Biology a level aqa - the retina and synapses

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username1946
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If there were no synapses, and therefore no selection of pathways, is it possible, at a level depth, to get too much sensory information from the retina?

In general, are some/most impulses from rods and cones deselected by synapses so only the important/relevant impulses are sent to the brain, ie maybe when you're trying to focus your eyes on something?

THank u in advance
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Wannabevetnurse
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(Original post by username1946)
If there were no synapses, and therefore no selection of pathways, is it possible, at a level depth, to get too much sensory information from the retina?

In general, are some/most impulses from rods and cones deselected by synapses so only the important/relevant impulses are sent to the brain, ie maybe when you're trying to focus your eyes on something?

THank u in advance
No synapse would mean a shorter diffusion distance for the neurotransmitter to travel through, so you would get alot of impulses, I think.

Well no, because cone cells are synapsed to one bipolar neurone. Whereas Rod cells are synapsed to three, so Cones have a higher visual acuity (see things more clearly) Rod cells go through spatial summation, so you see things less clearly.
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macpatgh-Sheldon
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Hi doglover and Mr/Mrs/Miss/Lord/Prof X (sorry!),

The answer above by doglover is broadly in tyhe right direction, but needs a little editing, unless there is a difference in the retinal architecture of cats/dogs (I would not know cos a dog bit me as a schoolboy - ouch!).

"No synapse would mean a shorter diffusion distance for the neurotransmitter to travel through, so you would get alot of impulses, I think"

The neurotransmitter [in this case in the synapse between photoreceptors and bipolar cells] is glutamate [btw], which has an inhibitory effect [hyperpolarization] on some bipolar cells and an excitatory effect [depolarization] on other bipolar cells. The point to grasp is that although the neurotransmitter in reality does travel from the cell body [where the mitochondria necessary to provide energy for the synthesis of the neurotransmitter reside], if there were no synapses [our hypothesis], then there would be no need for ANY neurotransmitter cos this chemical is ONLY ACTIVE IN TRANSMISSION OF AN IMPULSE ACROSS A SYNAPSE, NOT ALONG THE AXON. You have very modestly said "I think" so I hope my answer does not upset you!

"Well no, because cone cells are synapsed to one bipolar neurone. Whereas Rod cells are synapsed to three, so Cones have a higher visual acuity (see things more clearly) Rod cells go through spatial summation, so you see things less clearly."

You are right ion saying "well no" [!] and you are also correct in saying that each cone is connected to one bipolar cell, so that maximum resolution is possible with cones [no info loss]; however, with rods the picture is the other way round from what you say i.e. more than one rod [not necessarily three] synapse onto each bipolar cell so that this convergence reduces detail of info reaching [ultimately] the occipital cortex [Broddman's area 17 of the cerebral cortex]. It does lead to summation of photon enegy in the rod system, allowing scotopic vision [vision in subdued light] as against the photopic vision possible with cones [which are highly concentrated in the macula for central vision [i.e. seeing the item that the eyes are directed at].

Apologies to OP for delving into slightly more detail than needed at A level but I believe in teaching/learning more than what is needed so that what is needed becomes a trifle [yummy! :yum:

Be safe both of you [and the remaining six billion, 999 million, 999 thousand, nine hundred and 98 others!

M.
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