The provided code models the H-current (I_h
), a hyperpolarization-activated current, which in this case is assumed to use sodium ions (Na⁺). This current is often associated with pacemaker activities and rhythmic oscillations in neurons and other excitable cell types.
H-current Characteristics:
Gating Variable:
n
, representing the open probability of the channel. In biological terms, this reflects the proportion of channels available to conduct ions.ninf
, the steady-state value of n
, is dictated by the voltage dependence of the channel, embodying how the channel open probability changes with membrane voltage (v
).Membrane Voltage Sensitivity:
ninf
and taun
(time constant for reaching ninf
) are functions of membrane voltage v
, consistent with biological voltage-sensitive ion channels.vhalf
and K
characterize the voltage at which half of the channels are activated and the slope of the activation curve, respectively, reflecting the channel's voltage sensitivity.Conductance and Current:
gbar
represents the maximum conductance of the H-current channels, similar to how maximal surface expression of channels influences conductance levels in biological membranes.g
, the actual conductance, is dynamically updated based on the state variable n
, mirroring the biologically observed modulation of ionic conductance through channel opening.ihi
represents the current passed through the H-channel, influenced by the driving force (v - ehi)
, where ehi
is the reversal potential specific to the assumed Na⁺-specific conductance.Ion Selectivity:
USEION
mechanism indicates this current specifically involves hi
ions, which in the code and context appear akin to Na⁺ ions, though in nature, H-current is generally permeable to both Na⁺ and K⁺.Adaptation and Plasticity:
taun
allows adaptive responses to different voltage stimuli, reflecting physiological adaptability and temporal dynamics in neuronal responses due to reversible gating kinetics.The parameters and methods within this code segment reflect theoretical underpinnings based on experimental observations of H-current dynamics, facilitating simulation of its role in neuronal excitability and rhythmic activity.