Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
110 Cards in this Set
- Front
- Back
|
What modality makes up the majority if our cortex
|
vision
|
|
|
How many layers does the eye have
|
3
|
|
|
What is the outermost layer of the eye and what is it made up off
|
The outer most layer is made up of sclera (white of the eye) and the anterior 1/6th of this layer is made up of cornea (clear part of the eye)
|
|
|
What is the function of the cornea and where is it located
|
Cornea is the first place where the light hits the eye, it focuses light and has refractory power, it located in the outermost layer, it makes up the anterior 1/6th of the sclera
|
|
|
What is middle layer of the eye
|
All the structure located here are called uveal tract and the choroid(deeply pigmented) makes up the biggest portion, anteriorily it makes up the ciliary body that has the ciliary muscles located in it and stroma of the iris
|
|
|
what is inner most layer of eye
|
Retina
|
|
|
What is the most vascualr layer of the eye
|
Uvea or middle layer, this is located b/t sclera and retina
|
|
|
Where does the neural processing take place in the eye
|
At the inner most layer or retina
|
|
|
Where is choroid located
|
In the middle eye
|
|
|
How is shape of the eye maintained
|
It is maintained by the intraocular pressure by the fluid located inside the eye
|
|
|
What is the colored portion of the eye called
|
Iris
|
|
|
What is the white portion of the eye called
|
sclera
|
|
|
What is the fluid that exerts intraocular pressure called
|
Aqueous humor
|
|
|
How is aqueous humor secreted
|
It is secreted by the ciliary body, which makes it and secretes it into the posterior chamber
|
|
|
How is aqueous humor drained
|
It is drained by canals of schlemm
|
|
|
What happens if there is too much intraocular pressure
|
Glaucoma
|
|
|
What is papilledema
|
When the intracranial pressures ↑, it pushes up on the meninges, this pushes up on the subarachnoid space and interferes with the axonal transport to the optic nerve. If this pressure ↑ continuously, it will lead to engorgement and elevation of the optic disk and will cause hemorrhage
|
|
|
What is vitreous humor
|
It is behind the lens, makes up 80% volume of the eye and has phagocytic function and clears up the debris
|
|
|
What is output
|
It is layer of neuronal cells called retinal ganglion cells, the axons of these cells comprise optic nerve
|
|
|
Light hits what part of the eye first
|
Cornea
|
|
|
What is the most powerful focusing element of the eye
|
Cornea, it is 2x more powerful than lens,
|
|
|
What is a diopter
|
It is inverse of focal length and is used to describe the power of the lens, D=1/fl
|
|
|
What is the diopter of cornea vs. lens
|
Cornea = 40, lens=20
|
|
|
What is a convex lens
|
It is like a prism and bends the light in a way that it focuses on a common point,
|
|
|
What is a focal point
|
Point when light passed through the prism comes to a common point
|
|
|
What is the focal length
|
Distance between the focal pt. and the lens
|
|
|
What does a convex lens with thin or less curvature signify
|
Long focal length
|
|
|
What does a convex lens with thick or more curvature sig
|
Short focal length
|
|
|
How is focal length determined
|
It is determined by the shape and size of the lens
|
|
|
What does a concave lens do to the focal length
|
It lengthens the focal length
|
|
|
What is cataracts and what is the common cause
|
It is opacities of the lens or loss of clarity of the lens and mainly caused by excessive UV damage
|
|
|
What is the image that is formed
|
As light passes through the lens the image that is formed is inverted and reversed
|
|
|
Where does the image from lens form
|
It forms on the retina
|
|
|
What is myopia and what causes myopia
|
Near sightedness, caused by too thick cornea or eye ball too long
|
|
|
What is hyperopia
|
It is far sightedness, caused by low refractive index and eye ball being too short or cornea too thin
|
|
|
How is myopia or hyperopia corrected
|
They are corrected by contacts or glasses that are + for hyperopia and – for myopia
|
|
|
What is the job of the cornea and lens
|
Bend the light in a way so that our photoreceptors can see a focused image
|
|
|
Accommodation
|
Is the process by which we can change the length of our lens to ↑ our refractive period
|
|
|
What does accommodation depend on
|
