<em>Jimmy was right to say organisms grow because their cells grow.</em>
<u>The growth of organisms can happen in terms of an increase in the number of cells they have (through mitotic cell division) or an increase in the volume of the cells with or without an increase in the number of cells. </u>
A good example is found in plants, most of which undergo an increase in size without any increase in the number of cells in their bodies. The uptake and storage of water in the vacuole produces a pressure that pushes on the cell walls, causing an increase in length, girths, and other growth features of the cells of plants.
An action potential is defined as a sudden, fast, transitory, and propagating change of the resting membrane potential. Only neurons and muscle cells are capable of generating an action potential; that property is called the excitability.
