Excitation-contraction coupling refers to a somewhat abstract description of the processes involved in muscle contraction. The musculoskeletal system is intricately intertwined with the nervous system, allowing muscle contraction and movement to occur through communication with sensory and motor neural pathways. This happens through nerve excitement, which in turn causes a contraction of muscle fibers, together described as excitation-contraction coupling.
The two types of nerves in the body are sensory and motor. Sensory neurons act to perceive events from the surrounding environment and translate them into messages to the brain. The brain then processes these messages and converts them into signals that cause a necessary reaction to the stimuli. Although a number of these processes are involuntary, voluntary action such as purposeful movement also utilizes both sensory and motor components.
The way in which these messages are initiated is through the occurrence of action potentials. Action potentials are the short-lasting electrical events that are characteristic of an exited state. Excitation and action potentials are not synonymous but are closely related.
These processes are brought together like this: A stimulus occurs, causing the firing of action potentials and nervous excitement from sensory neurons. Either the brain or spinal cord processes the signal and sends a corresponding reaction to the motor neurons. The motor neurons act to contract numerous muscle fibers in a way that causes the desired action to occur.
An example of this excitation-contraction coupling in action would be touching a hot burner. These processes all occur in fractions of a second to help someone remove his or her hand from the hot surface. Excitation-contraction coupling was first coined as a term in 1952; however, physiologists have researched the complex interactions between the nervous system and movement for centuries.
One way in which the excitation-contraction coupling can be simulated is through an electrical stimuli. If a person is shocked with such a device, it simulates the natural occurrence of a stimuli. This causes a flooding of action potential and triggers the excitation-contraction coupling mechanism, producing a muscle contraction.
Due to the atomic nature characterizing most of these events, it is important to realize that many descriptions of such processes are speculative and theoretical. It is difficult to see an action potential; therefore, scientists and researchers rely on deductive reasoning to better understand the many events that go into an often overlooked action, such as bending an arm.