Lecture 7 Flashcards Preview

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Flashcards in Lecture 7 Deck (21)
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1
Q

What neurotransmitter is used between rods/cones and bipolar cells?

A

Glutamate

2
Q

What neurotransmitters do amacrine cells use?

A

8+ including GABA, glycine, dopamine, acetylcholine, indolamine; all inhibitory

3
Q

Photoreceptors

A

Includes rods and cones; transmit signals to outer plexiform layer (layer of synaptic connections); synapse with bipolar cells and horizontal cells

4
Q

Horizontal Cells

A

Transmit signals from rods and cones to bipolar cells, transmits signals to outer plexiform layer; output is always inhibitory (lateral inhibition)

5
Q

Bipolar Cells

A

Transmit signals from rods, cones, and horizontal cells, transmit signals to inner plexiform layer; synapse with amacrine and ganglion cells

6
Q

Amacrine Cells

A

Transmit signals directly from bipolar to ganglion cells, and within inner plexiform layer from axons of bipolar cells to dendrites of ganglion cells or to other amacrine cells; about 30 kinds (most are interneurons that help analyze visual signals before they leave the retina)

7
Q

Ganglion Cells

A

Transmit signals from retina to brain; axons make up optic nerves; these are the only retinal cells that transmit action potentials (others use electronic conduction which allows graded conduction of signal strength)

8
Q

Interplexiform Cells

A

Transmit from inner plexiform layer to outer plexiform layer (retrograde); inhibitory signals (lateral inhibition)

9
Q

Foveal Region

A

Represents a new type of vision based on cone vision; three neurons in direct pathway (cones, bipolar cells, ganglion cells); note that pure rod vision consists of four neurons (rods, bipolar cells, amacrine cells, ganglion cells)

10
Q

W Ganglion Cells

A

Make up about 40% of all ganglion cells; small and transmit signals 8m/s; receive most of their excitation from rods transmitted by way of small bipolar cells and amacrine cells; have broad fields in the peripheral retina because their dendrites spread widely in the inner plexiform layer

11
Q

X Ganglion Cells

A

Make up about 55% of all ganglion cells; medium diameter and transmit signals 14m/s; 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

12
Q

Y Ganglion Cells

A

Make up about 5% of all ganglion cells; large diameter and transmit signals 50m/s or faster; respond to rapid changes in visual a image; presumably apprise the CNS almost instantaneously when a new visual event occurs anywhere in the field without great accuracy with respect to location of field

13
Q

Dorsal Lateral Geniculate Nucleus

A

Receives input from optic nerve; relays information from optic tract to visual cortex by way of optic radiation (geniculocalcarine tract); 50% decussation in optic chiasm; six 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

14
Q

Layers I and II of Dorsal Lateral Geniculate Nucleus

A

Magnocellular layers; contain large neurons; receive input almost entirely from large Y ganglion cells; provides rapidly conducting pathway to visual cortex; transmits only black and white; point to point transmission is poor

15
Q

Layers III - VI of Dorsal Lateral Geniculate Nucleus

A

Parvocellular layers; contain small to medium size neurons; receive input almost entirely from large X ganglion cells; provides moderate conducting pathway to visual cortex; transmits color; accurate point to point transmission

16
Q

Transmission Gating

A

Lateal geniculate nucleus controls how much of the signal is allowed to pass to the cortex; source of gating control is corticofugal fibers from primary visual cortex and reticular areas of the mesencephalon (both are inhibitory and help highlight visual information that is allowed to pass

17
Q

Primary Visual Cortex

A

Also called striate cortex; located in occipital lobes; signals from macular area terminate near the occipital lobe; signals from the more peripheral retina terminate at or in concentric half circles anterior to the pole but still along the calcarine fissure; six distinct layers; geniculocalcarine fibers terminate mainly in layer IV

18
Q

Color Blobs

A

Located among the columns of the secondary visual areas; receive lateral signals from adjacent visual columns and are activated specifically by color signals

19
Q

Accommodation in Children

A

Refractive power of the lens can be voluntarily increased from 20 to 34 diopters (accommodation of 14 diopters)

20
Q

Accommodation in 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 tension that causes the lens to remain relatively flat under normal eye conditions; CN III controls both sets of ciliary muscles

21
Q

Accommodation in Older Person

A

Lens becomes larger, thicker, and less elastic with age; power of accommodation decreases to less than 2 diopters by the age of 45-50; decreases to 0 by the age of 70; this is called presbyopia