The provided code models a voltage-gated sodium (Nav) channel, specifically the fast transient sodium channel, within the framework of the NEURON simulation software. This channel type is crucial in generating action potentials in neuronal cells.
Ion Channel Type: The code represents a fast transient sodium channel, often denoted as Nav1.x channels in the biological literature. These channels are responsible for the rapid influx of Na+ ions during the depolarization phase of an action potential.
Gating Variables:
mInf
) and time constant (mTau
).hInf
) and time constant parameters (hTau
).Voltage Dependence:
v
). The code accounts for shifts in their half-activation and inactivation voltages via the offm
and offh
parameters, respectively, with slom and sloh determining the steepness of these dependencies. This reflects how real biological channels react to changes in membrane potential.Temperature Correction:
qt
) to adjust the kinetics based on the physiological temperature (34°C in this case), reflecting the temperature sensitivity of channel kinetics in biological systems.Ion Dynamics:
USEION na
statement indicates that this model interacts with the sodium ion pool, with ena
representing the reversal potential for Na+ ions. The sodium current (ina
) is calculated using the conductance (gNaTa_t
) and the driving force (difference between membrane potential and ena
).Conductance Calculation:
gNaTa_t
) is calculated using the maximum conductance (gNaTa_tbar
) and the activation/inactivation variables (m
and h
). The cubic power of m
indicates that three independent activation gates must be open for the channel to conduct ions, which is a common characteristic of Nav channels in neurons.This code segment models the dynamics of a fast transient sodium channel, emphasizing the fundamental role of Na+ flux in neuronal excitability and action potential propagation. It incorporates key biological characteristics such as voltage-dependence, gating kinetics, and temperature effects, enabling realistic simulation of neuronal behavior.