Question

Explain the process of skeletal muscle contraction from action potential being sent from the brain or spinal cord through muscle contraction and relaxation.

Answer 1

Ans:

Any skeletal muscle is made of fascicles, and each made of faccicle is made of muscle fiber, which are the individual multinucleated muscle cell.

The action potential generated will initiate excitation contraction coupling, the increase of action potential causes to increase the calcium levels to raise in the muscle fiber and this is what causes of filament to slide. When muscle cell is relaxed, tropomyosin blocks the myosin binding sites on the actin submunits.

But as more calcium ions become present , these will bind to troponin and once two ions bind,it will change shape, which will push tropomyosin half of the myosin binding sites, making them avilable or cross bridge cycling,in this process the myosin will shift and bend, pulling the actin filament along and using ATP in the process.the two position posssible for the head allow it to pull, detatch change position, bind,pull, dtatch and so forth many times, until contraction is complete.

As calcium level is deplete, troponin returns to its original shapee, tropomyosin blocks actin binding sites once more and the musclefiber relaxes.

steps involved in muscle contraction

• Signal arrives from the neuro muscular junction
• Acetylcholine is released which then binds to receptor on the sarcolemma.
• Sodium and potassium ions move through the channels, which results in a local change.
• Action potential travel down T tubules
• calcium is released and contraction begins  

Relaxation occurs when stimulation of action potential stops.calcium pumped back into the sarcoplasmic reticulam breaking the link between actin and myosin. actin and myosin return to therir unchain state causing muscle to relax.