Page 84 - The Miracle of Electricity in the Body
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82                 THE MIRACLE OF ELECTRICITY IN THE BODY





              than a million cells. Exceedingly complex biochemical processes take
              place in every one of them. Heart cells are nourished by sugar molecules
              and oxygen coming directly from the lungs. Every cell has its own
              pumps and channels and is joined to its neighbors by connective tissue. 51
                   Every long, thin cell has a cell membrane that divides the cell from
              the environment outside and fiber-like proteins that are able to contract.
              Proteins embedded in the membrane carry important signals or sub-
              stances from one side of the membrane to the other. In terms of electrical
              charge, this polarizes the cell, generating a voltage difference between
              the inside and the outside of the cell. This difference, known as mem-
              brane potential, enables certain proteins in the cell membrane, known as
              ion channels, to function like gates. When they are opened, ions flow in.
                   As a result of complex interactions of ion pumps and channels, a
              heart cell contracts thanks to the electrical and chemical differences oc-
              curring along the length of its cell membrane. Consider a cell in the heart
              ventricle as an example. At a state of rest, the membrane potential in any
              cell is more negatively charged than its external environment. However,
              the electrical stimulus arriving from the neighboring cell rapidly alters
              everything. This differential suddenly increases, and the sodium chan-
              nels quickly open up. In this way, sodium ions (Na+) rapidly enter the
              cell, triggering the opening of the calcium channels.
                   When calcium ions (Ca+2) collect around the cell proteins, these
              contract. At this point, the sodium and calcium channels close and the
              ion pumps move the ions outside the cell, causing it to return to its orig-
              inal state. In a healthy heart cell, this transition takes place in less than a
              second.
                   The events described here are in fact only a very general account of
              the true state of affairs, which is much more complex in its details. The
              heartbeat, which requires so many conditions to be met and work to-
              gether flawlessly, is one of the countless examples introducing us to the
              knowledge of our Lord.
                   In one verse of the Qur’an the following is revealed:

                   My Lord encompasses all things in His knowledge, so will you not
                   pay heed? (Surat al-An‘am, 80)
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