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Anatomy 2 > The Visual System > Flashcards

The Visual System Flashcards

1
Q

Neural component of the eye.

A
  • designed to transduce a photon of light into something the nervous system will recognize (action potential)
  • transduced through chemical reactions into action potentials
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2
Q

Primary (only) purpose of non-neural eye components.

A

refract (bending) photons of light

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3
Q

Non-neural components of the eye.

A

cornea, aqueous chamber, lens, vitreous chamber/fluid, neural retina, fovea/macular region, ciliary muscle and lens, iris

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4
Q

How does the cornea receive nutrients?

A

tears (avascular - CN VII damage can cause cornea to dry out)

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5
Q

Attach lens to ciliary muscles.

A

zonular ligaments

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6
Q

This helps maintain the shape of the eye.

A

vitreous chamber

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7
Q

Fovea Centralis

A

where all photons of light are refracted to, greatest acuity

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8
Q

Macula Lutea

A

surrounds fovea centralis, yellowish in color b/c of protein lutein (filters out ultraviolet light and helps to protect the eye)

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9
Q

Retina is an extension of the ___________.

A

diencephalon (thalamus, hypothalamus, etc.)

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10
Q

What occurs when the ciliary muscle fibers are relaxed?

A

suspensory ligament/zonular ligament are taught, pulling on lens to elongate lens for focusing on distance vision

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11
Q

What occurs when the ciliary muscle fibers are contracted?

A

narrows aperture, allowing suspensory ligaments to be relaxed, thickening/rounding the lens for focusing on near vision

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12
Q

Iris (two series of muscles)

A

circular: sphincter pupilli (parasympathetic)

radially orientation: dilation of iris (sympathetic)

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13
Q

Visible light

A

between 400-700 nm in wavelength

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14
Q

Round muscle around the border of the iris.

A

ciliary muscle (CN III)

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15
Q

Connect the photoreceptor cells to the retinal ganglion cells (output cells).

A

bipolar cells

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16
Q

Photoreceptor cells

A

Rods (1) and Cones (3: red, blue, green)

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17
Q

These cells spread info laterally rather than vertically.

A

Horizontal Cells and Amacrine Cells

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18
Q

Superficial: optic fiber layer

A

axons of retinal ganglion cells

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19
Q

Ganglion cell layer

A

cell body of retinal ganglion cells

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20
Q

Inner plexiform layer

A

synapses are occurring between amacrine and bipolar cells with ganglion cells

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21
Q

Inner nuclear layer

A

cell heavy with cell bodies of bipolar cells, horizontal cells, and amacrine cells

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22
Q

Outer plexiform layer

A

cell free layer! synapses for horizontal, bipolar cells, and photoreceptor cells

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23
Q

Outer nuclear layer

A

contains cell bodies of rods and cones

24
Q

Inner segments and Outer segments

A

contains photoreceptors

25
Q

Series of blood vessels that feed the deeper structures of the eye.

A

choroid plexus

26
Q

Retinal Layers

A

optic fiber layer–>ganglion cell layer–>inner plexiform layer–>inner nuclear layer–>outer plexiform layer–>outer nuclear layer–>inner segments and out segments–>pigment epithelium–>choroid

27
Q

Foveal pit

A
  • marks the center of the fovea, in the center of the macula lutea
  • greatest concentration of photoreceptors, bipolar, to ganglion cells (1:1:1 relationship)
  • creates your greatest visual acuity
  • prone to degenerative diseases
28
Q

Right visual world

A

Left Temporal Retina

Right Nasal Retina

29
Q

Left visual world

A

Right Temporal Retina

Left Nasal Retina

30
Q

The greatest acuity is in which field?

A

macular field

31
Q

Nasal retinas

A

in each eye will cross midline at the decussation/optic chiasm to go back to the lateral geniculate body

32
Q

Two locations for optic nerve fibers to synapse.

A

superior colliculus (visual tracking), lateral geniculate body (most fibers synapse here)

33
Q

Two loops of optic radiations.

A

Baum’s Loop: medially located - fibers from superior retina carry information from the inferior part of the visual field
Meyer’s Loop: laterally located- fibers from inferior retina carry information from the superior part of the visual field

34
Q

Lesion of the optic nerve.

