I can not even begin to describe how thankful I am for people like you. All your videos are EXTREMELY helpful and elaborate. We are in dire need of more teachers like you.
Hey Mr, I don't know your name but I wanted to send you my greatest gratitude from Ethiopia. Your lectures are crystal clear and your explanations are beyond amazing. Always remember you're helping out tons of students across seas and you're providing a quality education. Thankyou! God Bless You!
OMG, this is so helpful. I'm studying for an exam to get into a program. You explain your lectures in a way that makes it easy to understand. Thank You so much.
Man thanks for all your videos. I'm taking the MCAT soon and knowing that your videos got me through my clases for the past 4 years. I'm here again to recharge my memory. Not all people can afford tutoring or supper expensive recap classes.
Incredible. You made a extremely confusing topic very simple to understand. I was spending hours on this before and I learned it in less than 20 minutes watching this. You are awesome!!!
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May I ask some questions? 1. during the hyper-polarization period, the potential difference is lower than the usual resting potential, this means the cytoplasm is much more negative. If we want to restore it (increase voltage back to -70mV), aren't we going to bring more positive charges into the cytoplasm rather than bringing 3Na+ out and 2K+ into the axon? 2. If the stimulus is stronger, the frequency of this action potential cycle increases. Can I say if the stimulus is stronger (very painful after hitting something), the neurones use more ATP? (increased frequency of hyper-polarization using Na+/K+ ATP-ase. Thank you very much
I m preparing for postgraduate entrance exam in India.your lectures are very much helpful. one request can u give some lectures on pharmacology coz i find this subject a bit difficult.
First off, thank you for all your efforts and willingness to share your time and talents. I'm still not quite clear on how the return to resting membrane potential occurs after hyperpolarization. Many sources cite the Na+/K+ pump. This is confusing to me because if 3 positive ions (Na+) are leaving the -90mV cell and 2 positive ions (K+) enter the cell than in my mind the ICF would still have a negative defect in relation to the ECF. Now, we know that K+ is 25-30 times more permeable to the membrane than Na+ is...so is the return to resting potential (-70mV) achieved by lots of K+ crossing the membrane into the cell via leak channels?
+Michelle Christian Ah, yes I think you gave the critical info in the previous lecture: Resting membrane potential, but would just like confirmation. After hyperpolarization, the cells ability to return to resting membrane potential of -70mV is r/t the protein leak channels that are specific to K+ being present in vast numbers in relation to the other protein channels. So K+ is entering the cell in large quantities, allowing for RMP to be achieved. Am I understanding this concept correctly?
+Michelle Christian indeed the Na+/K+ pump causes a net negative charge in the cell as 2 K+ is pumped in while 3Na+ is pumped out. however due to the fact that there are more K+ leak channels than Na+ leak channels, more K+ influx occurs than the Na+ efflux, resulting in repolarisation.
What kind of stimulus causes a depolarization. Following the sequence of events after depolarization is fairly straightforward, but in trying to conceptualize action potential its helpful to understand (to whatever small extent) where the stimulus comes from and how it decreases the membrane potential. Is it cause by ions flowing out of the membrane, decreasing the potential? If so, through what channel do these ions flow out, what causes them to flow and thus eventuate in a threshold value?
Super late, but -70 mV is actually the resting membrane potential, while -45 mV is the threshold potential (and -70 mV is less than -45 mV, to be clear). So what happens is a stimulus is applied, and if it reaches -45 mV, an action potential is initiated. If it doesn't reach -45 mV, no action potential occurs
When the voltage drops below -70mV due to the K ions leaving the inside of the cell, how does the Na/K pump make the inside of the cell less negative if it is pushing out 3 Na ions with a +1 charge and only receiving 2 K ions with a +1 charge? Seems like the voltage on the inside of the cell would decrease to me. Can you clarify? Thanks
Aside from the Na/K ATPase pump, there are also non-gated leakage channels which allow the diffusion of Sodium and Potassium ions in and out of the cell. At an axon, there are typically more Potassium non-gated channels than sodium ones. The effect of this is a diffusion of Potassium back into the cell as well as active transportation form the ATPase pump. :)
You said that after reaching -45 mV (before hiperpolarization), the NaK-Pump starts to work. But when does the Voltage-gated Potassium channel get closed? Does it get closed by detecting any specific voltage?
