Once Ca2+ binds to troponin what happens to allow muscle contraction?
Troponin tropomyosin moves to expose myosin binding sites on the actin filaments, myosin heads form cross-bridges with thin filaments and the sarcomere shortens
What type of fibers are found in the A band?
myosin and actin
What type of fibers are found in the H band?
Only myosin
What type of fibers are found in the I band?
Only actin
Where is the Z band?
In the middle of the I band
Describe the structure of myosin
fibrous protein molecules anchored at the M line of a sarcomere each containing globular heads which point away from the M line
Describe the structure of actin?
globular protein molecules linked to form a chain which wrap to form a helical shape; tropomyosin is twisted around the two chains and troponin is also present
Why are muscle fibers not usually referred to as cells?
they are multinucleate
What impact does the action potential have on the sarcoplasmic reticulum?
it opens calcium ion channels on the SR which causes calcium ions to floor the sarcoplasm.
What causes the conformational change in the troponin-tropomyosin complex
calcium ions attach to troponin
