5. Calcium and the Biochemistry of Muscle Contraction (Invertebrate)

5. Calcium and the Biochemistry of Muscle Contraction (Invertebrate)


This scene shows the events that activate muscle contraction and the biochemical details of cross-linking and sliding of the actin filaments by the myosin heads. The cycle starts when an electrical impulse from a motor neuron stimulates a muscle fiber. Invertebrate animals may have one, two or three motor neurons that control the contraction of a single muscle fiber, and each motor neuron has multiple end plate junctions
spread over the fiber surface, The nerve signal from a motor neuron does not
generate an action potential in an invertebrate muscle fiber but rather
depolarizes the entire surface of the fiber to produce contraction. The electrical depolarization also spreads into tiny membranous invaginations of the fiber membrane called transverse tubules, or t-tubules. The t-tubules extend to the myofibrils. The t-tubules align with the A-band in invertebrate muscles. The t-tubules essentially carry the electrical signal into the sarcoplasm and along the sarcoplasmic reticulum – a complex of membranous
vesicles that serve to store calcium within the muscle. Depolarization of the t-tube membrane activates calcium release channels of the sarcoplasmic
reticulum to release stored calcium into the sarcoplasm. The released calcium then initiates the
muscle contraction by binding to a protein called troponin. Calcium-activated troponin causes a conformational shift in the protein tropomyosin which winds around the actin helix and blocks the myosin binding sites on the actin molecules, This frees the actin molecules to bind the myosin head units. The contraction cycle starts with the myosin head bound to adenosine triphosphate (ATP). The myosin head contains adenosine triphosphatase an enzyme that splits the high energy phosphate bond of ATP to produce adenosine diphosphate (ADP) and inorganic phosphate. The resulting ADP and inorganic phosphate remain associated with the myosin head which is also charged with the energy released by the splitting of the high energy phosphate
from the ATP. To start the contraction cycle, the myosin head attaches loosely to actin, then releases the inorganic phosphate which causes tight binding with the actin. After tight binding, proteins in the myosin head undergo a conformational change that results in repositioning the angle of attachment between the myosin head and the actin. The shift to the new conformation pulls the actin along the myosin. After pulling the actin, myosin exchanges ADP for a new molecule of ATP. This results in a release of the myosin head from the actin. The myosin head resumes its relaxed conformation and position, and the cycle is ready to repeat. let us watch the cycle repeats several times

44 thoughts on “5. Calcium and the Biochemistry of Muscle Contraction (Invertebrate)

  1. No, it is #5. For the entire video tutorial in sequence watch the 9:18 min video. Also my playliist plays all the scenes in sequence.The original series had a redundant scene that was posted before YouTube let me load longer movies. Afterward I left it because so many watch it. Also, there was a previous version of the Biochem Details that lacked the role of calcium and I left it because many people also view it. They are not wrong, just not as detailed. Many people like the individual scenes

  2. Thanks for the comment. I had considered writing a textbook after I retired, but when I saw how much my students liked the animations, esp. in physiology which happens in time and space and can be hard to conceptualize, I decided to pursue my hobby of computer animations instead. :-). Stay tuned others are in prep.

  3. The video on here by "ebpanimations" is more consistent with my textbook than this one… It is also more detailed if you are studying this at a higher level. Just saying. Hope this helps!

  4. This helped me so much with visualizing and understanding the chemical changes that go along with the contraction of muscles. Thank you, kind sir!

  5. You are correct, but I do not try and include all details which might be of interest to more advanced cell biology students. My goal is to provide basic concepts to help students that are new to physiology to understand the processes and, hopefully, stimulate their interest so they will seek more information. Too many details confuse beginning students and they lose interest. Videos help conceptualization, but they do not replace a good textbook.

  6. Yes and No. Depending on the type of learner. I am a visual learning. I need to see it to understand it. I can read the book after I see things and then the book makes any sense to me. Also depending on the video. Some videos are extremely detailed and therefore they reflect all the aspects that might be presented in a book which makes them again a valuable tool for a visual learner 🙂

  7. What you say is quite right. I have always been able to visualize what I am reading as I read it.However, in the classroom I met many such as yourself that like the overall conceptualization before trying to pick up the details. Learning is learning however it works best for yourself and both reinforce the other. Thanks for the comments.

  8. I'm a french student and tomorrow I'll have a physiology exam, and your video is so cool! I've understand all my lesson in 10 minutes thanks, to you.
    Good Job!

  9. OH wow!! you just saved me from a lot of stress on my upcoming test. Why can't my lecturer explain this as simply as this video! Thank you so much!!

  10. Thank you for the very informative vid. It would have been even better if it contained the after process and the role of calsequestrin as well. Thanks again for this much.

  11. sorry , but can you put the translation of the video , because i am not good in English 😁 …i understood from the pictures of the video but i need to know the sentences !!

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