Muscle Contraction Method:
Step 1 – Depolarization of Sarcolemma
The central nervous system (CNS) sends signals through a motor neuron that reaches the neuromuscular joint or the motor end plate.
The interaction between a fiber sarcolemma and a motor neuron is called a neuromuscular junction.
The release of a neurotransmitter called acetylcholine is created when the signal reaches the neuromuscular system. The strength of the action in the sarcolemma is set by this release.
Step 2 – The release of calcium ions
The sarcolemma transfers the action force to the sarcoplasmic reticulum to release calcium ions from the sarcoplasm
Step 3 – Occurrence of conformational changes in Actin filaments
Calcium ions are released, which tend to bind troponin and tropomyosin found in active fibers
This interaction results in a modification of the three-dimensional structure of the actin-troponin-tropomyosin complex. The active site of myosin found in actin filament is exposed.
Step 4 – Activation of Myosin heads
The release of calcium ions triggers the activation of myosin heads which in turn causes the release of energy in the form of ATP.
ATP Hydrolysis releases the energy that binds myosin heads to the active sites found in actin fibers which is why it forms a crossing bridge.
Step 5 – Actin Filaments slides over Myosin
Myosin head rotates due to the construction of a crossing bridge, pulling the actin fibers in the center of the A-band which is H zone.
The z-line attached to the actin strands also pulls inwards
The contraction of the sarcomere occurs when the actin filaments are drawn in different directions..
During the cutting process, the I-band decreases and the A-band maintains its length which causes the muscles to tighten.