When a person dies rigor mortis sets in as ATP synthesis ceases Explain why the lack of ATP in muscle cells would cause the muscles to become rigid rather than limp soon after death?

Answer 1

This question is straight out of the physiology and anatomyy book clinical #7 pg. 219 lol if you look up rigor mortis itll give you a better answer but this is what i have hope it helps... when a body dies stored calcium leaks and calcium pumps no longer funtion, so the exessive calcium causes actin and myosin filaments of the muscle fibers to remain linked, which stiffens the whole body until the muscle begins to decompose

From wikipedia.org:

After death, respiration in organisms ceases to occur, depleting the corpse of oxygen used in the making of ATP. ATP is no longer provided to operate the SERCA pumps in the membrane of the sarcoplasmic reticulum, which pump calcium ions into the terminal cisternae.[1] This causes calcium ions to diffuse from the area of higher concentration (in the terminal cisternae and extracellular fluid) to an area of lower concentration (in the sarcomere), binding with troponin and allowing for crossbridging to occur between myosin and actin proteins. [2]Unlike normal muscle contractions, the body is unable to complete the cycle and release the coupling between the myosin and actin, creating a perpetual state of muscular contraction, until the breakdown of muscle tissue by digestive enzymes during decomposition.[1][3]

Muscle rigidity after death is termed "rigor mortis" and it is a result of of calcium leaking from dead muscle cells...this ion results in contraction of the muscle simply "by default," but since they are dead there is no further progression or uncontraction...the muscles remain contracted and therefore we see rigor in corpses.