RIGOR MORTIS (MUSCLE CONTRACTION) Nurse Emma called for a code-blue from Mrs. We
ID: 3512564 • Letter: R
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RIGOR MORTIS (MUSCLE CONTRACTION) Nurse Emma called for a code-blue from Mrs. Weitzel's room. Several nurses and doctors rushed into the room with a crash cart. Mrs. Weitzel was not breathing, was ashen in color, and was very cold. The emergency team could not find a pulse or a heartbeat, and they could not detect respiration. On closer examination, the doctor found that every joint in her body was stiff Just then Mrs. Weitzel's son, Josh, entered the room. Josh had come to visit his mother and was shocked to see so many people in her room. He couldn't believe his ears when the doctor declared his mother deceased. Josh remembered that Emma had been taking care of her and demanded that she explain what happened Nurse Emma told Josh that she entered the room half an hour ago and let Mrs. Weitzel sleep while she tidied up. As Emma had approached the side of the bed, Mrs. Weitzel had suddenly moved her leg. Upon further investigation Emma noticed that Mrs. Weitzel was not breathing. When we heard this Josh was infuriated. He insisted that Emma was negligent because she was standing right there while his mother died. Later that week a board of inquiry convened at the insistence of Josh's lawyer. Emma was accused of negligence in the care of her patient, but you know this is not the truth. Help explain to Josh what happened in that hospital room. Give some background by explaining the chain of events that occur in muscle contractions I. What is the extemal stimulus on the skeletal muscle fiber that signals contraction and where does it come from? a. Which protein blocks the myofilaments, actin and myosin, from interacting to prevent a contraction? b. c. Where is calcium stored in the skeletal muscle fiber? Modified from : Braude, S, Goran, D., and Miceli, A., Case Studies for Understanding the Page 1 Human Body 2nd ed. Jones& Bartlett Learning: Sudbury, MA (2012).Explanation / Answer
Ans) Events occuring in muscle contraction :
Muscle contraction is the stimulation of muscle fibers that causes or generates tension in them causing them to contract which may or may not cause shortening of length of muscle.
1(a) The contraction of muscle starts with the first and important step by the activation or stimulation of the muscle fibers by the stimulus generated to the neuromuscular junction by the motor neuron that is attached to the muscle fiber. This signal is the action potential which triggers the neuromuscular junction and causes it to release a chemical acetylcholine , which binds to the receptors present on the muscle fiber. This initiation process then starts a chemical reaction in the muscle.
b) The actin and myosin filaments got interacted with the protein complex Tropomyosin , to keep interaction of actin to myosin site during resting stage of muscle the protein Tropomyosin prevents the cross bridge formation and thus prevents muscle contraction.
c) Calcium is stored in the Sarcoplasmic reticulum , which is the specialized smooth endoplasmic reticulum of skeletal muscle fiber. It also regulates the calcium ion concentration in the cytoplasm of the skeletal muscle fiber.
d) The activation or trigerring of muscle fiber from the neuromuscular junction causing an action potential , This triggers the depolarization of muscle membrane or sarcolemma and so the sarcoplasmic reticulum causes release of calcium from them to the muscle interior and binds to Troponin and this causes Tropomyosin to shift from the actin head resulting the resting muscle to contract.
e) For muscle contraction to occur with the action potential the cross bridge formation takes place in the presence of calcium from the sarcoplasmic reticulum. The released calcium ion binds to the Troponin protein and thus causing Tropomyosin protein to move from the actin filament site and thus help contraction.
2 (a) It is said in above case that Mrs Wietzel died already as Emma entered the room , but how she could see the leg moving. Contraction is followed by muscle relaxation which occurs when there is no actin and myosin binding. For muscle in relaxed state there is high energy state , but if ATP(energy) is unavailable then the already presence of calcium ions into the sarcoplasm which cannot return back to sarcoplasmic reticulum of the muscle due to absence of energy , causes the myosin heads to further bind to actin and tehrefore teitch of movements could be seen even if some person already died.
b) The contraction of muscle occurs in Rigor mortis due to the degradation of myosin heads by enzymes by the process of decomposition.
3 (a) In the cell ATP(Adenosine triphosphate) is generated by cellular respiration processes including Aerobic respiration and anaerobic respiration.
(b) ATP is generated in the cells by breakdown of glucose into carbon dioxide and water and the energy produced is used by metabolic processess.
(c) After activation of muscle fiber calcium ion is released into the muscle from the sarcoplasmic reticulum and for binding of Actin and myosin there required ATP and large energy amount for Cross bridge formation.
4) Rigor mortis is the stiffness stage of death. After death there is oxygen depletion to the body , calcium ion release into the cytosol of muscle cell due to deterioration of sarcoplasmic reticulum . It is the biochemical process occuring several hours after death. There is absence of ATP or energy in the body and without ATP there is adherence of myosin to actin filament causing the muscles to become rigid.
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