Skeletal muscle Flashcards
What type of filament is present in the A band?
Thick filaments are present here.
Contain myosin.
How many polypeptide chains does myosin have and how many are light vs heavy?
Myosin has six polypeptide chains including…
One pair of heavy chains
Two pairs of light chains
How many heads does each myosin moldecule have?
Each has two heads attached to a single tail.
The heads bind ATP and actin and are involved in the cross bridge cycle.
Where are thin filaments anchored?
The Z lines
Which band can thin filaments be predominantly found?
The I bands.
Although they do interdigitate with the thick filaments of the A band.
Which fibers are found in the thin filaments?
Actin
Tropomysin
Troponin
Which band contains both thick and thin filaments?
A band
What does Troponin T do?
attaches the troponin complex to tropomyosin.
What does Tropinin I do?
Inhibits the interaction of actin and myosin
What does Troponin C do?
Binds calcium to permit the binding of actin and myosin.
The cellular T tubules can be found at the junction between which two structures?
Found between A bands and I bands.
What is the dihydropyridine receptor?
This is a voltage sensative receptor found in the T tubules.
When triggered by depolarization it allows for the release of calcium throuh the terminal cisternae/ ryanodine receptor.
What does ATP do when attached to the myosin?
ATP removes the myosin head from the actin filament.
When ATP is hydrolyzed it moves to the plus end and myosin remains bound to actin until ADP is changed to ATP again.
What is the role of the SR Ca2+ ATPase “SERCA”?
Reaccumulates calcium back into the sarcoplasmic retculum.
This decreases cytosolic calcium levels relaxing the muscle.
What is passive muscle tension?
Tension developed in the muscle by stretching it to different lengths.
There is no contraction occurring here.
