Physiology of Muscle Contraction

Skeletal Muscle Contraction

Multiple Choice

Which forms the thick filament of a sarcomere?

• Actin

• Myosin

• Troponin

• Tropomyosin

Multiple Select

Which of the following make up the thin filaments of a sarcomere?

• Actin

• Myosin

• Troponin

• Tropomyosin

Multiple Choice

According to the sliding filament model , during muscle contraction

• a myosin head attaches to a binding site on the actin

• an actin head attaches to a binding site on the myosin

Multiple Choice

Which of the following the muscle fiber to shorten?

• The actin pulls on the myosin making it shorter

• The mysoin acts on the actin making it shorter

• Sarcomeres shortening at the same time

• all of these are correct

Multiple Select

Which of the following changes in the sarcomere during contraction?

• The A band gets shorter

• The I band gets shorter

• The Z lines get closer together

• The H zone gets smaller

Multiple Choice

The arrival of the nerve impulse at the axon terminal of the neuromuscular junction triggers.........

• the inhibition of nerve signals
• the absorption of calcium ions
• the release of neurotransmitters
• the contraction of muscle fibers

Multiple Choice

Which of the following is the neurotransmitter for muscle contraction at the neuromuscular junction?

• Acetylcholine

• acetylcholin-esterase

• calcium

• Adenosine Triphosphate

Multiple Choice

What is the substance released that interacts with the proteins on the actin filaments?

• acetlycholine

• acetylcholin-esterase

• calcium ions

• Adenosine Triphosphate

Multiple Choice

The attachment of the myosin heads to the actin filament forms what is known as a ____________.

• cross-bridge
• filament bond
• myosin link
• actin bridge

Multiple Choice

What substance is necessary for cross-bridges to form and pull on the actin filaments?

• Acetylcholine

• Acetylcholin-esterase

• Calcium

• Adenosine Triphosphate

Multiple Choice

What substance binds to the myosin heads, breaking the linkage between the myosin and actin?

• Acetylcholine

• Acetylcholin-esterase

• Calcium

• Adenosine Triphosphate

Multiple Choice

During muscle relaxation __________ are actively transported out of the sarcomere and into the sarcoplasmic reticulum.

• calcium ions (Ca2+)
• sodium ions (Na+)
• potassium ions (K+)
• chloride ions (Cl-)

Multiple Choice

The hydrolysis (breakdown) of ATP causes _________

• the cross bridge to form.

• the myosin heads to move to the "cocked" position.

• the myosin head to bind to the actin filament.

• the myosin heads to detach from the actin filament.

Multiple Choice

ATP breaks the cross bridge link between myosin and actin and becomes ADP.

• True

• False

Reorder

Place the following steps in the correct sequence as they occur during muscle contraction.

• Acetylcholine is released into the neuromuscular junction upon the arrival of a nerve impulse.

• Acetylcholine causes the sarcolemma to become permeable.

• Calcium ions are released into the sarcomere.

• Myosin heads bind to exposed sites on actin filaments.

• The sarcomere shortens as the myosin pushes the actin toward the center.

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