How Muscle Fibers Contract - EXCITATION-CONTRACTION COUPLING Flashcards
What is the first step in How the Action Potential Causes Muscle Contraction?
- The action potential flows into the muscle fiber by
traveling through transverse tubules.
What is the second step in How the Action Potential Causes Muscle Contraction?
Calcium channels open in the sarcoplasmic reticulum.
What is the third step in How the Action Potential Causes Muscle Contraction?
Calcium ions enter the muscle and bind to troponin.
What is the fourth step in How the Action Potential Causes Muscle Contraction?
Troponin pulls on tropomyosin.
What is the fifth step in How the Action Potential Causes Muscle Contraction?
Tropomyosin moves, exposing the active sites on the
actin filaments.
What is the sixth step in How the Action Potential Causes Muscle Contraction?
Myosin heads bind to active sites (crossbridge formation).
What is the seventh step in How the Action Potential Causes Muscle Contraction?
Myosin hinge regions bend.
What is the eighth step in How the Action Potential Causes Muscle Contraction?
Swinging of myosin heads pulls actin filaments toward each
other—the power stroke (muscle contracts).
What is the ninth step in How the Action Potential Causes Muscle Contraction?
Myosin heads release, filament returns to original position—
the recovery stroke (muscle relaxes).
What is the tenth step in How the Action Potential Causes Muscle Contraction?
Additional Note: Energy in the form of ATP is required
for attachment of myosin to actin and for the power stroke
What is the eleventh step in How the Action Potential Causes Muscle Contraction?
Calcium is pumped back into storage in the sarcoplasmic
reticulum. This also requires energy.
What is the twelveth step in How the Action Potential Causes Muscle Contraction?
The Troponin-Tropomyosin complex returns to its original
location blocking the active sites.
