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009 Depolarization: Phase 1 of the Action Potential

The action potential can be a complicated thing to understand, unless you are dealing with little white plusses on a table :)

In this video, I help you visualize the first phase of the action potential – the Depolarization phase.

Go ahead and watch the video and you should get a clear understanding of the events that cause depolarization of the neuron.

- Leslie Samuel

 

Transcript of Today’s Video

Hello and welcome to Interactive Biology TV, where we’re making biology fun! In this episode, we’re going to be talking about depolarization, which is the first phase of the action potential. We’re going to go into some more detail than we’ve been doing in the past when it comes to the action potential. It’s going to be a little different. You’re not going to be looking at me talking about something. You’re actually going to be looking at another one of my elaborate set-ups, and I’m going to call this set-up the “Action Potential Simulator.” I hope that gets you excited about it.

Alright, so what we have here is, this side represents outside the cell, outside the axon, and this side represents inside the axon. Here we have a bunch of pluses, and these pluses are representing sodium ions. Now, sodium ions have a positive charge, and that’s why I chose these very attractive pluses to represent sodium ions.

Now, here in the center, we have what we’re going to refer to as voltage-gated sodium channels. What happens is, you have all these sodium ions on the outside of the cell, and these sodium ions want to get into the cell, but they cannot get into the cell. Why can’t they get into the cell? Because the voltage-gated sodium channels are closed. In order for them to get into the cell, this channel needs to open.

Now, why does sodium want to get into the cell? Well, if you go back to Episode 6, this can refresh your memory a little bit, we spoke about Donnan equilibrium. And we spoke about the fact that the membrane potential at rest is somewhere between -50 to -70, -80 millivolts. At that negative charge, sodium ions are not happy. In order for these guys to be happy, the membrane potential needs to be around +58. And on the inside of the cell, we have a negative charge, so this is not something that sodium likes.

So how does sodium want to counteract this? Well, sodium wants to rush into the cell so that it can make the membrane potential more positive, which will be closer to the Donnan equilibrium potential for sodium ions. I hope that makes sense, if not, once again, go back to Episode 6 and refresh your memory on how the Donnan equilibrium works.

So, someone touches you or there’s some stimulation and there needs to be an action potential that’s sent along the axons of the neurons that are stimulated. What happens is, when the membrane potential reaches threshold, that is enough charge to cause voltage-gated sodium channels to open. Once those voltage-gated sodium channels open, sodium ions can then go into the cell.

Now, what is this going to do to the charge inside the cell? What is it going to do to the membrane potential? Well, now you see you have all these positives on the inside, so that’s going to make the membrane potential more positive. This is the process of depolarization. It is the first phase of the action potential, and this is how the charge starts that gets sent along the axon.

So once again, when the membrane potential reaches threshold, voltage-gated sodium channels open and once those open, sodium ions are going to rush into the cell, making the membrane potential more positive, and that is depolarization. I hope that makes sense to you. If you have any questions, as usual, feel free to ask them in the comments below, and I’ll be happy to answer your questions. And who knows, maybe even make a video answering your specific question. That’s it for this video, and I’ll see you in the next one.

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Leslie Samuel is the creator of Interactive Biology. His mission is to use this site to Make Biology fun for people all over the world.

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Leave An AWESOME Comment

170 Responses to “009 Depolarization: Phase 1 of the Action Potential”

  1. kavvyr February 14, 2011 at 1:50 am #

    nice love ur videos. ur a good teacher! 2 thumbs up

  2. InteractiveBiology February 14, 2011 at 8:24 am #

    @Livinglifehigh Thanks. I appreciate the compliment. Stay tuned because
    there’s much more coming :)

  3. heyitsmekris10 February 20, 2011 at 7:19 pm #

    I love all your videos so far! very helpful. thank you

  4. Farzana April 8, 2011 at 10:14 pm #

    WOWOWOW this video is amazing and I am really starting to understand the process of the action potential. THANK YOU SOOOOOOOOOOOOOOO much for making these videos!!!!!!

