<unk>  is the study of the electrical properties of biological cells and tissues.  It involves measurements of voltage change or electrical current flow on a wide variety of scales from single ion channel proteins to whole tissues like the heart.  In neuroscience, it includes measurements of the electrical activity of neurons, and particularly action potential activity.
Electrophysiology
Electromyography
Brain mapping
Cardiac electrophysiology
Electrophysiologic study
Multielectrode array
Electroencephalography
Cardiotocograph