ch 12

which of the following structural protein of skeletal muscle also acts as an enzyme?

• Actin filament

• Myosin light chain

• Myosin heavy chain

• Tropomyosin

Which of the following is the smallest structure?

• myofibirl

• myosin

• muscle fiber

• muscle fascicle

Which ion stimulates shape changes at the beginning of skeletal muscle contraction?

• K⁺

• Acetylcholine

• Ca²⁺

• Na⁺

__________ occurs when myosin crossbridges attach to actin filaments and pull them toward the middle of the sarcomere.

• power stroke

• hydrolysis

• action potential

• myosin head rotation

What happens when calcium binds troponin?

• Tropomyosin is pulled away from the myosin-binding site on actin.

• Troponin releases myosin and activates actin.T

• Troponin changes shape and covers the SR calcium channel, which is a form of negative feedback.

• Troponin binds to actin and causes sarcomere shortening.

Compared to fast-twitch glycolytic fibers (type IIX), slow-oxidative muscle fibers (type I) are characterized by a smaller diameter and __________.

• the presence of myoglobin

• faster pumping of Ca²⁺ into the SR

• the development of tension 2-3 times more quickly

• fewer mitochondria

What happens when skeletal muscle sarcomere length increases beyond about 2.3 micrometers (μm)?

• force decreases

• tension decreases

• less clacium is relaesed from SR

• the fiber can produce more force

A flexor is a skeletal muscle whose shortening moves attached bones

• laterally

• medially

• away from each other

• towards one another

Skeletal muscle cells are usually attached to bone by

• fasicles

• flexors

• tendons

• ligaments

The origin is the end of the skeletal muscle that attaches to the

• more mobile bone

• more stationary bone

• tendon

• ligament