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Functional Neuroanatomy > Exam 3 > Flashcards

Exam 3 Flashcards

1
Q

What is the sclera

A

tough outer layer of the eye
thins in front to become the cornea

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2
Q

what is the cornea

A

Performs 2/3 of the bending of light
Innervated by many sensitive nerve endings to protect it

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3
Q

What is the corneal reflex

A

Involuntary reflexive blinking of the eye when cornea is stimulated
Detected by afferents of CNV

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4
Q

what is blinking mediated by

A

motor efferents of CNVII

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5
Q

What is the lens

A

Performs 1/3 of bending light
Focuses images on retina
Shape is controlled by smooth ciliary muscles

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6
Q

what is eye accommodation

A

contraction of the ciliary muscles changes the shape of the lens to focus it at different distances

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7
Q

What is the Iris

A

Controls the amount of light entering the eye through the pupil

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8
Q

what controls the diameter of the pupil

A

pupillary constrictor
pupillary dilator

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9
Q

what is the anterior chamber

A

space between cornea and iris
filled with aqueous humor

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10
Q

what is the posterior chamber

A

space between iris and lens
filled with aqueous humor

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11
Q

what is the vitreous chamber

A

space between the back of the lens and the surface of the retina
filled with vitreous humor

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12
Q

what are the characteristics of the retina

A

part of the CNS, not the periphery
Derived from the neural tube
Layered structure ~250 micrometers thick

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13
Q

what is the pigment epithelium

A

layer of non neuronal cells that form the innermost layer of the retina
maintains rod and cone cells

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14
Q

what is the main types of retinal cells

A

photoreceptors
local circuit neurons
projection neurons

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15
Q

what are photoreceptors

A

rods and cones

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16
Q

what are local circuit neurons

A

bipolar, horizontal, and amacrine cells

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17
Q

what are the projection neurons

A

ganglion cells

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18
Q

what is the outer segment

A

near back of retina, embedded in pigment epithelium
phototransduction occurs here

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19
Q

what is the inner segment

A

closer to cell body
No phototransduction

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20
Q

what are the synaptic endings

A

release glutamate onto bipolar and horizontal cells

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21
Q

what are the physiological characteristics of photoreceptors

A

Rods and Cones do not generate APs
Amount of NT released is graded and inversely proportional to light levels

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22
Q

What does it mean that NT is inversely proportional to light level

A

More light = less glutamate released

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23
Q

What are Rods

A

Outer Segment is larger than cones
More photopigment
More sensitive to light (can be activated in low light)

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24
Q

what is the opsin molecule for rods

A

rhodopsin

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25
Q

what are cones

A

outer segment is smaller
less photopigment
activated at higher light level

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26
Q

what are the opsin molecules of cones

A

photopsins (red, green, blue)

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27
Q

what is rhodopsin

A

found in rods
changes conformation when light is absorbed by retinal
responds to a range of wavelengths in the middle of the visible spectrum

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28
Q

what are photopsins

A

found in cones
change in conformation when light is absorbed by retinal
respond to specific ranges of light that peak at blue, green, and red wavelengths

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29
Q

what is CNII

A

axons of retinal ganglion cells that project to the thalamus via the optic chiasm

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30
Q

What is the optic disk/papilla

A

location where axons of ganglion cells come together to exit the eye and form the optic nerve
forms a blind spot bc there are no photoreceptors

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31
Q

what is the macula

A

area near the center of the retina surrounding the fovea
High acuity

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32
Q

what is acuity

A

describes the clarity or sharpness of vision

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33
Q

what is the fovea

A

center of the macula
mostly cones, no rods
location of highest acuity in retina

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34
Q

why does the fovea have the highest acuity in the retina

A

high density of photoreceptors
no blood vessels
cell bodies moved aside to let light in

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35
Q

what is the distribution of retinal cells in the periphery

A

low acuity
lower density of photoreceptors
larger number of rods than cones

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36
Q

describe the convergence of rods in the periphery

A

high convergence of rods and bipolar cells onto ganglion cells
poor spatial resolution

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37
Q

describe the convergence of cones in the fovea

A

low convergence of cones and bipolar cells onto ganglion cells
high spatial resolution

