Visual System Flashcards
Why are eyes being fluid filled important?
the fluid helps bend the light and focus it on the posterior aspect of the eyeball
Anatomy of the eyeball (pathway that light travels through)
Cornea (transparent first lens that allows light into your eye)
Pupil (behind the cornea, opening that lets light in)
Iris (surrounds the pupil, part of the eye that is colorful
, capable of expanding and contracting in response to the amount of the light in our environment)
Aqueous Humor (fluid in between the lens and the pupil)
Lens (allows us to change our depth of focus to see clearly at various distances/depths)
Vitreous humor (fluid behind the lens)
Vitreous chamber (takes the light through the eye to be reflected onto the back of the eye)
Retina (transduces light energy into electrical signals)
Nerve fibers (leave from the retina to make up the optic nerve)
Optic nerve (brings visual info the brain)
What is the blind spot?
area of the eye where there are no light sensitive cells because it is where the optic nerve begins
What are the Macula and Fovea?
the center of our vision
where light reflects
have the most dense number of photoreceptors
What does the retina do in response to light input?
becomes hyperpolarized
What happens when the rods or cones absorb a photon
the cell undergoes a shape or conformational change which results in an electrical potential
What is the visual space
external world that both retinas can transduce
amount of the real world that you are currently looking at and both of the retinas are currently transducing
What is the visual field
portion of space seen by each retina
What is the monocular field and which retinas can see it?
your peripheral vision
both retinas can see it, but only your right eye can see your right monocular field, and only your left eye can see your left monocular field
What are bipolar cells responsible for
peripheral visual system integration
What makes photoreceptors unique?
They are the only cell type that is directly responsive to light energy
What type of cells are the only pathway out of the retina and the only cell class to produce action potentials?
retinal ganglion cells
Photoreceptors and bipolar cells can only operate through what in their electrical potentials?
graded changes in their electrical potentials, with neurotransmitter release from these cells proportional to the change in each cell’s membrane potential
Characteristics of Rods
high sensitivity to light
more plentiful quantity of photopigment
slow response rate to light
night vision = specialization
low visual acuity
saturate in day light
no role in color vision
not present in the fovea
more numerous in the retina
damage causes night blindness and loss of peripheral vision
Characteristics of cones
low sensitivity to light
less plentiful quantity of photopigment
fast response rate to light
day vision = specialization
high visual acuity
saturate in bright light
trichromatic role in color vision
high presence in the fovea
less numerous in the retina
damage causes blindness and loss of color vision
what relationship do rods and bipolar cells have and what is the significance?
Rods have a one-to-many relationship with bipolar cells, indicating that a single bipolar cell combines signals from many rods
Are cones or rods responsible for the majority of the retinas output
Cones, even though they are present in far fewer numbers in the retina
What relationship do cones have with bipolar cells
One-to-one
in light transduction, is there neurotransmitter release at rest?
Yes, even at rest there is some degree of neurotransmitter release
This is called being tonic
Objects in the right visual field are imaged where on the R and L eye?
temporal retina of the L eye and the nasal retina of the R eye
Objects in the left visual field are imaged where on the R and L eye?
the temporal retina of the R eye and the nasal retina of the L eye
Receptive field
what a cell or neuron responds to in the real world (not all the information that is possible, but just what the cell or neuron finds behaviorally important)
In what order does light wavelengths move through the visual system?
Photoreceptors –> bipolar cells –> retinal ganglion
*decrease in abundance as you move through (photoreceptors are the most abundant, retinal ganglion cells are the least abundant)
Do off-center bipolar cells produce an inhibitory or excitatory effect?
inhibitory
decreases its neurotransmitter release when light hits its center which results in decrease in firing of the retinal ganglion cell below it
Do on-center bipolar cells produce an inhibitory or excitatory effect?
excitatory
when the center of the field absorbs light, that causes excitation of the on-center bipolar cell which increases neurotransmitter release and therefore an increased firing of the retinal ganglion cell
What is the pathway of the optic pathway?
begins in the retina as axon ganglion cells –> leaves the eye at the optic disc –> becomes the optic nerve —> extends to the optic chiasm which is where optic nerves from both eyes cross –> nerve fibers are now called the optic tract –> ends in the lateral geniculate nucleus of the thalamus where information is then passed on to the primary visual cortex by travel of axons (called optic radiations)
What are examples of optic nerve damage (causes)
trauma, tumors, stroke, glaucoma
What does damage in the right optic nerve effect?
can’t see the right monocular space
What does damage in the optic chiasm effect?
Can’t see either monocular space
What does damage in the right optic tract effect?
can’t see the left visual field (both binocular and monocular spaces)
What is retinotopy
organization of real-world visual space maintained throughout the visual system
Dorsal streams (what happens when information is passed dorsally)
processing WHERE and MOVEMENT information
integration of sensory information via your visual system in order to make judgements about where the visual stimulus is coming from
Ventral streams (what happens when information is passed ventrally)
processing WHAT information
helping to integrate multiple stimulus characteristics to determine what is the thing you are looking at
*important for facial recognition
