The provided code models the Low-Voltage-Activated (LVA) calcium channel, specifically inspired by studies from Avery and Johnston (1996) as well as Randall (1997). Below are the biological elements addressed by this computational model:

Ion Channel Type and Biological Function

• Calcium (Ca2+) Channels: The code simulates LVA calcium channels, which are characterized by their ability to activate at relatively negative membrane potentials compared to High-Voltage-Activated (HVA) channels. These channels are critical in mediating calcium influx in response to small depolarizations near the resting membrane potential, influencing various neuronal processes such as excitability, synaptic integration, and signal transduction.

Channel Gating Dynamics

• Gating Variables (m and h): The model uses two gating variables, m for activation and h for inactivation. These characterize the probability of the channel being open or closed in response to changes in membrane potential.

• Steady-State Values (mInf, hInf): Represent the equilibrium state of the gates for activation and inactivation, defining how likely they are to be open at any given voltage.

• Time Constants (mTau, hTau): These are time-dependent characteristics of the gating variables, indicating how quickly the channels transition between states.

Temperature Dependence

• Q10 Factor: The qt parameter accounts for changes in channel kinetics with temperature. Calcium channel kinetics often exhibit temperature sensitivity, and the model adjusts the rates according to a Q10 of 2.3, reflecting the increase in biological reaction rates with a temperature change.

Voltage Dependency and Junction Potential

• Voltage Correction: The model includes a shift of -10 mV to account for the junction potential, reflecting corrections due to experimental conditions.

• Activation/Inactivation Curves: The voltage-sensitive properties of the calcium channel are incorporated using exponential functions defining mInf and hInf, capturing the voltage-dependent gating mechanisms observed in biological experiments.

Biophysical Properties

• Conductance (g): Conductance is calculated as a function of the gating variables and maximal conductance (gbar), which defines the maximal ionic conductance through the channel when fully open.

• Calcium Current (ica): Represents the ionic flow through the channel, calculated based on channel conductance and the driving force (difference between membrane potential v and reversal potential eca).

This model captures the essential biophysical properties and kinetics of LVA calcium channels, allowing simulations to explore their contribution to neuronal activity and signal processing. Through proper parameterization based on empirical data, such models are critical tools in understanding how ion channel dynamics influence neuron functionality.