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neuro final exam > Neuro weeks 14-15 (5-10) > Flashcards

Neuro weeks 14-15 (5-10) Flashcards

1
Q

Visual pathway ends retinotopically around the

A

calcarine sulcus of the primary visual cortex.

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2
Q

Where axons from the Superior retinal (inferior visual) field end

A

The superior aspect of calcarine sulcus

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3
Q

Where axons from the Inferior retinal (superior visual) field end.

A

cortex inferior to the calcarine sulcus

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4
Q

Foveal area is represented most

A

posterior

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5
Q

Peripheral areas are represented more.

A

Rostral

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6
Q

T / F- Some axons of the optic radiation bypass the primary visual cortex to terminate in the visual association cortex

A

True

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7
Q

The visual Cortex is arranged in .

A

functional columns

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8
Q

Principle LGN input into layer

A

IV.

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9
Q

Matrix of different overlapping columns include: BOO

A
  • Blobs
  • Ocular dominance columns
  • Orientation columns
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10
Q

Cells in Ocular dominance columns respond with preference to .

A

Right or left eye

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11
Q

Cells in Ocular dominance are the

A

Largest of column structures and are presented in the cortex with adjacent columns having alternating eye dominance

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12
Q

Orientation columns contain

A

Simple & complex cells and don’t respond to points of light but bars of light only in certain orientations with adjacent columns being related in position but different orientation

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13
Q

Types of cells in the orientation columns

A

simple and complex

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14
Q

Simple cells respond to

A

Bars of light only in a certain orientation with inhibitory surround

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15
Q

Since each LGN cell responds to a point of light with an opposing annulus, these simple cells represent a

A

Convergence of many LGN cells onto a single simple cortical cell.

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16
Q

Complex cells respond to

A

Bars of light only in a certain orientation but do not have the inhibitory surround

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17
Q

They are called complex cells because .

A

They respond with movement of the bar of light in one direction

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18
Q

Complex cells represent the

A

convergence and summation of several simple cells

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19
Q

Blob columns are located in

A

Cortical layers II & III.

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20
Q

Cortex is divided into

A

Blobs (for color processing) & interblob regions (form processing)

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21
Q

The modular organization of the visual cortex

A

2x2 mm areas of 1° visual cortex which contains a complete 360° set of orientation columns. Set of left right ocular dominance columns and a set of 16 blobs & interblob regions for color and form discrimination. Each module is interconnected with adjacent modules and there is also binocular organization

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22
Q

Binocular organization.

A

Layer IV cells of a single ocular dominance column are monocular but with the Interconnections between adjacent columns and layers produces binocular vision

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23
Q

Visual Association Cortex is in Brodmann areas

A

18 & 19

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24
Q

Visual Association Cortex is divided into

A

Pre-striate cortex (V2) and Extra-striate (V3)

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25
Q

Pre-striate cortex V2

A

Brodmannn area 18- has a complete map of the visual world with more complex orientation spatial frequency, and color characteristics than seen

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26
Q

Pre-striate cortex is the area that responds to

A

Illusory contours.

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27
Q

Type of recognition associated with Pre-striate cortex?

A

Figure ground recognition - appears to also be part of visual attentional modulation

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28
Q

Extra-striate cortex – V3 Brodmann area

A

Gives a sense of more global motion and may also be part of dorsal & ventral visual streams

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29
Q

What is Figure-Ground relationships

A

Detection of objects from their background- It also gives a form of visual illusion.

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30
Q

Illusory contours

A

Dark circles with random lines drawn on them. When arranged in a certain way, image of box is seen -same process that gives us the “ability” to see duckies in the clouds and Jesus on a burnt tortilla

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31
Q

Dorsal Stream (Where pathway)

A

Cortical pathway projecing from area 18 visual association cortex to parieto-occipital cortex (posterior parietal cortex)

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32
Q

Function of Dorsal Stream (Where pathway) - MAN

A
  • Manipulation of objects within the visual environment
  • Analyzing motion and spatial orientation within the visual field
  • Navigation around objects in the environment
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33
Q

Damage in the Dorsal stream (Where) pathway produces

A

Visual apraxia

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34
Q

Visual Apraxia signs & symptoms

A

Functional significance of objects is lost- can see and identify object but cannot use it. E,g can identify a comb by sight, but cannot use to comb hair

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35
Q

Ventral Stream (What pathway) projections

A

to occipito-temporal cortex and inferior temporal cortex

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36
Q

Function of the visual stream what pathway- IVm

A

Object Identification and further verbal manipulation.

