AQA BIOL5 ~ 17th June 2013 ~ A2 Biology

Original post by erniiee

I was reading through this part of the NT book (action potentials) as I was revising positive feedback and I got quite confused..

Surely after the action potential has occured, (post hyperpolarisation), the overall concentrations of the ions inside and out of the membrane are different to before it occured, even though the potential has been returned to its negative state?

Aren't there now way more sodium ions inside and potassium outside?

And does the Na/K pump try and return the relative concentrations back to what it is before the action potential? :s-smilie:

Haha the nelson thornes textbook used confusion, and its super effective on me today! :lol:

Yes there will more sodium ions on the inside during repolarization but the sodium-potassium pumps restore this, this concentration of sodium ions inside the axon is also one of the main reasons why the refractory period occurs, in that another depolarisation of the axon is much more difficult due to, as you can imagine, it being much harder to have an influx of sodium

Reply 923

Anniestasia

Could someone please create me a table of the axon and the changes it goes through in terms of gates being open and closed during action potentials and resting potentials, that is aside from gates that are permanently open? So, a row for creating a resting potential, maintaining it, creating an action potential, such and such... Different sources say different things, and I'm unsure as to how accurate I need to make it.

Reply 924

Original post by sechdent8

does anyone know any places where i can do that extra reading to get those breadth marks? Also, how are breadth marks awarded? If a question came up about DNA and it's importantance and i was talking about PCR and i mentioned taq polymerase, would that give me one breadth mark?
Thanks

This might be of use to you :smile:

Extra information is marked under scientific content, not breadth of knowledge.

Reply 925

Original post by Anniestasia

Could someone please create me a table of the axon and the changes it goes through in terms of gates being open and closed during action potentials and resting potentials, that is aside from gates that are permanently open? So, a row for creating a resting potential, maintaining it, creating an action potential, such and such... Different sources say different things, and I'm unsure as to how accurate I need to make it.

maintaining-->both sets closed
Action potencial (depolarisation)-->sodium gates open potassium gates closed
Repolarisation--> sodium gates closed, potassium gates open
Refractory period--> both sets of gates closed

this is ofcourse aside from the potassium gates and sodium potassium pumps that are always open/working

Reply 926

Original post by Anniestasia

Could someone please create me a table of the axon and the changes it goes through in terms of gates being open and closed during action potentials and resting potentials, that is aside from gates that are permanently open? So, a row for creating a resting potential, maintaining it, creating an action potential, such and such... Different sources say different things, and I'm unsure as to how accurate I need to make it.

This is what I've come up with...

Spoiler

(edited 10 years ago)

Reply 927

F1's Finest

21

Original post by Gnome :)

This is what I've come up with...

Spoiler

Does the Sodium Potassium pump work all the time or just when hyper-polarisation begins?

Reply 928

Original post by James A

Does the Sodium Potassium pump work all the time or just when hyper-polarisation begins?

I believe it's constant, not 100% sure though.
You're the one who seems to know all the answers :tongue:

Reply 929

Original post by Gnome :)

I believe it's constant, not 100% sure though.
You're the one who seems to know all the answers :tongue:

It is all the time

Reply 930

F1's Finest

21

Original post by Gnome :)

I believe it's constant, not 100% sure though.
You're the one who seems to know all the answers :tongue:

I don't even know myself :tongue:

The content in biology is not the issue, it's the exam technique that I always find hard.

Reply 931

feelinginfinite

6

Original post by Gnome :)

I believe it's constant, not 100% sure though.
You're the one who seems to know all the answers :tongue:

Original post by JAJC

It is all the time

Original post by James A

I don't even know myself :tongue:

The content in biology is not the issue, it's the exam technique that I always find hard.

