The first step in the journey of muscle movement, is the motor neuron. The motor neuron provides Acetylcholine (ACh) which is crucial in muscle movement. Acetylcholine (ACh) is released from the synaptic terminals of the motor neuron. The ACh then travels across the synaptic cleft by way of diffusion.
From the synaptic cleft, the ACh binds to the receptors located on the muscle fiber’s plasma membrane.
After the ACh has found its way to the receptors and is bound to them, the muscle fibers become stimulated. The stimulated muscle fibers result in an impulse being generated. This impulse travels down the membrane until it reaches the Sarcoplasmic Reticulum. The Sarcoplasmic Reticulum is responsible for regulating the Ca2+ ion concentration.
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The ATP was generated in the process of oxidative phosphorylation using oxygen, electron carriers, and phosphate groups to transform ADP (Adenosine Diphosphate) into ATP to use in muscle movements. As a result of this process, heat is produced and results in a rise of body temperature.
Now the muscle fibers begin to shorten as the Actin is pulled inward, resulting in contraction.
Now that we have reached the peak of muscle contraction, we must begin on the journey of muscle relaxation. ACh now begins to destimulate the muscle fiber. The Ca2+ ions that bound to the Troponin molecules are now removed and pumped back into the Sarcoplasmic Reticulum via active transport utilizing ATP molecules produced from cellular respiration.
The Troponin will now return to its original shape,breaking the connections between Actin and Myosin as well. Once the Ca2+ ions are no longer bound to the Troponin, Tropomyosin blocks the Myosin binding sites again.
This ends the muscle contraction and the muscle fiber relaxes. The ATP then breaks down and prepares the Myosin for the next muscle