Test 2 Flashcards Preview

neuroscience > Test 2 > Flashcards

Flashcards in Test 2 Deck (298)
Loading flashcards...
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

227

pupillary light reflex: afferent limb

axons of the retinal ganglion cells that project to the pretectal area

228

pupillary light reflex center

interneurons of the pretectal area that terminate bilaterally in the Edinger-Westphal nuclei of the oculomotor complex

229

amaurosis fugax

Transient ischemic attack of the retina

230

optic neuritis

- inflammatory demyelinating disorder often related to Multiple Sclerosis
- Symptoms of eye pain, decreased acuity, impaired colored vision
- Recovery is common

231

Papilledema

optic disc swelling associated with elevated ICP

232

Visual Field Defects:
Macular Sparing

- vascular lesions of the occipital lobe
- Both MCA and PCA nourish the cortical area representing the macula

233

Visual Agnosia

Can perceive but cannot understand meaning of what they see

234

Visual deficits associated with higher cortical processing

Visual agnosia
cortical blindness
prosopagnosia

235

cortical blindness

bilateral lesion of specific area of visual cortex

236

prosopagnosia

face blindness
damage to occipitotemporal cortex

237

3 components of vestibular system

peripheral sensory
central processor
motor output

238

Vestibular system function

-essential for postural control
- essential for control of eye movements

239

What do sensory receptors of vestibular system respond to?

Position of head relative to gravity and to head movements

240

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)

241

Projections from vestibular nuclei contribute:

- sensory information about head movement and position relative to gravity
- gaze stabilization
- postural adjustments
- autonomic function and consciousness

242

Vestibular apparatus:
Vascular

labryrinthine artery
branch of AICA
no anastomotic network

243

Vestibular apparatus:
Hair cells

- receptors in the membranous labyrinth
- bending of hairs determines frequency of signals to vestibular nerve

244

Peripheral vestibular system

bony labryinth
membranous labyrinth

245

bony labyrinth

contains labyrinth, cochlea, and vestibule
in petrous bone
contains perilymph: high in sodium, low in potassium

246

membranous labyrinth

3 semicircular canals
2 otolithic organs
contains endolymph: high potassium, low sodium

247

2 otholith organs

utricle
saccule

248

Anterior semicircular canal

superior
45 degrees to sagittal plane

249

posterior semicircular canal

inferior
45 degrees to sagittal plane

250

horizontal semicircular canal

lateral
30 degrees from horizontal plane; line from tragus to eye, important for testing

251

right posterior semicircular canal is in same plane as?

left anterior semicircular canal and vice versa

252

AICA is separated into what 2 branches?

common cochlear artery
Anterior vestibular artery

253

common cochlear artery branches into what?

cochlear branch
posterior SCC
cochlea
saccule

254

anterior vestibular artery branches into what?

vestibular nerve
lateral SCC
Anterior SCC
utricle

255

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

256

Each ampulla contains a ridge called what?

crista ampullaris

257

Which canal is responsible for forward tilt?

anterior and posterior canal
"bend and snap"

258

Which canal is responsible for head rotation

horizontal canal

259

Why are semicircular canals arranged anatomically perpendicular?

ensures that stimulation of one set of canals does not stimulate the other sets

260

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

261

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

262

Semicircular canal firing rate is increased for what motion?

ipsilateral

263

semicircular canal firing rate is decreased for what motion?

contralateral

264

Physiology of semicircular canals

sense movement from .5-7Hz
Respond only in first few seconds
sensory redundancy
brain ignores bilateral changes

265

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

266

Saccule

roughly vertical
detects vertical acceleration
detects head tilt

267

utricle

roughly horizontal
detects horizontal acceleration
detects head tilt

268

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

269

bending of stereocilia toward the kinocilia does what

depolarizes the cell

270

bending of stereocilia away from the kinocilia does what?

hyperpolarizes the cell

271

Striola

changes direction of hair cells
one part excited
one part inhibitory

272

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

274

Why do both otolith organs respond to head tilt?

curved shape of the striola

275

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

277

Superior vestibular ganglion

receives input from utricle, anterior saccule and anterior and lateral semicircular canals

278

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

280

4 vestibular nuclei

lateral vestibular nucleus
medial vestibular nucleus
inferior vestibular nucleus
superior vestibular nucleus

281

VOR

superior and medial VN

282

VSR

primarily lateral
also medial VN

283

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

284

cerebellum and vestibular input

receives vestibular input
sends input to vestibular nuclei

285

vestibular reflexes

vestibulocollic (neck)
vestibulospinal
vestibulo-ocular

286

Vestibular spinal reflex

lateral and medial vestibular nuclei give rise to 2 UMN descending tracts

287

LVST

- excitatory to ipsilateral spinal cord nuclei
- facilitates and maintains extensor tone in limbs and trunk
- receives most of input from otoliths

288

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

290

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

292

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

296

vestibular firing rate

decays 32% in 7 seconds
CNS decays in 20 seconds

297

estimator

-predicts sensory input: from multiple sensory input
- Therefore only small adjustments needed
- Changes with rehab and experiance

298

Context dependency

- can't transfer vestibular task
- Depend on position of head