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37
Q

Damage to ventral stream what pathway causes

A

Visual agnosia – inability to name an object even though it is seen.

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38
Q

Monocular visual loss

A

Damage to the optic nerve which causes loss of all axons from one retina (eye)

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39
Q

Contralateral homomynous hemianopsia

A

Complete lesion of optic tract fibers causes loss of half of visual field – contralateral to damage

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40
Q

Macular sparing

A

Vascular lesions of the cortex (occipital lobe) causes loss of vision because of damage to the optic cortex. However, since both MCA and PCA supply the cortical area representing the macula, macular sparing is obtained.

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41
Q

Signs of Macular Sparing- OSV

A

One of the first signs of MS is visual disturbances which include :

  • Optic neuritis
  • Scotoma and
  • Visual field defects dependent upon the nature of the optic nerve/tract demyelination.
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42
Q

Lesions of the parieto-occipital lobe (where pathway) or Balint’s syndrome produces: SOO

A
  • Simultagnosia
  • Optic ataxia
  • Ocular apraxia
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43
Q

Role of the Inferior temporal cortex in the visual stream pathway

A

Identification of complex stimuli such as faces.

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44
Q

Damage to the inferior temporal complex produces

A

Posopagnosia, the inability to identify people by their faces

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45
Q

Optic neuritis - MS

A

An Inflammatory demyelinating disorder often related to multiple sclerosis.

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46
Q

Which labyrinth preserves the basic form of the osseous labyrinth

A

The Membranous labyrinth

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47
Q

Characteristics of optic neuritis DIE

A
  • Decreased acuity
  • Impaired color vision.
  • Eye pain
  • Recovery is common
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48
Q

Papilledema

A

Optic disc swelling associated with elevated intracranial pressure

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49
Q

T / F -Damage to optic nerve/ chiasm and tract can lead to similar patterns of vision loss

A

False very different patterns

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50
Q

Monocular visual loss

A

Damage to the optic nerve causing loss of all axons from one retina (eye)

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51
Q

What is released when intracellular Ca++ increase and depolarization of hair cell occurs?

A

Glutamate to activate auditory primary afferent axons- slight K+ current all the time so regular depolarization of hair cell and low frequency firing of primary afferent neurons.

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52
Q

Contralateral homomynous hemianopsia

A

Complete lesion of optic tract fibers causing loss of half of visual field – contralateral to damage

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53
Q

Function of the Auditory system

A

To detect and analyze sounds from the environment

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54
Q

Conduction of the auditory vibrations are controlled by

A

Tensor tympani innervated by CN V which controls the movement of the tympanic membrane and the stapedius which is innervated by CN VII and controls the movement of the stapes. These two muscles reflexively contract to lessen movement & sound conduction.

55
Q

Scotoma

A

An area of partial alteration in the field of vision consisting of a partially diminished or entirely degenerated visual acuity that is surrounded by a field of normal – or relatively well-preserved – vision.

56
Q

Prodromal phase of classic migraine involves

A

Visual cortex. 1/3 of migraine sufferers experience a visual aura – described as fireworks – lights, colors, flashing. About 10% of people with migraine experience a

57
Q

Scintillating scotoma

A

A fixed or expanding spot of flickering light near or in the center of the visual field

58
Q

Simultagnosia

A

Can see only small parts of the visual field at a time – difficulty comprehending large visual areas and objects – see only the trunk of an elephant so cannot recognize the whole structure

59
Q

Optic ataxia

A

Impaired ability to point to or reach for an object

60
Q

Ocular apraxia

A

Difficulty directing gaze toward an object in peripheral field

61
Q

Cause of cortical blindness

A

Bilateral lesion of primary visual cortex.

