violetblue253
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Hi one of the questions I was asked was
Explain why vision using other parts of the retina has high sensitivity to light.

My answer was

Due to convergence. Many rod cells join to one bipolar cell. Producing many weak generator potentials which combine to reach the action potential threshold, triggering an action potential once this has been reached.

However, the mark scheme states

Many rods in other parts of retina;
Rhodopsin / pigment in receptors / rod cells very sensitive to light/
works in low light;
Receptors / rods connected in groups to ganglion cell / neurone;
Summation;
Description of summation, eg if enough light above threshold
hits any cells in the group, then get nerve impulses to brain/along
optic nerve;




Where did I go wrong please?
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AortaStudyMore
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(Original post by violetblue253)
Hi one of the questions I was asked was
Explain why vision using other parts of the retina has high sensitivity to light.

My answer was

Due to convergence. Many rod cells join to one bipolar cell. Producing many weak generator potentials which combine to reach the action potential threshold, triggering an action potential once this has been reached.

However, the mark scheme states

Many rods in other parts of retina;
Rhodopsin / pigment in receptors / rod cells very sensitive to light/
works in low light;
Receptors / rods connected in groups to ganglion cell / neurone;
Summation;
Description of summation, eg if enough light above threshold
hits any cells in the group, then get nerve impulses to brain/along
optic nerve;




Where did I go wrong please?
I wouldn't say you've gone particularly wrong. You've mentioned that many rods are connected to single ganglion cells and you've described the concept of summation. The only other thing to mention is the ability of rhodopsin to break down at low light intensities. I think you just need to word your answer a bit clearer. Always answer questions in continuous prose and include explanations with your statements.
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violetblue253
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(Original post by AortaStudyMore)
I wouldn't say you've gone particularly wrong. You've mentioned that many rods are connected to single ganglion cells and you've described the concept of summation. The only other thing to mention is the ability of rhodopsin to break down at low light intensities. I think you just need to word your answer a bit clearer. Always answer questions in continuous prose and include explanations with your statements.
Thank you!! The question was 3 marks so would I get 2/3 marks as I didn't talk about the ability of rhodopsin to break down at low light intensities?
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