2 things the internal recoil force of the lens and exterior force generated by ciliary muscles attached to zonule fibers
|
|
|
Distant object what happens
|
Zonule force dominates the lens internal elasticity, the lens flattens
|
|
|
What happens if a product is brought close to us
|
The lens internal elasticity wins and the lens rounds up
|
|
|
What happens to zonule fibers when the ciliary muscles contract
|
The lens tension is exerted on the zonule fibers and they relax and the lens rounds up
|
|
|
What diopter can we achieve with accommodation
|
We can go from 20D to 34D
|
|
|
What happens to accommodation with age
|
It is reduced and we only go up to 21D
|
|
|
What is a another way to ↑refractive power
|
We can do so by decreasing the size of our pupil
|
|
|
What is the pupil
|
It is the aperture of our lens, increases the depth of the field
|
|
|
How is changing the pupil possible
|
Pupil is the aperture of the iris and iris is innervated by the PS and Sym. S
|
|
|
What does PNS innervate
|
It innervates the sphincter muscles of the iris
|
|
|
What innervates the dilator muscles
|
Sympathetic muscles
|
|
|
What are the 3 physiological events involved with accommodation
|
Pupil shortens, eyes converge, and eyes accommodate
|
|
|
Where is light energy converted to the electrical energy? what does that organ do
|
Retina, it send this info to the brain and brain constructs an image that can be recognized by our eyes
|
|
|
What is + in the presence of a lot of light
|
Cones
|
|
|
What kind of vision are the cones responsible for
|
Color vision
|
|
|
What kind of cells are + in low light
|
Rods, they can detect even a single photon of light
|
|
|
What are the out put cells from the retina
|
Ganglion cells
|
|
|
What do ganglion cells do
|
They send their axons to the brain via (optic nerve) and this tell the brain about the signals detected in the retina
|
|
|
These cells relay information from the photo receptors to the brain
|
Bipolar cells
|
|
|
What are the bipolar cells
|
They are rod bipolar and cone bipolar
|
|
|
What are the interneuron that mediate lateral interactions between layers of the retina like inner and outer plexiform layers
|
Horizontal and amacrine cells
|
|
|
What does pigment epithelia do
|
It releases growth factor and phagocyses outer segment
|
|
|
What is the mechanical connection between retina and the pigment epithelia? Weak or strong? And what does it cause?
|
It very weak and leads to retinal detachment
|
|
|
What happens with retinal detachment
|
Retina depends on the pigment epithelia for nourishment like GF and if that’s gone, it leads to photoreceptors stop working because they are isolated from the choroid vasculature
|
|
|
What do bipolar cells do
|
They are direct conduits from photoreceptors and synapse directly onto the ganglion cells
|
|
|
What is the pathway when the light enters the eye
|
Light hits the rods and cones and they release NT on Bipolar cells, w/c then release NT on to ganglion cells
|
|
|
What type of cells are responsible for lateral integration
|
Horizontal and amacrine cells
|
|
|
Where does the light hit on Rods and Cones
|
On the outer segment
|
|
|
What type of protein is found in the outer segment of Rods and cones
|
Opsin
|
|
|
What is opsin and what is it called in rods
|
In rods it is called rhodopsin and it is small light absorbing G-protein
|
|
|
What is the process of phototransduction
|
The light enters and hits the outer segment of the rods, this causes a conformational change in a small light absorbing G-protein receptor called opsin. Opsin depends on a small molecule called retinal. When the light hits rhodopsin retinal undergoes a conformational change and alters rhodopsin conformation. This allows the + of heterotrimeric G-protein, called transducin, the a-subunit of transducin exchanges a GDP for GTP, and dissociates form the beat and gamma subunits and gets +, this then + a phophodiesterase which lowers the amount of cGMP . Since the cell has many cGMP gated voltage channels, and now less cGMP comes in, and less current comes in and the cell hyperpolarizes and releases less NT
|
|
|
What is rhopdopsin and what does it depend on
|
It is opsin inside the rods and it depends on retinal
|
|
|
What is transducin
|
heterotrimeric G-protein, w/c when + can cause + of a phosphodiestrase and that leads to low cGMP levels and therefore hyperpolariztion of cell and less release of NT
|
|
|
What kind of potential do photoreceptors launch
