Introduction to Biomedical Signals

This chapter provides an introduction to biomedical signals and illustrates a few signals for gaining familiarity with their typical appearance and features. Physiological processes are complex phenomena, including nervous or hormonal stimulation and control. Most physiological processes are accompanied by or manifest themselves as signals that reflect their nature and activities. Such signals could be of many types, including biochemical in the form of hormones and neurotransmitters, electrical in the form of potential or current, and physical in the form of pressure or temperature. Diseases or defects in a biological system cause alterations in its normal physiological processes, leading to pathological processes that affect the performance, health, and general well-being of the system. A pathological process is typically associated with signals that are different in some aspects from the corresponding normal signals. If one possesses a good understanding of a system of interest, it becomes possible to observe the corresponding signals and assess the state of the system. The task is not difficult when the signal is simple and appears at the outer surface of the body.