    • Leslie April 9, 2011 at 11:27 pm #

      That’s awesome. Glad you are getting so much value out of it. You are very much welcome. There are many more coming :)

  5. CoolItisBand May 7, 2011 at 6:22 pm #

    I want to thank you about this great explanation. I’m a medice student from
    Argentina, my english level is not as good as i would like but I understood
    the whole video. Thank you.

  6. InteractiveBiology June 4, 2011 at 9:22 pm #

    @DeMuslim You should go to my channel and check out the episode 047. It’s
    about the action potential in Cardiac muscle cells.

  7. jaguarangel2000 July 5, 2011 at 4:43 am #

    Thank you–your way of showing this helped me.

  8. jaguarangel2000 July 5, 2011 at 4:43 am #

    Thank you–your way of showing this helped me.

  9. jhazzqlet July 5, 2011 at 6:08 am #

    Thank You very very very very very Much! God Bless!:)

  10. magiusavvail July 16, 2011 at 1:55 pm #

    You’re a life saver, I appreciate your videos very, very much. Thank you.

  11. InteractiveBiology July 17, 2011 at 11:20 pm #

    @magiusavvail You are very much welcome. Glad to know they are helping you. Stay tuned for many more :)

  12. InteractiveBiology July 17, 2011 at 11:20 pm #

    @magiusavvail You are very much welcome. Glad to know they are helping you.
    Stay tuned for many more :)

  13. archana August 29, 2011 at 10:40 am #

    u make science really awesome….

    • Lrsamuel August 29, 2011 at 5:37 pm #

      Thanks Archana. I appreciate the feedback. Stay tuned for MANY more videos and other resources :)

  14. Djalitana September 9, 2011 at 8:37 am #

    does this have something to do with osmotic pressure or is osmotic pressure something different? thanks

  15. Christina S. September 12, 2011 at 2:59 am #

    You are awesome, Thank you very much for providing us with these, totally amazing!!!=]

    • Lrsamuel September 12, 2011 at 12:05 pm #

      Thanks for the feedback Christina.

      I do appreciate it!

  16. lovelylatina207 October 8, 2011 at 5:09 pm #

    You have a great speaking voice and you make your videos fun! thank you :)

  17. InteractiveBiology October 9, 2011 at 10:27 am #

    @lovelylatina207 You are welcome. Glad you are enjoying :D

  18. ely730 October 11, 2011 at 3:39 am #

    Thank you so much for this thorough presentation! :D

  19. InteractiveBiology October 14, 2011 at 8:45 am #

    @ely730 You are very much welcome

  20. Rebeg00 October 18, 2011 at 5:14 pm #

    Thank you for the vid!

  21. InteractiveBiology October 18, 2011 at 9:12 pm #

    @Rebeg00 You’re welcome. Stay tuned for more!

  22. louisa2017 October 25, 2011 at 7:16 pm #

    Awesome! Awesome! Awesome! You make it so easy to understand! Keep the video’s coming, PLEASE! : )

  23. TheMasterSlasher October 25, 2011 at 9:40 pm #

    Very nice!

  24. InteractiveBiology October 25, 2011 at 9:46 pm #

    @louisa2017 Thanks. Glad you are enjoying. Stay tuned for MANY more!

  25. InteractiveBiology October 25, 2011 at 9:46 pm #

    @TheMasterSlasher Thank you!

  26. BabysFace October 29, 2011 at 6:08 am #

    BLACK HANDS!!! *shivers*

  27. FreshBanana598 November 9, 2011 at 12:47 pm #

    @BabysFace get outta here racist -.-

  28. ONWUDIACHI24 November 18, 2011 at 1:35 pm #

    thanks im just following along u teach so well.. my brain is so happy lol

  29. InteractiveBiology November 18, 2011 at 3:46 pm #

    @ONWUDIACHI24 Glad to know that you’re finding value in the videos. Check out more of our videos in the website for more Biology learning with fun! :)

  30. InteractiveBiology November 18, 2011 at 3:46 pm #

    Glad to know that you’re finding value in the videos. Check out more of our videos in the website for more Biology learning with fun! :)

  31. chikifree November 22, 2011 at 10:23 pm #

    @BabysFace youre so ignorant.

