conduction of action potentials within the heart

[SamarEsawy]

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the closer the threshold to resting membrane potential, the slower the conduction velocity
I don't understand why

 

[Pic]

Say you have 1000 channels which you use to allow Na+ into the cell, and for all of these to get closed and rested for a new action potential, you need to get to your resting membrane of -90, but in the heart the resting membrane is -70; so only 865 channels can be opened because the other are still in limbo, unable to be opened trying to recover from the last action potential.

So conduction velocity is slower because there are less channels now to move Na+ ions into the cell taking slightly longer, and by longer this is on millisec scale which is only noticeable in the laboratory.

 

[SamarEsawy]

I still don't understand how is this related to the threshold being closer to the RMP.I guess you are changing the resting membrane potential here not the threshold
so instead of saying that we have in the first case RMP is -90 and the threshold is -60 and in the second case RMP is the same and the threshold is -70
but here you're changinh the RMP not the threshold right?
Can you explain this in another way?

 

[Pic]

No fuk you.

 

[DocVapor]

No fuk you.

Wow.

Sent from my DROID RAZR HD using SDN Mobile

 

[Little Soldier]

I still don't understand how is this related to the threshold being closer to the RMP.I guess you are changing the resting membrane potential here not the threshold
so instead of saying that we have in the first case RMP is -90 and the threshold is -60 and in the second case RMP is the same and the threshold is -70
but here you're changinh the RMP not the threshold right?
Can you explain this in another way?

look mate, ive seen you post a couple questions here that would more than easily be answered effectively and more efficiently by a simple google search or a textbook reference. these concepts are not too difficult to master, please reserve question time for things a little more obscure.

 

[salley]

the closer the threshold to resting membrane potential, the slower the conduction velocity
I don't understand why

I think there are several reasons. I watched a lecture from Dr. Najeeb- it was free about arrthmias and seemed to explain it really well. In cardiac cells that have a resting membrane potential of 60, they are the slow. In these cells voltage gated na channels are NOT used, and the cell has to relay on CA channels. Therefore, they are slower (vs if the cell has both na and ca channels). He also said something about if the cell is further away from resting potential the sodium and calcium come rushing in faster, and if it is closer to 60, they come in slower. There are also other things that have to do with conduction velocity, like the size of the cells and the number of gap juctions they have, and the fast conduction cells are different than the slow conduction cells. For example, they are larger cells with more gap junctions, while the AV node has small cells and fewer gap junctions which allows it to conduct the impulses more slowly. Thats really all I can remember, maybe someone else could elaborate on this. Hopefully that helps a bit.

 

[Midwestern Blot]

No fuk you.

 

[SamarEsawy]

the closer the threshold to resting membrane potential, the slower the conduction velocity
I don't understand why

I think there are several reasons. I watched a lecture from Dr. Najeeb- it was free about arrthmias and seemed to explain it really well. In cardiac cells that have a resting membrane potential of 60, they are the slow. In these cells voltage gated na channels are NOT used, and the cell has to relay on CA channels. Therefore, they are slower (vs if the cell has both na and ca channels). He also said something about if the cell is further away from resting potential the sodium and calcium come rushing in faster, and if it is closer to 60, they come in slower. There are also other things that have to do with conduction velocity, like the size of the cells and the number of gap juctions they have, and the fast conduction cells are different than the slow conduction cells. For example, they are larger cells with more gap junctions, while the AV node has small cells and fewer gap junctions which allows it to conduct the impulses more slowly. Thats really all I can remember, maybe someone else could elaborate on this. Hopefully that helps a bit.

Yeah good enough, thank you Sally 🙂