We saw in Chapter 15 that a voltage gradient, also called an electric potential, exists across the plasma membrane of all cells. The potential across the plasma membrane of large cells can be measured with a microelectrode inserted inside the cell and a reference electrode placed in the extracellular fluid.
A production company is responsible for the development and filming of a specific production or media broadcast. In entertainment, the production process begins with the development of a specific project.
1 A car production line is a system that consists of different production equipment, operators that run the equipment, etc., to manufacture that car.  A company is a system that consists of elements such as people, different (engineering and non-engineering) departments, policies, etc.