Fairfax, VA
When speaking of Frankenstein (1931), a particular scene springs to mind for us all. With a tremendous zap of electricity, Frankenstein shocks his creation, and upon seeing its arm tremble with movement, he crows with glee, “It’s alive! It’s alive!” Though this scene is suitably dramatized, enough to have stuck around as a timeless reference in pop culture, it does point out the significant import electricity has in the human body. Without these electrical signals in your body, an example of bioelectricity, you would be unable to think, move, or have a heartbeat.
Cells in your body, like your brain’s neurons, are well suited to produce and pass on such electrical signals. By controlling how much specific charged elements (e.g. sodium, potassium, calcium, and magnesium) are inside and outside of the neuron’s plasma membrane (the cell’s barrier), an electrical gradient can be generated. Since cell membranes are full of ways to transport these ions, like leaky channels or pumps, your neurons can create these gradients and transport the resulting signals through other nearby neurons in a network spanning your body called the nervous system. Thanks to this system of billions of neurons, your brain can think and control the rest of your body.
However, it isn’t just your brain that’s responsible for your ability to jog down a sidewalk; your muscles play a huge role, too. Your muscles are no different in that they, too, require signals to function. Though your muscular system does rely on breaking ATP (a molecule commonly used for energy in cellular processes) to move the muscle fibers it is composed of, it is equally reliant on the electrical signals sent from the brain. Specific neurons called motor neurons deliver these signals to muscles, causing contractions that make your muscles tighten. This is half of how movement works--with the full process being contraction and then relaxation of the muscle. To let your brain know that movement has occurred thanks to the earlier signals, additional special neurons, known as sensory neurons, send new signals back to the brain.
In recent years, technology has arisen to mimic the signals sent to your muscles by the nervous system. These devices, called electronic muscle stimulators (EMS), are used in medicine mainly for rehabilitation. In the case of patients who are immobilized or are at risk of muscle atrophy (the loss of muscles due to inactivity), EMS devices can stimulate contraction through the electrical impulses sent through pads attached to the skin of the region. The stimulation isn’t for random muscles all over the body but rather a specific group of complementary muscles at a time (e.g., biceps in the arms). Such contraction allows the muscle groups to experience some form of activity that may otherwise be difficult to do.
Another more famous example of a device that provides electrical shocks to the human body is a defibrillator. This device targets a very specific and important muscle: the heart. A defibrillator restores the heart's normal rhythm by delivering a sudden shock to the heart, momentarily stopping its beating. Upon resumption, the heart beats steadily at a regular rhythm. In cases where the abnormal heartbeat is a more life-threatening condition without a correctable cause, the person may be provided an implantable cardioverter defibrillator (ICD), which is placed under the skin with wires connecting to the heart. Due to this connection, when the ICD detects an irregular rhythm, it will perform the same task as a regular defibrillator to help the person.
Nevertheless, defibrillation effectively restores the heart's ability to pump blood at a consistent rhythm by capitalizing on the reliance of heartbeats on electrical impulses. These impulses are generated by the electrical conduction system in the heart. Purkinje fibers of the heart are important to this conduction system since they allow it to create synchronized contractions in the lower half of the heart (comprising two chambers called ventricles of the four chambers in the heart). These contractions are triggered by the electrical stimulus in the upper right chamber of the heart, which then travels to the lower half and then back up to the upper left chamber. With this pattern of contraction and relaxation, the heart can beat and pump blood to the body.
As the above paragraphs have shown, electrical signals are vital to the proper functioning of the human body. Though only three examples of organ systems in the body were provided (muscular, nervous, and cardiac), it should be noted that all organs in the body rely on such signaling through electricity for communication, which triggers other actions in the organ/body. Electricity itself is vital for our existence. Just as the technology described has shown, understanding the function and processes behind such signaling in the body furthers our understanding of the human body and allows for the creation of life-saving or crucial technology that pushes frontiers in human health. So the next time you feel your pulse or flex a muscle in your body, remember that under the surface of your skin, there exists an electrical system ensuring the precise execution of your body's activities.
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