Spontaneous speech has normal fluency, prosody, and grammatical structure
Speech is empty, meaningless, and full of nonsensical errors (inappropriate substitutions)
- saying ink instead of pen, or bus instead of taxi
- saying pish instead of fish, or rot instead of rock
43
Symptoms of global aphasia
impaired fluency
impaired comprehension
impaired repetition
44
Conduction aphasia pathology
infarct/ lesion in the peri-Sylvian area that interrupts the arcuate fasciculus
45
Conduction aphasia symptoms
normal fluency
normal comprehension
naming impaired
impaired repetition
46
Transcortical aphasia pathology
- motor, sensory, or mixed
- watershed infarct
- Broca's, Wernicke's, arcuate fasciculus spared
- Damage to frontal lobe and temporoparietal cortices responsible for language
47
Transcortical aphasia symptoms
resembles Broca's, Wernicke's, or global
repetition spared
48
Transcortical motor aphasia symptoms
impaired fluency
normal comprehension
spared repetition
49
transcortical sensory aphasia symptoms
normal fluency
impaired comprehension
intact repetition
50
Transcortical mixed aphasia symptoms
impaired fluency
impaired comprehension
intact repetition
51
Anomic aphasia symptoms
some naming difficulties
52
Dysphagia
impaired ability to swallow
usually brainstem involvement
53
dysarthria
impairment in the oral production of speech due to CNS or PNS lesion causing weakness, paralysis, or incoordination of the speech musculature
54
Echolalia
automatic repetition of sounds, words, phrases, or sentences that have just been heard.
- early sign of autism
55
limbic means what in latin?
border or edge
56
Limbic cortex forms what?
A ring like limbic lobe around the mantle of the cortex (corpus callosum and upper brainstem- diencephalic junction)
57
H-O-M-E of limbic system
Homeostasis
Olfaction
Memory
Emotion
58
Olfactory cortex
smell
59
Hippocampal formation
Memory
60
Amygdala
emotions and drives
61
Hypothalamus
Homeostasis
62
Olfaction
smell contributes to sensation of odors as well as taste
63
pathway of olfaction (7)
Olfactory receptor neurons
olfactory nerves
olfactory bulb
mitral cells/tufted cells
olfactory tract
olfactory cortex
anterior olfactory nucleus
64
why is the primary olfactory cortex unique?
does not receive input from intervening thalamic relay
65
Prefrontal cortex and memory
memory involving the sequence of events but not the events themselves
66
amygdala and memory
encodes emotional aspects of memories
67
medial temporal lobe and memory
encodes and transfers new explicit memories to long term memory
68
hippocampus and memory
encodes and transfers new explicit memories to long term memory
69
cerebellum and memory
memories involving movement
70
hippocampus
formed by infolding of temporal lobe into lateral ventricle
71
what is hippocampus greek for?
seahorse
72
papez circuit
1)fibers from hippocampal formation
2) enter fornix
3) fibers travel through Fornix and synapse at mammillary bodies
-->mammillothalamic tract
4) fibers course from mammillary bodies to thalamus
5) anterior thalamic nuclei
--> thalamocingular tract
--> internal capsule
6) Cingulate gyrus
--> cingulohippocampal fibers
7) Hippocampus
73
papez circuit establishes what?
a connection between information stored in the unconscious and conscious behavior
74
3 types of memory
1) declarative (facts, events, concepts, locations)
2) procedural/ nondeclarative (how to)
3) Emotional (feelings)
75
Memories are NOT what?
