Which then causes a cyclic GMP-gated cation channel to close.
So this is almost anti-intuitive, where when
light hits it, you're closing an ion channel.
So that means
that at rest, when there isn't much light around, that this
cation channel is open, which is letting cations enter the cell.
Which means that at rest, the photoreceptor cell is depolarized.
Again, anti-intuitive, that at rest the cell is depolarized.
So that means that when you close that channel,
that now the, the membrane potential is going to become hyperpolarized.
So we have a graded potential but it's a
hyperpolarization of the cell and that reduces neurotransmitter secretion.
So it's kind of very anti-intuitive that you reduce neurotransmitter
secretion from these photoreceptor cells when they're exposed to light.
But that's how
it works.
It works, so we let's all, there's other neurons involved.
So that's what this image shows.
Where actually at the back of the retina, the very back, is where you have
the photoreceptor cells. So, in this case we have six rods, and
then there are other cells called bipolar cells and a ganglion cell that are also
present there.
So we have layers of neurons at the
back of the retina, and interestingly the light has
to travel through those other layers of neurons, as
shown right here, to get to the photoreceptor cells.
But again it works.
