Discuss the role of Ca 2+ ions in muscle contraction. Draw neat sketches to illustrate your answer.
Ans:
Calcium ions play an important role in muscle contraction. There are minute channels in muscle cells through which the calcium ions enter, known as calcium channels. When a neurotransmitter enters the muscle cell, it initiates action potential. As a result, calcium channels open and allow entry to calcium ions. Calcium ion binds to the troponin on action filament. This results in removal of masking from the active site on myosin. Myosin then utilizes energy from ATP and moves towards actin to form a cross-bridge. This subsequently results in actin sliding towards each other and eventually muscle contracts. After that, the calcium ions move out from the muscle cells and actin filaments move back to their original position. This results in relaxation of muscle.