VISION PT 3

Question 1

whats the first step of phototransduction

Answer 1

light hits back of retina

Question 2

what happens after light hits back of retina

Answer 2

Retinal absorbs light and changes form

Question 3

what happens after retinal absorbs light and changes form

Answer 3

Retinal isomer binds opsin→rhodopsin

Question 4

what happens after retinal isomer binds opsin

Answer 4

Light activated rhodopsin activates G- protein (transducin)

Question 5

what happens after G-protein transducin is activated

Answer 5

Transducin activates phosphodiesterase (PDE)

Question 6

what happens after PDE is activated

Answer 6

PDE breaks cGMP to GMP

Question 7

what happens after cGMP is broken into GMP

Answer 7

Falling cGMP levels close cGMP-gated
cation channels and hyper polarization occurs

Question 8

whats IPSP vs EPSP

Answer 8

IPSP: inhibitory post-synaptic potential
EPSP: excitatory post-synaptic potential

Question 9

whats the first step of light phototransudction

Answer 9

Photoreceptor hyperpolarization (what we just describe at the beginning of these flashcards) → stops neurotransmitter release
(IPSPs) onto bipolar cell

Question 10

what happens after photoreceptor hyperpolartion stops neurotransmitter release
(IPSPs) onto bipolar cell

Answer 10

Bipolar cell depolarizes
→ release neurotransmitter (EPSPs) onto ganglion cell

Question 11

what happens after the bipolar cel repolarizes and releases EPSPs

Answer 11

Ganglion cell generates action potential → transmitted to brain by optic nerve

Question 12

describe photoreceptor stimulation in the dark

Answer 12

absence of stimulus (dark)
the default for photo receptor is on; photorecpors depolarize which makes
bipolar cell is inhibited

Question 13

describe photoreceptor stimulation in the light

Answer 13

in light, photo receptor is off and hyperpolarized which allows
for bipolar cell to be on and depolarize