Timeline for How would synapses behave if resting potential was zero?
Current License: CC BY-SA 3.0
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| Jun 16, 2013 at 1:04 | comment | added | Chuck Sherrington | Since you've contributed a lot to this discussion, I would definitely invite you to combine your comments into an answer, as I've learned quite a bit from them (sometimes you can teach an old Chuck Sherrington new tricks!) @Luke | |
| Jun 16, 2013 at 1:03 | comment | added | Chuck Sherrington | The N-type Ca++ channels have a range from -40 to -10 mV (from jneurosci.org/content/24/4/797.long), and I believe that they begin to close off after that to prevent excess Ca++ entry into the cell. Again, I think you make a good point, and perhaps the answer should be refined with more details, but I did qualify the comment with the parenthetical statement that there are still gradients. The sodium channels might transiently open, but there is the "foot in the door" type phenomenon that eventually closes them off. | |
| Jun 15, 2013 at 14:49 | comment | added | Luke | Even in the steady-state case, the statement that "there is no driving force for current changes" is false--there are still competing electrochemical gradients, opening sodium and calcium channels will still depolarize the cell, opening potassium and chloride channels will still hyperpolarize the cell. In fact, if we assume the presynaptic terminal is at 0 mV, then voltage-gated calcium channels will be open, calcium will flow into the terminal, and the synapse may release neurotransmitter even in the absence of action potentials. | |
| Jun 15, 2013 at 14:15 | comment | added | Chuck Sherrington | I understand your point, but I'm speaking about a steady state situation instead of a transient one. | |
| Jun 15, 2013 at 14:12 | comment | added | Chuck Sherrington | @Luke The calcium channels are (in this case) voltage gated, though. | |
| Jun 15, 2013 at 11:53 | comment | added | Luke | This is a bit misleading--a cell with 0 resting potential is not a 'dead battery'; it can still have chemical gradients and active synapses. I agree that action potentials will not be generated, but inhibitory synapses will still function (at least with spontaneous release) and excitatory synapses will still exchange ions when they are activated and admit calcium into the postsynaptic cell, even if they pass little net current. | |
| Jun 12, 2013 at 14:17 | comment | added | Chuck Sherrington | See if your library has the undergrad version of the Kandel book (amazon.com/Essentials-Neural-Science-Behavior-Kandel/dp/…). It's been out of print for about 15 years, but it's absolutely the best explanation of this sort of thing (aside from Kandel, Schwartz, Jessel, et al, itself). | |
| Jun 12, 2013 at 14:15 | history | edited | Chuck Sherrington | CC BY-SA 3.0 |
added 170 characters in body
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| Jun 12, 2013 at 14:04 | history | answered | Chuck Sherrington | CC BY-SA 3.0 |