Sliding Filament Theory Flashcards
1
Q
Process
A
- Impulse arrives at neuromuscular junction
- Calcium ions are released from sacroplasmic reticulum
- Calcium ions attach to troponin on actin filament causing it to move.
- As a result tropomyosin on actin filament shifts exposing myosin binding sites.
- Myosin head on myosin filament attaches to myosin binding site on actin filament forming cross bridges.
- ADP and Pi are released from myosin head
- Causes myosin head to change shape and nod forward and causing attached actin filament to slide over myosin.
- ATP attaches to myosin head causing myosin head to detach from actin filament.
- ATPase in myosin head hydrolysed ATP to ADP and Pi causing myosin head to change shape and return to its upright position.
2
Q
What happens when a muscle relaxes?
A
The muscle is no longer stimulated by a nerve impulse.
- Calcium ions are actively pumped out of the muscle sacroplasm back into the sacroplasmic reticulum using ATP (form of active transport)
- Troponin and Tropomysoin move back to their original positions where Tropomysoin blocks the myosin binding sites.
- Actin filament slides over to their relaxed position and this lengthens the sacromere.
3
Q
What happens in the absence of ATP?
A
Cross bridges remain attached
Muscle is remains contracted
Calcium ions can not leave sacroplasm of muscle