What does the sliding filament model describe?
The sliding filament model describes how during contraction, the two ends of a sarcomere come closer, and the thin filaments slide past the thick ones, so actin and myosin overlap.
What is ATP?
Adenosine triphosphate; the source of energy for use and storage at the cellular level.
What are tropomyosin and troponin? What do they do?
Proteins wrapped around actin. They prevent myosin from bonding with actin until calcium is introduced, causing them to bind to the calcium and change shape.
What is calcium released by?
Action potential nerve signals which go to the T-tubule.
What does the calcium do?
Binds with and lifts the troponin, moving the tropomyosin out of the way.
What does myosin and ATP do?
Myosin binds with ATP, which it converts to ADP and phosphate.
How does myosin attach to actin?
Myosin converts ATP to ADP/phosphate, causing myosin to enter a stretched position. It then releases the stored energy and attaches to actin, sliding the actin strand which contracts the muscle.
What causes muscle contraction?
The myosin in the sarcomere attaching to actin and sliding the filament.
What are actin and myosin?
Filaments.
What is the structure that holds calcium ions?
Sarcoplasmic reticulum.
What is released from nerve endings? What does it do?
Acetylcholine. This binds to acetycholine receptors when triggered by an action potential nerve signal, causing sodium channels to open.
What does the sarcoplasmic reticulum do?
It stores calcium ions and releases them to the T-tubules.
What do T-tubules contain?
Numerous (sodium) ion channels and acetycholine receptors.
Once the muscle relaxes, what happens to the sliding filament model?
Calcium is grabbed by calcium pumps and returned to the sarcoplasmic reticulum where it is stored for later use. The troponin and tropomyosin unbind with calcium and return to their original shape, surrounding the actin again.
What are sarcomeres divided into?
Two myofilaments called myosin and actin.
What are the threads that form your muscle fibres? What are they divided into?
Myofibrils which are divided lenghtways into segments called sarcomeres.
What produces ATP?
The mitochondria in your muscles.
What are sarcomeres separated by?
A Z-line, which is a repeating pattern of overlapping filaments, giving skeletal and cardiac muscles their striated appearance.