passive or literal recordings of reality
- our memories lose accuracy over time
76
Declarative Memory
conscious memory
explicit memory
cognitive memory
3 stages: immediate, short term, long term
77
3 stages of declarative memory
1) immediate (sensory register)- lasts 1-2 sec
2) short term- brief storage, events that occurred loss of information in 1 min unless continuously rehearsed
3) long term- relatively permanent storage, short term memories consolidated
78
Converting memory from short term to long term
continues to be studied
Arousal and alertness play a role in this conversion
combine with motor to aid conversion
79
Nondeclarative memory
procedural memory
implicit memory
recall of skills and habits
nonconscious memory
- produces changes in performance without conscious awareness
- practice required to store procedural memory
--> once skill learned, less attention required to perform task
80
3 stages to learn motor skill
cognitive
associative
autonomous
81
cognitive step to motor skill
beginner trying to understand task and find out what works
verbally guide movement
82
associative step to motor skill
refining movements selected as most effective
less variation and less dependent on cognition
83
autonomous step to motor skill
movements automatic
multitasking
84
Bicycle riding
declarative memory used for describing terrain, companions on ride, weather
Procedural memory used to help keep rider on bike without falling
85
Henry Molaisan background
history epileptic seizures
surgical procedure to remove bilateral medial temporal lobes to include hippocampal formation
86
H.M surgery
effective in reducing seizures
unintended side effects:
- he could remember explicit memories acquired before surgery
- He could not form new explicit memories
- He could recognize a picture of himself from before his surgery but not from after and doesn't recognize himself in the mirror
87
H.M disorder
severe explicit/declarative memory disorder
- almost normal on procedural or implicit memory tasks including priming, classical conditioning, and learning motor skills
- when given the same logical puzzle to solve for several days in a row, he was able to solve the puzzle more quickly each day
- Shows explicit memory depends on the temporal lobes and implicit does not
88
H.M summary
personality and IQ tests were normal
retained ability to learn tasks that did not require conscious recall
had declarative memory loss- Amnesia
Non declarative intact
89
Amnesia
loss of declarative memory
2 types
90
retrograde amnesia
inability to recall information stored prior to insult
91
anterograde amnesia
inability to store new information after an insult
92
damage to the hippocampus
would result in the inability to form new explicit memories but the ability to remember the skills of implicit memories
93
Amygdala
nuclear complex
means almond in greek
3 main nuclei:
1) corticomedial (cortical)
2) basolateral
3) central
94
function of amygdala
emotions and drives
involved in all 4 limbic lobes
95
corticomedial nuclei of amygdala
olfactory function
96
basolateral nuclei of amygdala
attach emotional significance to stimuli
97
central nuclei of amygdala
mediates emotional responses
98
amygdala and emotions
reciprocal connections between amygdala and hypothalamus/ brain stem centers mediate control of HR, peristalsis, sweating, among other changes seen with strong emotions
99
amygdala attaches emotional significance to what?
memories
100
afferent
sensory neurons
101
efferent
motor neurons
102
somatotopic
organization of areas within the CNS
103
somatosensory peripheral neurons
cells bodies of most peripheral sensory neurons lie outside spinal cord in dorsal root ganglia or outside of the brain in cranial nerve ganglia
104
peripheral sensory neurons have 2 axons
- distal axons conduct messages from receptor to cell body
- proximal axons project from cell body into spinal cord or brainstem
105
how are peripheral sensory neurons classified
according to axon diameter
- larger diameter transmit faster than smaller
106
receptive field
area of skin innervated by single afferent neuron
distally smaller and greater density
proximal larger and less density
- allows greater ability to distinguish between 2 closely applied stimuli on fingertips; not true on trunk
107
three types of skin sensation
touch
pain
temperature
108
somatic receptors
in general the type of environment energy that a specific receptor responds to is unique and unimodal; some receptors are polymodal
-primary source of information to spinal cord
- determine activity and output of the CNS
109
classification of somatic receptors
by structure
by source of stimulus
by type of stimulus energy
by rate of adaptation
110
classification of somatic receptors by structure
free and diffuse nerve endings
encapsulated receptors
111
classification of somatic receptors by the source of stimulus
exteroreceptors
interoreceptors
proprioceptors
112
classification of somatic receptors by rate of adaptation
slowly adapting
rapidly adapting
113
primary source of information to spinal cord?
somatic receptors
114
chemoreceptors
smell
taste
pH
metabolites
115
photoreceptors
visual receptors
116
thermoreceptors
temperature
117
mechanoreceptors
physical deformation (touch, pressure, stretch, vibration)
118
nociceptors
noxious- sensitive to stimuli that damage or threaten to damage tissues
Stimulation of these receptors lead to pain
119
Superficial fine touch receptors
Meissner's corpuscles (light touch/vibration)
Merkel's Disks (pressure
120
Hair follicle receptors
displacement of hair
121
subcutaneous fine touch receptors
- large receptive fields (less localization)
- Pacinian Corpuscles (touch and vibration)
- Ruffini endings (stretch of skin)
122
Free nerve endings (crude localized touch/ pressure and tickle and itch)
coarse touch
Nociceptors (respond to stimuli that threaten tissue)
Thermal receptors (respond to warmth or cold that does not threaten tissue)
123
cutaneous innervation- naturally occurring stimuli
while each receptor type responds to specific types of stimulation, naturally occurring stimuli will affect more than one receptor at any given time
124
muscle spindle
sensory organ in muscle
Proprioceptors
contains muscle fibers, sensory endings, and motor endings
sensory endings respond to changes in muscle length and velocity of length change (stretch)
Fusiform shaped (tapered both ends)
125
Muscle spindles transmit information regarding what?
