Question

Which one is required for muscle contraction and nerve transmission?
A. $Ca^{2+}$
B. $Mg^{2+}$
C. $Fe^{2+}$
D. Both A and B

Answer 1

Hint:The mechanism of muscle contraction is best explained by a theory named sliding filament theory. This theory defines muscle contraction occurs due to the sliding of thin filaments over the thick filaments. These filaments are the contractile proteins in the muscle fibers.

Complete answer:
Muscle contraction is caused by a signal sent by CNS via motor neurons. Motor neurons with motor fibers connected to it constitute the motor unit. The junction between motor neurons and the sarcolemma of muscle fiber is defined as the neuromuscular junction. Thereby a signal via motor neuron causes the release of acetylcholine, a neurotransmitter which in turn generates an action potential in the sarcolemma causing the release of calcium ions into the sarcoplasm of the muscles. With the increase in the concentration of calcium ions, it binds with the subunit of troponin which is troponin C present on actin filaments or thin filaments. This causes unmasking of the active site on actin filaments. With the utilization of energy from ATP hydrolysis, the myosin head binds with the active site on actin forming a cross-bridge thereby causing muscle contraction by sliding filament theory.
Magnesium is another important ion in the process of muscle contraction as it is known for regulating both muscle contraction and relaxation. It is also necessary or required for the uptake of calcium ions from the sarcoplasmic reticulum. Magnesium is also important in modulating ADP release in myosin and also actin-binding thereby regulates the speed of muscular contraction.
Thus both the calcium and magnesium ions are important and required for muscle contraction and nerve transmission.

So, the correct answer to this question is the option"D".

Note:
Skeletal muscles are the striated muscles of the body primarily responsible for locomotion and movements of the body. These muscles undergo muscle contraction and help in various movements of the body. With the contraction and relaxation of these muscles, we are able to walk and do exercises.