Hey Brian. No, I said after the membrane reaches - 45 mV, some of the inactivated Na voltage-gated channels begin to recover! Remember, the Na channels need to recover so that we can initiate another action potential after the first one is over. The Na-K pump begins to work at around the time the potassium voltage-gated channels begin to close. Potassium channels close at the end up the repolarization period, when the membrane potential is lowered to slightly below the normal membrane potential. Hope that helped! :)
Thanks! So, there isn't an specific voltage to get the channel closed? is it approximately below rest potential? I ask you this, cause I haven't found nothing yet in textbooks (I haven't searched that much neither). Thanks for the quick answer!
Brian Díaz Flores The potassium voltage gated channels begin to close at around the membrane potential (approximately the - 70 mV range). As they close, the Na-K pump helps reestablish the normal membrane potential.
I can not even begin to describe how thankful I am for people like you. All your videos are EXTREMELY helpful and elaborate. We are in dire need of more teachers like you.
this is how explaining of something should be done!
as a medicine student I'm very thankfull to you
Hey Mr, I don't know your name but I wanted to send you my greatest gratitude from Ethiopia. Your lectures are crystal clear and your explanations are beyond amazing. Always remember you're helping out tons of students across seas and you're providing a quality education. Thankyou! God Bless You!
OMG, this is so helpful. I'm studying for an exam to get into a program. You explain your lectures in a way that makes it easy to understand. Thank You so much.
Man thanks for all your videos. I'm taking the MCAT soon and knowing that your videos got me through my clases for the past 4 years. I'm here again to recharge my memory. Not all people can afford tutoring or supper expensive recap classes.
hi im studying for the MCAT now, did you watch all his vids for the mcat if so do u recommend them?
@@junebug8241 for the topics I had some doubts I did.
you are the first person who made me fully understand this lecture. you are an amazing teacher, thanks a lot!
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Greetings from a nursing student:)
1Flower2010 Thanks! Awesome! :-) Best of luck in your studies!
Best teacher in the world.... :-)
You're the best! I wish I could donate you someday so you'll produce more videos. Yours helped me a lot. When I graduate in 4 years soon, I'll surely recommend your channel!!
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Do you post your notes in pdf so that we can download and review later on?
I finally understand. Thank you. You have been so helpful
May I ask some questions?
1. during the hyper-polarization period, the potential difference is lower than the usual resting potential, this means the cytoplasm is much more negative. If we want to restore it (increase voltage back to -70mV), aren't we going to bring more positive charges into the cytoplasm rather than bringing 3Na+ out and 2K+ into the axon?
2. If the stimulus is stronger, the frequency of this action potential cycle increases. Can I say if the stimulus is stronger (very painful after hitting something), the neurones use more ATP? (increased frequency of hyper-polarization using Na+/K+ ATP-ase.
Thank you very much
Really thankful to AK Lectures
Best teacher i hv ever seen..
I loooove your videos ... make more topics for medical students pleeeease ….thank you so much :)
Thank you SOOOO much (Medicine student)
nmar vlonam you're welcome! :-)
who asked what type of student you are?
I really love ur lactures .they have helped me alot
I m preparing for postgraduate entrance exam in India.your lectures are very much helpful. one request can u give some lectures on pharmacology coz i find this subject a bit difficult.
The best teacher!
Thank you so so much Sir, you're absolutely amazing
Excellent lecture easy to follow
First off, thank you for all your efforts and willingness to share your time and talents.
I'm still not quite clear on how the return to resting membrane
potential occurs after hyperpolarization. Many sources cite the Na+/K+
pump. This is confusing to me because if 3 positive ions (Na+) are
leaving the -90mV cell and 2 positive ions (K+) enter the cell than in
my mind the ICF would still have a negative defect in relation to the
ECF. Now, we know that K+ is 25-30 times more permeable to the membrane
than Na+ is...so is the return to resting potential (-70mV) achieved by
lots of K+ crossing the membrane into the cell via leak channels?
+Michelle Christian
Ah, yes I think you gave the critical info in the previous lecture: Resting membrane potential, but would just like confirmation. After hyperpolarization, the cells ability to return to resting membrane potential of -70mV is r/t the protein leak channels that are specific to K+ being present in vast numbers in relation to the other protein channels. So K+ is entering the cell in large quantities, allowing for RMP to be achieved. Am I understanding this concept correctly?
