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Calcium and Nerve Impulses

By Laura Niedziocha

Calcium, a positively charged molecule, is useful many places within the human body. The role of calcium inside the nervous system extends from the initiation of a nerve signal to the action taking place. Calcium signals an impulse to a muscle cell and continues to be useful until the contraction is complete.

Anatomy

Neurons are the cells that compose your nervous system. These consist of a body that receives a nerve transmission as well as an axon that signals the transmission. The axon terminates in branches called synaptic knobs which innervate the cell that the impulse is traveling to.

Nerve Impulse Conduction

A nerve impulse begins conduction as electrical impulses, initiated by the brain, travel down through nervous system cells. The electricity causes a change in polarity by opening channels to move positive sodium or potassium ions in or out. Positive molecules are stored in membranes guarded by gated channels. This means they must be stimulated in order to release the positive ions which help to conduct the nerve impulse.

Nerve Impulse and Calcium

It is well-known that calcium is another positive molecule useful for the conduction of a nerve impulse to a muscle fiber. However, Clay Armstrong, a neurobiologist, believes that calcium may play a larger role. Armstrong suspects that calcium is in charge of the gated channels that release potassium and sodium to facilitate a nerve impulse. Armstrong's theory proposes that calcium ions are like a door to these gated channels. Calcium must move to release the ions and calcium must return before the impulse will stop and homeostasis is returned.

Calcium and Muscle Contractions

When a nerve impulse reaches a muscle cell, movement of the muscle requires calcium as well. Your muscle cells store calcium and upon nerve impulse, the cell is flooded with calcium. In order for a skeletal muscle to move, two myofilaments, actin and myosin, inside a muscle fiber must bind to one another to create a pulling action which shortens the muscle. However, a molecule known as tropomyosin blocks the binding site and must be moved to create a contraction. Calcium binds to troponin which is attached to tropomyosin. Upon binding with calcium, troponin moves tropomyosin, exposing the binding site and creating movement.

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