Action Potentials??? (1 Viewer)

[spackness]

Hi ppl, could anyone out there please explain to me in PLAIN TERMS what the hell and action potential is and teh threshold and why not all stimuli generate an action potential and blah blah blah. p.s i have read all the threads and still cant make sense of them...an example would help

 

[bluesky100]

Action potential = wave of current in nerve and muscle cells that results from the movement of ions across the plasma membrane.

Re: Threshold and All-or-None Response
The potential at which a membrane is depolarised to generate an action potential is called the threshold potential and stimulus that is strong enough to depolarise the membrane is called threshold stimulus.
A stimulus of more than threshold magnitude also elicits an action potential of the same amplitude as that caused by a threshold stimulus. This is because once the threshold is reached membrane events are no longer dependent upon the stimulus strength. Therefore, action potentials occur maximally or do not occur at all and this is called an all-or-none response. This is why a single action potential cannot convey information about the magnitude of the stimulus that initiated it

Nb: for anything to happen the threshold must be reached.

Diagram of how an action potential is generated.

Hope that helps!!

 

[Shell]

omg i was wanting to ask that exact question on here. BUT IN SIMPLER TERMS PLEASE! that whole slab of shit, means nothing to me. i need it explained in dumber terms, before i can understand it well enough to write about it in technical terms

 

[always_smile]

omg i was wanting to ask that exact question on here. BUT IN SIMPLER TERMS PLEASE! that whole slab of shit, means nothing to me. i need it explained in dumber terms, before i can understand it well enough to write about it in technical terms

I don't understand it either. The Advice Line told me to look at the following link:
http://hsc.csu.edu.au/biology/options/communication/2955/CommPart7.html#3

 

[Twiggyy]

heyy

hey ok ill try explain it lol it is preety difficult but heere goes lol

ok a THRESHOLD is an AMOUNT - so its a specific quantity- of positive charge that is needed before an action potential can be produced!

so the amount of threshold is important for producing an action potential

now this threshold(amount) has to be at least 15mL more positive than the resting potential of -70mL.. so for an action potential to occur.. the potential in a membrane needs to be at least -55mL or higher.

ok now ur probably thinking wats a resting potential .. so a resting potential is a NERVE where the concentration of sodium ions OUTSIDE this nerve is Higher than the amount of sodium ions INSIDE this nerve..
Then an nerve impulse arrives.
This stiimulates the outside membrane of the NERVE to become more permeable to sodium ions... meaning more sodium ions are able to enter the NERVE.. now this rush of sodium ions which has to be at least 15 mL more positive than the resting potential of -70mL (known as depolarisation) REVERSES the resting potential into an ACTION potential... This is because the inside of the NERVE HAS MORE sodium ions than it did b4 the action potential..

ok so thats a description for action potentials and threshold lol

now the reason why not all produce action potentials is :
a/ each stimulus has to produce a FULL potential or NO potential (so its all or nothing.. the only way it can be an action potential is if the threshold must be at least 15ML !!) UNLESS THIS THRESHOLD IS PASSED NO ACTION POTENTIAL WILL HAPPEN.

b/ another reason is that each action potential is a seeperate event.. so wen one action potential happens.. ONLY THEN will another action potential occur... so they cannot occur at the same time.

i hope that helped

 

[Bokky]

This is what i have in my notes in probably the most GENERAL terms

Threshold is the minimum stimulation required to create an action potential in a nerve cell. The resting potential of a neurone is about -70mV (milli Volts). The minimum amount is usually a change in membrane potential difference of at least 15mV. Not every stimulus generates an action potential because insufficient change in membrane potential difference occurs.

YOU ALSO HAVE TO BE ABLE TO DRAW THE TYPICAL ACTION POTENTIAL GRAPH coz i have a feeling they will ask us to

 

[georgechah1]

action potential is gay!

its simple its when the node of ranvier becomes permiable to NA+(sodium ions) and so this chemical enters the nside and becomes rapidaly positive relative to the outside. this is action potential and this allows the nerve impulse to pass through.