Vision Flashcards
Chromatic adaptation: the ____ system’s ability to adjust to changes in ______ order to preserve the appearance of object _____.
Visual
Illumination
Colors
The primary vision cortex and visual association areas are located in which lobe of the cortex?
Occipital
Through what part of the eye does light enter?
Pupil
Which eye structure is the first that light passes through? What is a function of this structure in relation to light?
Cornea
Bending light
Lens function: adaptation to looking at ____-___ objects
Close-up
The retina is capable of _____ and ____ visual stimuli.
Detecting
Transmitting
What is the side of the retina near the nose called? The side near the temple?
Near the nose: nasal
Near the temple: temporal
What structure of the eye confers a blind spot because it has no photoreceptors? This structure is part of the ____ ____, which is connected to the brain.
Optic disk
Optic nerve
What causes glaucoma?
High pressure in the eye
Image formation occurs through refraction through what 2 eye structures? Which has greater refractive power? Which enables accommodation?
Cornea
Lens
Greater refractive power: cornea
Accommodation: lens
An image coming through the eye is focused on the ____. How is this changed in myopia (nearsightedness) and hyperopia (farsightedness)?
Retina
Myopia: image falls short of the retina
Hyperopia: image goes past the retina
What type of muscles are necessary for accommodation?
Ciliary muscles
In accommodation, the image is focused (short of/ beyond) the retina. How do the ciliary muscles fix this problem?
Beyond
Ciliary muscles contract, elongating the lens and thus putting the image back on the retina
How does age affect accommodation?
Age decreases accommodation ability
The retina is part of the (CNS/PNS). Are its cells arranged in one layer or multiple?
CNS
Multiple
From front to back of retina, name the 5 major cell types.
Back: cones and rods
Middle: horizontal, bipolar
Front: retinal ganglion cells
What retinal cell type serve as photoreceptors? What is the role of photoreceptors?
Cones and rods
Detect signal
Which 2 retinal cell types have both an on and off variety? What is the difference between the on and off varieties?
Bipolar
Retinal ganglion
On cells release more neurotransmitter when light is on
Off cells release more neurotransmitter when light is off
What are the only retinal cell type that fires action potentials?
Retinal ganglion
Horizontal cells modify the function of _____ cells.
Bipolar
________ cells in the back of the retina are the first to respond to light.
Photoreceptor
Though light travels from (front/back) to (front/back) of the retina, the neurological signal travels from cells in the (front/back) of the retina toward cells in the (front/back) of the retina.
Front to back
Back to front
____ _____ cells send their axons out of the retina to the brain.
Retinal ganglion
What is the part of the retina with the highest visual acuity?
Fovea
Cones dominate what part of the retina? For what type of vision are they most important? Do they have high or low sensitivity? Do they provide high or low resolution and acuity? One or many cones per bipolar cell pair? What type of G protein-coupled receptor do they use to detect light?
Fovea Color Low sensitivity High resolution and acuity 1 cone per bipolar cell pair GPCR: opsins
Rods dominate what relative part of the retina? For what type of vision are they most important? Do they have high or low sensitivity? Do they provide high or low resolution and acuity? One or many rods per bipolar cell pair? What type of G protein-coupled receptor do they use to detect light?
Periphery Night High Low resolution and acuity Many rods per bipolar cell pair GPCR: rhodopsin
Phototransduction: transformation of ____ energy to ____ energy.
Light
Electrical
Light (depolarizes/hyperpolarizes) photo receptors. This response lasts (the same amount of time as/ longer than) the stimulus.
Hyperpolarizes
Longer than
Photoreceptors show graded responses to light. What does that mean?
The more intense the stimulus, the more hyperpolarization occurs
Photoreceptors have what 2 types of channels? Which one is always open, no matter if it is light or dark?
K+ ion channels
Cyclic nucleotide gated channels (cGMP)
Always open: K+ channels
The cGMP-gated channels of the photoreceptors pass what 2 ions?
Na+
Ca+2
What enzyme makes cGMP that binds to cGMP-gated channels of photoreceptors? This enzyme is on (in the light/in the dark/all the time)
Guanylyl cyclase
All the time
Dark current: in the dark, which of the 2 photoreceptor channels are open? What ions are coming into the cell, and what ions are going out of the cell? Is the net effect depolarization or hyperpolarization? In the light, which of the 2 photoreceptor channels are open? What ions are coming into the cell, and what ions are going out of the cell? Is the net effect depolarization or hyperpolarization?
Dark: K+ ion channels and cGMP-gated channels are open Into cell: Na+ and Ca+2, out of cell: K+ Depolarization Light: Only K+ ion channels are open No ions coming into cell, K+ going out of cell Hyperpolarization
Opsins and rhodopsin serve as ____ ____-____ ____ that are required for light detection in the ____. Which one corresponds to cones and which one corresponds to rods? How many opsin(s) are there and how many rhodopsin(s) are there?
