Steps of Excitation-Contraction Coupling in Skeletal Muscle [Whole Video

The video explains the process of skeletal muscle contraction, starting with the excitation of the muscle fiber. It details the role of the motor neuron axon, synaptic end bulb, and acetylcholine in initiating muscle contraction. The action potential's propagation through voltage-gated sodium channels is described, leading to calcium influx and neurotransmitter release at the neuromuscular junction. The video covers muscle cell depolarization, the T tubule system's role in calcium release, and the crossbridge cycling within the sarcomere. It concludes with the importance of ATP in muscle contraction and the cycle's repetition.

What triggers the release of acetylcholine from the synaptic end bulb?

• A decrease in calcium levels

• A chemical signal from the brain

• The presence of ATP

• An action potential moving down the axon

What happens when acetylcholine binds to its receptors on the motor endplate?

• The muscle fiber contracts immediately

• Calcium is released from the sarcoplasmic reticulum

• The action potential stops

• Sodium and potassium ions move across the membrane

What is the primary function of the T tubule system?

• To release acetylcholine

• To produce ATP

• To transmit action potentials deeper into the muscle

• To store calcium ions

What role does calcium play in muscle contraction?

• It binds to acetylcholine receptors

• It triggers the release of ATP

• It depolarizes the muscle cell membrane

• It binds to troponin, allowing crossbridge formation

Which protein covers the myosin binding sites on actin at rest?

• Troponin

• Tropomyosin

• Myosin

• Actin

What is required for the myosin head to detach from actin?

• Binding of ADP

• Binding of ATP

• Release of phosphate

• Release of calcium

What happens during the power stroke of the crossbridge cycle?

• The myosin head detaches from actin

• The myosin head rotates, pulling the actin filament

• ATP is hydrolyzed to ADP and phosphate

• Calcium is released from the sarcoplasmic reticulum

How is the crossbridge cycle terminated?

• By the removal of calcium from the sarcoplasm

• By the binding of acetylcholine to its receptor

• By the influx of sodium ions

• By the release of ATP

What is the role of ATP in the crossbridge cycle?

• It causes the myosin head to detach from actin

• It depolarizes the muscle cell membrane

• It binds to troponin to initiate contraction

• It provides energy for the power stroke

What is the result of ATP hydrolysis in the crossbridge cycle?

• Release of calcium from the sarcoplasmic reticulum

• Detachment of myosin from actin

• Formation of a new crossbridge

• Activation of the myosin head