Question

Which one is required for muscle contraction and nerve impulse transmission?

• A. $C{a}^{2+}$
• B. $M{g}^{2+}$
• C. $F{e}^{2+}$
• D. Both A and B

Answer 1

The correct option is A $C{a}^{2+}$

• A neural signal reaching this junction releases a neurotransmitter (Acetylcholine) which generates an action potential in the sarcolemma. This spreads through the muscle fibre and causes the release of calcium ions into the sarcoplasm
  
• Active sites for myosin are present on actin which are masked by troponin-C in resting state. When Ca++ level increases it leads to the binding of calcium with a subunit of troponin i.e Troponin-C on actin(thin) filaments and thereby remove the masking of active sites for myosin.
  
• Utilizing the energy from ATP hydrolysis, the myosin head now binds to the exposed active sites on actin to form a cross bridge.
• This pulls the attached actin filaments towards the centre of ‘A’ band.
  
• The ‘Z’ line attached to these actins are also pulled inwards thereby causing a shortening of the sarcomere, i.e., contraction. The myosin, releasing the ADP and P1 goes back to its relaxed state. Hence Ca${}^{2+}$ is required for muscle contraction and nerve impulse transmission.
• So, the correct answer is 'Ca 2+'.