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Neuro Exam 3 > Visual System > Flashcards

Visual System Flashcards

1
Q

The fact or phenomenon of light being deflected in passing obliquely through the interface between one medium and another through a medium of varying density

A

Refraction

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2
Q

First site of refraction as light enters eye; is this refraction variable?

A

Cornea; not variable (accounts for 2/3 of light bending)

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3
Q

The second site of refraction in the eye is the ___ which adds a variable amount of bending. Variability depends on curvature, which is under physiological control. The ______ the structure above, the more refraction there is; the ______ the structure, the less refraction

A

Lens; rounder; flatter

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4
Q

Increasing curvature of the lens = ciliary muscle ______, which alows suspensory ligaments to ______. The lens assumes a more _____ shape; this is used for ______ vision

A

Contracts; loosen; rounded; near

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5
Q

Decreasing curvature of the lens = ciliary muscle ______, causing suspensory ligaments to _______, thus causing the lens to _____; used for ____ vision

A

Relaxes; tighten; flatten; far

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6
Q

Condition in which lens becomes stiffer in aging, loss of elasticity

A

Presbyopia

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7
Q

The near response of the eyes requires what 3 events?

A

Contraction of ciliary muscles

Convergence of eyes

Constriction of pupil

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8
Q

Path of light from entry to eye to activation of photoreceptor

A 
Ganglion cells
Amacrine cells
Muller glia
Bipolar cells
Horizontal cells
Rods/cones
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9
Q

What are the 3 vertically oriented cell-types in the retina?

A 
Receptor cells (rods/cones)
Bipolar cells
Ganglion cells (subtype melanopsin ganglion cells)
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10
Q

Which type of photoreceptor is associated with convergence, dim light, and sensitivity but NOT acuity?

A

Rods

[cones have less convergence, but maximized acuity]

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11
Q

Rod/cones constantly release NT ________; this release is at its highest in the _____, and lowest when there is _______ (hyperpolarization of cells)

A

Glutamate; dark; light

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12
Q

In differentiating ON-centers from OFF-centers:

Activation of a photoreceptor in the center of an ON-center bipolar cell’s receptive field causes ______

Activation of the periphery of this bipolar cell’s receptive field causes ________

The opposite is true for OFF-center cells

A

Depolarization

Hyperpolarization

[so for OFF-center cells, activation of a photoreceptor in the center causes hyperpolarization while activation in the periphery causes depolarization]

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13
Q

________ bipolar cells increase their discharge rate to luminance increments in the receptive field center

______ bipolar cells increase their discharge rates to luminance decrements in the receptive field center

A

ON-center

OFF-center

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14
Q

The glutamate receptor in depolarizing bipolars is a GPCR that _____ cGMP-gated ion channels similar to light transduction in photoreceptors.

Channels _____ when less glutamate is present

A

Closes

Open

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15
Q

Describe activity of an ON-center bipolar cell by a cone photoreceptor in the dark

A
  1. Glutamate would activate a Gi GPCR-metabotropic receptor on the ON-center cell
  2. Results in a decrease in cation influx into bipolar cell
  3. Cell is hyperpolarized
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16
Q

Describe activity of an ON-center bipolar cell in the light

A
  1. Light decreases presence of glutamate
  2. Less activation of metabotropic receptor
  3. Less Gi signaling
  4. Increase in cation influx
  5. Cell depolarization
17
Q

When the bipolar cell is activated, it releases glutamate to depolarize ______ cells which also have ON-center and OFF-center varieties. These cells then become the fibers of the _____

A

Ganglion; optic n

18
Q

Many rods converge on one _______bipolar cell, which connects to a rod-bipolar cell and a rod-amacrine cells, which function as interneurons releasing ____ or ______. These then connect to a cone-bipolar cells, then to a ganglion cell

A

ON-center; glycine; GABA

19
Q

Overall function of ON- and OFF-center cells

A

Help us increase the ability to detect edges and sharpen our vision

ON-center cells tell us where something is

OFF-center cells tells us where something ends

20
Q

Direct targets of the retina

A 
Lateral geniculate body
Superior colliculus
Pretectum
Hypothalamus
Accessory optic nuclei (AON)
21
Q

Signals from the 2 eyes are kept apart in the LGB. What are the functions of the LGB?

A

Control motions of the eyes to converge on point of interest

Control focus of the eyes

Determine relative position of objects to map them in space

Detect movement relative to an object

22
Q

There are 6 layers to the primary visual cortex. Layers I, II, and III allow for networking between VI and other areas of the cortex.

Layer ___ receives input from the LGB

Layers ___ and ___ are main output layers; LGB, thalamus, subcortical regions

A

IV

V; VI

23
Q

Slab of cells that preferentially respond to input from one eye or the other

A

Ocular dominance columns

24
Q

Organized region of neurons that are excited by visual line stimuli of varying angles, oriented perpendicular to cortical surface

A

Orientation columns

25
Q

_____ exist in primary visual cortex as an organized region of neurons that are sensitive to color and assemble into cylindrical shapes

A

Blobs

26
Q

The arrangement of neurons in columns and blobs is not nearly as linear or rectangular as previously depicted but they are mapped into the following stuctures:

The ____ of ocular dominance columns

The ______ of orientation columns

Cytochrome oxidase stain shows ______

A

Stripes

Swirls

Blobs

27
Q

Major job of primary visual cortex VI

A

Identify edges and contours of objects

28
Q

Major job of primary visual cortex V2

A

Depth perception

29
Q

Major job of primary visual cortex V3a

A

Identification of motion

30
Q

Major job of primary visual cortex V4

A

Complete processing of color input

31
Q

The dorsal pathway in visual processing arises from _____ and is responsible for completing motor acts based on visual input (tracking an object)

A

V3

32
Q

Which pathway of visual processing is primarily involved in interpreting images and facial recognition?

A

Ventral pathway

Neuro Exam 3 (9 decks)

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