  32. chikifree November 22, 2011 at 10:23 pm #

    youre so ignorant.

  33. NeedsAHardOne November 29, 2011 at 5:28 pm #

    how is the threshold potential reached?
    I’ve read that the axon is MUCH more permeable to K+ than Na+,
    so is the threshold potential initially reached because of some K+ flowing in?
    Would that also answer why there are K+ ions in the axon?

  34. lindaandjeffsampson November 29, 2011 at 9:37 pm #

    Your a great teacher! I have a test tomorrow on this. I am glad I found these videos. I am finally beginning to understand. Thank you so much!

  35. InteractiveBiology December 1, 2011 at 4:41 am #

    @lindaandjeffsampson Wow! That’s good to hear. Hope you did well on your exams. Please stay tuned. WE have more Biology videos coming soon!

  36. InteractiveBiology December 1, 2011 at 4:41 am #

    Wow! That’s good to hear. Hope you did well on your exams. Please stay tuned. WE have more Biology videos coming soon!

  37. kvmackay1321 December 7, 2011 at 1:59 am #

    ohmygoodness! Lifesaver! You made this clear as day, thanks!

  38. Kirsten Victoria MacKay December 7, 2011 at 1:59 am #

    ohmygoodness! Lifesaver! You made this clear as day, thanks!

  39. InteractiveBiology December 8, 2011 at 9:35 am #

    @kvmackay1321 Glad to know it made it all clear for you. We have more Biology videos that you might find useful, as well. Stay tuned!

  40. InteractiveBiology December 8, 2011 at 9:35 am #

    Glad to know it made it all clear for you. We have more Biology videos that you might find useful, as well. Stay tuned!

  41. InteractiveBiology December 8, 2011 at 9:35 am #

    @kvmackay1321 Glad to know it made it all clear for you. We have more
    Biology videos that you might find useful, as well. Stay tuned!

  42. panamasrose January 8, 2012 at 11:09 am #

    Great teacher. You really make a tough subject easy to understand!

  43. panamasrose January 8, 2012 at 4:09 pm #

    Great teacher. You really make a tough subject easy to understand!

  44. shlooganyah January 12, 2012 at 9:12 pm #

    This is excellent! Thank you so much for posting this video!

  45. ravinderguliasls January 13, 2012 at 2:09 am #

    thanx for such a nice videos but need video of spinal cord, amygdala, hippocampus, stratum,

    I will be than full to you.

  46. ravinderguliasls January 13, 2012 at 2:09 am #

    thanx for such a nice videos but need video of spinal cord, amygdala, hippocampus, stratum,

    I will be than full to you.

  47. shlooganyah January 13, 2012 at 2:12 am #

    This is excellent! Thank you so much for posting this video!

  48. ravinderguliasls January 13, 2012 at 7:09 am #

    thanx for such a nice videos but need video of spinal cord, amygdala, hippocampus, stratum,

    I will be than full to you.

  49. InteractiveBiology January 13, 2012 at 7:26 am #

    @ravinderguliasls I always find it interesting when people TELL me what they NEED me to do as opposed to asking me if I would be able to do it. You would think they are paying me ;)

  50. InteractiveBiology January 13, 2012 at 7:26 am #

    I always find it interesting when people TELL me what they NEED me to do as opposed to asking me if I would be able to do it. You would think they are paying me ;)

  51. InteractiveBiology January 13, 2012 at 12:26 pm #

    I always find it interesting when people TELL me what they NEED me to do as opposed to asking me if I would be able to do it. You would think they are paying me ;)

