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Neural and Hormonal Control > Visual System > Flashcards

Visual System Flashcards

1
Q

What are the three layers that comprise the eye?

A

Sclera, choroid, retina (from outermost to innermost)

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2
Q

What are the two fluid compartments of the eye?

A

Aqueous humous & vitrous humor

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3
Q

What is the function of the aqueous humor?

A

supplies the nutrients to surrounding structures (present in anterior chamber)

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4
Q

What is the function of the vitrous humor?

A

maintains the shape of the eye and supplies nutrients to surrounding structures (present in space between back of lens and retina)

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5
Q

What is the difference between the sclera and cornea?

A

Sclera is a white fibrous tissue that forms the outermost layer of the eye. It becomes the cornea at the front of the eye. The cornea is a transparent tissue that separates and protects the eye from external environment and allows light in

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6
Q

What is the choroid?

A

Capillary bed that nourishes the retinal cells

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7
Q

What is the ciliary body?

A

a ring of tissue that encircles the lens. Consists of muscular and vascular part

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8
Q

What does the ciliary muscle do?

A

Controls shape of lens. Connected to lens by zonule fibers

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9
Q

What do the ciliary processes do?

A

produce the aqueous humor in anterior chamber

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10
Q

What is the iris?

A

Coloured portion of the eye seen through the cornea. Contain 2 sets of muscles that contract and to adjust size of pupil

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11
Q

What does the lens do?

A

it refracts light rays coming into the eye and generates a focused image on the retina

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12
Q

What are accommodations of the lens and how do they happen?

A

changes in refractive power of lens to form a sharp image on the retina. The changes happen thanks to the contraction of the ciliary muscle

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13
Q

What happens to the lens during distant vision?

A

Lens becomes thin and flat. Less refractive power

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14
Q

What happens to the lens during near vision?

A

lens becomes thick and round. More refractive power

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15
Q

What is emmetropia?

A

Normal vision, proper accomodation

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16
Q

What is myopia?

A

the lens over accommodates (i.e. high refractive power), the image is focused in front of the retina. Hard to see distant objects. Corrected by concave (converging) eye glasses.

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17
Q

What is hyperopia?

A

the lens does not accommodate enough (i.e. weak refractive power), the image is focused beyond the retina. Hard to see a nearby objects. Corrected by convex (diverging) eye glasses.

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18
Q

What is the retina?

A

Innermost layer of eye. Considered part of nervous system. Contains light sensitive neurons. Converts visual info into electrical signal to transmit to brain

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19
Q

What are the photosensitive neurons?

A

Rods and cones

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20
Q

List the characteristics of Rods.

A

Rod shaped, 120 million, located in periphery, dim light (highly sensitive to light, night vision), low resolution, pigments: rhodopsin, type of cells: monochromic (absorbs white color), no color vision.

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21
Q

List the characteristics of cones.

A

Cone-shaped, 8 million, center (fovea), bright light (low sensitivity to light, day vision), high resolution, pigments: iodopsin, porphyropsin, cyanopsin, 3 types of cell: S-cones (blue), M-cones (green), L-cones (red), color vision

22
Q

What are the five classes of neurons in the retina?

A

Photosensitive, bipolar cells, ganglion cells, horizontal cells (regulate photosensitive activity), amacrine cells

23
Q

What are the 2 classes of ganglion cells?

A

on-center cells and off-center cells

24
Q

What do the on-center cells respond to?

A

Active to light spot in center and silent to dark spot in center

25
Q

What do the off-center cells respond to?

A

Silent to light spot and active to dark spot in center

26
Q

what other class of neurons has on and off center cells?

A

Bipolar cells

27
Q

What control the activity of the on-center/off-center ganglion cells?

A

The multiple interactions between the photosensitive cells, bipolar cells and horizontal cells

28
Q

What are the horizontal cells thought to regulate?

A

Regulate the amount of transmitter that the photosensitive cells release onto bipolar cell dendrites

29
Q

How is the image perceived on the retina?

A

it is inverted top to bottom and reversed right to left

30
Q

How can the visual field be divided?

A

into right visual hemi-field and left-visual hemi-field

31
Q

The right visual hemi-field is seen by what part of the retina?

A

the right nasal retina and left temporal retina

32
Q

The left visual hemi-field is seen by what part of the retina?

A

The left nasal retina and right temporal retina

33
Q

What is the binocular visual field?

A

Visual fields of both eyes overlap in the central portion of the visual field

34
Q

What forms the optic nerve?

A

axons of the ganglion cells

35
Q

What happens to the optic fibres at the optic chiasm?

A

60% of the optic fibre crosses to the opposite side of the brain, 40% stays on the same side of the brain

36
Q

Fibres from the nasal retina project to which side of the brain?

A

The contralateral side

37
Q

Fibres from the temporal retina project to which side of the brain?

A

The ipsilateral

38
Q

What do the optic fibres form after the optic chiasm?

A

the optic tract

39
Q

Where do the majority of the optic fibres terminate in?

A

In the lateral geniculate body (LGB) in the thalamus

40
Q

What do neurons in the LGB form and where do they terminate?

A

Neurons from the LGB form the optic radiation and terminate in the striate cortex (occipital cortex)

41
Q

What other midbrain areas do the axons of ganglion cells project to?

A

Hypothalamus (regulation of circadian rhythm), Pretectum (control of pupillary light reflex), superior colliculus (orienting the movements of head and eyes)

42
Q

What is the visual cortex?

A

Visual cortex= striate cortex= primary visual cortex = V1= Brodmann’s area 17

43
Q

What does the visual cortex do?

A

Processes the basic of the sensory info sent by retina (places back the inverted image to its original position)

44
Q

How much representation does the sensory information from the central region of the retina have in the visual cortex?

A

Large representation

45
Q

Are the geniculate neurons monocular or binocular?

A

Monocular

46
Q

Are the neurons in layer 4 of the striate complex still monocular?

A

yes

47
Q

At what stage does the images from both eyes converge into a single image?

A

When layer 4 neurons send their output to other cortical layers

48
Q

The primary visual cortex projects to what other cortex areas?

A

The extrastriate cortex which is involved in complex visual perception

49
Q

The dorsal pathway projects to what?

A

Projects to the parietal lobe. Responsible of spatial aspect of vision

50
Q

The ventral pathway projects to what?

A

projects to the temporal lobe. Responsible for object recognition

Neural and Hormonal Control (12 decks)

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