Production of Electricity A portion of the total energy set free in muscle when it is stimulated appears as electrical potential. The output of electrical energy is quite negligible, however, relative to the total energy, but its appearance is indicative of activity and has been of invaluable assistance to the physiologist in the study of muscle, nerve, and other forms of active tissue. It is associated with excitation generally or with those changes which occur in the muscle preceding the mechanical response. During the latent period before the mechanical response begins, there occurs within the muscle a series of chemical changes from which the threshold of free energy necessary to elicit the mechanical response is developed. This state of excitation is a local condition which quickly spreads from the point first stimulated to all portions of-the muscle. In the wake of this excitation wave will follow the mechanical response, also in wave-like form. At one time during the response all points of the muscle will be in a state of excitation and hence of the same electrical potential (isoelectric). The contraction wave soon passes off and disappears in the same order in which it appeared. Excitation is always accompanied by a change at the point excited of such a nature as to produce a condition of lower electrical potential as compared to unexcited portions of the same tissue. If now a conductor is connected with two such points a current of electricity is set up. This may be measured by introducing a sensitive string galvanometer into the circuit. Special non-polarizable electrodes must, however, be employed at the contacts with the muscle surface. When the muscle is stimulated a wave of excitation with its contemporaneous electrical variation will sweep over it and then finally subside. This wave of electrical change is known as the negative variation or action current. Certain fishes, such as the electric torpedo and eel, are able to generate electrical potentials of great magnitude. In these animals are to be found special organs, in some instances modified muscles, in which these currents are developed. By means of such high potentials these animals are able to stun and kill their prey. Fatigue of these muscles by overactivity decreases the strength of the electric discharges.		Home Classes of levers Varieties of muscle Smooth muscle The blood supply to muscles The neurone Cardiac muscle On the nomenclature of skeletal muscles The nerve supply to muscles Structure of a skeletal muscle Central nervous system The reflex arc and reflex action Physiologic properties of muscle Mechanical Changes The effects of temperature on muscular contraction Muscle glycogen, its source and fate The reaction of muscles Oxygen consumption of muscle Determination of the oxygen consumption of muscle The viscosity factor in muscle and muscle efficiency Significance of the recovery heat Production of Electricity