muscle length
muscle tension
muscle load
126
what do muscle spindles detect?
when there is a stretch on the muscle and initiate reflex to resist that stretch
127
Muscle spindle density
the greater the density of muscle spindles in a muscle, the more precise the muscle can be
- muscle of the upper extremity digits
128
muscle spindle- intrafusal fibers
specialized fibers inside the muscle spindle
Ends connect to extrafusal fibers and are contractile
stretching muscle stretches these fibers
129
2 type of intrafusal fibers
nuclear bag fibers (clump of nuclei in central region)
nuclear chain fibers (nuclei arranged single file)
130
muscle spindle- Extrafusal fibers
ordinary skeletal fibers outside the spindle
131
muscle spindle- primary endings (annulospiral endings)
type 1A
large myelinated (fast)
wrap around central region of each intrafusal fiber
respond to the rate of muscle stretch and changes in muscle length
132
muscle spindle- secondary endings (flower spray endings)
type 2
medium-slower
end on nuclear chain fibers
respond to changes in length of the muscle no matter the rate of stretch
133
function of primary endings
discharge phasic and tonic
-phasic discharge maximal during quick stretch and fades quickly (reflex hammer)
- Tonic discharge sustained during constant stretch. rate is proportional to stretch of spindle fibers
134
secondary ending function
tonic only
135
function of muscle spindle
-muscle passively stretched- extrafusal fiber
-causes intrafusal fiber to stretch
-spindles elongated activating sensory receptors (1A) in spindle- will fire no matter the rate of stretch
136
normal muscle contraction
- alpha and gamma motor neurons active simultaneously
- gamma firing causes intrafusal fibers to contract- maintains stretch on intrafusal fiber central region
137
Golgi tendon organs
-encapsulated nerve endings woven among collagen strands of the tendon near the musculotendinous junction
- structures that relay tension in tendons
- sensitive to <1g changes tension
- info from GTO transmitted to SC by type 1B afferents
138
Golgi tendon organs function
-control speed of contraction for coordinated, fine, precise movements
- protective, protects against muscle tears and pulls
- these are activated to reduce the effects of cramping
139
Joint receptors
in CT of a joint
-Ruffini's Endings (2)
- Paciniform corpuscles (2)
- Ligament receptors (1B)
- Free nerve endings (alpha and C)
140
Joint receptors- ruffini's endings
2
signal extreme of joint range
respond more to passive stretch than active stretch
141
joint receptors- paciniform corpuscles
2
respond to movement (not when joint position is constant)
142
Joint receptors- ligament receptors
1b
similar to GTOs- signal tension
143
Joint receptors- free nerve endings
alpha and C
stimulated by inflammation
144
Conscious relay pathways to brain
touch, proprioception, pain, and temperature sensations all reach conscious awareness
145
How do conscious relay pathways reach the brain?
-via projection neurons in the white matter of the SC
-myelinated pathways provide for rapid transmission/conduction of information
146
2 conscious relay pathways to brain
dorsal column/medial lemniscus
anterolateral tracts
147
dorsal column is pathway for processing of?
