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What System Stimulates Muscles to Contract

Each organ system performs specific functions for the body, and each organ system is usually studied independently. However, organ systems also work together to help the body maintain homeostasis. (3) When the signal from the nervous system is no longer present, the chemical process reverses, the muscle fibers rearrange and the muscle relaxes. The process by which a signal is transmitted to a neuromuscular compound is shown in figure (PageIndex{2}). The sequence of events begins when an action potential is initiated in the cell body of a motor neuron and the action potential propagates along the neuron`s axon to the neuromuscular connection. Once the action potential reaches the end of the axonal termination, it causes the neurotransmitter acetylcholine (ACh) from synaptic vesicles in the axonal termination. ACh molecules diffuse through the synaptic cleft and bind to receptors in muscle fibers, initiating muscle contraction. Muscle contraction is initiated by the depolarization of the sarcolemma, which is caused by the entry of sodium ions through the sodium channels associated with ACh receptors. As we have learned, our bodies are complicated systems composed of cells, tissues, organs and organ systems. However, for life to function properly, these systems must work together. Organs often play a role in multiple systems because of their unique functions.

In this section, we will learn how systems work together, and we will learn about some essential functions of life that require the work of several bodily systems. Bodily functions such as heart rate regulation, muscle contraction, enzyme activation, and cellular communication require strictly regulated calcium levels. Usually we get a lot of calcium from our diet. The small intestine absorbs calcium from digested food. The liver and pancreas are part of both the endocrine system and the digestive system. What are the benefits of integrated digestion and regulation? In skeletal muscle, this sequence begins with signals from the somatic motor department of the nervous system. In other words, the “no excitation” in skeletal muscle is always triggered by signals from the nervous system. An organ is made up of tissues that work together to perform a specific function for the body as a whole. Groups of organs performing related functions are organized into organ systems that perform more general functions. Table 1 describes the structures and functions of selected common organizations.

Although the term excitation-contraction coupling confuses or frightens some students, it boils down to this: for a skeletal muscle fiber to contract, its membrane must first be “excited” – in other words, it must be stimulated to trigger an action potential. The action potential of muscle fibers, which sweeps like a wave along the sarcolemma, is “coupled” to the actual contraction by the release of calcium ions ((text{Ca}^{++})) from the SR. After release, the (text{Ca}^{++}) interacts with the shielding proteins, troponin and tropomyosin complex, forcing them to move to the side so that actin binding sites are available for fixation by myosin heads. The myosin then pulls the actin filaments towards the center, shortening the muscle fiber. Muscle contraction begins when the nervous system produces a signal. The signal, a pulse called the action potential, travels through a type of nerve cell called a motor neuron. The neuromuscular connection is the name of where the motor neuron reaches a muscle cell. Skeletal muscle tissue is made up of cells called muscle fibers. When the signal from the nervous system reaches the neuromuscular connection, a chemical message is released by the motor neuron. The chemical message, a neurotransmitter called acetylcholine, binds to receptors outside muscle fibers.

This triggers a chemical reaction in the muscle. A sport like arm wrestling depends on muscle contractions. Arm wrestlers must contract the muscles of their hands and arms and contract them to resist the opposing power of their opponent. The wrestler, whose muscles can contract with more force, wins the match. 7. How do muscles change as they increase in size or decrease? Skeletal muscles are attached to the bones of the skeleton. When these muscles contract, they move the body. They allow us to use our limbs in different ways, from walking to rotating trolley wheels. Skeletal muscles also maintain posture and help maintain balance.

The endocrine system is the control center for regulating calcium homeostasis in the blood. The parathyroid gland and thyroid gland contain receptors that respond to the level of calcium in the blood. In this feedback system, the level of calcium in the blood is the variable because it changes in response to the environment. .