Question

Which of the following ions are necessary in the chemical events muscle contraction?
A. Sodium and potassium
B. Sodium and magnesium
C. Calcium and magnesium
D. Sodium and calcium

Answer 1

Muscles are soft tissue which are found in most animals and the muscle cells contain protein filaments like actin and myosin. Muscle contraction refers to an increase in the tension or a decrease in the length of a muscle.

Complete Answer:
Muscle contraction occurs when the nervous system generates a signal. The signal, an impulse called an action potential. It travels through a type of nerve cell called a motor neuron. The process of muscular contraction occurs over a number of key steps, including:
- Depolarisation and calcium ion release.
- Actin and myosin cross-bridge formation.
- The sliding mechanism of actin and myosin filaments.
- Sarcomere shortening (muscle contraction).

- In a resting muscle fiber, the potential difference is maintained by sodium and potassium ions. Sodium ions predominate on the outside of the sarcolemma and potassium ions predominates on the inside.

- During chemical events, muscle contraction of muscles, a stimulus is required.
The impulse is generated when an action potential is initiated, the muscles then shorten in length and trigger sarcoplasmic reticulum to release calcium ions into the interior of muscle and they bind to troponin, thus causing tropomyosin shift from the face of actin filaments to which myosin head need to bind to produce a contraction. Thus, Calcium plays an important role in muscle contraction. The role of magnesium is to form a MgATP complex to bind to a myosin active site, thus promoting actomyosin dissociation. Both calcium and magnesium are required during chemical events and muscle contraction.

- Sodium plays an important role in maintaining the potential difference in resting muscle fiber. However calcium binds to troponin, thus causing tropomyosin shift from the face of actin filaments to which myosin head needs to bind to produce a contraction. Both calcium and magnesium are required during chemical events and muscle contraction.

Hence the correct answer is option C.

Note: It is to be noted that sliding of actin along with myosin, shortens the sarcomere, therefore, causing muscle contraction.