ak_plot

README

A-type Potassium Channel

This voltage-gated K channel, found especially on dendrites of pyramidal neurons for example, has a narrow window of activation between the M and H gates, around -37 mV. The M activating gate has a fast time constant on the scale of a msec, while the H inactivating gate has a linearly increasing time constant as a function of V.

It is particularly important for counteracting the excitatory effects of voltage gated calcium channels which can otherwise drive runaway excitatory currents.

	K = -1.8 - 1/(1+exp((vbio+40)/5))

    Alpha(V,K) = exp(0.03707 * K * (V - 1))

	Beta(V,K) = exp(0.01446 * K * (V - 1))

    H(V) = 1 / (1 + epx(0.1133 * (V + 56)))

    Htau(V) = 0.26 * (V + 50) > 2

    M(Alpha) = 1 / (1 + Alpha)

    Mtau(Alpha, Beta) = 1 + Beta / (0.5 * (1 + Alpha))

NOTE: to work properly with 1 msec Dt updating, the MTau adds a 1 -- otherwise MTau goes to high.

The Time Run plot (above) shows how the Gak current develops over time in response to spiking, which it tracks directly due to very fast M dynamics. The H current inactivates significantly when the consistent Vm level (TimeVstart) is elevated -- e.g., -50 as shown in the figure.

Simplified AKs channel

The AKsParams provides a much simpler, stateless version of the AK channel that is useful to just get a high-level cutoff to membrane potentials in the dendrites, e.g., as might otherwise emerge from the VGCC channel.

This function is:

	if vbio > -37 { // flat response above cutoff -- real function goes back down..
		vbio = -37
	}
	return 0.076 / (1.0 + math32.FastExp(-0.075*(vbio+2)))

Documentation

Overview

ak_plot plots an equation updating over time in a table.Table and PlotView.