Plan
► History of bioelectricity. Resting currents and action currents.
► Resting membrane potential and methods of its recording.
► Origin of resting membrane potential.
► Variations in membrane potential at excitation.
► Comparative characteristics of local response and action potential.
► Modern concept of action potential.
► Action potential and excitability of cell.
History of Bioelectricity. Resting Currents and Action Currents
The first scientific research on ''animal electricity'' was conducted as early as in the mid-18th century and was connected with investigation of electrical organs of sea animals (stingray, some deep-water fish). It prepared a good ground for works of Luigi Galvani, who is considered the founder of electro-physiology. Discovery of "animal electricity" in frogs was the result of the so-called "balcony experiment" conducted by Galvani in 1786 when he studied effects of electric discharges of different nature on nerve-muscle preparations and preparations of hind legs of a frog.
Once, when Galvani was preparing his experiment, he discovered a curious phenomenon: when a preparation of hind legs of a frog hanging on copper hooks, occasionally came into contact with iron balcony rails, muscles contracted. Galvani suggested existence of potential difference between the muscle and nervous tissues in the preparation: in his opinion, contraction of muscles resulted from closure of the electric circuit where a copper hook and an iron rod were conductors. A famous physicist A. Volta, who was a contemporary of Galvani, interpreted this phenomenon as a result of initiation of direct current in a circuit between different metals. In his opinion, the conductor in this circuit was the preparation. Nowadays it is known that in this particular case