Flashcards in Vision II Deck (51):
What are the two types of photoreceptors?
Rods and cones.
They transmit signals to the outer plexiform layer.
What do photoreceptors synapse with?
Bipolar cells and horizontal cells.
What do horizontal cells transmit signals from and to?
They transmit signals from rods and cons to bipolar cells.
They transmit signals to outer plexiform layers.
What is the output of horizontal cells?
It is always inhibitory (lateral inhibition).
Where do bipolar cells transmit signals from and to?
They transmit signals from rods, cones and horizontal cells.
They transmit signals to the inner plexiform layer.
What do bipolar cells synapse with?
Amacrine and ganglion cells.
What do amacrine cells transmit signals from?
They transmit signals directly from bipolar to ganglion cells.
They also transmit signals within the inner plexiform layer from axons of bipolar cells to dendrites of ganglion cells or to other amacrine cells.
Where do ganglion cells transmit signals?
From the retina to the brain.
What are the axons of ganglion cells also known as?
What are the only retina cells that transmit action potentials?
Optic nerves (ganglion cells)
Where do interplexiform cells transmit signals from?
The inner plexiform layer to the outer plexiform layer.
What are the inhibitory signals of the interplexiform cells?
They are from lateral inhibition.
What are the three neurons in the direct pahway of cone vision?
What is the foveal region?
It represents a new type of vision based on cone vision.
What are the four components of pure rod vision?
What neuotransmitter is used when rods/cons and bipolar cells communicate?
What transmitters are used in amacrine cells?
Eight or more kinds of neurotransmitters including GABA, glycine, dopamine, actylcholine and indolamine.
All of them are inhibitory.
What is the function of amacrine cells?
They are part of the directy pathway for conduction.
Others respond strongly to continuing visual signals, but fade rapidly.
Some respond strongly at the offset of visual siganls, but the response fades rapidly.
Some respond when a light is turned on or off.
Some respond to movement of a spot across the retina in a specific direction.
What is the general function of amacrine cells?
They are interneuons that help analyze visual signals before they leave the retina.
How many rods and cones converge on each gangion cell?
60 rods and 2 cones.
When approaching the fovea, fewer rods and cones converge on each optic fiber and rods and cones become more slender. What is the result of this?
Visual acuity is increased in the central retina.
What is only found in the central fovea?
Only slender cones, no rods.
What is the peripheral retina more sensitive to?
What to W ganglin cells receive most of the exciation from?
Rods transmitted by way of small bipolar cells and amacrine cells.
Why to W ganglion cells have broad fields in the peripheral retina?
Because their dendrites spread widely in the inner plexiform layer.
Every ___ cell receives an input from at least one cone cell;l therefore, it is probably responsible for all color vision.
What is the diameter of Y ganglion cells?
It is large
What is the function of Y ganglion cells?
They respond to rapid changes in visual image.
When do Y ganglion cells apprise the CNS?
When a new visual event occurs anywhere in the field without great accuracy with respect to location of the field.
What is the function of the dorsal lateral geniculate nucleus?
It receives input from the optic nerve.
It relays information from the optic tract to the visual cortex by way of optic radiation.
There are six nuclear layers in the gniculate nucleus. What do layers II, III and V receive signals from?
The lateral half of the ispilateral retina.
There are six nuclear layers in the lateral geniculate nucleus. What do layers I, IV and VI receive signals from?
The medial half of the opposite retina.
What layers of the dorsal lateral geniculate nucleus receive input from large Y type gangion cells?
Layers I and II
What layers of the dorsal lateral geniculate nucleus transmits only black and white?
Layers I and II.
Point to point transmission is poor.
What layers of the dorsal lateral geniculate nucleus provide rapidly conducting pathways to the visual cortex?
Layers I and II
What are the magnocellular layers of the dorsal lateral geniculate nucleus?
Layers I and II.
What are the parvocellular layers of the dorsal lateral geniculate nucleus?
Layers III - VI
What layers of the dorsal lateral geniculate nucleus receive input almost entirely fro large X type ganglion cells?
Layers III - VI
What layers of the dorsal lateral geniculate nucelus transmit color?
Layers III - VI.
What layers of the dorsal lateral geniculate nucleus have accurate point-to-point transmission?
Layers III - VI
What is transmission gating?
It refers to the fact that the lateral geniculate nucleus controls how much of the signal is allowed to poass the cortex.
What are sources of gating control in transmission gating of the lateral geniculate nucleus?
Corticofugal fibers from the primary visual cortex
Reticular areas of the mesencephalon.
Both of these sources are inhibitory and help highlight visual information that is allowed to pass.
What is another term for the primary visual cortex?
It is located in the occipital lobes.
Where do signals from Y ganglion cells terminate?
In layer IVc alpha of the primary visual cortex.
Where do signals from X ganglion cells terminate in the primary visual cortex?
Layer IVc beta and IVCa
What are color blobs?
Columns in secondary visual areas. They receive lateral signals from adjacent visual columns and are activated specifically by color signals.
Signals from the two separate eyes enter alternating stripes of columns in what layer of the primary visual cortex?
What area of the primary visual cortex deciphers whether the respective areas of the two visual images from the two separate eyes are in register with each other?
The cortical area.
What is the shape of the lens under normal conditions?
It is relatively flat.
How does the eye change with age?
The lens becomes larger and thicker.
It also becoms less elastic.
The power of accommodation decreases to less than 2 diopters by the age of 45 to 50.