ABSTRACT
Every living organism is built with a ne twork of billions of cells, which c ommunicate a mong e ach ot her a nd w ith t he su rroundings by the controlled exchange of chemical and electrical signals. ese signals are molecules and ions that carry information used by t he c ells to p erform c ertain t asks, suc h a s t he ac tivation o f enzymes or genes, cellular proliferation, and death. A major role in this exchange is played by the cell membrane and more speci - cally by structures called ion channels and gap junctions. e purpose of this paragraph is to introduce ion transport in cells from the point of view of thermodynamics. We will start with the basic terms and laws that are the building blocks of thermodynamics. Attention will be given to excitable cells, that is, cells that respond to electrical signals, especially heart muscle cells.
