PSYO10202_Week_8_Signal_Transduction_3.5.21

Because Na+ keeps leaving even when Na+ isn't coming into the cytosol anymore.

rhodopsin normally in cis. Light hits --> 11-cis changes to 11-trans to make a cascade (b/c then transducen, and finally PDE are activated). PDE eats cGMP which is what the Na+ channel needs to open. NT release declines because dark current reduced. WHY DOES THE MEMBRANE HYPERPOLARIZE TO -70?

dim; bright

rods are __ as cones are to __ light

seeing dim light

rods are important for...

light hits the rod, cis lets go of opsin by moving into transconfiguration.

Bleaching occurs when...

retina.

Contains cones for color vision. Contains rods for night vision.

retinal.

If we lack vitamin A, we will lack _______. Thusly, since _______ is a constituent of rhodopsin, we will decrease amounts of ________ because we lack vitamin A to start with. Rhodopsin helps us see when light hits, and if we don't have enough of it, we won't be able to see well when the lights are low (night blindness) --- with less rhodopsin, we need more stimulation.

dark current; triggers IPSPs; depolarized; hyperpolarized.

In darkness, inflow of Na+ is called the ___. --- Membrane potential = -40mV --- Rod and cone photoreceptors release glutamate (it's inhibitory in the eye) which __ (thus inhibits bipolar cell signal transmission to ganglion cells)) --- At rest (in the dark) the cell is ______ (-40). THE GREATER THE LIGHT, THE GREATER THE ELECTRONEGATIVITY (AKA ___________ (-70)).

met-ar-hod-opsin II

Light activated rhodopsin:

glutamate.

Light causes rod photoreceptors to decrease their release of the inhibitory neurotransmitter _____ --- In the vertebrate central nervous system (CNS), glutamate serves as the major excitatory neurotransmitter, whereas GABA and glycine serve as the major inhibitory neurotransmitters. Source: https://www.pnas.org/content/110/25/10294

rhodopsin (visual purple)

Membranes of outer-segment of rods contain

vitamin A.

Precursor of all-trans retinal --- hint: pigment portion of rhodopsin.

scotopsin; retinal; cis

Rhodopsin is a combination of ____ (a protein) and ____ (a pigment). --- Retinal is in __ configuration, because it is only this configuration that can bind scotopsin to form rhodopsin.

false.

T/F: Cone pigments regenerate slower, and rod pigments faster.

true.

T/F: Cones have iodopsin.

true.

T/F: light adaptation occurs more expediently compared to dark adaptation secondary to the discrepancy in bleaching rates and regeneration of photopigments in rods and cones.

scotopsin.

The trans- configuration does not fit binding site on _______, and the retinal splits away as shown, meantime, whilst splitting, intermediary compounds are formed.

isomeration of retinal and trans-retinal separating from opsin (bleaching).

There are two steps in the bleaching of photopigment.

retinal isomerase converts trans to cis-retinal and cis retinal binds to opsin (regeneration).

There are two steps in the regeneration of photopigment.

G transducin

These photoreceptors are metabotropic receptors (couple to G proteins, ___)

Rhodopsin kinase.

This needs to happen in order for cGMP levels to be reestablished and reopen Na+ channels.

fovea centralis (macula).

This provides the greatest visual acuity because there are only cones in it, and also neuronal cells and blood vessels are displaced to each side so there is no obstruction.

A rod IN THE DARK. sodium ions are entering the outer segment. potassium ions are leaving the inner segment at the same time.

What is this image portraying?

decreased NT release.

What tells the bipolar cell that a photoreceptor has absorbed a photon?

it causes hyperpolarization of rods by decreasing Na+ permeability of outer segment.

When rhodopsin decomposes (activated by light) --- the greater the amount of light the greater the electronegativity.

Retinal isomerase.

Which enzyme converts trans to cis retinal? Cis retinal binds again and opsin becomes colored pigment again.

the fovea.

at the center of the retina

fovea centralis (macula).

at the center of the retina is the fovea and at the center of the fovea is the __ with ONLY CONES (1:1 of cones:ganglion cells) in it which mainly function to detect detail.

true.

cones take less time than rods to regenerate?

10.

how many layers of retina?