The tissue of living organisms does not contain solid metal, like a copper wire or a zinc plate. However, electric current flows through nerves and muscles. How does current flow through living tissue?

The human body contains certain elements such sodium, potassium, calcium, chlorine, and magnesium which possess specific electrical charges. These charged particles, called ions are obtained in our diet and are used by the body to generate electrical signals through their flow in and out of the cells.

Explanation:

The human body contains certain elements such sodium, potassium, calcium, chlorine, and magnesium which possess specific electrical charges. These charged particles, called ions are obtained in our diet and are used by the body to generate electricity by allowing them in or out of the cells. Thus, the flow of these ions through the body is the source of electricity in our bodies.

The cell membrane acts as a barrier separating these charges inside and outside the cells. Resting cells are negatively charged on the inside, while the outside environment is more positively charged. This is due to a difference in concentration  between positive ions e.g. Na⁺ and K⁺ , and negative ions e.g. Cl⁻, inside and outside the cell. This separation of charges sets up a potential difference across the membrane known as membrane potential.

The flow of ions in and out of the cell is regulated by special proteins called ion channels. When impulse is received from the brain or other sensory receptors, positive charges flow into the cell through open ion channels in a process known as depolarization of the cell membrane. The depolarization of the cell triggers further electrical currents that can turn into electrical pulses, called action potentials. These action potentials occur at nerves and muscle (neuromuscular) junctions and are responsible for the different external responses we give to stimulus, like blinking of the eye, muscle contractions, heartbeats as well thought processes etc. Certain hormones and chemicals known as neurotransmitters are also involved in this process e.g. epinephrine, norepinephrine.