Neurons expend the majority of their energy powering ion pumpsto maintain the chemical gradients that power their electricalactivity. To have a negative resting potential, neurons leakpotassium across the membrane, which seems like a terrible waste ofenergy to me. I would like to know what benefit a neuron receivesin exchange for this seemingly unnecessary metabolic load.
I am not asking how the resting potential is achieved.I am also not interested in the trivial answer: that thevoltage-gated channels are configured to require a transitionacross the -40mV or so threshold in order to fire an actionpotential. It seems to me that this threshold is arbitrary; ifthere was no advantage to maintaining this gradient then neuronswould have evolved to avoid it.
Any ideas? Or better yet, pointers to places where this hasalready been answered?
My best guess so far looks like this: The total range ofavailable voltages is more-or-less fixed from -90 to +50mV. We wantto avoid getting too close to either end, since the channels becomeless effective near their reversal potentials, so maybe theeffective range is more like -70 to +30 (to go outside that range,we must sacrifice speed). Within that 100mV range, we leave thebottom 30mV or so for EPSP integration, and the other 60mV foraction potentials. Now, if the resting potential was 0mV, theavailable dynamic range for integration and spiking would be muchsmaller which probably translates to making the output noisier.
Neurons expend the majority of their energy powering ion pumpsto maintain the chemical gradients that power their electricalactivity. To have a negative resting potential, neurons leakpotassium across the membrane, which seems like a terrible waste ofenergy to me. I would like to know what benefit a neuron receivesin exchange for this seemingly unnecessary metabolic load.
I am not asking how the resting potential is achieved.I am also not interested in the trivial answer: that thevoltage-gated channels are configured to require a transitionacross the -40mV or so threshold in order to fire an actionpotential. It seems to me that this threshold is arbitrary; ifthere was no advantage to maintaining this gradient then neuronswould have evolved to avoid it.
Any ideas? Or better yet, pointers to places where this hasalready been answered?
My best guess so far looks like this: The total range ofavailable voltages is more-or-less fixed from -90 to +50mV. We wantto avoid getting too close to either end, since the channels becomeless effective near their reversal potentials, so maybe theeffective range is more like -70 to +30 (to go outside that range,we must sacrifice speed). Within that 100mV range, we leave thebottom 30mV or so for EPSP integration, and the other 60mV foraction potentials. Now, if the resting potential was 0mV, theavailable dynamic range for integration and spiking would be muchsmaller which probably translates to making the output noisier.
