Notes from NEET topper
Sliding Theory of Muscle Contraction:
- The sliding filament theory is a widely accepted model that explains how muscle contraction occurs.
- According to this theory, during muscle contraction, thin actin filaments slide past thick myosin filaments, causing the sarcomeres (the contractile units of muscle fibers) to shorten.
- The sliding is facilitated by the cyclic interaction between myosin heads and actin filaments.
- The steps involved in muscle contraction include:
- Calcium ions (Ca²⁺) are released from the sarcoplasmic reticulum in response to a nerve impulse.
- Ca²⁺ ions bind to troponin, causing a conformational change in tropomyosin, exposing the binding sites on actin.
- Myosin heads (cross-bridges) bind to actin at these exposed sites.
- ATP is hydrolyzed to ADP and inorganic phosphate (Pi), providing energy for myosin to undergo a conformational change (the power stroke).
- This change in myosin’s shape causes the thin actin filaments to slide along the myosin filaments, shortening the sarcomeres and leading to muscle contraction.
- The cycle repeats as long as Ca²⁺ ions are present and ATP is available.
This process of actin and myosin interaction, powered by ATP, allows for muscle contraction and movement. The sliding filament theory provides a detailed explanation of the molecular events that occur during muscle contraction.
