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Neuro Exam 3 > Physiology of Visual System > Flashcards

Physiology of Visual System Flashcards

1
Q
  • The eye uses _ to focus image on retina
  • Which site accounts for most?
  • When the lens is rounder is there more or less?
  • When the lens is flatter is there more or less?
A
  • Refraction
  • Cornea (also first site)
  • Rounder lens=more refraction
  • Flatter lens=less refraction
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2
Q
  • The curvature of the lens requires what muscle and ligaments?
  • Increasing curvature occurs with contraction or relaxation of these muscle/ligaments?
  • Decreasing curvature occurs with contraction or relaxation of these muscles/ligaments?
A
  • Ciliary m and suspensory L
  • Increasing curvature
    • Ciliary m contracts
    • Suspensory L relaxes
  • Decreasing curvature
    • Ciliary m relaxes
    • Suspensory L contracts
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3
Q
  • Describe the near vision response and how it works in the eye
A
  1. Contraction of ciliary muscles
  2. Convergence of eyes to point of focus
  3. Constriction of pupil
    1. Reduces opening for light to enter
    2. Eliminates diverging rays
    3. Allows better focus
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4
Q
  • Describe the far vision response and how it works in the eye
A
  • Ciliary muscles relax
  • Suspensory ligament pulls on lens
  • Lens becomes flatter to focus on distant objects
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5
Q
  • What are the 5 neuron types in the retina?
  • Where do electrical signals begin?
A
  • Vertically oriented
    • Receptor cells (rods and cones)
    • Bipolar cells
    • Ganglion cells
      • MG subtype of ganglion cells
  • Horizontally oriented cells
    • Horizontal cells
    • Amacrine cells
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6
Q
  • Rod system
A
  • Lots of convergence from many rods onto one ganglion cell
  • Allows rods to operate in dim light
  • Sacrifices acuity to gain sensitivity
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7
Q
  • Cone system
A
  • Less convergence
  • Maximal acuity
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8
Q
  • The highest density of cones is located in the _ whereas the highest density of rods are _
A
  • Fovea
  • Periphery (20 deg away from fovea)
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9
Q
  • Rods and cones constantly release what NTX?
A
  • Glutamate
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10
Q
  • Release of glutamate is highest when it is _
  • Release of glutamate is lowest when it is _
A
  • Dark
  • Light
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11
Q
  • Activation of bipolar cell by a cone receptor in the light (just as an example)
A
  • Photons will stimulate cone receptor
  • Photoreceptor hyperpolarizes
  • Less glutamate is released onto the bipolar cell
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12
Q
  • On center bipolar cells /Depolarizing Bipolars
A
  • Activation of a photoreceptor in the center of this bipolar cell’s receptive field will cause depolarization
  • Activation in the periphery of this cell causes hyperpolarization
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13
Q
  • Off center bipolar cells /Hyperpolarizing Bipolars
A
  • Activation in center of this bipolar cell will cause hyperpolarization
  • Activation in periphery of this bipolar cell will cause depolarization
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14
Q
  • The glutamate receptor in a depolarizing bipolar/on center cell is a _ receptor
  • The glutamate receptor in a hyperpolarizing bipolar/off center cell is a _ receptor
A
  • GPCR (Gi)-sign change occurs
  • non-NMDA (AMPA and Kainate)-no sign change
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15
Q
  • Example:
    • Activation of an on-center/depolarizing bipolar by a cone receptor in DARK
A
  • Dark-more glutamate
  • Glutamate will activate GPCR (Gi) on ON-Center Bipolar Cell
  • Results in decrease in cation influx in bipolar cell
  • Hyperpolarization of the cell
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16
Q
  • Example
    • Activation of an on-center/depolarizing bipolar cell by a cone photoreceptor in the light
A
  • Light-less glutamate release
  1. Light decreases presence of glutamate
  2. Less glutamate around
  3. Less activation of metabotropic receptor (GPCR-Gi) of on-center cell
  4. Less Gi signaling
  5. Increase in cation influs into bipolar cell
  6. Depolarization of cell
17
Q
  • Example:
    • Activation of an off-center bipolar cell by a cone photoreceptor in the dark
A
  • Dark-more glutamate
  1. More glutamate present (cuz we are in the dark)
  2. Glutamate activates AMPA receptor on off center cell
  3. Increase cation influx
  4. Depolarizaton of the cell
18
Q
  • Example
    • Activation of an off center bipolar cell by a cone photoreceptor in the light
A
  • Light-less glutamate
  1. Light decreases presence of glutamate
  2. Less glutamate around
  3. Less activation of AMPA receptor of off-center bipolar cell
  4. Decrease in cation influx into bipolar cell
  5. Hyperpolarization of the cell
19
Q

