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Human Physiology 2 - Unit 1 - Zach H. > Lecture 8: Vision II > Flashcards

Lecture 8: Vision II Flashcards

1
Q

List in order the cellular layers of the retina.

A
  • Photoreceptors
  • Horizontal cells
  • Bipolar cells
  • Amacrine cells
  • Ganglion cells
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2
Q

Which cells make up the photoreceptor retinal layer?

A
  • rods
  • cones
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3
Q

What does photoreceptors do?

A

Transmit signals to outer plexiform layer.

** plexiform layer = layer of synaptic connections **

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4
Q

What type of cells does the photoreceptors synapse with?

A
  • Bipolar Cells
  • Horizontal Cells
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5
Q

Where do horizontal cells transmit signals to?

A
  • Transmit signals from rods and cones to bipolar cells
  • Transmit signals to outer plexiform layer
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6
Q

Is the output of horizontal cells inhibitory or excitatory?

A

Output is always inhibitory (lateral inhibition).

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7
Q

Where do bipolar cells transmit signals to?

A
  • Transmit signals from rods, cones, and horizontal cells.
  • Transmit signals to inner plexiform layer.
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8
Q

Which cells do bipolar cells synapse with?

A
  • Amacrine cells
  • Ganglion cells
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9
Q

What signals do amacrine cells transmit?

A
  • Transmit signals:
    • directly from bipolar to ganglion cells
    • within inner plexiform layer from axons of bipolar cells to dendrites of ganglion cells or to other amacrine cells
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10
Q

Which type of cells in the retinal layers transmits signals from the retina to the brain?

A

Ganglion Cells !!!!!

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11
Q

What do the axons of ganglion cells make up?

A

Optic Nerves

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12
Q

What are the only retinal cells that transmit action potentials?

A

Ganglion Cells

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13
Q

Except for ganglion cells, what type of conduction does the other cell types use?

A

Electrotonic conduction which allows graded conduction of signal strength.

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14
Q

What do interpexiform cells do?

A

transmit from inner plexiform layer to outer plexiform layer (retrograde)

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15
Q

Are interplexiform cells involved in lateral inhibition?

A

Yes - fine tune original image that is picked up by the rod and cone cells.

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16
Q

What are the four neurons that compose pure rod vision?

A
  • rods
  • bipolar cells
  • amacrine cells
  • ganglion cells
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17
Q

In the foveal region, what are the three neurons that compose the direct pathway?

A
  • cones
  • bipolar cells
  • ganglion cells
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18
Q

Which neurotransmitter goes from the rod and cones to bipolar cells?

A

Glutamate

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19
Q

Which neurotransmitters are released from amacrine cells?

A
  • GABA
  • glycine
  • dopamine
  • acetylcholine
  • indolamine

**they are ALL INHIBITORY**

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20
Q

What are the functions of amacrine cells?

A
  • About 30 kinds:
    • one type is part of direct pathway for rod conduction
    • one type responds strongly to onset of continuing visual signal but fades rapidly
    • some types respond strongly at the offset of visual signals, but the respone fades rapidly
    • some respond when a light is turned on or off
    • one type responds to movement of a spot across the retina in a specific direction
    • THEREFORE, MOST AMACRINE CELLS ARE INTERNEURONS THAT HELP ANALYZE VISUAL SIGNALS BEFORE THEY LEAVE THE RETINA!
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21
Q

What are the 3 types of ganglion cells?

A

W, X, and Y

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22
Q

How many rods and cones converge on each ganglion cell and the optic nerve fiber from the ganglion cell?

A

Average 60 rods and 2 cones.

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23
Q

What happens to the number of rods and cone that converge on each ganglion cell as you approach the fovea?

A

Fewer rods and cones converge on each optic fiber and rods and cones become more slender:

  • increased visual acuity in central retina
  • in central fovea there are only slender cones ( about 35,000) and NO rods.
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24
Q

Is the peripheral retina more sensitive to weak light?

A

Yes - thus night vision is better out of the corner of your eye.

