Muscle Contraction

What initiates muscle contraction?

• Release of calcium ions

• Direct stimulation of muscle fibers

• A signal from the nervous system

• The skeletal system

What is released at the neuromuscular junction to stimulate muscle fibers?

• Adenosine triphosphate (ATP)

• Calcium ions

• Acetylcholine

• Myosin

How is the action potential transmitted within a muscle fiber?

• Through transverse tubules

• By direct stimulation of myofibrils

• Via the sarcoplasmic reticulum

• Through the skeletal system

What are the two types of filaments involved in muscle contraction?

• Myosin and collagen

• Actin and elastin

• Collagen and elastin

• Myosin and actin

What happens during the power stroke phase of muscle contraction?

• Myosin heads pull actin filaments towards the center of the sarcomere

• Calcium ions are released into the muscle fiber

• Acetylcholine is released at the neuromuscular junction

• ATP is synthesized

What is the role of ATP in muscle contraction?

• It binds to myosin, allowing it to detach from actin

• It is broken down to release calcium ions

• It acts as a neurotransmitter at the neuromuscular junction

• It generates the initial action potential

How do myosin heads reactivate for another cycle of contraction?

• By releasing acetylcholine

• By detaching and reattaching to actin with the help of ATP

• By synthesizing more calcium ions

• By generating an action potential

What is stored in the sarcoplasmic reticulum?

• sodium

• potassium

• calcium

• Acetylcholine

When ACh bind to the receptors on the muscle fiber sarcolemma, it opens channels allowing ____ into the muscle fiber.

• potassium

• calcium

• sodium

What does calcium bind to once released from the sarcoplasmic reticulum?

• the troponin protein complex on actin

• the myosin head

• the crossbridge