  52. psipsychologytutor January 13, 2012 at 10:11 pm #

    @InteractiveBiology rflmao

  53. psipsychologytutor January 13, 2012 at 10:11 pm #

    rflmao

  54. psipsychologytutor January 13, 2012 at 10:11 pm #

    Oh very cool~ and here am I at the table with students using cardboard axons and spreading rock salt all over the shop ~:-)

  55. psipsychologytutor January 13, 2012 at 10:11 pm #

    Oh very cool~ and here am I at the table with students using cardboard axons and spreading rock salt all over the shop ~:-)

  56. psipsychologytutor January 14, 2012 at 3:11 am #

    rflmao

  57. psipsychologytutor January 14, 2012 at 3:11 am #

    Oh very cool~ and here am I at the table with students using cardboard axons and spreading rock salt all over the shop ~:-)

  58. AmoebaLasVegas January 14, 2012 at 5:59 am #

    I love your hands-on approach to this very tricky topic.
    The only thing I would suggest is to avoid statements such as “Sodium wants…”, “Sodium likes…”. It is pedantic, but I have found that when I have made such statements in the past (and it is really hard not to) students start to think that, for example, atoms have human traits. Anyway, keep up the great work.

  59. Gerald Carey January 14, 2012 at 10:59 am #

    I love your hands-on approach to this very tricky topic.
    The only thing I would suggest is to avoid statements such as “Sodium wants…”, “Sodium likes…”. It is pedantic, but I have found that when I have made such statements in the past (and it is really hard not to) students start to think that, for example, atoms have human traits. Anyway, keep up the great work.

  60. Gerald Carey January 14, 2012 at 10:59 am #

    I love your hands-on approach to this very tricky topic.
    The only thing I would suggest is to avoid statements such as “Sodium wants…”, “Sodium likes…”. It is pedantic, but I have found that when I have made such statements in the past (and it is really hard not to) students start to think that, for example, atoms have human traits. Anyway, keep up the great work.

  61. dancernoregon January 25, 2012 at 7:03 pm #

    thank you~! you are wonderful! I subscribed for when I have a question… I am sure one will come!!!

  62. dancernoregon January 26, 2012 at 12:03 am #

    thank you~! you are wonderful! I subscribed for when I have a question… I am sure one will come!!!

  63. timothymanzella January 28, 2012 at 5:09 pm #

    This is one very “belligerent” video. =p

  64. timothymanzella January 28, 2012 at 10:09 pm #

    This is one very “belligerent” video. =p

  65. olivia February 3, 2012 at 9:57 am #

    Hi Leslie,Thank you soooooo much for doing these videos for us!!These videos help alot!!!
    Btw i found the power point of the neurons system and just wondering where is the video bout this PW?

  66. hmds88 February 9, 2012 at 5:17 pm #

    I sincerely appreciate your existence and the time you took out of it to create these wonderfully helpful explanations. Trust me, hungry minds cherish this stuff. Thank you

  67. hmds88 February 9, 2012 at 10:17 pm #

    I sincerely appreciate your existence and the time you took out of it to create these wonderfully helpful explanations. Trust me, hungry minds cherish this stuff. Thank you

  68. Laurie February 9, 2012 at 6:48 pm #

    What would I do without your quizzes and your videos? I’ve learned more from your site than in class. So,I want to thank you for all your time that you put into sharing your knowledge with the world!

    • Leslie Samuel February 9, 2012 at 11:25 pm #

      Thanks or the feedback Laurie. So glad to know that you are finding such value in the site. Stay tuned for more ;)

  69. transnaturel0709 February 12, 2012 at 6:06 pm #

    Awesome!!

  70. johncena04red February 12, 2012 at 7:38 pm #

    In 4 minutes you cleared up a week worth of confusing lectures appreciate the video bro

  71. transnaturel0709 February 12, 2012 at 11:06 pm #

    Awesome!!

