Question

What happens to the actin and myosin filaments when a muscle contracts?

Answer 1

Actin filaments slide along myosin filaments so that the sarcomere shortens and muscle fibre contracts. Individual actin or myosin filaments do not contract.

Explanation:

According to Sliding Filament model of muscle contraction (proposed by H. Huxley, A.F. Huxley and their colleagues) following changes occur during muscle contraction.

• The actin filament slide on the myosin filament. So, that the two filaments overlap to a greater degree.
• The Z lines come close to each other.
• The I-band shortens and H-zone disappears.
• This happens as cross bridges of myosin filament become attached to the binding sites on actin filament
• The cross bridges pull the actin filaments towards the center of the sarcomere (the region between two successive Z-lines is sarcomere).

(a) Before contraction

(b) After contraction

https://themusclemechanicuk.com/the-role-of-titin-and-the-winding-filament-theory-in-muscle-mechanics/

Hope it helps...