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38
Q

what is the visual field

A

any location in space from which light could reach a cell in the visual system

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39
Q

what is a receptive field

A

the part of the visual field from which light can change the activity of a given cell in the visual system

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40
Q

what is the ON center of cells

A

activated (depolarized) when light is in the center of the RF

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41
Q

what is OFF center of cells

A

activated (hyperpolarized) when light is in the surrounding of the RF

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42
Q

what are the properties of photoreceptors

A

graded response to light
constant release of glutamate in the dark
hyperpolarize in response to light
round receptive field

43
Q

what are bipolar cells

A

graded response to light
constant release of glutamate in the dark
center-surround receptive field
ON center and OFF center

44
Q

what are ganglion cells

A

generate APs
axons project to the thalamus
center surround receptive fields
ON center and OFF center

45
Q

What are the responses of OFF BPs and GCs

A

PR hyperpolarize in response to light
BPs have depolarizing glutamate receptors
GCs have depolarizing glutamate receptors

46
Q

What are the responses of ON BPs and GCs

A

PR hyperpolarize in response to light
BPs have hyperpolarizing glutamate receptors
GCs have depolarizing glutamate receptors

47
Q

what are horizontal cells

A

graded response to light
release baseline of GABA
depolarized by glutamate from PR
generate LATERAL INHIBITION

48
Q

what is the pathway from the retina to the primary visual cortex

A

Retinal Ganglion cells –>
Optic chiasm via optic nerve –>
thalamus via optic tract –>
V1 via optic radiations

49
Q

what are M cells

A

Large cells bodies, dendritic trees and receptive fields
Specialized for:
large objects
sharp contrasts in light
objects moving rapidly across visual field

50
Q

what are P cells

A

small cell bodies, dendritic trees, and receptive fields
specialized for:
small objects
fine details
objects moving slowly across visual field

51
Q

what is the lateral geniculate nucleus of the thalamus

A

six layers
each layer has a retinotopic map

52
Q

where is V1 located

A

along the calcarine fissure/sulcus in the occipital lobe

53
Q

Describe the retinotopic map in V1

A

Contralateral visual field

54
Q

what are the receptive fields in RGC and LGN thalamus

A

circular receptive fields, each with a center and surrounding region
either region can be “on” or “off”

55
Q

what are the receptive fields of the V1

A

elongated receptive fields with bands of “on” and “off” regions
sensitive to stimulus orientation and movement of a stimulus in a specific direction

56
Q

How are neurons grouped together in the V1 cortex

A

Ocular dominance
Receptive field orientation
color preference or no color preference

57
Q

what results from damage to ventral stream association cortices

A

recognition and identification of stimuli
patients are aware of objects in their visual field but cannot identify them

58
Q

what is Achromatopsia

A

inability to perceive color
caused by bilateral lesions of area V4

59
Q

what is visual apperceptive agnosia

A

impaired ability to group/integrate parts of an object to perceive it as a whole
cannot draw/copy an object or identify what it is
damage to inferior temporal cortex

60
Q

what is visual associative agnosia

A

patients can perceive an object but cannot recognize it or describe what it is for
can draw/copy objects but not identify it
damage to anterior temporal lobe

61
Q

what is Prosopagnosia

A

patients cannot identify people by their faces though they can identify components of faces and can identify people by other cues
damage to face area of the fusiform gyrus

62
Q

what results from damage to the dorsal stream association cortices

A

inability to:
relate objects to their location
visually integrate parts of an object or multiple objects
perceive motion

63
Q

what is optic ataxia

A

inability to use visual guidance for accurate reaching to an object
can reach accurately when give auditory cues
damage to parieto-occipital junction

64
Q

what simultanagnosia

A

cannot perceive more than one object at a time
due to bilateral damage in the area of the parieto-occipital junction

65
Q

what is akinetopsia

A

inability to perceive motion
bilateral lesion to area MT/V5

66
Q

when is the area MT/V5 activated

A

tasks that require an individual to pay attention to a moving stimulus

67
Q

what is contralateral neglect syndrome

A

tendency to ignore sensory information from and perception of the side of the body contralateral to a lesion
lesions of right parietal cortex

68
Q

what are the functions of the vestibular system

A

detects head position and head movements
helps maintain posture and balance
involved in some reflexive eye movements

