The spontaneous activity is the electrical activity of an excitable cell , z. B. a nerve cell that is not influenced by any excitatory or dampening signals . Almost all excitable cells in the body have a spontaneous activity that is changed (modulated) by external influences. These influences can originate from other cells or act on the cells from the outside in the sense of sensory stimuli.
The spontaneous activity of the sinus node in the heart and the measurable spontaneous activity of the muscles are of medical importance . Due to its higher spontaneous discharge rate, the sinus node ensures synchronization of downstream centers of excitation generation and spread in the heart. If it fails, substitute rhythms set in, which do not always ensure a coordinated and sufficient contraction of the heart muscle. The electrical activity of the sinus node is assessed with the help of the electrocardiogram (EKG), where the atrial excitation emanating from it is shown in the P wave. The spontaneous activity of relaxed muscles can be recorded with electromyography (EMG). The EMG allows an assessment of the motor system with regard to various muscle and nerve diseases.