- discriminative touch: localization of touch and being able to tell if touch is 1 point or 2
- Conscious proprioception: awareness of movements and relative position of body parts
148
dorsal column 1st order neurons
-sensory stimulus to sensory receptor (pacinian corpuscle-mechanoreceptors)
-stimulus travels through dorsal root ganglion of SC and continues superiorly via ipsilateral fasciculus cuneatus (UE) or fasciculus gracilis (LE)
- stimulus travels within same axon to medulla where it synapses at the nucleus cuneatus or nucleus gracilis
149
examples of sensory stimulus
vibration
proprioception
fine touch
150
dorsal column second order neurons
post synapse the fibers decussate and travel contralaterally via the medial lemniscus through the pons, midbrain, and synapse at the thalamus (VPL nucleus)
151
Dorsal column 3rd order neurons
fibers from the thalamus then travel to the appropriate location on the primary somatosensory cortex
152
anterolateral pathways
spinothalamic
spinoreticular
spinomesencephalic
153
anterolateral pathways process sensations of
pain
temperature
crude touch
154
spinothalamic
mediates discriminative aspects of pain and temperature- location and intensity of stimulus
155
spinothalamic tract- sensory receptors
free nerve endings
156
spinothalamic tract- first order neurons
enter SC and synapse immediately in grey matter of SC
157
spinothalamic tract- 2nd order neurons
cross spinal cord immediately via anterior commisure and ascend through spinothalamic tract until reaching the VPL nucleus of the thalamus
158
spinothalamic tract- 3rd order neurons
synapse with the primary somatosensory cortex in post central gyrus
159
How to test for fast pain
anterolateral tract
examiner randomly alternates stimulating the skin with the sharp or dull end of a safety pin
160
how to test for temperature
anterolateral tract
examiner places tubes with hot or cold water on the patient's skin
161
light touch test
anterolateral tract
strokes the skin of the patient with a wisp of cotton
162
point localization test
DC-ML tract
touches points on the body and patient places index finger on point stimulated
163
2pt discrimination test
DC-ML/AL
distances between 2 points stimulated on the skin are determined
164
position sense test
DC-ML
patient has eyes closed and examiner moves body segments into flexion or extension
patient identifies the position of the body part
165
kinesthesia test
DC-ML
patient has eyes closed and the examiner moves one extremity through space
patient mimics movement on contralateral side
166
graphesthesia test
DC-ML
patient has eyes closed and examiner draws a geometric symbol, number, or letter on the skin, or draws a line in a specific direction
167
stereognosis test
DC-ML
without use of vision, patient identifies objects placed in hand by manipulation
168
vibratory sense test
DC-ML
examiner places a vibrating tuning fork over a bony prominence
169
Gate control theory proposed by who
melzack and wall 1965
170
Gate control theory hypothesis
first order neurons carrying low-threshold mechanical afferents AND nociceptive high threshold converge on same second order neuron in SC
- if mechanical afferents more active, closes the gate to nociceptive input
171
counterirritant theory
inhibit nociceptive signals by stimulation of nonnociceptive receptors
-in dorsal horn
-pressure on skin stimulates mechanoreceptors (Merkel's discs)
-In theory branches from the mechanoreceptor pathway synapse with an interneuron that active to release enkephalins
172
what to enkephalins depress?
release of Substance P which inhibits the transmission of nociceptive signals
173
temperature sensation
detected by free nerve endings of small myelinated and unmyelinated neurons
-alpha fibers carry impulses for cooling
- C fibers carry information for heating
174
Functions of the eye
-regulate the amount of light reaching photosensitive surface
- focusing on near and far objects
- maintaining a stable relationship between these 2 functions
- recording the pattern of incoming light
175
Eyes and the retina
-light enters the eye --> passes through the lens --> forms image on retina that is inverted and reversed
- right visual space projects to left hemiretina and vice versa
- Central fixation point is on the fovea
176
central fixation point of the eye
on the fovea
177
Myopia
-nearsightedness
- eye is longer than normal
- light focused on eye hits in front of the retina
- corrective lenses move the light to the retina
178
Hyperopia
- farsightedness
- eye is shorter than typical
- light image focused behind the retina
- corrective lenses move the image to the retina
179
Astigmatism
see blurry and distorted images
cornea shaped more like a football than a basketball
180
retina rods and cones
deepest retinal layer
photoreceptors
181
retina bipolar cells
- intermediate retinal layer
- information integrating neurons
182
Rods and cones: scotopic-rod system
works at low levels of illumination insensitive to color, limited resolution
183
Rods and cons: photopic- cone system
works at high levels of illumination, responsible for color vision, sharp vision, and acuity
184
how many rods does each eye have?
80-110 million
185
how many cones does each eye have?
4-5 million
186
Where are cones densest?
macula lutea with its center, the fovea, being the area of keenest vision
187
Photoreceptor layer in peripheral retina
has a higher density of rods
188
photoreceptor layer in the central retina
have a high density of cones
189
fovea
small depressed region centrally located in the retina. contains only cones.
