STPM Biology - chapter 10: Revision essay question 1

1. Describe the sequence of events occurring during muscle contraction.                                       [9]


Answer:

1. * Please refer to notes chapter 10: Action Potential and muscle contraction & Breakdown of ATP     
       and Cross-Bridge Movement During Muscle Contraction




 -Transmission of impulse along the T tubule to the sacroplasmic vesicle
 - secretion of Ca2+ ions by the sacroplasmic vesicle 1 calcium ions, bind to troponin
 - troponin displaces tropomyosin / troponintropomyosin complex 
 - cause exposure of binding sites on actin 
 - myosin heads attach to actin filament
 - myosin head contain ATPase
 - myosin head changes position / actin filaments slide past myosin filaments
 - myosin detaches from actin filament

 - ATP cause this release /hydrolysis of ATP occurs to release energy to form and reform cross bridge /
    myosin head cocked
 - ratchet mechanism
 - process continues provided enough ATP / calcium ions present
 - AVP ; e.g. I band shortens , Z lines closer together, H zone shortens / sarcomere shortens , A band
 - remain constant
 - when there is no longer an impulse the Ca2+ ions re-enter the vesicle and the sacromere stop
   contraction