  72. johncena04red February 13, 2012 at 12:38 am #

    In 4 minutes you cleared up a week worth of confusing lectures appreciate the video bro

  73. Azalea Johnosn February 12, 2012 at 9:03 pm #

    I wish I found these videos last year. However they are a huge help to me now I’m in my second year of study. Thanks a lot.

    • Leslie Samuel February 15, 2012 at 11:16 am #

      You are very much welcome. Glad you are finding them helpful! All the best!

  74. agivandagi February 16, 2012 at 1:35 am #

    nice video, cool accent too, where from ?

  75. agivandagi February 16, 2012 at 1:35 am #

    nice video, cool accent too, where from ?

  76. agivandagi February 16, 2012 at 6:35 am #

    nice video, cool accent too, where from ?

  77. VallejoVizcaino February 26, 2012 at 8:43 pm #

    Great video !!!

  78. VallejoVizcaino February 26, 2012 at 8:43 pm #

    Great video !!!

  79. VallejoVizcaino February 27, 2012 at 1:43 am #

    Great video !!!

  80. Mr Dependable February 27, 2012 at 11:11 pm #

    You are truly a legend and an awesome teacher!
    Thankyouuu!

    • Leslie Samuel February 28, 2012 at 8:00 am #

      Thank you for your feedback. So glad you are enjoying the content. Stay tuned for more :)

  81. MrEllettb March 13, 2012 at 2:58 pm #

    how does potassium change the membrane potential and make i depolarized?

  82. MrEllettb March 13, 2012 at 6:58 pm #

    how does potassium change the membrane potential and make i depolarized?

  83. 2000moonbeams March 15, 2012 at 10:06 pm #

    Great teacher! Thanks!

  84. 2000moonbeams March 16, 2012 at 2:06 am #

    Great teacher! Thanks!

  85. misscaser March 26, 2012 at 8:58 am #

    thank you so much for all your vids!!!! I understand pns & cns better bcoz of u!

  86. misscaser March 26, 2012 at 12:58 pm #

    thank you so much for all your vids!!!! I understand pns & cns better bcoz of u!

  87. SafinaShah March 27, 2012 at 1:57 pm #

    Thank you so much for your teaching. this is the best site of biology for students.

  88. Marilyn Perez April 1, 2012 at 8:44 pm #

    THANK YOU, THANK YOU, THANK YOU!! You turned complicated to simple! I really appreciate it!

  89. ratdance April 8, 2012 at 9:33 pm #

    thank you so much for these videos.

  90. ratdance April 9, 2012 at 1:33 am #

    thank you so much for these videos.

  91. bellepixie April 10, 2012 at 4:01 pm #

    Can potassium levels have an effect on spontaneous depolarization? And if so, how?

  92. bellepixie April 10, 2012 at 4:05 pm #

    Also, these videos are absolutely brilliant. Bookmarked forever.

  93. bellepixie April 10, 2012 at 8:01 pm #

    Can potassium levels have an effect on spontaneous depolarization? And if so, how?

  94. bellepixie April 10, 2012 at 8:05 pm #

    Also, these videos are absolutely brilliant. Bookmarked forever.

  95. MegaKev29 April 12, 2012 at 12:13 pm #

    good video. Keep em coming!

  96. MegaKev29 April 12, 2012 at 4:13 pm #

    good video. Keep em coming!

  97. Eylem May 8, 2012 at 7:10 pm #

    You are great Leslie…..Thank you

  98. Em May 9, 2012 at 11:44 am #

    Hello Leslie! I am a postgrad student in the UK doing experimental psychology, trying to revise action potentials for an exam in a few weeks and wanted to let you know that your videos are wonderful. Succinct and neat – the perfect revision and study tool! Thank you so very much!

    • Leslie Samuel May 10, 2012 at 10:21 am #

      So glad to hear that you are finding value in the videos. All the best!

  99. TheNightbeauty1 May 20, 2012 at 4:02 am #

    Will you marry me?

