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Rigor mortis

1. After death, the muscles of the body become very stiff and inextensible. This phenomenon is referred to as rigor mortis, and the muscles are said to be in a state of rigor.

(a) Explain the biochemical basis of rigor mortis, in terms of the interaction of actin and myosin; ie, where in the contraction cycle is the muscle arrested?

(b) Would your muscles be likely to go into rigor faster if you were to die while racing to class, or while sitting in lecture? Explain.

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Biochemical Basis of Rigor Mortis


When you die, oxidative phosphorylation comes to a halt once oxygen runs out in the cells. Therefore, ATP production stops and as a result, cellular processes requiring free energy stop.

Keep that in mind as we go.

In order to understand rigor mortis, we must understand the contraction cycle involving myosin and actin.

First, an action potential arrives at the neuromuscular junction, causing a wave of depolarization in the T-tubule system ...