Muscle Contraction

​Muscle Contraction: Sliding Filament Theory

By Adrienne Aguilar

Complete video handout using next slide (video). Then use information to answer concept check questions

Multiple Choice

True or False: Cross-bridges is when a myosin head attaches to an actin during contraction

• True

• False

Multiple Choice

The diagram provided shows how a sarcomere changes when a muscle fiber contracts. Which of the following best describes how the sarcomere changes?

• The sarcomere extends as the actin filaments pull the myosin away from the M line.

• The sarcomere shortens as the myosin pulls the actin filaments toward the M line.

Multiple Choice

What causes the muscle to stop contracting?

• Lack of effort

• Myosin-Heads fail to attach

• Calcium Ions are pumped away

• Muscle fibre tears

Multiple Choice

When ATP binds to the myosin head the myosin head then _____________.

• completes a power stroke

• attaches to actin

• rotates

• detaches from actin

Multiple Choice

Which of the following best describes the structure of an actin filament?

• A thin filament that is made up of two molecules twisted around each other

• A thick filament with a globular head and a cylindrical tail

Multiple Choice

In the sliding filament theory of muscle contraction, what is the primary role of calcium ions?

• To provide the energy required to return the myosin heads back to their normal position

• To initiate the release of a molecule of ADP as the myosin heads pull the actin filament along

• To stimulate the detachment of the myosin heads from the actin binding sites

• To bind to tropomyosin, changing its shape and moving it away from myosin binding sites