  100. TheNightbeauty1 May 20, 2012 at 4:02 am #

    Will you marry me?

  101. zss123456789 July 1, 2012 at 11:18 pm #

    you are ten times better than my prof who is technologically impaired!!!

  102. zss123456789 July 1, 2012 at 11:18 pm #

    you are ten times better than my prof who is technologically impaired!!!

  103. ramesh July 11, 2012 at 7:02 am #

    Thank you Samuel. It was refreshing going through your videos. keeping doing this for the fun of learning biology.

  104. minho gul July 15, 2012 at 4:15 pm #

    hahaha…gud question :P

  105. minho gul July 15, 2012 at 4:15 pm #

    hahaha…gud question :P

  106. Alexa July 16, 2012 at 9:33 pm #

    Leslie,

    Excellent videos! I’m using them to brush up on my cardio stuff before my rotation with a cardiologist. This is a big help. You have a really nice voice and explain things very concisely. Keep up the great work!

    Best of luck,

    Alexa

  107. Manni N July 22, 2012 at 8:34 pm #

    Thanks a lot for the videos you make,,, you’ve made biology so easy and interesting to me ,,,

  108. Manni N July 22, 2012 at 8:34 pm #

    Thanks a lot for the videos you make,,, you’ve made biology so easy and interesting to me ,,,

  109. allthruu August 2, 2012 at 4:16 am #

    love this…can you recap all of intro bio for pre-med majors…thx

  110. 774800006 August 9, 2012 at 4:51 pm #

    thank you, these videos are really helpful.

    cheers from Sri Lanka :) :)

  111. mathelida September 8, 2012 at 7:57 pm #

    hey plz.. make me clear about threshold?? thanks !

  112. PmCZAkuan September 10, 2012 at 4:59 am #

    What would happen to the resting membrane potential if the extracellular potassium concentration was increased and how would this affect the neuronal action potential?

  113. khye912 September 10, 2012 at 12:34 pm #

    what is the differences between this action potential and sodium potassium pump??

  114. DrMythology September 24, 2012 at 2:29 pm #

    Hi, i understand why the entry of Na will cause depolarization for example from -90mV to -10mV the polarity ‘negativity of the cell’ is being lost.. this is totally understandable but here is where i get mixed up >>> when the cell is in a depolarizing state when it reaches to ”’+” mV for example +10mV isn’t that being also polarizing to the other side ?? why is it still called depolarizing?? can anyone explain to me .. Thank you

  115. bautista1 October 1, 2012 at 6:14 am #

    At rest, the action potential is negative due to more Sodium ions flowing out of the axon correct? And it is less Potassium that flows inside, correct?

  116. SplashFlip October 6, 2012 at 2:03 pm #

    Just wondering if there is a chapter 8? i couldn’t find it in youtube though i searched. I don’t wanna miss any of these awesome videos!

  117. InteractiveBiology October 7, 2012 at 2:47 pm #

    Yes. Please check our channel to see a list of all the videos we have posted. Have fun!

  118. Bruno Balbino October 13, 2012 at 11:34 am #

    What an amazing video! I’ve looked for the next chapter in yt, but I couldn’t find that! I wanna watch all of them.

  119. luvlyvero14 October 16, 2012 at 8:47 pm #

    I love the first line of all his videos.. “Hello and Welcome to interactive biology tv. Where we’re making biology fun!” lol.. sounds like he really enjoys his subject matter. Pleasant voice for learning..

  120. Tasha Tolbert November 2, 2012 at 2:12 am #

    Wow! You are an EXCELLENT teacher!!! I have been watching your videos all day going over some of the subjects that I did not understand in class. Your videos have made me more interested in the material, and I have actually been understanding the information as well!! I haven’t gotten bored at all!! You are a truly gifted man. God bless you:-) You are quite handsome as well:-) Thank you.

