Muscular System Flashcards
What gives skeletal muscle fibers a striated appearance?
Striations are repeating series of dark and light bands evident along the length of each myofibrils. Dark A band and light bands
What is a sarcomere?
Region of a myofibril between two successive z discs, smallest contractile unit of fiber
Identify proteins which make up thin filaments.
actin: polypeptide subunits of actin are called G actin to twine as F actin
troponin: binds as a blob on tropomyosin
tropomyosin: covers actin and its active site as a fiber
regulatory proteins are what?
troponin and tropomyosin
Describe actin structure.
G actin subunits make up intertwining F actin
Which protein covers active sites on actin filament in resting muscle fiber?
Tropomyosin
What are t-tubules and what is their function?
elongated tubes that protrude into muscle cell between I and A band, carries electrical impulses into muscle to help stimulate release of calcium from terminal cisterns
Calcium binds to which protein?
Troponin
What happens to A band, I band, H zone and Z disc during contraction?
A bands move closer together but doesn't change lengthen. I bands shorten. H zone disappears. Sarcomere shortens I bands (shorten), H zones (disappears), and sarcomeres (shorten)
What does calcium ions do sliding filaments mechanism?
Binds to troponin to cause troponin to change shape and pull tropomyosin off active site, allowing myosin head to bind to active site.
What is role of troponin and tropomyosin?
Troponin binds to calcium ions and change shape to pull tropomyosin off active site so myosin heads can bind to active site. Until there is enough calcium in sarcoplasm binding to troponin, active sites are covers and muscle fibers cannot contract.
Role of ATP and myosin head in contraction process?
Hydrolization of ATP energizes myosin head to cocked position to attach to active site and form cross bridge. This releases ADP and the phosphate so myosin heads can pivot and pull actin filament towards M line. New ATP attachment causes myosin head to detach from active site.
At what point during cross bridge cycling does ATP hydrolyze?
When ATP attached to
