Threshold potential:
Aim: Estimate the parameters!
In our experiments, we use the voltage-clamp technique, which allows us to apply and maintain a fixed membrane potential (“clamped”) during the recording. Typically, square voltage pulses are used, and the sodium current flowing through NaV channels is measured during the pulse.
Estimate:
mV
Reversal potential:
mV
Aim: Estimate the parameters!
In our experiments, we use the voltage-clamp technique, which allows us to apply and maintain a fixed membrane potential (“clamped”) during the recording. Typically, square voltage pulses are used, and the sodium current flowing through NaV channels is measured during the pulse.
Estimate:
Voltage of half activation:
mV
Voltage of half inactivation:
mV
Sodium Channels and Their Gating Dynamics
Sodium (Na⁺) channels are essential membrane proteins that play a critical role in the initiation and propagation of action potentials in excitable cells, such as neurons and muscle fibers. When a cell membrane depolarizes, voltage-gated sodium channels open, allowing Na⁺ ions to flow into the cell — a key step in generating a rapid electrical signal.
The behavior of sodium channels is typically described by two gating processes:
- Activation, which determines how easily the channel opens.
- Inactivation, which governs how quickly the channel closes again, even if the depolarization continues.
These dynamics are often modeled using gating variables:
- m∞ (minf) — the steady-state activation curve. It describes the fraction of channels ready to open at a given voltage. It increases with depolarization and has a sigmoidal (S-shaped) profile.
- h∞ (hinf) — the steady-state inactivation curve. It represents the fraction of channels not inactivated and capable of conducting current. It decreases with depolarization, also in a sigmoidal way, but in the opposite direction to m∞.
Together, the product m∞3 · h∞ describes the overall probability of a sodium channel being open and able to conduct ions — crucial for modeling ionic currents like INa in neuron simulations.