Muscle Fiber Contraction

What are the two essential components for cross bridge cycling to occur?

• calcium and ATP

• sodium and potassium

• creatine phosphate and lactic acid

• muscles and energy

What causes a muscle to stop contracting?

• when myosin head attachment fails

• when potassium is released

• when calcium is pumped back into the SR

• when voltage-gated sodium channels close

Which of the following statements is false?

• Calcium binds to troponin

• Myosin heads bind to actin

• Potassium influx (into the cell) restores initial resting membrane voltage

• Ach causes the opening of chemically-gated sodium channels on the motor end plate

________ attaches to actin to form the cross bridge.

• calcium

• tropomyosin

• myosin

• troponin

What is released from the sarcoplasmic reticulum?

• inorganic phosphate

• ADP

• ATP

• calcium

What is the name of the neurotransmitter released at a neuromuscular junction?

• acetylcholine

• troponin

• calcium

• dopamine

Which of the following is a true statement about myofilaments?

• actin pulls on titin

• actin pulls on myosin

• myosin pulls on titin

• myosin pulls on actin

Which ion, when present, changes the conformation of troponin?

• lithium

• calcium

• potassium

• sodium

What happens during repolarization?

• interior of cell becomes more positive

• voltage-gated Na+ channels open causing an influx of sodium

• voltage-gated Na+ channels close, and voltage-gated K+ channels open

• voltage-gated K+ channels open causing an influx of potassium

What is muscle tone?

• feeling you get after a workout

• a type of isotonic contraction

• muscles seen on a fit individual

• constant, slightly contracted state of all muscles