  • As many as 200 rod converge on a single optic fiber in the more peripheral regions of the retina.
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25
Q

What percentae of ganglion cells are made up of W type and what is its function?

A
  • 40%
  • Small
  • Transmit signals 8 m/sec
  • Receive most of their excitation from rods transmitted by way of small bipolar cells ad amacrine cells
  • They have broad fields in the peripheral retina because their dendrites spread widely in the inner plexiform layer.
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26
Q

How do W ganglion cells receive most of their excitation?

A

From rods transmitted by way of smal bipolar cells and amacrine cells.

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27
Q

Why do W ganglion cells have broad fields in the peripheral retina?

A

Because their dendrites spread widely in the inner plexiform layer.

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28
Q

What percentage of ganglion cells are made up of X-type and what are their functions?

A
  • 55%
  • Medium diameter
  • Transmit signals 14 m/sec
  • They have small fields
    • signals represent discrete retinal locations
  • Every X ganglion cell receives input from at least one cone cell; therefore, probably responsible for ALL color vision.
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29
Q

Which type of ganglion cell is probably responsible for ALL color vision?

A

X ganglion cells

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30
Q

Do X-ganglion cells have a small or large field in the retina?

A

Small - signals represent discrete retinal locations.

31
Q

What percetage of ganglion cells are made up of Y-type cells and what is their function?

A
  • 5%
  • Large diameter
  • Transmit signals 50 m/sec or faster
  • Respond to rapid changes in visual image
  • Presumably apprise the CNS almost instantaneously when a new visualevent occurs anywhere in the field without great accuracy with respect to location of field.
32
Q

Which ganglion cell type presumably apprise the CNS almost instantaneously when a new visual event ocurs anywhere in the field without great accuracy with respect to location of field?

A

Y Ganglion Cells

33
Q

What is the function of the dorsal lateral geniculate nucleus?

A
  • Receives input from the optic nerve
  • Relays information from optic tract to visual cortex by way of optic radiation (geniculocalarine tract).
34
Q

How much decussation occurs in the optic chiasm?

A

50% decussation in optic chiasm.

35
Q

How many nuclear layers make up the lateral geniculate nucleus?

A

6 nuclear layers in lateral geniculate nucleus.

  • II, III, V receive signals from lateral half of ipsilateral retina
  • I, IV, VI receive signals from medial half of opposite retina
36
Q

Where do layers II, III, and V of the lateral geniculate nucleus receive signals from?

A

Lateral half of ipsilateral retina

37
Q

From where does layers I, IV, and VI of the lateral geniculate nucleus receive signals from?

A

medial half of opposite retina

38
Q

Where does the dorsal lateral geniculate nucleus relay information from and to?

A
  • From Optic Tract
  • To Visual Cortex by way of the optic radiation (geniculocalcarine tract)
39
Q

Where does the left visual cortex get visual information from?

A

Temporal field of the left eye and the nasal field of the right eye.

40
Q

Where does the right visual cortex receive visual information from?

A

Temporal field of the right eye and the nasal field of the left eye.

41
Q

What kind of neurons do layers I and II of the dorsal lateral geniculate nucleus contain?

A

Large Neurons

42
Q

Which layers of the dorsal lateral geniculate nucleus are considered the magnocellular layers?

A

Layers I and II

43
Q

What type of cell do layers I and II of the dorsal lateral geniculate nucleus receive input almost entirely from?

A

Large Y type ganglion cells.

44
Q

Which layers of the dorsal lateral geniculate nucleus transmit only black and white?

A

Layers I and II

45
Q

Is point to point transmission poor in layers I and II of the dorsal lateral geniculate nucleus?

A

Yes

46
Q

What do layers I and II of the dorsal lateral geniculate nucleus provide?

A

Provides rapidly conducting pathways to visual cortex.

47
Q

Which layers of the dorsal lateral geniculate nucleus are considered parvocellular layers?

A

layers III through VI (3, 4, 5, and 6)

48
Q

What size of neurons do layers III through VI of the dorsal lateral geniculate nucleus contain?

