PHYSIOLOGY
MUSCLE CONTRACTION
|
Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
|
|
|
Na+
|
|
|
Ca++
|
|
|
ATP
|
|
|
acetylcholine
|
Detailed explanation-1: -Troponin, which regulates the tropomyosin, is activated by calcium, which is kept at extremely low concentrations in the sarcoplasm. If present, calcium ions bind to troponin, causing conformational changes in troponin that allow tropomyosin to move away from the myosin-binding sites on actin.
Detailed explanation-2: -Troponin C has four Ca2+-binding sites, termed sites I, II, III, and VI from the N-terminus, each of which consists of a Ca2+-coordinating loop rich in acidic residues flanked with two -helical segments (E-F-hand motif).
Detailed explanation-3: -Troponin C (TnC; 18 kDa) is the calcium-binding component of the contractile apparatus and upon binding intracellular Ca2 + ions induces a conformational change in the troponin–tropomyosin complex, reducing TnI inhibition of the actinomysin ATPase and allowing muscle contraction to occur [18].