A

Lose total vision in ipsilateral eye, both temporal and nasal retina (anopsia), more loss of vision in the peripheral field

35
Q

Lesion of the optic chiasm.

A

pituitary tumors are common, and can cause lesions in the optic chiasm; loss of nasal retina of both left and right side, resulting in tunnel vision; no peripheral vision (heteronymous hemianopsia)

36
Q

Lesion of the optic tract.

A

with a right lesion loss of temporal retinal on right side and nasal retina on left side, so you lose the entire left hemifield; Homonymous hemianopsia

37
Q

Lesion of optic radiations (Meyer’s and Baum’s loops)

A

loss of upper (Meyer) or lower (Baum) quadrant depending of what portion of the loop is involved; Quadrantanopia

38
Q

Lesion at striate cortex.

A

Loss of both upper and lower quadrant; Called macular sparing (loss of vision is not a complete hemifield, but a notched hemifield); Will have central vision

39
Q

Two types of cells of the lateral geniculate body.

A

Large Cells: Magnocellular

Smaller denser pact cells: Parvocellular

40
Q

Laminas in the LGB.

A

1, 4, 6 lamina get info from contralateral eye

2, 3, 5 lamina get info from ipsilateral eye

41
Q

Geniculo-cortical inputs

A
  • as info goes from LGB it goes within various parts of optic radiations, back to VI and segregated into ocular dominance columns
  • throughout VI we have columns of cells that layer: right eye, left eye, right eye, etc.
42
Q

17, 18, 19 brodmann’s areas

A

17: V1
- takes up cuneus and lingual portions
- macular region will be most posterior and the rest of the eye is represented more anterior in area 17
18 & 19:
- wrap around to the lateral surface
- visual Processing areas, where the what/whys/knowledge is added

43
Q

Area 17

A

V1 primary visual cortex

44
Q

Area 18

A

V2, V3, V3a

45
Q

Area 19

A

V4, V5 Association Cortex

46
Q

Line of Gennari

A

gives the striate cortex its name (only place to see the line)

47
Q

Visual processing - 3 types of cells

A

Each type of cell will respond best to a bar/point of light in a specific orientation; simple, complex, hypercomplex

48
Q

Retinal Physiology

A

1) Certain types of photoreceptor cells will respond to specific photons of light, starts a chain reaction that leads to an action potential
2) In some cases retinal ganglion cells will only respond to a bar of light
3) On-Centers and Off Surrounds Cells
light will only be “turned-on” in the on-centers
helps to see contrast
4) Off-centers and On Surround Cells, when light hits this cells you would see stimulus, stop, stimulus (creating contrast)

49
Q

Orientation columns and response to light.

A

Certain cells only respond to certain orientation, or bar of light, or bar of light moving in a particular fashion; all are composed in these orientation columns, alternating between information from the Left and Right Eye; Columns next to each other have interconnections for communication

50
Q

Within the visual cortex there is also some segregation of information depending on if the information is coming from?

A

rods or cones

51
Q

Rods info (Fast, black and white vision):

A

goes to retinal “Y” ganglion cells; those axons will go to magnocellular of LGB, those axons travel via optic radiations to Layer 4 of the visual cortex

52
Q

Cone info (Very accurate, color vision):

A

Retinal type “X” cells receive cone info, synapse in the parvocellular region of LGB and come in and synapse in cells in Layer 4 of visual cortex

53
Q

Visual streams hypothesis.

A
  • separation of information of the inferior portions of the temporal lobe (ventral stream), putting what or meaning to the visual information
  • 2nd pathway (dorsal stream) into the parietal lobe that puts the where or how on the information we see
54
Q

Visual Agnosia

A

Lesions of the “what” (ventral stream) pathway will cause pt. not be able to recognize the object, but could describe it (doesn’t know it’s a pencil, but knows it is long, yellow, etc)

55
Q

What happens when you shine a light into a pt.’s eye?

A
  • some info comes into the pretectal area of midbrain, and synapses on edinger-westphal nucleus (both ipsilateral and contralateral)
  • causes the pupil to constrict, and also the contralateral pupil will constrict
  • If the contralateral pupil doesn’t constrict, the contralateral pathway from pretectal area to edinger-westphal has been broken

Anatomy 2 (23 decks)

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