- Vision is more acute in the foveal region
190
4 major functional regions of rods and cones
1) outer segment
2) inner segment
3) nucleus
4) synaptic terminal
191
synaptic terminal of a rod
called a spherule
192
synaptic terminal of a cone
called a pedicle
193
Where does the transduction of light waves to electrochemical signals occur?
photoreceptors
194
disks in the outer segments of sensory transduction contain what?
visual pigment protein
- rods contain rhodopsin
195
how many different types of cones are there?
three with pigment sensitive to either blue, green, or red wavelengths
196
Retina- ganglion cells
superficial layer
information- integrating neurons that exit eyeball as the optic nerve
197
retinal processing involves what in regards to ganglion cells?
massive convergence onto ganglion cells
198
Optic disk and the blind spot
-circular, elevated region where ganglion cell axons gather to leave the eye as the optic nerve
- devoid of rods and cones, represents the blind spot in the visual field
199
Transmission of vision from retina to cortex
- cells in retina convert light into neural signals
- signals processed in retina and conveyed to retina output cells
- retinal output conveyed by axons that travel in optic nerve, optic chiasm, optic tract
- Axons synapse in lateral geniculate nucleus of the thalamus
- From thalamus neurons travel in the geniculocalcarine tract (optic radiations) within the internal capsule to the primary visual cortex
200
what do the cells in the retina convert?
light into neural signals
201
Where are signals processed in the retina conveyed to?
retina output cells
202
retina output is conveyed by what?
axons that travel in optic nerve, optic chiasm, optic tract
203
Where do retina axons synapse?
in lateral geniculate nucleus of thalamus
204
From the thalamus where do the retinal neurons travel?
in the geniculocalcarine tract (optic radiations) within the internal capsule to the primary visual cortex
205
What is the area of projection on the visual cortex dependent on?
origin of signal
206
Nasal retina
- closest to nose
- signals cross midline at optic chiasm projecting to contralateral visual cortex
207
Temporal retina
- closest to temporal bone
- signals continue ipsilaterally to project to the ipsilateral cortex
208
Outcome of the arrangement of projection of visual information
1) information from each visual field is projected to the contralateral cortex
2) right visual field information projects to left cortex
3) left visual field information projects to right cortex
209
Monocular Scotoma
-lesion of the retina
- location size and shape is dependent on the location and extent of the lesion
210
monocular scotoma causes
retinal infarcts
hemorrhage
degeneration
infection
211
Monocular vision loss
- If retinal lesion is severe enough, entire retina may be involved leading to total loss of vision
- Lesions of optic nerve can cause monocular vision loss
212
Causes of monocular vision loss
glaucoma
optic neuritis
elevated ICP
optic glioma
schwannoma
meningioma
trauma
213
Bitemporall hemianopia
- damage to the optic chiasm
- Visual loss more asymmetric
- Common lesions: pituitary adenoma, menigioma
214
homonymous hemianopia
-retrochiasmal lesions- lesions of optic tracts, LGN, optic radiations, or visual cortex cause homonymous hemianopia
215
Contralateral superior Quandrantanopia
- Caused by lesions of the temporal lobe leading to infarcts in the optic radiations
- pie in the sky defect
216
Contralateral inferior quadrantanopia
- lesion in the parietal lobe cause interruptions in the upper portions of the optic radiations
- pie on the floor defect
217
Cataract
-an opacity of the lens resulting in decreased acuity
-vision hazy overall, particularly in glaring light
- does not impact field of vision
- there is NO scotoma (empty, distorted, dark area)
218
Macular degeneration
- deterioration of the macula, the central area of the retina
- most prevalent eye disease
- central scotoma
- peripheral or side vision remains unaffected
219
diabetic retinopathy
- the leaking of retinal blood vessels may occur in advanced or long-term diabetes
- affects the macula or the entire retina and vitreous
- likelihood of retinopathy and cataracts, along with the consistency and level of blood glucose control
220
glaucoma
chronic elevated eye pressure causes optic nerve atrophy and loss of peripheral vision
221
retinitis pigmentosa
congenital degeneration of the pigmented layer of the retina leads to a severe loss of peripheral vision
222
pupillary size reflex
-constriction of the pupil due to parasympathetic innervation
- dilation of pupil due to sympathetic innervation
223
fixation reflex
functions to maintain the position of the eyes so that the image of the object of interest is kept on the fovea of both eyes
224
near reflex
occurs when the gaze is shifted from a distant object to a near one
225
4 aspects of an assessment of the visual system
acuity
opthalmic inspection
pupillary light reflex
assessment of visual fields
226
pupillary light reflex
- anisocoria: denotes pupillary size inequality
- Direct: response of eye stimulate with light
- Consensual: response of opposite eye
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pupillary light reflex: afferent limb
axons of the retinal ganglion cells that project to the pretectal area
