Muscle contraction

Muscle Contraction is a process that occurs when the muscle fibers generate tension through the action of actin and myosin cross-bridge cycling. While under tension, the muscle may lengthen, shorten, or remain the same. Although the term 'contraction' implies shortening, when referring to the muscular system, it means muscle fibers generating tension with the help of motor neuron action potentials.

Types of Muscle Contraction

There are three types of muscle contraction: isotonic contractions, isometric contractions, and isokinetic contractions.

Isotonic Contractions

In isotonic contractions, the muscle changes length as it contracts and causes movement of a body part. There are two types of isotonic contractions: concentric and eccentric.

Concentric Contractions

In a concentric contraction, the muscle tension rises to meet the resistance, then remains stable as the muscle shortens.

Eccentric Contractions

During an eccentric contraction, the muscle lengthens as the tension decreases.

Isometric Contractions

In an isometric contraction, the muscle does not change length and the joint angle does not change.

Isokinetic Contractions

In an isokinetic contraction, the muscle changes length while the contraction speed remains constant.

Mechanism of Muscle Contraction

The mechanism of muscle contraction involves several steps, including the neuromuscular junction, excitation-contraction coupling, and cross-bridge cycling.

Neuromuscular Junction

The neuromuscular junction is the synapse between a motor neuron and a skeletal muscle fiber. It transmits signals from the neuron to the muscle fiber.

Excitation-Contraction Coupling

Excitation-contraction coupling is the process by which an electrical stimulus triggers a myocyte to contract.

Cross-Bridge Cycling

Cross-bridge cycling is the mechanism by which muscles contract. It involves the sliding of actin and myosin filaments past each other.

See Also

• Muscle
• Actin
• Myosin
• Motor neuron

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