A2 Biology - Resting potential and action potential (OCR A Chapter 13.4) 

Glad to be of help! Thanks for watching :)

Amazing! So glad to hear you're doing so well and well done! :D

Congrats buddy!!

Aww glad you find it helpful! Thanks for watching :)

@@BioRach during depolarization is the potassium channel close

@@gracex3 The non-voltage-gated potassium ion channels remain open throughout the process (hence the leakage of K+ ions out), however the voltage- gated ion channels only open during repolarisation and begin to close at hyperpolarisation. This is because it is a slow process to close the voltage-gated potassium ion channels, therefore causing the charge to go beyond -70mV. Edit: Typo

Same fr

That's great to hear! It really is an interesting topic! :D

I'm glad you find it helpful! Thanks for watching :D

haha really glad it helps! :D All the best in uni and thanks for watching!

Glad it helped! Thanks for watching :D

Thank you! :D Glad it helped!

I'm glad you found the videos helpful! Yes, it's always good to repeat something so much that you hook your memory onto specific parts :)

Haha thanks!

Glad it was helpful! Do you mean the hyperpolarised period? That happens right after the end of action potential :)

Whenever the sodium ion channels are closed for example during both hyper and repolarisation

Haha this can be confusing, glad you find the video helpful! Thanks for watching :)

I'm really glad you found it helpful :) thanks for watching!

Glad you found the video helpful :) I can do, though it's not much extra on top of what's already covered in this video. Saltatory conduction is referring to the fact that the sodium ions diffuse from one node of Ranvier to the next, rather than having every ion channel opening in between the nodes, therefore the impulse transmission is extremely quick. Impulse propagation is pretty much referring to the same thing, unless I interpreted your question wrong? In which case then please let me know and I'll cover it in a bit more detail :) Thanks for watching!

@@BioRach what I meant by impulse propagation was the several changes in potential difference across membrane that let the impulse to move across neurone in one direction. I want to know what happens in the membrane to let that happen

@@abdelrahmanshams6016 Ah I see. That would be due to the opening/closing of the ion channels along the membrane due to it reaching the threshold potential of -55mV. 1.) When an action potential is initiated, the sodium ion channels open, which increases the membrane's PD from -70mV to -55mV. 2.) At that point, the voltage-gated sodium ion channels nearby will then open to allow more sodium ions to come in (reaching 40mV). 3.) These ions then diffuse along the membrane, which then causes the "next area" to also increase its PD (as more positive ions inside than outside). 4.) Then the same thing happens - the channels in the "next area" open due to reaching -55mV. 5.) The membrane in the "previous area" will then experience a drop in PD (due to the "loss" of sodium ions) and the voltage-gated potassium ion channels will then open, which helps further decrease the PD (ie. repolarisation), even beyond -70mV, which is then called hyperpolarisation... before the sodium/potassium ion pumps work again to regenerate the PD to -70mV. If you use the OCR A textbook, there is a really good diagram that shows this on p.13 (in 13.4 Nervous transmission).

I appreciate this is confusing - I can go over it with the diagrams that I drew in front of me maybe in a Q&A livestream? :)

@@BioRach Finally I have understood it really thank you and I appreciate your work

haha glad it was of help to you :D Thanks for watching!

Yes. We think of something a larger stimulus based on us feeling it more. That implies that more receptors are trigger in the beginning, hence more initial sodium ion channels are opened to reach the threshold potential, which then opens more of the subsequent voltage-gated channels.

@@BioRach Thanks make sense

Another question Biorach you said at 5:58 the 'first sodium' channels by that did you mean the first voltage gated channels or the normal sodium ion channels. I thought that the voltage gated channels only opened at -55mv

Haha working my way through the spec! Definitely will be covering those at some point in the next academic year so keep an eye out for the new videos :) thanks for watching!

There are different versions of Na+ channels. Some are voltage gated, meaning they're sensitive to changes in potential difference. Some are stretch mediated, such as the ones found in the Pacinian corpuscles, which are literally stretched apart for sodium influx.

Haha will do! Thanks for watching :)

Hahaha glad you find it helpful! And will do when I have more time! Thanks for watching :)

Glad you found it helpful! Thanks for watching :)

Thanks for watching! :)

We want K+ out! At resting potential K+ are actively transported into the neurone to facilitate Na+ going out, but we want to maintain -70mV by moving most positive ions out, so the K+ ion channels are open to allow any K+ to diffuse back out after active transport.

@@BioRach thank you for your fast reply! I get it now. K+ must go away to keep the inside negative! Got it😄btw I love the oxford revise workbook it’s been really helpful

Yes.

mate thats not even a gcse question(ud expect foundation to have that) not a level standard🤣

Yes, correct!

Yes :)

Thanks for watching! :)

They are replenished through active transport during hyperpolarisarion. The Na-K pump will re-establish the Na+ concentration gradient.

Voltage-gated channels are those that open due to a change in the potential difference in the membrane. They are mostly involved in triggering an action potential, or in any situation where the release of a substance is regulated (eg. insulin). Whereas non-voltage channels (so normal protein channels) are not necessarily involved in regulation of any substance release - examples include protein channels for water absorption, which happens all the time and isn't controlled to only occur at certain moments. Hope this make sense!

Yes it is :)

Lol

Yes they are usually large chloride ions :)

BioRach I thought the negative charge inside the cell membrane was of negatively charged proteins ?

Not sure if Minecraft uses music from the same artist? 😂 Just got it off RU-vid music library! But glad you found the video helpful :)

Any particular chapters? I've made quite a few videos on various chapters on module 2 so check it out! They should be organised in chapter playlists in the AS playlists :)

@@BioRach ahhh iv just checked thankyou ! could you make a video cofactors and enzyme inhibition please x