Muscle Contraction Flashcards
What is creatine phosphate?
A compound in muscle that acts as a store of phosphates and can supply phosphates to make ATP rapidly.
What are the two types of filament contained in a myofibril?
Thin and thick filaments.
Describe the thin filaments.
They are aligned to make up the light band. They are held together by the Z line.
Describe the thick filaments.
They make up the dark band.
What is the name of the zone where there is no overlap
The H zone.
What is the distance between two Z lines called?
A sarcomere.
What is the name of the thin filaments?
Actin
Describe the structure of the thin filaments.
Two chains of actin subunits twisted around each other. Wound around the actin is a molecule of tropomyosin to which are attached globular molecules of troponin.
Describe the structure of each troponin complex.
Each troponin complex consists of three polypeptides: one binds to actin, one to tropomyosin and the third binds to calcium when it is available.
Describe the structure of thick filaments.
Each filaments consists of a bundle of myosin molecules. Each myosin molecule has two protruding heads, which stick out at each end of the molecule. These heads are mobile and can bind to the actin when the binding sites are exposed.
What is the sliding filament hypothesis?
During contraction the light band and the H zone get shorter. Therefore, the Z lines move closer together and the sarcomere gets shorter. During contraction the thick and thin filaments slide past each other.
What happens when the muscle is stimulated?
The action potential passes along the sarcolemma and down the transverse tubules into the muscle fibre.
Where is the action potential carried to?
The sarcoplasmic reticulum, which stores calcium ions and causes the release of calcium ions into the sarcoplasm.
What does the calcium ion do?
Binds to the troponin, which alters the shape pulling the tropomyosin aside. This exposes the binding sites on the actin.
What happens once the myosin heads bind to the actin?
The myosin heads move, pulling the actin filament past the myosin filament. The myosin heads detach from the actin and can bind again further up the actin filament.
