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biology > senses III > Flashcards

senses III Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

How many classes of photoreceptors are in the retina?

A

4 classes

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2
Q

how many classes of horizontal, bipolar and amacrin cells are in the retina?

A

50-70

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3
Q

how many classes of ganglion cells are in the retina

A

20-30

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4
Q

What are the first stages of visual processing?

A
  • Edge detection in visual scenes
  • Edge enhancement in patterns
  • Filtering of spatial, wavelength, movement and directional information
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5
Q

What does the brain extract from physical cues

A

menaingful info

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6
Q

perceptual effects originate from where?

A

interactions between cells in the retina

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7
Q

What is the machband pattern?

A

each bar appears lighter on its left edge and darker on its right edge. However, bars are uniform in their physical brightness (reflectance)

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8
Q

Where does lateral inhibition occur?

A

where the neurons in a region—in this case, retinal cells—are interconnected, either through their own axons or by means of interneurons, and each neuron tends to inhibit its neighbours

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9
Q

What is lateral inhibition (Hartline)

A

Neighboring neurons in the same layer of the retina inhibit each other mutually

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10
Q

Neighbouring neurons in the same layer of the retina…

A

inhibit each other mutually

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11
Q

How does the retina process edges

A

• When an edge (dark and light illumination) is created, the cells on both sides of the edge will influence each other strongly. This changes their signals such that a much stronger contrast is coded than physically exists. More distant cells are not affected. As a result the perception of the edge is enhanced.

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12
Q

What is the koffka-ring illusion

A

A grey ring on a dark and bright background

A white bar separate the two halves of the ring

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13
Q

What happens when we have little context cues?

A

we perceive the physical reflectance of the surfaces which carries little information

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14
Q

What are horizontal connections in the retina?

A
  • horizontal cells

* amacrine cells

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15
Q

What are vertical connections in the retina?

A
  • Fovea: 1 cone to 1 bipolar
  • Periphery: Many cones to 1 bipolar, many bipolars to 1 ganglion cell. Same for rods, but connect to rod bipolar cells other classes of ganglion cells.
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16
Q

Cones (or rods) converging on a bipolar cell form its…

A

receptive field

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17
Q

the receptive field of a ganglion cells is formed by all converging ….

A

bipolar cells

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18
Q

Receptive fields are what in the periphery

A

large in the periphery (low acuity)

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19
Q

receptive fields are what in the fovea?

A

small in the fovea (high acuity)

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20
Q

What cells have centre-surround receptive fields?

A

bipolar and ganglion

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21
Q

How do horizontal cells influence bipolar cells?

A

either directly or by feeding back information to the cones (probably both)

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22
Q

what does the bipolar cell integrate?

A

EPSPs and IPSPs (spatial and temporal summation)

23
Q

signals from several bipolar cells define the activity in where

A

ganglion cell

24
Q

what does turning on a light in the centr of an on-centre bipolar cell’s receptive field do?

A

excites the cell because it receives less glutamate, which otherwise inhibits on-center bipolar cells.

25
Q

What does turning off light in the centre of an off-centre bipolar cells receptive field do?

A

excites the cell because it receives more glutamate, which depolarizes off-center bipolar cells. (Behavioural Neuroscience 8e, p. 313)

26
Q

In the vertebrate retina photoreceptors release what when not simtulated

A

glutamate

27
Q

WHat does exposure to light do in the photoreceptor?

A

hyperpolarises and decreases release of glutamate

28
Q

On-centre bipolar cells have what synapse?

A

inhibitory

29
Q

Off-centre bipolar cells have what synapse

A

excitatory

30
Q

If a non-bipolar cell, the decreased neurotransmitter release means what

A

youll depolarise and increase your neurotransmitter release which goes on to increase firing release

31
Q

In an On-centre bipolar cell, when the spot is off-surround…

A

there will be more IPSPs than EPSPs (because no or fewer cones are stimulated in the On-centre than in the OFF-surround)

32
Q

What are axons like in ganglion cells?

A

long axons that project (through the blind spot of the eye) as optic nerve to the LGN in the midbrain

33
Q

What do the axons do in ganglion cells?

A

They generate action potentials (spikes) when transmitting a signal

34
Q

what do most ganglion cells have

A

centre-surround receptive fields and will show a sombrero-shaped response similar to the bipolar cells

35
Q

What happens whilst the on-centre bipolar cell depolarises?

A

the ON-centre ganglion cell responds by increasing its spike rate

36
Q

what happens whilst the off-centre bipolar cell hyperpolarises?

A

the OFF-centre ganglion cell responds by decreasing its spike rate

37
Q

How deos the ganglion cell respond when the light spot covers the whole on-centre?

A

the ganglion cell responds with its highest spike rate

38
Q

What happens when a ring of light covers all of the surround but not the ON-centre

A

the ganglion cell responds with the lowest spike rate or even no spikes at all.

39
Q

What happens when the whole receptive field is equally stimulated,

A

the ganglion cell is at rest and fires with a spontaneous frequency.

40
Q

What are P-ganglion cells?

A

small Receptive Fields, slower conduciton speed, high acuity, poor response to transient stimuli, colour sensitive.

41
Q

What are M-ganglion cells?

A

large Receptive Fields, higher conduction speed, sensitive to motion, low acuity, no colour discrimination

42
Q

Retinal ganglion cells project…

A

retinotopically to each layer of the LGN

43
Q

In addition ot the 6 horizontal layers, how are neurons in the V1 further seperated?

A

into functionally distinct hypercolumns (ca 1mm2)

44
Q

Hoe do neurons respond when a slowly rotating bar reaches the neuron’s preferred orientation

A

Neuron responds with maximal spike rate

45
Q

What did Hubel and Wiesel’s 1977 ice cube model of the V1 show?

A
  • All neurons in an orientation column share the same preference for a particular orientation of a bar stimulus in their receptive field
  • Retinotopic organisation: Signals from co-located ganglion cells in the retina are processed by respectively co-located cortical neurons within each orientation column
46
Q

What do microelectrode recordings reveal?

A

that cells differ greatly in their receptive fields.

(A) Visual cells in the lateral geniculate nucleus (LGN) have concentric receptive fields, like those of retinal bipolar cells and ganglion cells

(B) Visual cells in the cerebral cortex are more responsive to bars of light

(C) they may respond only to motion in a particular direction

Neurons have preferred orientatiosn

47
Q

What is V1 fundamentally important for?

A

perceptual processing

48
Q

What is the dorsal system?

A

(where system): Interacting with the world

49
Q

what is the ventral stream?

A

(what system): Making sense of the world

50
Q

What is responsible of edge enhancement?

A

lateral inhibition

51
Q

• Bipolar and ganglion cells can have centre-surround receptive field. These can be on-centre/off surround ….

A

inhibitory synapse with the receptors that form the centre of the receptive field

52
Q

• Bipolar and ganglion cells can have centre-surround receptive field. These can be off-centre/on-surround

A

excitatory synapse with the receptors that form the centre of the receptive field

53
Q

what cells repond to ratios of light/dark

A

ganglion

biology (26 decks)

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