Video Quiz: Muscle Contraction

A ​ (a)   conducts a(n)​ (b)   its link with a ​ (c)   .

• sensory neuron
• motor neuton
• action potential
• muscle fiber
• synaptic cleft
• different neuron

What is the role of acetylcholine in muscle contraction?

• It powers the movement of the myosin head.

• It generates an action potential in the motor neuron.

• It stores calcium ions in the sarcoplasmic reticulum.

• It binds to receptors on the muscle fiber to allow sodium ions to enter.

What happens when calcium ions are released from the sarcoplasmic reticulum?

• They bind to a protein complex called troponin, exposing myosin binding sites.

• They generate an action potential in the motor neuron.

• They cause the sarcomeres to break apart.

• They directly power the movement of the myosin head.

What are sarcomeres made up of?

• Only thick filaments of myosin.

• Only thin filaments of actin.

• Both thick filaments of myosin and thin filaments of actin.

• Calcium ions and acetylcholine.

What is the power stroke in muscle contraction?

• The binding of acetylcholine to its receptor.

• The movement of the myosin head that pulls actin toward the sarcomere center.

• The release of calcium ions from the sarcoplasmic reticulum.

• The detachment of myosin from actin.

What is inside of the sarcoplasmic reticulum?

• calcium ions

• sodium ions

• potassium ions

• acetylcholine

What does ATP do?

• Allows myosin to break the crossbridge and storing energy in the myosin head for the next power stroke

• Creates ADP and P which allow the myosin head to bind to tropomyosin

• Moves tropomyosin out of the way so the myosin head can bind to actin

• Attaches to actin causing the actin to slide across myosin

Select each of (three) the following actions that could STOP muscle contraction and CAUSE relaxation.

• Calcium ions are actively pumped back into the sarcoplasmic reticulum

• Acetylcholine stops being released from the axon terminal

• Calcium ions remain in the sarcoplasm

• Voltage-gated calcium ion channels in the axon terminal do not open when stimulated by an action potential.