What exactly is a threshold potential?

Question

I don't understand it when its often used to describe "triggering the action potential" and what exactly is the "all-or-none event"?

Please help me understand.

Answer 1

I already responded to this question which you just asked:


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The threshold potential is the potential across a membrane that much be reached for the cell to fire an action potential. Imagine starting up a lawn mower. You can keep pulling on the cord (similar to generating a local potential), but in order for the mower to start (similar to the cell firing an action potential), you have to pull the cord a certain force for it to start. That force is the equivalent to a threshold potential.

What happens in a cell when the threshold potential is reached is that the charge gradient causes a conformational change in many Na+ channels, allowing lots of Na+ to rush into the cell, generating the all or none response known as an action potential.

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The lawn mower analogy pretty much explains what all or none means. When you pull on the cord to start a lawn mower, it doesn't always start it. You have to pull it with a certain strength to start it. That is exactly what all or none means, can't think of a better way to explain it. You can't partially start a lawn mower, and a cell can't fire a "partial" action potential. So the threshold refers to the amount of strength you need to pull on the cord to actually start the mower. A threshold potential refers to the potential a cell must develop across its membrane to fire off an action potential.

Answer 2

Threshold Potential

Answer 3

A threshold potential is the level at which an action potential will fire. For example, if a cell has a resting membrane potential of -90mEV, and the threshold potential is -60mEV, a stimulus must depolarize the membrane by 30mEV to cause the action potential to fire. If the stimulus is less than 30mEV, threshold will not be reached and you will not get an action potential, hence an action potential firing is an all or nothing phenomenon. You can't have partial firing of an action potential.

Answer 4

A neuron, presented with a stimulus, either fires (if the stimulus is strong enough) or doesn't, if it isn't. The borderline is called the "threshold potential". This potential may depend on other stimuli, either positively or negatively.

Answer 5

It's a bit like the film Charlie and the Chocolate factory , you struggle in life and then bomb something happens it all comes true , you'll be happy some day and will wonder why you ever asked a question like you did on here , Trust me Dreams do come true lol .

Answer 6

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RE:
What exactly is a threshold potential?
I don't understand it when its often used to describe "triggering the action potential" and what exactly is the "all-or-none event"?

Please help me understand.