Which of the following is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers? acetylcholine. action potentials. calcium ions. sodium ions.

Calcium ions

Explanation:

The excitation-contraction coupling process is the process by which the electrical activation of muscles (the depolarization of the action potential) leads to the activation of contraction.

An action potential in the skeletal muscles or muscle excitation leads to Ca release from the sarcoplasmic reticulum via calcium channel protein. Released Ca regulates the contraction of the muscle.

carbon

explanation:

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these macromolecules could either be amino acids, proteins or nucleic acids. they are responsible for the chemical changes and reactions that affects largely the cell and its composition. take for instance the cytoplasm of the cell where these organelles are settled. these simple organelles are composed of macromolecules which ignites and catalyses different functions that enables cells, in macro-perspective in motion and metabolism. in intestines for example, metabolism happens and breaking down parts of a food to simpler compounds that are used and these nutrients delivered throughout the body and again broken down by into smaller components.