Fill it he blanks with the suitable words
The thick filaments in the 'A' band are also held together in the middle of this and by a thin fibrous membrane called (a)_____. The 'A' and 'I' bands are arranged alternately throughout the length of the (b)____. The portion of the myofibril between two successive 'Z' lines is considered as the functional unit of contraction and is called a (c)_____.