Vision Flashcards
what is the receptor for taste and smell
chemoreceptors
what is the receptor for pain
nociceptors
what is the receptor for hearing and balance
mechanoreceptors
what is the receptor for temperature
thermoreceptors
what is the receptor for vision
Photoreceptors
define sensory perception
deconstruction of external world and reconstruction of the internal representation
____ is when sensory endings respond to a particular type of energy applied to them
adequate stimulus
the conversion of energy into ____ is called
electrochemical , primary transduction
what are the two scenarios of primary transduction in the visual and hearing systems
visual - converting photos of light in to change in membrane potential
hearing - converting pressure waves to the bending of hair cells
what needs to happen if the generator potential is hyperpolarizing
K leaves the cell
the magnitude of the generator potential is proportional/inversely proportional to the strength of stimulus
proportional
true or false - generator potentials are usually depolarizing
true
humans can detect light with wavelengths between
a) 200-700nm
b) 390-700nm
c) 390-500nm
b
humans can distinguish ____ colors
a) million
b) billion
c) hundreds
a
the tough white fibrous part of the eye is
the sclera
what part of the eye is covered by a thin membrane called a conjunctiva
cornea
what is right behind the cornea
the anterior chamber
___ is the clear fluid secreted by the _____
aqueous humor, ciliary body
where does the aqueous humor drain
canal of schlemm at the cornea scleral junction
what is a similarity between the anterior and posterior chamber
they are both filled with aqueous humor
the sclera is made of
a) connective tissue
b) elastic tissue
c) fibrous tissue
a
true or false the crystalline lens gets more elastic as we age
false - gets less elastic as we get older
what is immediately behind the anterior chamber
crystalline lens
explain the vitreous chamber
it is right behind the crystalline lens and filled with a gelatinous fluid called vitreous humor; it is under a lot of pressure
what part of the eye contains several layers of cells and where is it located
back of the eye is the retina
rods and cones are
a) processing cells
b) receptor cells
b
what are the three types of processing cells
bipolar, ganglion and amacrine
how are the retinal visual cells nourished
by retinal pigment epithelium outside the neurosensory retina
how are the outer layers of retina nourished
by the choroid which provides oxygen and nourishment
what is the pathway of light
strikes cornea -> passes through anterior chamber -> pupil -> focuses on lens -> passes through the vitreous chamber -> strikes retina -> light absorbed by receptor cells -> any excess light not absorbed will be absorbed by the pigment cells to prevent reflection
what part of the eye is most affected by accommodation
the anterior curvature of the lens
suspensory ligaments are also called ____
zonule fibers
define refraction
deflection undergone by a light ray passing from one medium to another in which the velocity is different
____ is the distance from the cornea to the point where parallel light rays converge
focal distance
1/focal distance =
diopters
name the three refractive errors
myopia, hyperopia and presbyopia
myopia causes
a) nearsightedness because of a too long eye
b) far sightedness because of a too short eye
c) nearsightedness because of a too short eye
d) far sightedness because of a too long eye
a
what are the two parts of the eye that are the most important in properly focusing light entering the eyes
cornea and lens
explain this prescription
-1.00, -1.25 X 180
-1.00 indicates the prescription corrects for nearsightedness
-1.25 is the lens power for correction of astigmatism
X 180 is the axis of lens power
what are the first layer of cells that the light strikes
a) ganglion cells
b) receptor cells
a
list the functions of retinal pigment epithelium
- absorbs the light not absorbed by the photoreceptors
- transports nutrients/ions to photoreceptors
- helps regenerate 11-cis-retinal
true or false - photoreceptors undergo renewal
true - daily
choose if this is a feature of cones or rods
100-125 million per retina
rods
choose if this is a feature of cones or rods
low sensitivity
cones
choose if this is a feature of cones or rods
day vision
cones
choose if this is a feature of cones or rods
more numerous in the retinal periphery
rods
choose if this is a feature of cones or rods
lots of convergence
rods
choose if this is a feature of cones or rods
vision in shades of grey
rods
choose if this is a feature of cones or rods
concentrated in fovea
cones
choose if this is a feature of cones or rods
6 million per retina
cones
choose if this is a feature of cones or rods
high acuity pathway
cones
list the steps of visual transduction in the DARK
DARK -> high concentration of cyclic GMP -> triggers depolarization -> initiates the opening of calcium channels in the synaptic terminal -> photoreceptors will release of glutamate -> inhibition of bipolar cells -> no longer any AP in ganglion cell and lateral geniculate nucleus
list the steps of visual transduction in the light
LIGHT -> isomerization of retinal -> G protein. transducin is activated -> activates phosphodiesterase -> breakdown of cGMP -> sodium channels close -> hyperpolarization -> calcium channels close -> prevents release of inhibitory transmitter -> excitation of bipolar cells -> AP in ganglion cell and lateral geniculate nucleus
what vitamin is retinal derived from
vitamin A
what are the differences between OFF and ON bipolar cells
OFF events - photoreceptor is depolarized -> light hyperpolarizes photoreceptor cells -> inhibition of glutamate release -> reduced excitation by glutamate receptors -> hyperpolarization of bipolar cells -> less neurotransmitter -> hyperpolarization of ganglion cells -> less AP
ON cells - photoreceptor is depolarized -> light hyperpolarizes photoreceptor cells -> inhibition of glutamate release -> reduced inhibition -> depolarization of bipolar cells -> more neurotransmitter -> depolarization of ganglion cells -> more AP
all trans retinal is reduced to ____
trans retinol
how is pigment reformed
trans retinal is reduced to trans retinol -> exits cell -> transported to retinal pigment epithelium -> converted to 11-cis-retinal -> returns to rod -> combined with opsin
_____ is the only cell whose output goes to the brain
ganglion cells
stimulation of what causes a change in the output of bipolar/ganglion cells
receptive field
true or false - receptive fields do not overlap
false - they do
where are the axon terminals of the ON channels
inner plexiform layer
what do OFF bipolar cells express
AMPA and kainate type receptors
AMPA and kainate type receptors are anion/cation channels
cation
what do ON bipolar cells express
mGluR6, a metobotropic receptor
what happens when the metobortropic receptor binds to glutamate
closing of the cation channel TRPM1
true or false - all optic fibers cross at the optic chiasma
false - not all
