What, in addition to adenosine triphosphate, must be present for a muscle to contract?

Question

Quizplus · Accepted Answer

Calcium and adenosine triphosphate (ATP) must be present for a muscle cell to contract.
Nervous stimulation from efferent (motor) neurons causes the release of calcium ions from the sarcoplasmic reticulum in the muscle. The calcium ions then attach to inhibitory proteins of the actin filaments within the cell, moving them aside so that cross-bridges can form between actin and myosin filaments. Then, using energy supplied by ATP, the filaments slide together to contract.
Lactate (lactic acid) does not play a role in muscle contraction but does cause a burning sensation in muscles when your muscles run low on oxygen.
The diagram of muscle contraction below is more in-depth than what you will need to know for the HESI A2. However, note that the nerves stimulate the muscle, releasing calcium, allowing for muscle contraction.
 11ec0fda_9993_2fff_a67f_914a868ecec6_NR0004_00 OpenStax / CC BY (https://creativecommons.org/licenses/by/4.0)

What, in Addition to Adenosine Triphosphate, Must Be Present for a Muscle