Which of the following represents site of reversal of polarity of myosin molecules in thick muscle filaments?: (A) M line, (B) Z line, (C) I line, (D) H line
Answer is A. The M line is the site of the reversal of polarity of the myosin molecules in each of the thick filaments. At these points, there are slender cross-connections that hold the thick filaments in proper array.