A

Small to medium-size neurons.

49
Q

Which type of ganglion cell do layers III through VI of the dorsal lateral geniculate nucleus receive input almost entirely from?

A

X-type ganglion cells.

50
Q

What do layers III through VI of the dorsal lateral geniculate nucleus provide?

A

Provides moderate conducting pathway to visual cortex.

51
Q

Does layers III through VI of the dorsal lateral geniculate nucleus have accurate point to point transmission?

A

Yes

52
Q

What is tranmission gating in the dorsal lateral geniculate nucleus?

A

Lateral geniculate nucleus controls how much of the signal is allowed to pass to the cortex.

53
Q

What are the 2 sources of gating control in the dorsal lateral geniculate nucleus?

A
  • Corticofugal fibers from primary visual cortex
  • Reticular areas of the mesencephalon

**Both of these sources are inhibitory and help highlight visual information that is allowed to pass**

54
Q

What is another name for the primary visual cortex?

A

Striate Cortex

55
Q

Where is the primary visual cortex located?

A

Occipital Lobes

56
Q

Where do geniculocalcarine fibers of the primary visual cortex terminate mainly?

A

Layer IV

57
Q

How many layers make up the primary visual cortex?

A

Six Distinct Layers

58
Q

In the primary visual cortex, where do signals from the more peripheral retina terminate?

A

At or in concentric half circles anterior to the pole but still along the calcarine fissure.

59
Q

In the primary visual cortex, where do signals from the macular area terminate?

A

Near the occipital pole.

60
Q

In which subdivision of layer IV of the primary visual cortex, where do signals from Y ganglion cells terminate?

A

Layer IVc-alpha

61
Q

In which of the subdivisions of layer IV of the primary visual cortex do signals from X ganglion cells terminate?

A

Layer IVc-beta and IVa

62
Q

True or Fasle:

The visual cortex is organized into several thousand vertical columns of neurons.

A

False - organized into several million vertical columns of neurons.

  • diameter = 30 - 50 micormeters
  • about 1000 neurons per column
63
Q

What type of special column-like areas are located among the columns of the secondary visual areas?

A

Color Blobs

64
Q

What do color blobs receive?

A

Receive lateral signals from adjacent visual columns and are activated specifically by color signals.

65
Q

What specifically activated color blobs?

A

Color signals

66
Q

What subdivision of layer 4 of the primary visual cortex does fast, black and white signals from Y type ganglion cells terminate in?

A

IVc-alpha

67
Q

What subdivision of layer 4 of the primary visual cortex does very accurate, color signals from X type ganglion cells terminate in?

A

IVa and IVc-beta

68
Q

What does the cortical area of the primary visual cotex decipher?

A

Whether the respective areas of the two visual images from the two separate eyes are in register with each other.

69
Q

What is the deciphered information from the cortical area of the primary visual cortex used for?

A

To adjust the directional gaze of the separate eyes.

70
Q

What is required for stereopsis?

A

The deciphering by the coritcal area to whether the respective areas of the two visual images from the two separate eyes are in register with each other.

71
Q

What nerve controls both sets of ciliary muscles?

A

CN III controls both sets of ciliary muscles (occulomotor nerve).

72
Q

What is the mechanism of accommodation in a young person?

A
  • when the lens is in a relaxed state with no tension on its capsule, it assumes an almost spherical shape.
  • suspensory ligaments attached radially around the lens create a tenion that causes the lens to remain relatively flat under normal eye conditions.
    • meridional fibers of ciliary muscle contract and release tension of lens
    • circular fibers of ciliary muscle also decrease tension on lens
73
Q

Explain accommodation in an older person.

A
  • lens becomes larger and thicker with age
  • lens becomes less elastic with age
  • power of accommodation decreases to less than 2 diopters by the age of 45 - 50
  • it decreases to 0 by the age of 70
  • prebyopia
74
Q
A

Human Physiology 2 - Unit 1 - Zach H. (9 decks)

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