I was under the impression (through that little paragraph in the NT book) that the Na K pump only works when it's at resting potential (since it requires active transport), and the rest of the time the Na + K diffuse (naturally- i.e not with active transport)... So wouldn't that mean the Na K pump doesn't work during hyper-polarisation, and it returns to resting potential through the leakage channels opening up and more diffuses out? :redface:

Correct me if this is completely wrong please! Biology confuses me when people think different things :tongue:

Reply 932

Original post by feelinginfinite

I was under the impression (through that little paragraph in the NT book) that the Na K pump only works when it's at resting potential (since it requires active transport), and the rest of the time the Na + K diffuse (naturally- i.e not with active transport)... So wouldn't that mean the Na K pump doesn't work during hyper-polarisation, and it returns to resting potential through the leakage channels opening up and more diffuses out? :redface:

Correct me if this is completely wrong please! Biology confuses me when people think different things :tongue:

I did a quick Google search and it appears to be constant.

Reply 933

Original post by feelinginfinite

I was under the impression (through that little paragraph in the NT book) that the Na K pump only works when it's at resting potential (since it requires active transport), and the rest of the time the Na + K diffuse (naturally- i.e not with active transport)... So wouldn't that mean the Na K pump doesn't work during hyper-polarisation, and it returns to resting potential through the leakage channels opening up and more diffuses out? :redface:

Correct me if this is completely wrong please! Biology confuses me when people think different things :tongue:

It's sort of like the permeability to potassium, there are a few gates that are ALWAYS open - even when the axon is depolarising with the influx of sodium which seems kind of counter productive in the same way the SP pumps tick away constantly while the process is occuring

Reply 934

feelinginfinite

6

Original post by Gnome :)

I did a quick Google search and it appears to be constant.

Original post by JAJC

It's sort of like the permeability to potassium, there are a few gates that are ALWAYS open - even when the axon is depolarising with the influx of sodium which seems kind of counter productive in the same way the SP pumps tick away constantly while the process is occuring

My bad for confusing anyone then. Thanks for correcting me! :tongue:

Reply 935

erniiee

13

Original post by James A

The Na/K pump restores the relative concentrations of ions to how it was before the action potential, yes.

What do you mean by your 2nd paragraph?

Im on my phone typing this loool

Well, before the action potential, aren't there quite a lot more sodium ions outside the axon? After the action potential, the majority are now inside the membrane of the axon..so how is the potential returned to normal?!

Is that little refractory period the movement of some sodium out of the axon, so as to restore the original concentrations?

Reply 936

erniiee

13

Original post by JAJC

Yes there will more sodium ions on the inside during repolarization but the sodium-potassium pumps restore this, this concentration of sodium ions inside the axon is also one of the main reasons why the refractory period occurs, in that another depolarisation of the axon is much more difficult due to, as you can imagine, it being much harder to have an influx of sodium

Oh okay. Yes that last sentence has really helped me, thank you!

So repolarisation doesn't return the concentrations to what they were before, thats done by the sodium potassium pump?

Reply 937

F1's Finest

21

Original post by erniiee

Well, before the action potential, aren't there quite a lot more sodium ions outside the axon? After the action potential, the majority are now inside the membrane of the axon..so how is the potential returned to normal?!

Is that little refractory period the movement of some sodium out of the axon, so as to restore the original concentrations?

Before the action potential, there are lots of sodium ions outside the axon, yes.

The sodium potassium pump restores the resting potential. That's it's job and that is how we return back to having more sodium ions outside the axon and more potassium ions in the axon.....

If that makes sense :s-smilie:

Reply 938

erniiee

13

Original post by feelinginfinite

I was under the impression (through that little paragraph in the NT book) that the Na K pump only works when it's at resting potential (since it requires active transport), and the rest of the time the Na + K diffuse (naturally- i.e not with active transport)... So wouldn't that mean the Na K pump doesn't work during hyper-polarisation, and it returns to resting potential through the leakage channels opening up and more diffuses out? :redface:

Correct me if this is completely wrong please! Biology confuses me when people think different things :tongue:

LEAKAGE CHANNELS?! :lolwut:

what are those?

Reply 939