G protein-coupled receptors Retina Opsins-cones Rhodopsin- rods 3 opsins 1 rhodopsin
How many transmembrane domains do opsins and rhodopsin have?
7
What is the name of the G protein that opsins and rhodopsin couple to?
Transducin
What is the name of the light absorbing chromophore that is part of opsin and rhodopsin? What is the version of this chromophore that is in the inactivated version of opsin or rhodopsin, and what is the version of this chromophore that is in the activated version of opsin or rhodopsin?
Retinal
11-cis-retinal
All-trans-retinal
Light causes ____-____ retinal to change to ____-____ retinal, which causes a change in the ____ or _____ G protein-coupled receptor that enables it to activate _____, the G protein.
11-cis retinal
All-trans retinal
Opsin or rhodopsin
Transducin
What is the name of the protein to which 11-cis retinal binds? What is an intermediate in the retinoid cycle between all-trans retinal and 11-cis retinal, and what vitamin does it function as?
Retinoid binding protein
All-trans retinol
Vitamin A
Phototransduction pathway:
1) _____ ____ (enzyme) is always making _____ (2nd messenger): constitutively active
2) Light causes ___-___ ____ to change to ___-____ ___
3) _____ (GPCR in rods) changes conformation
4) _____ trimeric G protein with G alpha T is activated
5) Activated _____-G alpha T subunit binds to and activates _____
6) ____ breaks down cGMP
7) ___-gated ___/___ (ions) channel (closes/opens)
8) ____ channel is still open, so photoreceptor is (depolarized/hyperpolarized)
9) Photoreceptor _____ (neurotransmitter) output is (increased/decreased)
1) Guanylyl cyclase cGMP 2) 11-cis retinal All-trans retinal 3) Rhodopsin 4) Transducin 5) GTP- G alpha T Phosphodiesterase 6) Phosphodiesterase 7) cGMP-gated Na+/Ca+2 Closes 8) K+ Hyperpolarized 9) Glutamate Decreased
Graded neurotransmitter release: cell can (increase/decrease/either) amount of neurotransmitter released depending on level of (depolarization/hyperpolarization). What cell(s) of the retina demonstrate graded release?
Either
Depolarization
Photoreceptors (cones and rods), bipolar cells, horizontal cells
Action potential induced neurotransmitter release: cell must reach ____ of ___-____ channels and fire ____ ____ in order to release neurotransmitter. What cell(s) of the retina demonstrate action potential induced release?
Threshold
Voltage-gated
Action potential
Retinal ganglion only
Photoreceptors:
1) Neurotransmitter released
2) Type of neurotransmitter receptor/ what neurotransmitter binds
3) Effect of neurotransmitter binding: activation or inhibition
4) Effect of light on cell: depolarize (activate) or hyperpolarize (inactivate)
1) Glutamate
2) GABA
3) Inhibition
4) Hyperpolarize/ inactivate
Horizontal cells:
1) Neurotransmitter released
2) Type of neurotransmitter receptor/ what neurotransmitter binds
3) Effect of neurotransmitter binding: activation or inhibition
4) Effect of light on cell: activation or inhibition
1) GABA
2) Glutamate (AMPA or kainate)
3) Activation
4) Inhibition
ON Bipolar cells:
1) Neurotransmitter released
2) Type of neurotransmitter receptor/ what neurotransmitter binds
3) Effect of neurotransmitter binding: activation or inhibition
4) Effect of light on cell: activation or inhibition
1) Glutamate
2) Glutamate (mGluR6)
3) Inhibition
4) Activation
OFF Bipolar cells:
1) Neurotransmitter released
2) Type of neurotransmitter receptor/ what neurotransmitter binds
3) Effect of neurotransmitter binding: activation or inhibition
4) Effect of light on cell: activation or inhibition
1) Glutamate
2) Glutamate (AMPA or kainate)
3) Activation
4) Inhibition
ON Ganglion cells:
1) Neurotransmitter released
2) Type of neurotransmitter receptor/ what neurotransmitter binds
3) Effect of neurotransmitter binding: activation or inhibition
4) Effect of light on cell: activation or inhibition
1) Glutamate
2) Glutamate (AMPA, kainate, NMDA)
3) Activation
4) Activation
OFF Ganglion cells:
1) Neurotransmitter released
2) Type of neurotransmitter receptor/ what neurotransmitter binds
3) Effect of neurotransmitter binding: activation or inhibition
4) Effect of light on cell: activation or inhibition
1) Glutamate
2) Glutamate (AMPA, kainate, NMDA)
3) Activation
4) Inhibition
What type of retinal cell releases a different neurotransmitter than the others?
Horizontal