topic.7.the.senses.powerpoint.7.2.-vision Flashcards
Blind spot
where the optic nerve passes through the optic disk
T/F there are detecting photoreceptive cells in the blind spot
False, just look at the name bitch
cornea
transparent, admits and refracts light
Iris
eye color; controls diameter of pupil by regulating amount of light that enters it
sclera
white outer protective layer of the eyeball
choroid
vascular of the eye, in between the sclera and retina
lens
focuses image on retina
retina
layer of neural cells that line the back of the eye
what part of the eye has photoreceptor cells and neurons that integrate that info?
retina
macula
pigmented area in the retina, contains fovea. Involved in high acuity vision
Fovea
Fovea: region of the macula in the retina, has a high density of cone cells
(photoreceptive cell for color); also needed for sharp vision (detail)
Which of the following lists in correct order the structures through which light passes in the
human eye?
A. lens, aqueous humor, vitreous humor
B. cornea, lens, vitreous humor
C. pupil, aqueous humor, cornea
D. vitreous humor, lens, retina
B. cornea, lens, vitreous humor
Anterior chamber:
lies between the cornea and the iris. Filled with aqueous humor
Posterior chamber
located behind the iris and in front of the lens. Filled with aqueous humor
Vitreous chamber:
located behind the lens. Filled with vitreous humor
Aqueous humor
THIN WATERY FLUID
-maintains intraocular pressure
-remove wastes
-supply nutrients to avascular parts of the eye
vitreous humor
thick, viscous fluid (gel like substance)
that helps maintain the shape of the eye and absorb shocks
vitreous humor can be found where?
Occupies the space behind the lens and in front of the retina at the
back of the eye
aqueous humor can be found in what chambers of the eye
posterior and anterior
where can the ciliary body be found
at both sides of lens
Ciliary body:
part of the eye that includes the ciliary muscle; ring of smooth muscle fibers,
which controls the shape of the
the lens in order to achieve ACCOMODATION
where is aqueous humor produced?
ciliary epithelium
_____ connect the ciliary muscle to the lens.
Suspensory ligaments
How does accommodation relate to hand flex/crunch?
The ciliary body wants to achieve accommodation through the ciliary muscle.
-distant object/ ciliary muscles relax(hand)/ligaments tighten(string between palm and fingers)/flattening the lens(hand)
-close object/ciliary muscle tighten(hand)/ tendons relax(string between palm and fingers),lens become rounded(fist/hand)
Photoreceptors are also called____ and they are needed for ____
rods and cones, the eye to process light
photoreceptive molecules do what?
-absorb energy of light (photon)
-Generate changes in membrane potential
In vision, light is converted to action potentials and sent to brain through ___
optical nerve
Processed signal is sent via the optic nerve through the
lateral geniculate nuclei to
the visual cortex.
what is the direct pathway of vision
photoreceptors-bipolar cells-ganglion cells
horizontal cells
receive information
from the photoreceptors and transmit
it to surrounding bipolar neurons
amacrine cells
receive their inputs
from the bipolar cells and activate the
ganglion neurons that are in their
vicinity.
amacrine cells are located in
retina of the eye
amacrine release what type of neurons?
dopamine secreting neuron
T/F During the daylight, i expect horizontal cells to be active
False-amacrine cells release dpamine during daylight.To enhance the activity of cone cells in the retina while suppressing rod cells
cone cells are beneficial during the day because they..
increase sensitivity
for detecting light of different wavelengths
(colors)
rods are beneficial during the night to be active because…
Specialized for detection of low-intensity light
horizontal cells are responsible for what?
responsible for allowing eyes to adjust to see well under both bright and dim light conditions (involved with lateral
inhibition)
How are structures of cones and rods similar?
Both contain
-outer segment(photopigment)
-inner segment
-synaptic terminal
(retina)
T/F Rods are conical
False:
Cones are conical
Rods are cylindrical
In rods, photopigment (or photoreceptive molecule)
rhodopsin.
Rhodopsin
= retinal + opsin= photopigment found in rods; is a G-protein coupled receptor
In cones, photopigment (or photoreceptrive molecule)
is iodopsin
-absorb light of overlapping wavelength ranges
-Gives rise to the perception of a particular color in the brain
Iodopsins contain the protein complexes:
photopsin I, II, or III.
photopsin in iodopsins respond to what 3 colors?
blue, red, green
Photopigments (such as rhodopsin, iodopsin) are found in the
discs of photoreceptor cells (that is, the rods and cones)
photopigment made up of
retinal combined with an opsin protein
In the rods and cones, light causes a
hyperpolarization
In the dark the rod cell is
depolarized because sodium channels are open and releases glutamate, glutamate has inhibitory reaction on bipolar cells prevent AP, saying their is no light
how does glutamate relate to AP?
When glutamate is
not released (or
reduced) from the
rod cell, the bipolar cell
is no longer inhibited
and can now stimulate
ganglion cells produce
APs, send signal to brain
Explain the mechanism of how light causes hyperpolarization
1/light activates rhodopsin on rod cell
2.G protein complex activated
3. activates phosphodiesterase cGMP to GMP
4. closes Na+ channels
4.gluatmate from rod cell decreases
5. bipolar cells can stimulate AP, no longer inhibited
T/F there are more ganglion cells than photoreceptors
ganglion recieve signals from bipolar cells get signals from the receptive field(group of photoreceptors)
Receptive field of a bipolar cell
is a circular area of the retina
Receptive field has what two parts
Receptive field center
Receptive field surround
Receptive field surround
provides an indirect input from the
photoreceptors to the bipolar cells via horizontal cells
Receptive field center:
provides a direct input from the
photoreceptors to the bipolar cells
When stimulated, bipolar cells
exhibit
graded potentials.
Each on-center bipolar cell, in turn, synapses with an on-center ganglion cell and each off-center bipolar cell synapses with an off-center ganglion cell (simplified).
When the receptive field center is in dark,
photoreceptor cells (e.g. rods)
are depolarized
and they release glutamate constantly.
describe the on-center pathway when receptive field is dark
Glutamate stimulates metabotropic glutamate receptors on
the on-center bipolar cells, K+ (potassium)
channels are opened, on-center bipolar cell is hyperpolarized, which
results in a decrease in the release of their
transmitter to ganglion cells. aka not transferring light
describe the off-center pathway when receptive field is dark
Glutamate stimulates ionotropic glutamate
receptors on the off-center bipolar cells, Na+ channels are opened,
off-center bipolar cell is depolarized, and the release of its transmitter (probably glutamate) is increased, results in an increase in the firing of
the corresponding off-center ganglion cells
When the photoreceptor cell (e.g. rod) in the receptive field center receives a light stimulus
it is hyperpolarized and glutamate release from its terminals is decreased
the reduction in the release of glutamate from the photoreceptor terminals causes
depolarization of the on-center bipolar cell and an increase in its transmitter release which, in turn, results in an increase in the firing of thecorresponding on-center ganglion cells
The reduction in the release of glutamate from the photoreceptor terminals causes
hyperpolarization of the off-center bipolar cell and there is a decrease in its transmitter release, which results in a decrease in the firing of the corresponding off-center ganglion cells.
One _____can synapse with a set of photoreceptive cells.
bipolar cell
in on-center bipolar cells glutamate
results
in an efflux of K+ (hyperpolarization)
In off-center bipolar cells, glutamate results in an
influx of Na+ (depolarization)
Retina processing by on-
center and off-center
ganglion cells enhances
differences in relative (rather
than absolute) brightness, which
helps define contours
