The code provided models a passive leak current in a neuronal membrane. In biological contexts, a leak current represents the constant flow of ions through non-gated ion channels in the neuronal membrane, which contributes to maintaining the resting membrane potential. ### Biological Basis 1. **Ion Channels**: The primary focus of this model is ion channels that are always open, allowing ions to "leak" across the cell membrane. These channels are not voltage-gated and remain perpetually open, unlike other ion channels such as those for sodium or potassium, which open and close in response to changes in membrane potential. 2. **Resting Membrane Potential**: The leak current plays a crucial role in setting the resting membrane potential of neurons. This potential is maintained by different ionic concentrations on either side of the membrane and is influenced by the permeability of ions through leak channels. 3. **Conductance (g)**: The parameter `g` in the model represents the conductance of the leak channels (measured in siemens per square centimeter, S/cm²). Conductance is a measure of how easily ions can pass through the channels, thereby contributing to the overall current. 4. **Reversal Potential (e)**: The reversal potential for the leak current (`e = -80 mV`) indicates the equilibrium potential where the direction of net ionic flow reverses. This value is typically close to the resting membrane potential in real neurons, suggesting the leak primarily involves ions that stabilize the resting state, like potassium. 5. **Current (i)**: The model calculates the leak current `i` based on the difference between the membrane's current potential (`v`) and the channel's reversal potential (`e`). This relationship is driven by Ohm’s Law, which states that the current through a conductor between two points is directly proportional to the voltage across the two points. ### Summary The code provided models a passive leak channel that contributes to the resting membrane potential of neurons by allowing specific ions to flow through the membrane according to a constant conductance. This flow is crucial for maintaining the electrical characteristics of neurons at rest, enabling them to respond appropriately to the synaptic inputs and other stimuli encountered in their biological context. The model does not specify which ions are involved, but typically, such a leak current could involve ions like potassium (K⁺) and chloride (Cl⁻), which play significant roles in setting the resting potential.