Question

muscle contraction interactive and video
when calcium stops being released, what happens?
the muscle breaks down and rebuilds, resulting in increased muscle strength and size.
the muscle contracts continually.
the muscle relaxes because myosin - binding sites on actin get blocked, allowing actin to slide back.
the muscle contracts more strongly due to interactions between troponin and actin.
all of these.
save score: 100% submit response

Explanation:

When calcium stops being released, the muscle relaxes. Calcium is crucial in muscle contraction as it binds to troponin, which then moves tropomyosin to expose myosin - binding sites on actin. Without calcium, tropomyosin blocks these sites again, and the muscle relaxes. The first option (muscle breakdown and rebuilding) is related to muscle growth through exercise - induced micro - trauma, not directly to calcium release. The second option (continuous contraction) is incorrect as calcium is needed for contraction. The fourth option (more contraction) is also wrong as calcium withdrawal leads to relaxation. And since only one of the statements is correct, “all of these” is incorrect.

Answer:

The muscle relaxes because myosin - binding sites on actin get blocked, allowing actin to slide back.