The code provided models the receptor potential of an inner hair cell (IHC) in the cochlea, a key element in the auditory system of mammals. Here’s an overview of the biological basis represented in the code: ### Inner Hair Cells and Auditory Transduction Inner hair cells are sensory cells in the cochlea that play a crucial role in transforming sound vibrations into electrical signals, which are then transmitted to the brain. This process involves several key biological phenomena: 1. **Mechanotransduction at the Apical Membrane:** - The apical surface of inner hair cells is topped with hair-like structures called stereocilia. The displacement of these stereocilia due to sound-induced fluid motion in the cochlea leads to the opening of mechanotransduction channels. - The model uses variables such as `Ga` (apical conductance) to represent the conductance changes as stereocilia are displaced by sound (cilia displacement given by `InArray`). This conductance is modeled using parameters like displacement sensitivity (`Sx0`, `Sx1`) and maximum conductance (`Gmax`). 2. **Receptor Potential Generation:** - The change in conductance allows ions (primarily potassium and calcium) to flow into the cell, causing changes in the cell's membrane potential, known as the receptor potential. - The code calculates the receptor potential `IR` as a function of the conductance difference between the endocochlear potential (`EP`) and the IHC's membrane potential (`Vm`). 3. **Basolateral Membrane and Electrical Properties:** - The inner hair cell's basolateral membrane is assumed to have a linear conductance. This is modeled using parameters such as the membrane equilibrium potential (`Em`), basal membrane resistance (`Rb`), and the time constant (`Tau`). - The model implements a digital filter that reflects the membrane's impedance characteristics, mimicking the biological filtering properties of the IHC membrane, which influences how quickly the cell can respond to stimuli. 4. **Membrane Time Constant and Filtering:** - The bilinear transform is used to convert the continuous-time model to a discrete-time digital filter, which models how the cell's membrane potential filters incoming signals over time (`A` and `B` coefficients). ### Key Parameters Reflecting Biological Properties - **Equilibrium Potentials and Driving Forces:** The driving potential is calculated as the difference between `EP` and `Em`, capturing the electrochemical force driving ion movement. - **Membrane Conductance:** The model assumes a static value for the basal membrane resistance and scales apical conductance for plotting, reflecting changes over time with respect to stimulus. This computational model encapsulates the biological processes underlying mechanotransduction in inner hair cells with a focus on how external mechanical stimuli (like sound) are converted into electrical signals through changes in conductance and membrane potential.