|
They launch local potentials, they cannot launch action potentials
|
|
|
What type of cells in the aye are capable of launching an AP
|
Only ganglion cells
|
|
|
The release of NT released by photoreceptors depends on
|
The stimulus, in this case it is the amount of light
|
|
|
How is photo transduction signal terminated
|
Arrestin is + it prevents the rhodopsin from activating transducin and that way the retinal dissociates fro rhodopsin
|
|
|
Why should the photoreceptors be located at the back of the eye
|
Because rods and cones both have to be next to the pigment epithelium and the choroid
|
|
|
What kind of purpose do rods and cones serve
|
They recycle the shed disks of the outer segments
|
|
|
What kind of visions is mediated by the rods
|
Scotopic
|
|
|
When are rods used the most
|
During the conditions of low light
|
|
|
If you are looking at the stars, what kind of vision are u using, and what cell mediates it
|
You are using scotopic vision and the rods are mediating it
|
|
|
What happens if the rods are not working
|
Night blindness, you have trouble seeing in low light
|
|
|
What is rods sensitivity to light
|
It is very high, they can detect even a single photon
|
|
|
What kind of vision is mediated by the cones
|
photopic
|
|
|
When are cones used the most
|
During high light conditions
|
|
|
What happens if you lose the cones
|
Legally blindness
|
|
|
What is the cone sensitivity to light
|
Not as high as rods, require about 100 photons
|
|
|
What cells mediate our everyday vision
|
Cones
|
|
|
What molecule is important for cones to work properly
|
11 cis-retinal
|
|
|
What cells do our color visions
|
Cones
|
|
|
How many classes of cones are there
|
Three, long, medium and short
|
|
|
What are the classes of cones depnd on
|
Their ability to absorb photons
|
|
|
What color is absorbed via long spectra cones
|
Red
|
|
|
What color is absorbed via short spectra cones
|
blue
|
|
|
What color is absorbed via medium spectra cones
|
Yellow green
|
|
|
2 things, 1 is same in all cones and 1 is different based on their spectra
|
11 cis retinal is same and they all use different opsin
|
|
|
What does opsin determine
|
It determines the cones ability to absorb a certain intensity of the light
|
|
|
Does our vision depend more on one type of cone as opposed to the other
|
No, we equally depend on all three cones
|
|
|
When we come with a color of light, like red, and it is absorbed by the cell, what is cells response
|
It hyperpolarizes
|
|
|
Which sex has higher incidence of color blindness and why
|
Males, because the genes are located in the x-chromosome
|
|
|
What is fovea and where does it lie
|
Fovea lies in a depression the macula lutea and it has the highest visual acuity
|
|
|
Where does the macula lutea lie
|
It lies near the optic disk
|
|
|
What is significant about the optic disk
|
Optic disk has no neurons and it makes our blind spot, and it is in here that all the axons of the ganglion cells leave and make up the optic nerve
|
|
|
What cells are found in higher density
|
Cones are higher than rods
|
|
|
What is the central part of fovea called and what is absent from it and what is in high abundance
|
Foveola, no rods, and cones are in high number
|
|
|
Is foveola a vascular or avascular structure and what is the significance
|
It is avascular, it renders cones highly dependent on the PE and choroid
|
|
|
What is the main reason for such a high visual acuity in fovea
|
Increased connectivity of the cones
|
|
|
What is the difference between the circuitry in the fovea as opposed to rest of the retina
|
In the fovea the connection is 1-1, i.e. one cone will synapse on one bipolar cell and that one bipolar cell will synapse on one ganglion cells and that way the acuity is heightened
|
|
|
What is the ganglion cell in the fovea called
|
It is called midget cell ganglion and it has a very small receptive field
|
|
|
Why is the visual field less in rest of the retina
|
Because of convergence, in parts of retina other than fovea, the rods and cones can converge. For example, the rods in other part of retina, the rods to bipolar ratio is 15-1
|
|
|
Does convergence result in fine resolution
|
No, since things are converging, all it means is that there are too many impulses, so no fine resolution but instead these are fast conducting cells and all they transmit is that there is an impulse i.e. fast and sensitive
|