69
Q

what is the vestibular apparatus

A

located in inner ear, near cochlea

70
Q

what are semicircular canals

A

detect rotational acceleration of head

71
Q

what are otolith organs

A

detect static position of head and linear acceleration

72
Q

what are the three canals of the semicircular canals

A

horizontal
superior/anterior
posterior/inferior

73
Q

what is the canals of the semicircular canals filled with

A

endolymph

74
Q

Describe inertia of the endolymph

A

when you turn your head, the endolymph lags behind head motion
endolymph moves in direction opposite to head rotation
cupula only displaced during change in motion

75
Q

How does the left horizontal semicircular canal respond to movement to the left

A

endolymph stays put and pushes the cupula and hair cells inside it to the right (toward the anterior side of the body)
Stereocilia toward kinocilium
Depolarized –> more NT

76
Q

how does the right horizontal semicircular canal respond to movement to the left

A

endolymph stays put and pushes the capula to the right (poster side of body)
stereocillia away from kinocilium
hyperpolarize –> Less NT

77
Q

what do otolith organs detect

A

static position of the head in space
linear acceleration

78
Q

what are the two otolith organs

A

utricle and saccule
two different orientations

79
Q

what are otoconia

A

calcium carbonate crystals
embedded in otolithic membrane

80
Q

describe the utricle

A

oriented mainly horizontal
linear acceleration in the horizontal plane and head tilt

81
Q

describe the saccule

A

oriented mainly vertically
linear acceleration in the vertical plane and head tilt

82
Q

where does the vestibular nuclei receive projections from

A

vestibular afferents (cells bodies in vestibular ganglion)
proprioceptive information from muscle spindles in the neck

83
Q

what is the rectus muscle in the eye

A

pulls eye in single straight direction (up and down)

84
Q

what is the oblique muscle in the eye

A

cause the eye to rotate (torsion)

85
Q

what does the medial rectus muscle do

A

adduction toward the nose

86
Q

what does the lateral rectus muscle do

A

abduction away from the nose

87
Q

what does the superior rectus muscle do

A

elevation

88
Q

what does the inferior rectus muscle do

A

depression

89
Q

what does the superior oblique muscle do

A

intorsion (top of eye toward nose)

90
Q

what does the inferior oblique muscle do

A

extorsion (top of eye away from nose)

91
Q

Describe CNIII

A

oculomotor cranial nerve
all eye muscles except superior oblique and lateral rectus (somatic motor)
lens accommodation and pupil dilation (visceral motor)
pure motor

92
Q

Describe CNIV

A

trochlear nerve
superior oblique muscle
pure somatic motor

93
Q

Describe CNVI

A

Abducens Nerve
Lateral rectus muscle
pure somatic motor

94
Q

what is the goal of the vestibulo-ocular reflex

A

keep eyes fixated on the same location in space despite head movement

95
Q

what are the brainstem nuclei of the vestbulo-ocular reflex

A

medial vestibular nucleus
abducens nucleus
oculomotor nucleus

96
Q

what is the pathway for VOR

A

Vestibular afferents –> Medial vestibular nucleus –> abducens nuclei (ipsilateral inhibitory, contralateral excitatory) –> lateral rectus muscles (CNVI) and oculomotor nuclei –> extraocular muscles (CNII)

97
Q

what does it mean that VOR circuitry is bilaterally symmetrical

A

Abducens nuclei receive excitatory input from the contralateral side and inhibitory input from the ipsilateral side

98
Q

what does no head movement mean for the VOR

A

No head movement –> input is balanced so motor neurons in the abducens nuclei are not active

99
Q

What is nystagmus

A

unilateral damage causes loss of balance of inputs resulting in alternating reflexive eye movements

100
Q

what is the slow phase of nystagmus

A

eye move slowly toward the side of lesion (VOR)

101
Q

what is the quick phase of nystagmus

A

eyes jerk away from side of lesion (attempting to fixate)

102
Q

how do you test vestibular function

A

put warm or cold water in the ear canal
causes movement of fluid in horizontal semicircular canal on that side only
triggers nystagmus

103
Q

Describe what happens when warm water is in the left ear canal

A

depolarizes vestibular afferents on LEFT
VOR triggered:
slow phase: eyes to right
quick phase: eyes to left

Functional Neuroanatomy (12 decks)

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