In NEURON .MOD files what is the order of operations of the sections?

Question

In what order do the commands in NEURON .MOD/NMODL file sections get executed? Specifically, within these blocks: DERIVATIVE, BREAKPOINT and NET_RECEIVE.

Answer 1

For every time-step, the order of execution is as follows:

1. NET_RECEIVE: If there is net_send() an event that targets this mechanism, lines here are executed first. Skipped otherwise.
2. Lines in BREAKPOINT: The SOLVE ... METHOD line is ignored. All lines after SOLVE are executed. With a printf() statement, you would see two calls. However, one of the calls does not actually set any state variables. It is used to compute the derivatives.
3. Finally, the DERIVATIVE block: The values for the derivatives (X' = ...) are computed. Keep in mind, to get the value by which the state variable actually changes, multiply by dt.