Options are not provided in the question. The complete question is:
Muscle contraction occurs in a cyclic process. Which of the following sequences is in the correct order?
A. power stroke, cross bridge formation, cross bridge dissociation, cocking of myosin
B. cross bridge formation, power stroke, cross bridge dissociation, cocking of myosin
C. cross bridge formation, cross bridge dissociation, cocking of myosin, power stroke
D. cross bridge formation, power stroke, cross bridge dissociation, power stroke, cocking of myosin
E. cross bridge formation, cocking of myosin, power stroke, cross bridge dissociation
Answer: B. cross bridge formation, power stroke, cross bridge dissociation, cocking of myosin
Explanation:
Muscle contraction is the activation of sites that produce stress within the muscle fibres.
The process of contraction begins with the Calcium ions that bind to the protein complex troponin and reveal the active-binding actin sites. The high-energy myosin head fills the gap, creating a cross-bridge, until the actin-binding sites are exposed. The filaments shift roughly 10 nm towards the M line as the actin is removed which leads to power stroke because it is the phase at which force is generated. Then teh ATP binds to the myosin and allows the bridge between actin-myosin dissociate. So soon so myosin attaches to actin, myosin's cocked head releases the actin fibre to slide. The cross-bridge generates energy, and actin displaces the myosin cross-bridge reaction products (ADP and Pi). This allows the process of contraction.
Hence, the correct order is B.