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pupillary light reflex center
interneurons of the pretectal area that terminate bilaterally in the Edinger-Westphal nuclei of the oculomotor complex
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amaurosis fugax
Transient ischemic attack of the retina
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optic neuritis
- inflammatory demyelinating disorder often related to Multiple Sclerosis
- Symptoms of eye pain, decreased acuity, impaired colored vision
- Recovery is common
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Papilledema
optic disc swelling associated with elevated ICP
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Visual Field Defects:
Macular Sparing
- vascular lesions of the occipital lobe
- Both MCA and PCA nourish the cortical area representing the macula
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Visual Agnosia
Can perceive but cannot understand meaning of what they see
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Visual deficits associated with higher cortical processing
Visual agnosia
cortical blindness
prosopagnosia
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cortical blindness
bilateral lesion of specific area of visual cortex
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prosopagnosia
face blindness
damage to occipitotemporal cortex
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3 components of vestibular system
peripheral sensory
central processor
motor output
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Vestibular system function
-essential for postural control
- essential for control of eye movements
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What do sensory receptors of vestibular system respond to?
Position of head relative to gravity and to head movements
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input to the receptors of the vestibular system converted to what?
neural signals and transmitted via vestibular nerve to vestibular nuclei in the brainstem (at junction of pons and medulla)
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Projections from vestibular nuclei contribute:
- sensory information about head movement and position relative to gravity
- gaze stabilization
- postural adjustments
- autonomic function and consciousness
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Vestibular apparatus:
Vascular
labryrinthine artery
branch of AICA
no anastomotic network
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Vestibular apparatus:
Hair cells
- receptors in the membranous labyrinth
- bending of hairs determines frequency of signals to vestibular nerve
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Peripheral vestibular system
bony labryinth
membranous labyrinth
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bony labyrinth
contains labyrinth, cochlea, and vestibule
in petrous bone
contains perilymph: high in sodium, low in potassium
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membranous labyrinth
3 semicircular canals
2 otolithic organs
contains endolymph: high potassium, low sodium
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2 otholith organs
utricle
saccule
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Anterior semicircular canal
superior
45 degrees to sagittal plane
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posterior semicircular canal
inferior
45 degrees to sagittal plane
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horizontal semicircular canal
lateral
30 degrees from horizontal plane; line from tragus to eye, important for testing
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right posterior semicircular canal is in same plane as?
left anterior semicircular canal and vice versa
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AICA is separated into what 2 branches?
common cochlear artery
Anterior vestibular artery
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common cochlear artery branches into what?
cochlear branch
posterior SCC
cochlea
saccule
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anterior vestibular artery branches into what?
vestibular nerve
lateral SCC
Anterior SCC
utricle
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Semicircular canals
- 3 hollow rings arranged perpendicular to each other (anterior, posterior, horizontal)
- Each canal opens at one end to the utricle
- Each has a swelling-the ampulla
- Crista ampullaris contains supporting cells and the hair cells
- Hair cells embedded in cupula (gelatinous mass)
- receptors (hair cells) detect movement of the head by sensing motion of endolymph
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Each ampulla contains a ridge called what?
crista ampullaris
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Which canal is responsible for forward tilt?
anterior and posterior canal
"bend and snap"
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Which canal is responsible for head rotation
horizontal canal
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Why are semicircular canals arranged anatomically perpendicular?
ensures that stimulation of one set of canals does not stimulate the other sets
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Why do semicircular canals work in pairs (left and right side)?