  121. OriginalRipndip November 14, 2012 at 5:45 am #

    West Indians apply a simple approach and logic to learning. feel free to merge the 2 vids on this subject we don’t have the attention span of a neuron we are here to learn for our intense classes. thx doc

    do u have playlists grouped by systems?

  122. kittykaaboom December 12, 2012 at 3:23 am #

    This makes everything much easier to understand. Thank you so much!

  123. NaniiStarlight December 13, 2012 at 7:08 pm #

    I’m from The Netherlands and I’m studying Psychology and the English Biology books we have to use are soooo hard but this is amazing!! it makes it really easy to understand, thank you!

  124. hellopiggy15 December 30, 2012 at 7:03 am #

    how does it reach threshold?

  125. TheAdmiston January 6, 2013 at 10:17 pm #

    hey! sorry a have a dilema.,i see that you respownd at this question..how is possible that one small stimulation at the one part of neuron can be transmited to oposite part ..neurons can be very long..over 30 cm.. i don’t underestand how ions chanels is opened..i understand the first chanel is open by the stimulation but after that? i look all over the youtube but i find smth like this..”the signal is transmited afther that to all over the cel..”how more exactly?who opens the others ion chanels?

  126. TheAdmiston January 6, 2013 at 10:18 pm #

    ion chanels for sodium i mean:D

  127. ASternTravesty January 6, 2013 at 11:45 pm #

    you sound so excited in the beggining, almost like your trying not to laugh.

  128. zmerka1 January 7, 2013 at 2:54 am #

    I want to sincerely thank you for this fountain of knowledge. Your videos have gotten me thru A&P classes and biochemistry classes. I am always amazed at the generosity of people like you who put so much time and effort bringing something like this to the world.

  129. Tan Run Yu January 8, 2013 at 8:29 am #

    2:46 how to make the membrane potential reaches threshold ? is it by increasing the amount of Na ions outside the cell ?

  130. DAHRealTrump January 16, 2013 at 5:04 am #

    Thank Jesus! You made this so clear!

  131. idomanlythings January 21, 2013 at 4:15 pm #

    Thank you very much. Appreciate it.

  132. erikaj13 February 14, 2013 at 2:07 am #

    Thanks so much for all your videos. You are really helping me through my anatomy & physiology course :)

  133. Bubble Batth March 4, 2013 at 3:44 pm #

    we appreciate your time and expertise greatly!

  134. mohib ullah March 12, 2013 at 2:22 am #

    Nice method and very easy to understand thanx

  135. alexandrayla March 17, 2013 at 4:16 pm #

    thank you!

  136. caxsmith March 18, 2013 at 5:00 pm #

    Is there food you can eat that will affect the threshold? I’m thinking of people with gluten reactive disorders, not celiac disease as such. And is this related to the threshold of pain a person has?

  137. AM loki March 30, 2013 at 8:00 pm #

    i thought that was a black duct tape

  138. main126 April 14, 2013 at 5:48 pm #

    Thank you for making this video ~

  139. Coco Duncan April 17, 2013 at 2:42 am #

    A friend advised me to come check out your videos and I am understanding so much from you than my own anatomy&physiology professor. Your videos are a great study tool. Thank you for your expertise.

  140. Bryce Daniel April 19, 2013 at 12:13 am #

    Very “Attractive” pluses. Haha.

    Thanks for making these videos.

  141. Dragonflowi April 19, 2013 at 11:40 am #

    Hey excellent video !!! I have a question. I dont understand why inside the membrane the charge is negative if it contains Potassium K+ that also has a positive charge ? Could you explain to me why is this ? Thx in advance

  142. Abdul al-najjar April 20, 2013 at 5:17 pm #

    Impressive

  143. Underground308 April 23, 2013 at 9:51 pm #

    When something “clicks”, Its the best feeling in the world!!! I understand!!! After feeling hopelessly lost for so many night, I get it!!! l! You sir are awesome!! Thanks!!

