Question

What is the cause of rigor mortis, a fixed muscular contraction after death?

1) Absence of ATP
2) Loss of mitochondrial activity
3)reation of actin-myosin cross bridges
4) All of the above

Answer 1

Rigor mortis is caused primarily by the absence of ATP postmortem, which is needed to detach myosin heads from actin to allow muscle relaxation. Depletion of ATP results in lasting actin-myosin cross-bridge formation and muscle stiffness.

Step-by-step explanation:

The cause of rigor mortis, which is a fixed muscular contraction after death, is the absence of ATP (Adenosine Triphosphate). After death, there is no ATP production, and the existing ATP gets depleted. ATP is essential for the detachment of myosin heads from the actin-binding sites. In life, when ATP binds to myosin heads, it causes them to detach from actin, allowing muscle relaxation. However, in the absence of ATP, as seen in death, myosin heads cannot detach, which leads to actin-myosin cross-bridges remaining intact and the muscles becoming rigid.Rigor mortis onset is a result of the combination of loss of mitochondrial activity, which prevents the production of new ATP, and the creation of actin-myosin cross bridges that cannot be broken without ATP, leading to the stiffness in the muscles.