The code provided is intended to run simulations of a simple neuronal model, specifically a biophysical model of neuronal activity that includes key ionic currents. This model is based on the Hodgkin-Huxley framework, which is a foundational mathematical description of action potentials in neurons. ### Biological Basis of the Code #### Ionic Currents (`iNa`, `iK`) The primary biological components modeled in the code are two major ionic currents commonly found in neurons: 1. **Sodium Current (`iNa`)**: This represents the inward flow of sodium ions (Na⁺) through voltage-gated sodium channels. The rapid influx of Na⁺ ions is critical for the depolarization phase of the action potential, causing the inside of the neuron to become more positive relative to the outside. 2. **Potassium Current (`iK`)**: This represents the outward flow of potassium ions (K⁺) through voltage-gated potassium channels. The efflux of K⁺ ions is important for repolarizing the neuron back to its resting membrane potential after an action potential and for the refractory period that follows, which prevents back-propagation of the action potential. #### Membrane Potential (`v`) - The variable `v` represents the membrane potential of the neuron, which changes over time based on the differential equation given as `dv/dt = @current + I`. Here, `@current` will be replaced by the ionic currents specified (`iNa`, `iK`), and `I` represents an external current that is varied in the simulations. #### External Current (`I`) - The variable `I` is an external applied current that is being varied in the simulations. This simulates different levels of synaptic input or stimulation to a neuron, which can affect the neuron's firing rate and pattern. The range `0:10:30` indicates that simulations will be run with external currents at discrete values between 0 and 30, inclusive. ### Purpose of the Model The model aims to simulate how changes in external current input affect the membrane dynamics of a neuron, particularly focusing on the generation of action potentials. By including the sodium and potassium currents, the model captures the essential biophysical processes underlying the action potential generation and propagation in neuronal cells. In summary, this simulation models the electrical behavior of neurons based on the interplay of sodium and potassium ion channels, which are crucial for action potential dynamics. The effect of variations in external stimuli (current injections) on these processes is investigated through these simulations.