MEPS1996
Badges: 4
Rep:
?
#1
Report Thread starter 6 years ago
#1
Why does having multiple rod cells attached to same neurone mean it is more likely a generator potential can be produced?
0
reply
Tappouni
Badges: 8
Rep:
?
#2
Report 6 years ago
#2
(Original post by MEPS1996)
Why does having multiple rod cells attached to same neurone mean it is more likely a generator potential can be produced?
It's spacial summation, so a small stimulus to each builds up to generate a generator potential, if the small stimuli are sufficient to trigger one...think of it another way:

Say you've got 20% light intensity, and 5 rod cells. If they've each stimulated with 20%, it'll add up so you achieve the whole 100%, and a generator potential is produced.

If you have one cone cell at the 20% intensity, then that's only 20% out of 100%, so you won't have anywhere near enough for a generator potential to be generated.

Does that make a bit of sense?
0
reply
MEPS1996
Badges: 4
Rep:
?
#3
Report Thread starter 6 years ago
#3
(Original post by Tappouni)
It's spacial summation, so a small stimulus to each builds up to generate a generator potential, if the small stimuli are sufficient to trigger one...think of it another way:

Say you've got 20% light intensity, and 5 rod cells. If they've each stimulated with 20%, it'll add up so you achieve the whole 100%, and a generator potential is produced.

If you have one cone cell at the 20% intensity, then that's only 20% out of 100%, so you won't have anywhere near enough for a generator potential to be generated.

Does that make a bit of sense?
cheers so is it about getting enough sodium ions across the membrane to generate enough of a electrical potential to start an action potential?
0
reply
Tappouni
Badges: 8
Rep:
?
#4
Report 6 years ago
#4
(Original post by MEPS1996)
cheers so is it about getting enough sodium ions across the membrane to generate enough of a electrical potential to start an action potential?
Yes that's right - the light causes a chemical change in the photoreceptors, which makes the membrane more permeable to sodium. Sodium then begins to move across the membrane, creating a generator potential, and if enough sodium moves across, you 'exceed the threshold', and an action potential is triggered. If that generator potential is too weak though, the threshold won't be exceeded, and an action potential won't be fired.

Hope that helps
0
reply
Revenged
Badges: 14
Rep:
?
#5
Report 6 years ago
#5
rods detect are the parts that detect black and white. they work at low levels of light and as said they do this by spatial summation where more than many pre-synaptic neurone all link to a single optic nerve neurone.

this is in contrast to our colour vision which works only in the light. cones only have one pre-synaptic neurone to a single optic nerve neurone (in contrast to the rods). this is why you only get colour vision when it is bright.
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

Do you have the space and resources you need to succeed in home learning?

Yes I have everything I need (398)
56.37%
I don't have everything I need (308)
43.63%

Watched Threads

View All