The physiological cause for rigor mortis is the lack of to release cross bridge formation.

lack of ATP

Explanation: Muscles need ATP in order to release from contracted state

when an organism die the reactions that recycle ATP eventually comes to a halt .

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

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