62
Q

How are inner hair cells depolarized

A

By movement of endolymph in inner spiral sulcus which pivot their stereocilia

63
Q

Blindsight

A

Cortical blindness, but preserved ability to use some visual information Sparing of pulvinar to posterior parietal area projections

64
Q

Two main divisions of both the bony & membranous Labyrinth- VC

A

Cochlear Vestibular

65
Q

A series of bony cavities and channels within the petrous part of the temporal bone is known as

A

Osseous or bony labyrinth

66
Q

A series of fluid filled communicating ducts & sacs within the bony labyrinth secured to bony labyrinth by fibrous bands.

A

Membranous labyrinth

67
Q

What preserves the basic form of the osseous labyrinth

A

The Membranous labyrinth

68
Q

The primary afferent axons of primary afferent bipolar neurons end on the

A

dorsal & ventral cochlear nuclei. These relay nuclei are tonotopically map with high frequencies dorsal & low frequencies ventral

69
Q

Fluid that separates the osseous & membranous labyrinth- Contiguous with CSF of subarachnoid space via peri-lymphatic duct.

A

Perilymph

70
Q

Fluid within membranous labyrinth that has the same ionic composition as intracelluar fluid.

A

Endoilymph

71
Q

Axons from 3° neurons of the inferior colliculus ascend to

A

Thalamus as brachium of inf colliculus. Some of these fibers decussate and some rise ipsilaterally. Note- this is another point that contributes to the bilateral nature of the ascending auditory pathways. Tonotopic mapping continues in the inferior colliculus with high frequencies more ventral & low more dorsal

72
Q

Endoilymph is formed by

A

Specialized secretory cells of the membranous labyrinth

73
Q

The Primary Auditory cortex transverses

A

Temporal gyrus & adjacent planum temporale.

74
Q

How is endolymph removed?

A

By specialized cells of endolymphatic sac

75
Q

Larger representation of the primary auditory cortex is on which side?

A

Left than right in most individuals. It appear to parallel the distribution of the speech centers because of the strong linkage between audition and speech

76
Q

How are receptor cells of vestibular & auditory systems similar?

A

Both when activated secrete neurotransmitters to excite terminal endings of vestibulocochlear nerve (CN VIII).

77
Q

Hair cells are

A

Receptor units or first order sensory cell not a nerve cell.

78
Q

Structure of hair cells

A

Polar with a very large single kinocilium and 60-100 smaller stereocilia arranged away from the kinocilium by decreasing height. The Kinocilium degenerates during development in cochlear receptor surface but is retained in the vestibular system

79
Q

What happens when hair cells are adequately stimulated? Function

A

Stimulus causes mechanical “bending” of cilia or hairs. Although referred to as bending, pivoting better term. Actin myofilament holds cilia stiff so cilium pivots at flexible base where it connects to hair cell. The Cilia bundle is displaced as a unit- held by top links.

80
Q

Pivoting of cilia on hair cell causes

A

Depolarization of hair cell. Endolymph rich in K+ & poor in Na+ & positively charged compared to negative intra-cellular environment. Pivoting of cilia produces increased influx K+ into cell and the depolarization resulting from this influx of K+ produces cell depolarization- opens voltage-gated Ca++ channels

81
Q

What is released when intracellular Ca++ increased and depolarization of hair cell occurs?

A

Glutamate to activate auditory primary afferent axons. There are actually slight K+ current all the time so regular depolarization of hair cell and low frequency firing of primary afferent neurons. So activation of the hair cell increases the spontaneous firing of these hair cells.

82
Q

Activation of the hair cell causes

A

Increases in the spontaneous firing of these hair cells.

83
Q

Hair cell polarity plays an important role in

A

Vestibular function.

84
Q

Pivoting of the Stereocilia away from kinocilium

A

Decreased spontaneous firing rate of the vestibular nerve primary afferent

85
Q

Function of the Auditory system

A

To detect and analyzes sounds from the environment

86
Q

Outer ear consists of

A

Pinna & external auditory meatus and is designed to collect sound and transfer it to the middle ear.

