Question

Muscle contraction: Select one O a occurs when myosin pulls on actin and the sarcomere shortens b. occurs when actin pushes on myosin and the sarcomere elongates O c occurs when the myosin tail splits the actin filament in half Od occurs when actin and myosin entangle, generating more distance between Z lines

Answer 1

option A is the correct answer.Muscle ccontraction is the process of activation of tension generating sites within muscle fibres.The motion of the muscle shortens as the myosin heads bind to actin and pull the actin inwards.As the actin is pulled toward the M line ,the sarcomere shortens and the muscle contracts.ATP can then attach to myosin,which allows the cross bridge cycle to start again and further muscle contraction can occur.A sarcomere is defined as the distance between two consecutive Z lines,when muscle contracts ,the distance between the Z lines is reduced only.During muscle contraction ,the distance between Z lines never increases and the sarcomere never elongates,it only shortens.The globular heads of the myosin bind actin and forms cross bridges between the thick and thin filaments.This movement slides the actin filaments from both sides of the sarcomere towards the M line,which causes the shortening of the sarcomere and results in muscle contraction.During muscle contraction actin gets pulled along myosin,not myosin gets pulled towards actin,and it is towards the centre of the sarcomere until the actin and myosin filaments gets completely overlapped.And they slide by one another,sarcomere shortens but the filaments remains the same length.