_ axons become fibers of the optic nerve

A
  • Ganglion cell
20
Q

Ganglion cells release what NTX in the cortex?

A
  • Glutamate
21
Q
  • Activation of a bipolar cell by rod photoreceptors
A
  1. Rods signal vision in low light situations
  2. Many rods converge onto one on-center bipolar cell
  3. COnnects to a rod-bipolar cell and a rod amacrine cell (use glycine or GABA to inhibit cone pathway)
22
Q
  • What does the on-center system tell us?
  • What does the off-center system tell us?
  • What do the amacrine and horizontal cells do?
A
  • On center system tells us
    • Where something is
  • Off center system tells us
    • Where something ends
  • Horizontal/Amacrine cells release GABA/Glycine to inhibit nearby cells in retina
23
Q
  • Direct targets of the retina
A
  • LGB (Lateral Geniculate Body)
  • Superior colliculus
  • Pretectum
  • Hypothalamus
  • AON (Accessory optic nuclei)
  • Pulvinar
24
Q
  • Properties and functions of the LGB
A
  • Signals from two eyes kept apart
  • Functions
    • Control motions of eyes to converge on point of interest
    • COntrol focus of eyes based on distance
    • Determine position of objects to map them in space
    • Detect movement relative to an object
  • Relay cells via optic radiations to visual cortex on IPSILATERAL side
25
Q
  • What layer of the primary visual cortex (V1) receives input from the LGB?
  • What layers of V1 send outputs? Where do these outputs go?
A
  • IV
  • V and VI
    • LGB
    • Thalamus
    • Subcortical regions
26
Q
  • Ocular dominance columns
    • Where are they located?
    • What do they do?
A
  • Located in V1 (Primary Visual Cortex)
  • Columns spand all 6 layers
    • Preferentially respond to input from one eye or the other (hence the name ocular dominance)
27
Q
  • Orientation columns
    • Where are they located?
    • What is their function?
A
  • Also located in V1
  • Columns that span all 6 layers of V1
  • Excited by visual line stimuli of varying angles
  • Oriented perpendicular to the cortical surface
28
Q
  • Blobs
    • Where are they located?
    • What is their function?
A
  • Located in V1
  • Span all 6 layers of V1
  • Sensitive to color
29
Q
  • Major job of V1
A
  • Identify edges and contours of objects
30
Q
  • Function of V2
A
  • Depth perception
31
Q
  • Visual cortex (V3a) function
A
  • Identification of motion
32
Q
  • Function of V4 area of visual cortex
A
  • Complete processing of color inputs
33
Q

Dorsal pathway (Where pathway)

A
  • From primary visual cortex to parietal/frontal cortex
  • Parimary path associating vision with movement
  • Completes motor acts based on visual input
  • Passes thru V3
34
Q
  • Ventral Pathway (What Pathway)
A
  • From primary visual cortex to inferior temporal cortex
  • Involved in interpreting images (recognizing or copying shapes, forms, faces) and complex patterns

Aside:

Copying/naming objects are separate functions. Damage to one is possible without damaging the other

Facial recognition is in a specialized area

35
Q

MG Ganglion Cells

A
  • Light, via melanopsin causes changes in Ca2+ levels in MG cells
  • non-image forming but sends this information to the hypothalamus (suprachiasmatic nucleus)
  • AIDS w. CIRCADIAN RHYTHMS

Neuro Exam 3 (14 decks)

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