COGS 17 Midterm 2 UCSD Johnson
W18 Latest Exam and All Correct
Answers 2026 Updated.
Visual Receptors - Answer Contain photopigment molecules that react to light
Spontaneous, graded release of NT
Isomerization - Answer Converting light into neural signal:
Causes Na+/Ca++ gates to close, increasing receptor's polarity, decreasing NT release
Outer Segment - Answer This portion of receptors is composed of lamellae with embedded
photopigment
Photopigment - Answer Molecules that react to light (made of opsin)
Opsin - Answer Long protein chain, makes up photopigment
Changes color ("bleached") when retinal detaches
Retinal - Answer Short lipid segment, synthesized from Vitamin A, attached to opsin
When absorbs photon, changes shape and detaches from opsin
Photopigment Regeneration - Answer Recombination of retinal and opsin using enzymes
from pigment epithelium; takes time
Light Adapted - Answer Hard to see indoors after bright sunlight; as the photopigment
regenerates, sensitivity is restored
Dark Adapted - Answer Hard to see just after turning off the lights; as the photopigment
regenerates, sensitivity is restored
Retina - Answer Composed of neurons, multi-layered, covering rear, inner wall of eyeball
,Receptors - Answer Rods and Cones, rearmost layer of retina
Rods - Answer Larger, in periphery, ~120 million/eye
Cones - Answer Smaller, dispersed throughout retina, ~ 6 million/eye
Fovea - Answer Small central area of high conc. of cones (no rods); for detail resolution
Very Low Convergence, 1:1 ganglions.
Bipolars - Answer Postsynaptic to receptors, spontaneous firing, graded potentials, releases
excitatory NT
Ganglions - Answer Postsynaptic to bipolars, action potentials
Axons form Optic Nerve
Blind Spot - Answer Where Optice Nerve leaves eye & blood vessels enter/leave; No
receptors
Optic Disk - Answer aka Blind Spot
Interneurons - Answer Perpendicular to pathway, influence interactions between above
neurons
Horizontals - Answer Graded potentials, mostly inhibitory NT, modify interface of receptors
and bipolars
Amacrines - Answer Graded potentials, mostly inhibitory NT, modify interface of Bipolars and
Ganglions
(many kinds)
Pigment Epithelium - Answer Rearmost layer of (non-neural) cells; feeds/recycles from
receptors; helps reflect/maximize light
Off - Answer Light turns receptor cells...
, On - Answer Darkness turns receptors cells...
Dark Current - Answer In the absence of stimulation, Receptor's Na+ gates open, Na+ flows
in and out, Ca++ gates open, causing continuous release of NT, Ca++ gates actively pumped out
Dark - Answer In (the dark/bright light/dim light), receptors release inhibitory NT to prevent
Bipolars from triggering Ganglions, so Ganglions (by not firing) report: "dark/bright/dim"
Bright Light - Answer In (the dark/bright light/dim light), receptors are shut down, don't
inhibit bipolars, bipolars spontaneously release excitatory NT to pass Ganglion's threshold,
ganglions report: "dark/bright/dim"
Dim Light - Answer In (the dark/bright light/dim light), receptor's spontaneous release is
decreased so bipolars only somewhat inhibited, release enough NT to sometimes trigger
ganglions
Connectivity Patterns - Answer Critical role in information-transmission functions
Convergence in Retina - Answer Individual receptors synapse onto multiple ganglions
Rods: High, 120:1
Cones: Low, 6:1.
Accounts for acuity and sensitivity differences between rods/cones
Acuity - Answer Detail resolution; high in cones, low in rods
Sensitivity - Answer In dim light, rods are more likely to trigger ganglions (bc more rods per
ganglion than cones - summation)
Receptive Field (RF) - Answer Set of Receptors whose activity influences activity of target cell
(any downstream cell)
Size/type determined by patterns of convergence and lateral influences
Large Receptive Field - Answer Ganglions along path from converging rods have a
(large/small receptive field)
W18 Latest Exam and All Correct
Answers 2026 Updated.
