Excitement is the main physiological process, which excitable cells and tissues respond to stimulation. The ability of cells and tissues to respond to stimulation of the process of excitation is called anxiety. The level of excitability determine the strength and frequency of the stimulus, as well as on the duration of its effect. Minimum strength of the stimulus, which excitable tissue responds to arousal during this functional state, is called the threshold. Less than the threshold size of the stimulus, the higher the level of excitability, i.e. cloth easier excited.
When the excitation is characterized by the transfer of cells from the state of physiological rest to the state of physiological activity, characteristic of the given cell: muscle contracts, gland secretes, nerve cell generates a pulse excitation, which is distributed by nerve fiber. In a single nerve cell cycle excitation process is equal to 1-1,5 milliseconds. At the moment of impact of the stimulus on excitable tissue permeability of the membrane at the point of irritation for sodium ions increases in connection with this significantly decreases the potential difference on the cell membrane (depolarization). This generates a short electrical pulse, which is available in the neighbouring plot membranes and causes a new process of excitation. With long-term effect of the stimulus excitation in the nerve cells occurs in the form of flow pulses propagating through the nerve fibers to the muscles and other tissues.
A characteristic feature of the cells at the time of excitation is its inability to respond to new irritation (state nevozmozhnosti). This state may last for a long time due to delayed development and attenuation process of excitation under the action of excitable tissue of any chemical substances (cocaine, chloroform, potassium chloride). This leads to the changes of the functional state of the tissues, called namely parabiosis ("about life"). Termination of the impact of harmful irritant restores the normal functional state of the tissue.
In medical practice and in everyday life often the term "incitement" means a strengthening of the activities of an entity (for example, heart), system (Central nervous system) or organism as a whole, when, due to the painful condition of human behavior is characterized by excessive motor, speech activity, etc.