  144. vladbio May 9, 2013 at 7:40 am #

    Hi Leslie, great video – as usual.
    I was wondering what stimulus can create the initial difference sufficient to open Na gated channels?
    Thanks in advance.

  145. tey croco May 12, 2013 at 3:28 am #

    I really enjoy watching your video! Thanks for making biology fun! It’s enjoyable!

  146. Hayah Bellatrix June 14, 2013 at 3:43 am #

    thanx a lot 4 ya video brother. May Allah reward u.. will u please guide me to ur episode 6… i’m unable to find it!

  147. Ray July 11, 2013 at 1:58 pm #

    Great vids, but can you Please remove the sign up box that pops up from the beginning of every window? Because even though I’ve signed up, it still pops up before every videos and it’s hard to keep writing that info in when you’re watching 40-50 videos and you have to write it in before each one. But other than that, amazing videos!!!

  148. Ravneetu July 31, 2013 at 9:56 pm #

    Hey! Could you please make a video on Cardiac action potentials, SA node,and ventricular action potentials? Along with Cardiac muscle contraction? Maybe even the Cardiac cycle if you have time! You would be a lifesaver!!!

  149. lovely gamboa August 26, 2013 at 7:03 am #

    i could see,the previous video’s you are talking about,the equilibrium thing.please help!!

  150. Taminu Bawa Dary August 28, 2013 at 6:05 pm #

    good

  151. Foxy Roxy September 28, 2013 at 8:41 am #

    I love your videos. As I read each chapter of my Anatomy & Physiology book I watch one of your videos for a clear understanding of what I’m reading. Your videos are easier to follow. Keep up the good work!!! You have been a great help.

  152. Stephanie Conley October 8, 2013 at 10:12 am #

    Finally makes sense. Thanks.

  153. Karen Peaden October 14, 2013 at 7:58 pm #

    thank you! I am 56 yrs old and taking ECG and need all the help I can get! the heart is very complicated and you are great at explaining things! you are great at teaching! thank you again!

  154. Akash Ahmed October 26, 2013 at 5:26 pm #

    Hello everyone. Fabulous video clip. My close friend had been fat. He converted himself from 283lbs of pure fat to 215lbs of purely natural muscle. Everyone was amazed. I just subscribed personally coz I’m planning to get stronger muscle mass. He used the Muscle Building Bible (Google it)…

  155. James Bronson November 5, 2013 at 5:07 am #

    hes black

    • teresa December 7, 2013 at 12:51 am #

      You have been soooooo helpful. I am thankful for your videos. Really, because of them I have passed difficult tests in the last year!
      Thank you so very much <3

  156. James Bronson November 5, 2013 at 5:08 am #

    its 5;00 AM!!!!!! WOOOOOOOOOOOOOOOOOOOOOOOOOOOOO

  157. Allyson Rodriguez November 9, 2013 at 3:45 am #

    Thanks, my professor makes me dizzy….

  158. Bina Ch January 13, 2014 at 12:05 pm #

    your videos are of great help to me as i have many of my doubts cleared…….thanks:)

  159. leo May 8, 2014 at 10:14 am #

    Great videos !!!!
    just a question how can it reach the threshold if the voltage gated channel is closed? is that with the passive transport ?
    thans a lot

  160. Ingrid June 5, 2014 at 4:48 am #

    Hi Leslie!

    Thank you SO SO very much for these wonderfully composed and easy to understand lessons; the combination of visual video with simple, well-written transcripts increased my rate of learning and absorption by ten-fold (at least). I am an English major attempting to get into a Nursing program and thus am spending my summer filled to the gills with biology and physiology courses. I’d been pouring over my textbook, our class lab book, and website after website trying to understand the connections between concepts that you made so rapturously clear in your beautifully organized lessons all across your website. Keep up the good work, you’re helping a great number of people, and I wish you the best of luck in whatever path you choose to take.

    Thanks again,
    Ingrid
    (Bethesda, Maryland USA)