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13 Οκτ 2023 · In this article, we explore the three main types of muscle contractions: isotonic, isometric, and isokinetic. Understanding these types will provide valuable insights into how our muscles work during specific exercises and activities. Join us as we delve into the characteristics, examples, and applications of each type of muscle contraction.
According to this theory, muscle contraction is a cycle of molecular events in which thick myosin filaments repeatedly attach to and pull on thin actin filaments, so they slide over one another. The actin filaments are attached to Z discs, each of which marks the end of a sarcomere.
Muscle contraction is described by the sliding filament model of contraction. ACh is the neurotransmitter that binds at the neuromuscular junction (NMJ) to trigger depolarization, and an action potential travels along the sarcolemma to trigger calcium release from SR.
Muscles of the shoulder and upper limb can be divided into four groups: muscles that stabilize and position the pectoral girdle, muscles that move the entire arm, muscles that move the forearm, and muscles that move the wrists, hands, and fingers.
During the contraction phase, Ca 2+ ions in the sarcoplasm bind to troponin, tropomyosin moves from actin-binding sites, cross-bridges form, and sarcomeres shorten. During the relaxation phase, tension decreases as Ca 2+ ions are pumped out of the sarcoplasm and cross-bridge cycling stops.
The process of muscle contraction (excitation-contraction coupling) is as follows: An action potential arrives at a neuromuscular junction . As a result of the action potential reaching the end of the axon and depolarizing it, acetylcholine (ACh) is released from the neuron and binds to receptors on the muscle fiber, opening sodium ion channels.
An example of this is the contraction of the biceps brachii muscle when a hand weight is brought upward toward the body. An eccentric contraction occurs when the muscle tension produced is less than the load and a muscle lengthens while under tension.
