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Rigor mortis

Got a question about rigor mortis as I have just learnt about muscle contraction.

I understand that it happens because body can no longer take in oxygen so cant respire so there is no ATP. One of the jobs of ATP is to make myosin detach from actin causing the muscle to relax. This doesnt happen leading to permanant contracting (Stiff body)

My question is, if the human is dead, then how do the myosin attach to the actin in the first place. The sarcolemma wont depolarise as there will be no action potential so the sarcoplasmic reticulum will not release calcium ions so the tropomysin will be blocking the actin binding sites so mysin shouldnt be able to attach. This would lead to the body muscle being relaxed when the person dies which obviously isnt the case. can anybody explain please
(edited 11 years ago)
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ash92:)
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Original post by helpme456
Got a question about rigor mortis as I have just learnt about muscle contraction.

I understand that it happens because body can no longer take in oxygen so cant respire so there is no ATP. One of the jobs of ATP is to make myosin detach from actin causing the muscle to relax. This doesnt happen leading to permanant contracting (Stiff body)

My question is, if the human is dead, then how do the myosin attach to the actin in the first place. The sarcolemma wont depolarise as there will be no action potential so the sarcoplasmic reticulum will not release calcium ions so the tropomysin will be blocking the actin binding sites so mysin shouldnt be able to attach. This would lead to the body muscle being relaxed when the person dies which obviously isnt the case. can anybody explain please


Hey.

The point is that the myosin and actin are already attached, and REMAIN IN THEIR STATE upon death (after which, as you mentioned, their is ATP depletion).

As to why this particular state occurs, it may be influenced by the contraction following an experience of intense pain in the person just before death. Any how, to bend an arm (for example) requires the myosin/actin interaction - even if someone bends it for you - it allows the bicep muscles to contract and change shape (vice versa with triceps), enabling the arm to physically bend. And this is required antagonistically, in co-ordinated manners to bend the arm. Hence why it is hard to move the arm either way.

Hope this helps

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