+Michelle Christian indeed the Na+/K+ pump causes a net negative charge in the cell as 2 K+ is pumped in while 3Na+ is pumped out. however due to the fact that there are more K+ leak channels than Na+ leak channels, more K+ influx occurs than the Na+ efflux, resulting in repolarisation.
You make it soo easy! thank you very much! :)
You are just awesome sir.. Thank you very much for your lectures..
What kind of stimulus causes a depolarization. Following the sequence of events after depolarization is fairly straightforward, but in trying to conceptualize action potential its helpful to understand (to whatever small extent) where the stimulus comes from and how it decreases the membrane potential. Is it cause by ions flowing out of the membrane, decreasing the potential? If so, through what channel do these ions flow out, what causes them to flow and thus eventuate in a threshold value?
Thank you for all your videos!
אחלה הסברים! דיקציה טובה!
יעל כץ You're welcome! Glad to hear that :)
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Thats what I call explaining 👏
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the relatively refractory period is it in which the canal voltage sodium will be closed or open ?or the active atpase canal will be closed?
Excellent work !!
Beautiful description..I have a question what happens at the threshold that it immediately drops from -70 to -45?
Super late, but -70 mV is actually the resting membrane potential, while -45 mV is the threshold potential (and -70 mV is less than -45 mV, to be clear). So what happens is a stimulus is applied, and if it reaches -45 mV, an action potential is initiated. If it doesn't reach -45 mV, no action potential occurs
Thank you so much for explaining !!
Thank you so much
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u r a great lecturer .... these videos are so helpful
thank u so much
thank you! :) happy to be of help!
Thank you so much........but voltage gated k+ channel has only one gate not two........
Many references have the threshold point as -55mV not -45mV??
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When the voltage drops below -70mV due to the K ions leaving the inside of the cell, how does the Na/K pump make the inside of the cell less negative if it is pushing out 3 Na ions with a +1 charge and only receiving 2 K ions with a +1 charge? Seems like the voltage on the inside of the cell would decrease to me. Can you clarify? Thanks
Aside from the Na/K ATPase pump, there are also non-gated leakage channels which allow the diffusion of Sodium and Potassium ions in and out of the cell. At an axon, there are typically more Potassium non-gated channels than sodium ones. The effect of this is a diffusion of Potassium back into the cell as well as active transportation form the ATPase pump. :)
Shouldn't the the depolarization stop when the system reaches equilibrium i.e. potential difference be 0?
Thank you so much
U are amazing
sir ..i have a doubt ...is resting potential is -90mv or -70mv ...some book state that its around -90mv ...please clarify my doubt sir
threshold is -55mV or -45mV?
When do VOLTAGE GATED K+ channels close?
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Great explanation. Watch the video at 1.25 speed and thank me later 😜
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You said that after reaching -45 mV (before hiperpolarization), the NaK-Pump starts to work.
But when does the Voltage-gated Potassium channel get closed? Does it get closed by detecting any specific voltage?
Hey Brian.
No, I said after the membrane reaches - 45 mV, some of the inactivated Na voltage-gated channels begin to recover! Remember, the Na channels need to recover so that we can initiate another action potential after the first one is over. The Na-K pump begins to work at around the time the potassium voltage-gated channels begin to close. Potassium channels close at the end up the repolarization period, when the membrane potential is lowered to slightly below the normal membrane potential. Hope that helped! :)
Thanks!
So, there isn't an specific voltage to get the channel closed? is it approximately below rest potential?
I ask you this, cause I haven't found nothing yet in textbooks (I haven't searched that much neither).
Thanks for the quick answer!
Brian Díaz Flores The potassium voltage gated channels begin to close at around the membrane potential (approximately the - 70 mV range). As they close, the Na-K pump helps reestablish the normal membrane potential.
thanks so much..you're awesome :)
most of the books gives me threshold value equal -55mv .is ur value also correct ? @AK LECTURES
Bichemistry, Stryer, gives -60mV. I guess just stick to what your book says as your exams are judged based on your syllabus books.
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thaaanks
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Thank you so much