Question -
Answer -
Steps in muscle contraction :
A nerve impulse arriving at the neuromuscular junctions initiates the contractile response.
- A neurotransmitter released at the neuromuscular junction enters the sacromere through its membrane channel.
- The opening of the channel also results in the inflow of Na+ ions inside the sacromere and generates an action potential that travels along the entire length of the muscle fibres.
- The sacromere reticulum releases Ca++ ions, which bind with the specific sites present on the troponin component of the thin filament.
- Asa result of conformational changes in the troponin, the active sites on the F-actin are exposed.
- These are the active sites specific to myosin head, which exhibits myosin- dependent ATPase activity.
- The myosin heads acts as hooks and attach to F-actin to form cross bridges.
- When the muscle is stimulated to contract, the cross bridges move, pulling the two filaments past each other.
- When thousands of actin and myosin filaments interact this way the entire muscle cell shortens.