The textbook presents modern data on the ionic and cellular-molecular mechanisms of the emergence and propagation of electrical signals of excitable cells, as well as their physiological role. The manual contains control questions, test tasks and examples of situational problems with a solution algorithm. This manual is intended for students of medical universities studying in the specialties 05/31/01 General Medicine, 05/31/02 Pediatrics, 05/30/01 Medical biochemistry and biological faculties of universities.