Question

question 17
as a muscle contracts, which of the following things happens?
○ the z disks move closer together.
○ the myofibrils break down.
○ the muscle creates energy.
○ the sarcomeres extend.

Explanation:

To solve this, we analyze each option:

• Option 1: During muscle contraction, the sliding filament theory explains that actin and myosin filaments slide, causing Z - disks (which mark the ends of sarcomeres) to move closer together. This is consistent with muscle contraction mechanics.
• Option 2: Myofibrils do not break down during normal muscle contraction; they are the structural units involved in contraction.
• Option 3: Muscles use energy (like ATP) for contraction, they don't create energy (energy is derived from cellular respiration etc.).
• Option 4: Sarcomeres shorten (Z - disks move closer) during contraction, they do not extend.

Answer:

The Z disks move closer together.