Muscular Contraction Quiz Review

Muscle contraction is caused by

• actin filaments sliding past each other.
• actin filaments sliding past myosin filaments.
• myosin filaments sliding past each other.
• myelin filaments sliding past each other.

Which of the following statements about H zones and I bands is TRUE?

• the H zones contain only actin, while the I bands contain only myosin
• the H zones contain only myosin, while the I bands contain both actin and myosin
• the H zones contain only myosin, while the I bands contain only actin
• the H zones and the I bands each contain both actin and myosin

During muscle contraction

• the A band remains the same and the I band narrows.
• the I band remains the same and the A band narrows.
• both the A band and I band remain the same.
• both the A band and I band become wider.

In a contracting muscle the Z lines come closer together.

• True
• False

In a relaxed muscle, the H zone is at its narrowest width.

• True
• False

Each actin filament is composed of

• a single strand of actin molecules.
• four strands of actin molecules wrapped together.
• hundreds of strands of actin molecules wrapped together.
• two strands of actin molecules wrapped together.

As actin and myosin filaments slide past each other during muscle contraction,

• actin filaments shorten, while myosin filaments do not.
• myosin filaments shorten, while actin filaments do not.
• neither actin nor myosin filaments shorten.
• both actin and myosin filaments shorten.

Which of the following statements about the "heads" of the myosin molecules is TRUE?

• they form permanent links with actin filaments
• they can attach to different sites on the actin filament
• they allow the myosin filaments to wrap around each other
• they straighten the myosin filaments

Each myosin protein has a globular head that extends outward from the myosin filament.

• True
• False

During contraction of a muscle, calcium ions bind to...

• the actin myofilament.
• the myosin myofilament.
• the tropomyosin molecule.
• the troponin molecule.