87
Q

What separates outer and middle ear

A

Tympanic membrane

88
Q

Middle ear

A

An air-filled cavity within the temporal bone that contains 3 ear ossicles: malleus, incus, and stapes 2 muscles – tensor tympani & stepedius

89
Q

In the Middle ear, vibrations of tympanic membrane is conducted by

A

Ear ossicles to vibrate oval window. There is a 25 fold increase in pressure on oval window compared to tympanic membrane due to both the difference in the sizes of the two membranes and the mechanical advantage ear ossicles

90
Q

Conduction of the vibrations are controlled by

A

Tensor tympani innervated by CN V which controls the movement of the tympanic membrane and the stapedius which is innervated by CN VII and controls the movement of the stapes. These two muscles reflexively contract to lessen movement & sound conduction.

91
Q

Inner ear is separated from the middle ear by

A

oval & round windows.

92
Q

Inner ear is comprised of

A

Cochlea- the spiral bony container with the modulus wound around central core of the spiral. Bipolar cells of spiral ganglion in modulus. The spiral ganglia is where the cell bodies of the auditory primary afferent axons sit.

93
Q

The inner ear is fluid filled with

A

Perilymph between bony & membranous labyrinth. Endolymph in the several membranous structures form the cochlear duct.

94
Q

3 chambers within the inner ear:

A

Scala vestibuli & scala tympani – filled with perilymph Scala media or cochear duct formed by vestibular & basilar membranes which is filled with Endolymph

95
Q

Vibrations in perilymph are produced by

A

Vibration of oval window and are carried down the scala vestibuli & around the heliotrema into the scala tympani. Here these vibrations vibrates the basilar membrane.

96
Q

The Basilar membrane varies in width and stiffness from base to apex of cochlea. The basilar membrane is thinner & more compliant near the ———— where it is vibrated by higher frequency vibrations of ___________

A

oval window, perilymph

97
Q

Basilar membrane is thicker & stiffer toward which apex?

A

cochlear apex – vibrated by lower frequency vibrations of perilymph.

98
Q

With tonotopic mapping of cochlea the highest frequencies are received at the ________and the Lowest frequencies sensed at the

A

base, apex

99
Q

where does auditory transduction occurs

A

In hair cells of the organ of Corti in the cochlear duct.

100
Q

Basic structure of the organ of Corti

A

Outer & inner rows of hair cells rest on basilar membrane. Above these hair cells is the tectorial membrane. The tectorial membrane is gelatinous shelf resting on stereocilia of the outer hair cells

101
Q

Peripheral processes of the bipolar cells of the spiral ganglion surround

A

Base of hair cells and are held in place with supporting cells

102
Q

where are hair cells found / located?

A

Within the endolymph-filled scala media. There are approximately 3500 flask-shaped inner hair cells and >15,000 cylindrical outer hair cells

103
Q

Inner hair cells sit on the _________portion of basilar membrane while the outer hair cells are on the______ .

A

least flexible, most flexible portion

104
Q

T / F- Inner hair cells do not touch tectorial membrane but the tectorial membrane rest on the stereocilia of the the outer hair cells

A

True

105
Q

How are outer hair cells depolarized

A

By pivoting hair cells against tectorial membrane

106
Q

How are inner hair cells depolarized?

A

By movement of endolymph in inner spiral sulcus which pivot their stereocilia

107
Q

What % of afferent axons in cochlear nerve receive their input from inner hair cells

A

95%

108
Q

what % of afferent axons in cochlear nerve receive their input from outer hair cells?

A

5%

109
Q

Primary sensory element of the organ of Corti

A

Inner hair cells

110
Q

Outer hair cells have motor proteins activated by

A

Depolarization of hair cell. These proteins shortens outer hair cell which amplifies movement of basilar membrane up to 100 fold producing a much greater depolarization of the inner hair cells. So it appears that the outer hair cells regulate the excitability of the organ of Corti by regulating the movement of the basilar membrane.

111
Q

Cell bodies of the primary afferent bipolar neurons reside in

A

Spiral ganglion

112
Q

Axons of cell bodies of the primary afferent bipolar neurons enter the brainstem

A

Lateral and slightly caudal to vestibular 1° afferents as part of CN VIII – Vestibulocochlear nerve.

113
Q

The primary afferent axons of primary afferent bipolar neurons end on the

A

dorsal & ventral cochlear nuclei. These relay nuclei are tonotopically map with high frequencies dorsal & low frequencies ventral

114
Q

Cochlear Nuclei are

A

2° or relay auditory neurons.

