in this video I’m going to explain an
action potential an action potential or a nerve impulse causes a movement
of ions across the cell membrane of a neuron similar to a ripple passing
along the surface of a pond the cell membrane of the neuron contains
thousands of tiny molecules known as channels these channels allow either
sodium or potassium ions to pass through generally the channels on the neuron are
closed and the membrane is said to be in a resting state in this state the charge
of the inside of the cell membrane is more negative than the outside and if
you could imagine sticking microelectrode connected to a voltmeter
inside this membrane the reading would show about negative 70 millivolts
meaning that the inside of the neuron is about 70 millivolts less than the outside the cell membrane of a neuron is polarized because of this electrical difference
across the membrane now a nerve impulse starts when pressure or other sensory
inputs disturbs a neuron’s plasma membrane to the point that the potential
difference reaches a threshold voltage of about negative 55 millivolts
this causes hundreds of sodium channels in that region of the membrane to open
briefly this in turn allow positively charged sodium ions to flow inside the
cell membrane now the inside of the membrane temporarily becomes more
positive than the outside which in turn causes the voltage to rise this is
called depolarize state the membrane is now depolarized because the net charge
inside the axon change from negative to positive as sodium ions enter in as
the impulse passes the potassium channels begin to open allowing
positively charged potassium ions to flow out which causes inside of the axon
to resume a net negative charge at this point the voltage would fall the
membrane is now said to be repolarized because again it’s negatively charged on
the inside and positively charged on the outside now this depolarization and
repolarization of a neuron membrane is called an action potential
action potential is just another name for a nerve impulse after a nerve
impulse some voltage-gated potassium channels remain open resulting in
further movement of potassium out of the cell as the voltage falls below the
reading of the resting state the membrane is said to be hyperpolarized
because it is even more negative than at the beginning at this stage neuron is
unable to conduct a nerve impulse and it’s said to be in the refractory period
the refractory period is a very short period during which the sodium potassium
pump continues to return sodium ions to the outside and potassium ions to the
inside of the axon thus returning the neuron to resting potential so in
summary an action potential is just a wave of depolarization and
repolarization it’s not an electric current it’s just a series of
voltage-gated ion channels open and close thank you for watching make sure
you subscribe and hopefully I made it wicked easy to understand


  1. woww, thankk you so much , sir . really appreciate your work. Now i know why its negative 70 inside ,bcoz we r comparing it with outside .

  2. The Na+/K+ pump is NOT responsible for the membrane potential to go from hyperpolarization to its resting state. This happens through the passive movement of ions through leak channels!!

  3. Is it bugging anyone else that hes showing the action potential happening within the section covered by the myelin sheath?
    As far as i know, this process occurs at the Nodes of Ranvier.

  4. You did make it easy. I keep forgetting how it works no matter how many times I read. I think a video would help me to stick the material in my brain. Thank you!

  5. Please can anyone help me understand the purpose of Sodium activation and inactivation channels? And why Potassium has only one activation gate?

  6. Unresolved contradictions in the science of the origin of life. The membrane theory of biopotentials leads to a dead end. Watch the video for details:

  7. I agree! The best explanation by far I've found. Can I find more about this topic (neuronal electro-physiology) in your channel?

  8. This is great, but I believe the channels are only located on the nodes of Ranvier, not on the myelin sheath. The myelin sheath speeds the passage of the ions.

  9. Respected sir if you could explain that how action potential is transfeered from one Na vgc to neighboring Na vgc along axon, sir i will be thankful to you. In vedio it is only explains generation at one Na vgc

  10. You are describing it on the Myelin sheath! But I think the thing you are describing happens in the nodes of Ranvier! Am I right or not?

    If I am right so this explanation and visualization is misleading.

  11. As far as I can remember sodium potasium, calcium and chloride are required for neruons to function. So where does calcium and chloride play it's role? I've just managed to grasp the basics of action potential here, but I'm really curious about the use of the calium channels.

  12. My course has a 20 min lecture video about this yet I've learnt it in 4 minutes from this video. Brilliant. Thank you so much.

  13. The first step of repolrization is closing the Na channels then opening the K channels…not opening K channels immediately as you mentioned… Just a small note… Great video 👏👏

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