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My understanding is that the bulk of an axon is myelinated, greatly adding to the efficiency of transmitting action potentials. However, the axon terminals are not myelinated. I'm wondering if the energy of an action potential is divided among the various branched terminals of an axon and, if so, how it's divided. For the purpose of this question, I think it's safe to assume that an action potential loses no energy while travelling down the main myelinated part of an axon.

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From my understanding, no, this is not the case: action potentials, in the axon terminal(s) and other non-myelinated areas, travel like a wave, thus activating all terminals with the same starting energy.

In the myelinated areas of the axon, however, the charge instead performs Saltatory conduction, where the charge jumps from one node of Ranvier to the next extremely quickly.

You may be interested in the Wikipedia article on Neurotransmission. Unfortunately, a few of the citation links on that page are dead, but it should offer some good material anyway.

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  • $\begingroup$ Thanks! I had looked at those articles before, but they didn't seem to say anything about whether the energy of an action potential was divided across the terminals of an axonal arbor or if the energy was "replicated" in each branch of the arbor. But in thinking about it further, since an action potential is an "all-or-nothing" event, it stands to reason that the latter possibility would be the case. Here's a paper which provides some supporting empirical evidence for this. $\endgroup$ – visual-kinetic Jan 4 '13 at 1:29
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    $\begingroup$ Actually, I don't think the end of my comment above is all that clear. The paper I linked to reports evidence of action potentials reaching all branches of an axonal arbor in at least some neurons. Given the "all-or-nothing" nature of an axon potential, it then stands to reason that, where an action potential reaches all the branches of an axonal arbor, the energy propagating through each branch will be the same as that which propagated through the "trunk" of the axon. $\endgroup$ – visual-kinetic Jan 4 '13 at 13:33

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