115
Q

Axons of cochlear nuclei can take one of three paths:

A

Ventral acoustic stria (trapezoid body) – runs ventrally thru caudal pontine tegmentum Dorsal & intermediate acoustic stria (runs more dorsally through caudal pons) or Ascend contralaterally as lateral lemniscus. some ascend in ipsilateral lateral lemniscus, and some synapse on a variety of nuclei in pons – most prominent is superior olivary nucleus. But even at this point the auditory ascending system is bilateral.

116
Q

The Lateral lemniscus have Axons from

A

2° auditory neurons & few 3° from superior olivary nucleus. Some fibers ascend ipsilaterally and some ascending contralaterally. The lateral lemniscus ascends just lateral to the STT. Some of the axons in the lateral lemniscus synapse in nucleus of lateral lemniscus but most ascend to inferior colliculus

117
Q

Most 2° auditory neurons end on neurons in

A

Inferior colliculus but a few will continue to ascend to the meidal geniculate body of the thalamus.

118
Q

Axons from 3° neurons of the inferior colliculus ascend to

A

Thalamus as brachium of inf colliculus. Some of these fibers decussate and some rise ipsilaterally. Note- this is another point that contributes to the bilateral nature of the ascending auditory pathways. Tonotopic mapping continues in the inferior colliculus with high frequencies more ventral & low more dorsal

119
Q

Mostly 3° axons end on 4° in

A

Medial geniculate nucleus of thalamus (however some of the fibers that synpase here are already 4° fibers in the pathway and some are only 2° fibers.

120
Q

Medial Geniculate Nucleus Axons give rise to

A

Auditory radiations to 1° auditory cortex. There continues to be tonotopic mapping in the Medial Geniculate nucleus with high frequencies medial & low frequencies lateral

121
Q

Much of the primary auditory cortex lies within the

A

Insular side of the superior temporal gyrus.

122
Q

Larger representation of the primary auditory cortex is on which side?

A

Left than right in most individuals. It appear to parallel the distribution of the speech centers because of the strong linkage between audition and speech

123
Q

2° axons from cochlear nuclei decussate in 1 of 3 locations

A

Axons of superior olivary nucleus also decussate in the trapezoid body (inferior acoustic stria) Commissural connections between the inferior colliculi

124
Q

Bilaterality of acoustic projections at each point of decessation and decussation of already decussated pathway means that

A

Loss of one central pathway or loss of auditory cortex does not produce deafness in one ear but issues related to sound localization & identification

125
Q

Two peripheral mechanisms that contribute to the ability to localize sounds: ITD & IID

A

Difference in timing between sound arriving at one ear versus the other (interaural time difference - ITD) Difference in sound intensity between the two ears (interaural intensity difference - IID)

126
Q

Time difference is best at determining

A

Direction of low frequencies

127
Q

Intensity difference best at distinguishing

A

Direction of high frequencies. This may be true since the head is a greater sound barrier to high frequencies than it is to low freqeuncies, so high frequencies may be attenuated to a greater degree and therefore be more localizable using this mechanism.

128
Q

The Pinnae of the ear assists in

A

Sounds to the front, back and above which would not be distinguishable otherwise. But sounds immediately to the front, back or just above the head are still the hardest to localize. That is why we will often move our head to one side or the other to localize a sound.

129
Q

Neural mechanisms involve

A

Superior olivary nucleus.

130
Q

Lateral superior olivary nucleus is specialized for

A

High frequencies and cells measure interaural intensity difference by integrating ipsilateral excitatory and contralateral inhibitory inputs

131
Q

Medial superior olive is specialized for

A

Low frequencies and measures interaural time differences using excitatory inputs from both sides

132
Q

Tensor tympani/stapedius reflex- Afferent (sensory) limb of reflex:

A

A few fibers from the auditory nuclei terminate in the nuclei of the facial and trigeminal motor nuclei

133
Q

Tensor tympani/stapedius reflex- Efferent (motor) limb of reflex:

A

Branch of facial nerve to stapedius and a Branch of trigeminal nerve to tensor tympani

134
Q

Function of the tensor tympani / stapedius reflex

A

To limit amplitude of loud and high-frequency sounds and to filter out noise arising from the head itself

neuro final exam (10 decks)

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