Visual Receptors - Answer Contain photopigment molecules that react to light
Spontaneous, graded release of NT
Isomerization - Answer Converting light into neural signal:
Causes Na+/Ca++ gates to close, increasing receptor's polarity, decreasing NT release
Outer Segment - Answer This portion of receptors is composed of lamellae with embedded
photopigment
Photopigment - Answer Molecules that react to light (made of opsin)
Opsin - Answer Long protein chain, makes up photopigment
Changes color ("bleached") when retinal detaches
Retinal - Answer Short lipid segment, synthesized from Vitamin A, attached to opsin
When absorbs photon, changes shape and detaches from opsin
Photopigment Regeneration - Answer Recombination of retinal and opsin using enzymes
from pigment epithelium; takes time
Light Adapted - Answer Hard to see indoors after bright sunlight; as the photopigment
regenerates, sensitivity is restored
Dark Adapted - Answer Hard to see just after turning off the lights; as the photopigment
regenerates, sensitivity is restored
Retina - Answer Composed of neurons, multi-layered, covering rear, inner wall of eyeball
,Receptors - Answer Rods and Cones, rearmost layer of retina
Rods - Answer Larger, in periphery, ~120 million/eye
Cones - Answer Smaller, dispersed throughout retina, ~ 6 million/eye
Fovea - Answer Small central area of high conc. of cones (no rods); for detail resolution
Very Low Convergence, 1:1 ganglions.
Bipolars - Answer Postsynaptic to receptors, spontaneous firing, graded potentials, releases
excitatory NT
Ganglions - Answer Postsynaptic to bipolars, action potentials
Axons form Optic Nerve
Blind Spot - Answer Where Optice Nerve leaves eye & blood vessels enter/leave; No
receptors
Optic Disk - Answer aka Blind Spot
Interneurons - Answer Perpendicular to pathway, influence interactions between above
neurons
Horizontals - Answer Graded potentials, mostly inhibitory NT, modify interface of receptors
and bipolars
Amacrines - Answer Graded potentials, mostly inhibitory NT, modify interface of Bipolars and
Ganglions
(many kinds)
Pigment Epithelium - Answer Rearmost layer of (non-neural) cells; feeds/recycles from
receptors; helps reflect/maximize light
Off - Answer Light turns receptor cells...
, On - Answer Darkness turns receptors cells...
Dark Current - Answer In the absence of stimulation, Receptor's Na+ gates open, Na+ flows
in and out, Ca++ gates open, causing continuous release of NT, Ca++ gates actively pumped out
Dark - Answer In (the dark/bright light/dim light), receptors release inhibitory NT to prevent
Bipolars from triggering Ganglions, so Ganglions (by not firing) report: "dark/bright/dim"
Bright Light - Answer In (the dark/bright light/dim light), receptors are shut down, don't
inhibit bipolars, bipolars spontaneously release excitatory NT to pass Ganglion's threshold,
ganglions report: "dark/bright/dim"
Dim Light - Answer In (the dark/bright light/dim light), receptor's spontaneous release is
decreased so bipolars only somewhat inhibited, release enough NT to sometimes trigger
ganglions
Connectivity Patterns - Answer Critical role in information-transmission functions
Convergence in Retina - Answer Individual receptors synapse onto multiple ganglions
Rods: High, 120:1
Cones: Low, 6:1.
Accounts for acuity and sensitivity differences between rods/cones
Acuity - Answer Detail resolution; high in cones, low in rods
Sensitivity - Answer In dim light, rods are more likely to trigger ganglions (bc more rods per
ganglion than cones - summation)
Receptive Field (RF) - Answer Set of Receptors whose activity influences activity of target cell
(any downstream cell)
Size/type determined by patterns of convergence and lateral influences
Large Receptive Field - Answer Ganglions along path from converging rods have a
(large/small receptive field)
