Can someone please explain action potential?!! (1 Viewer)

[cornchips1]

Argh. i just don't get it. help ?

 

[medicore]

yes, need help with that aswell.

 

[TheOptimist]

Imo this forum needs a new moderator Survivor39 hasn't been around for a while...
So what is an Action Potential?:
An action potential occurs when a neuron sends information down an axon, away from the cell body. It is an explosion of energy that is created bya depolarizing current.

So why don't all stimuli create action potentials?:
In order for an action potential to be fired it must be able to reach a threshold (-55mV), the action potential operates under an "all or none" principle so if the threshold is not reached no action potential will be fired and if it is reached then a full action potential is fired. Thus some stimuli are not able to generate a current that willl be able to reach the theshold. N.B. All action potential fired are of the same size i.e. they will reach +40mV every time.

So what happens during an Action Potential?:

At rest:
-overall negative charge within the cell(caused by the presence of negative protein molecules), and positive outside the cell
-the electrical potential(difference) between the inside and the outside of the cell is 70mV (written as -70mV due to the negativity within the cell)

Action Potential Propagated;(Depolarisation)
-neuron membranes become more permeable to Sodium(Na)
-Na moves into neuron via the Na channel faster than Pottasium(K) moves out via the Pottassium channels
-creates more positive charges within the cell--->changes electrical potential of the cell
- if the change is greater than +15mv i.e. -70mV--->-55mV, then the threshold(-55mV) is reached and an action potential is fired (depolarisation) - At this point membrane has become massively permeable to Na and it rushes in. The depolarisation can end up as being as high as +40mV, i.e. -55mV--->+40mV(spike of the action potential graph).
-once the action potential occurs due to a change in the cell membrane it travles down the axon like a chain reaction (N.B. It takes approx 1 milisecond for an action potential to be fired) from the cell body ---> axon.

Resting potential (Repolarisation):
-the neuron recovers to its resting potential (-70mV) by actively transporting Na and K ouside of the cell, note it goes below -70mV during the refractory period (to around -90mV), then goes back up to -70mV. This takes about 1 millisec in which the neuron can't fire during this time, so 1000 action potential spikes an be fired per second.

Tranference of the Action potential to another neuron:
-Once the Acction potential reaches the axon terminals, the continuation of the impulse is caused by the release of neurotransmitter's, these go to the dendrites of the next neuron and cause's Na channels to open and the process repeats again.

Hope this all makes sense, this info makes the best of sense when used in collaboration with images, sooner or later it will make sense

 

[wavess]

Here's a useful video: http://m.youtube.com/watch?v=pnAwtX_UCbg
There's the next video after it, repolarisation http://m.youtube.com/watch?v=xmn0Vcd_wLA

 

[jane bubble]

Do we need all that detail about Na and K moving in and out?

 

[Wajahat zia]

Do we need all that detail about Na and K moving in and out?

yes you do that is one of the main parts of action potential which shows the depolarization, repolarisation and hyperpolarisation.

 

[Eduard_Khil]

Theoptimist for bio forum moderator 2013!