When a sarcomere is stretched beyond the ideal length (more than 120%), the thick and thin filaments do not completely overlap, resulting in lower tension. If the muscle is stretched to the point where the thick and thin filaments do not overlap at all, no transverse bridge can be formed and no tension is generated. This amount of stretching usually does not occur because accessory proteins and connective tissue stand in the way of extreme stretching. Contractions of contractions are short-lived. Although they have a high speed, they begin to rest before reaching the maximum strength. Tetanus contractions that last a long time reach their maximum strength and plateau. Muscle tone is achieved through a complex interaction between the nervous system and skeletal muscles, which leads to the activation of certain motor units simultaneously, most likely cyclically. In this way, the muscles never get tired completely, because some motor units are in a state of recovery, while others actively create tension. The main regulator of muscle tone is the muscle spindle, a small sensory unit closely related and parallel to a muscle. Muscle spindles connected to the endomysium of a muscle fiber consist of core sac fibers and core chain fibers. Both are similar to muscle fibers in that they contain actin and myosin myofilaments that allow them to stretch with the muscle.
However, unlike skeletal muscle fibers, where the nuclei are widespread and located at the periphery of the cell, the nuclei in the nucleus sac and the nucleus chain fibers are located in a central region enlarged into core sac fibers. Isometric contraction occurs when a muscle creates tension without changing the length of the muscle. Isometric contractions involve a shortening of the sarcoma and an increase in muscle tension, but do not displace the load because the force generated cannot overcome the resistance provided by the load. For example, if you try to lift a hand weight that is too heavy, there will be activation and shortening of the sarcoma to a certain point and ever-increasing muscle tension, but no change in the position of the hand weight. In everyday life, isometric contractions are active in maintaining posture and maintaining the stability of bones and joints. And people who use HGH can exercise longer than others, which means they have more stamina and therefore they can build muscle and become leaner. Scientist. A graduated muscle response works as follows: if the fibers are stimulated while a previous contraction is still occurring, the second contraction is stronger.
This response is called wave summation because the excitation-contraction coupling effects of successive motor neuron signaling are added or added together (Figure 10.4.4a). At the molecular level, summation occurs because the second stimulus triggers the release of more Ca++ ions, which become available to activate more cross bridges while the muscle contracts again from the first stimulus. Summation leads to a stronger contraction of the motor unit. As already mentioned, the contraction of skeletal muscle fibers is triggered by the signaling of a motor neuron. Each muscle fiber is innervated by a single motor neuron, but a single motor neuron can innervate several muscle fibers. A motor unit is defined as a single motor neuron and all the muscle fibers it innervates (Figure 10.4.1a). The motor unit is the functional unit of muscle contraction and includes the motor nerve fiber and the muscle fibers that innervate it. In both cases, cross-bridge cycling maintains tension in the muscle; The sarcobe, muscle fibers and muscles do not change in length. Not all muscles in the world can perform movement unless the muscle interacts with a skeletal system. A skeletal system is necessary to support the body, protect internal organs and allow the movement of an organism. All skeletal systems have one important feature in common: muscles function in antagonistic pairs.
A muscle that works on its own can only contract (pull); There is no mechanism in a muscle that causes it to expand (compression). The expansion of a muscle is therefore achieved by the contraction of an antagonist muscle or a muscle pulling in the opposite direction. .