An increase in the calcium ion level in the sarcoplasm starts the sliding of the thin filaments. when the level of calcium ions declines, what happens to the sarcoplasm?

When the level of calcium ions declines the sarcoplasm stops the sliding.

Explanation:

Sarcoplasm can be described as the cytoplasm for the cells of muscles. It contains important structures such as the myofibrils.

The following steps would occur when the level of calcium ions would decline:

The sarcoplasm would stop the sliding of the thin filaments.

The actin filaments would be migrated in the M line

This would lead the bands in the I region to shorten.

The Z region would compress.

The H region would diminish.

just go with your heart buddy