- increased signal from left side correspond with decreased signal on right side
- reciprocal signals imperative for proper function and maintenance of balance
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semicircular canals detect angular accelerations
- endolymph fluid moves opposite direction of head movement
- deflects the cupula
- cupula bends the hair cells
- hair cells cause firing of 8th cranial nerve
- firing rate is increased for ipsilateral motion
- firing rate is decreased for contralateral motion
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Semicircular canal firing rate is increased for what motion?
ipsilateral
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semicircular canal firing rate is decreased for what motion?
contralateral
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Physiology of semicircular canals
sense movement from .5-7Hz
Respond only in first few seconds
sensory redundancy
brain ignores bilateral changes
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Saccule and Utricle
- contain hair cells
- hair cells embedded in gelatinous membrane
- membrane contains otoconia (ear rocks)
- weight of otoconia increases density
- therefore responds to gravity
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Saccule
roughly vertical
detects vertical acceleration
detects head tilt
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utricle
roughly horizontal
detects horizontal acceleration
detects head tilt
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Hair cells
-structurally polarized
--> one large kinocilium
--> 60-100 smaller stereocilia
--> adequate stimulus is bending of cilia
- bending stereocilia toward the kinocilia depolarizes the cell
- bending stereocilia away from kinocilia hyperpolarizes cells
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bending of stereocilia toward the kinocilia does what
depolarizes the cell
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bending of stereocilia away from the kinocilia does what?
hyperpolarizes the cell
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Striola
changes direction of hair cells
one part excited
one part inhibitory
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horizontally oriented utricular maculae
respond to linear acceleration in a horizontal plane.
273
saccular maculae
oriented vertically and respond to linear acceleration in a vertical plane
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Why do both otolith organs respond to head tilt?
curved shape of the striola
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vestibular nerve
sense motion 300+ degrees/ sec
regular afferents
-constant firing
276
Ewald's Law
- Rotations that excite a canal are greater than rotations that inhibit a canal
- Head velocities over 180 degrees
a. no inhibition
b. firing rate down to 0 on inhibitory side
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Superior vestibular ganglion
receives input from utricle, anterior saccule and anterior and lateral semicircular canals
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inferior vestibular ganglion
receives input from posterior saccule and posterior semicircular canal
279
Ganglia to brainstem
vestibular ganglia transmit their impulses via vestibular division of CN VII to the vestibular nuclei
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4 vestibular nuclei
lateral vestibular nucleus
medial vestibular nucleus
inferior vestibular nucleus
superior vestibular nucleus
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VOR
superior and medial VN
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VSR
primarily lateral
also medial VN
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Vestibular nuclei on each side
reciprocally interact by way of commissural fiber system
- system is inhibitory: activity in one side of the nuclear complex results in inhibition of the opposite side
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cerebellum and vestibular input
receives vestibular input
sends input to vestibular nuclei
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vestibular reflexes
vestibulocollic (neck)
vestibulospinal
vestibulo-ocular
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Vestibular spinal reflex
lateral and medial vestibular nuclei give rise to 2 UMN descending tracts
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LVST
- excitatory to ipsilateral spinal cord nuclei
- facilitates and maintains extensor tone in limbs and trunk
- receives most of input from otoliths
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MVST
- descend in the medial longitudinal fasciculus (MLF) to cervical and upper thoracic spinal cord
- stabilizes and regulates head movements for fixation of gaze
289
Vestibular motor system UMN project from where?
vestibular nuclei forming the LVST and MVST
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LVST descends:
-ipsilaterally in the anterolateral SC and terminates in the ventral gray of all levels of the spinal cord
291
MVST descends
- in the medial longitudinal fasciculus and has bilateral connections at cervical and rostral thoracic levels of the SC
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Vestibular occular reflex
- Superior and medial VN
- project to CN 3,4,6 via MLF
- Ascending tract of Dieters
- VN to ipsilateral abducens nucleus
293
Projections from superior and medial vestibular nuclei project to?
- nuclei of CN 3,4,6 to assist in regulation of extraocular eye muscle contractions
- These ascending projections travel in the MLF and project bilaterally but with laterality pattern
294
vestibulocular reflex maintains what?
the stability of the retinal image during head movement by moving the eyes in the opposite direction of head movement
295
Velocity storage
- preserved by brainstem: info from retinal slip, somatosensory, otolith, etc
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vestibular firing rate
decays 32% in 7 seconds
CNS decays in 20 seconds
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estimator
-predicts sensory input: from multiple sensory input
- Therefore only small adjustments needed
- Changes with rehab and experiance
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