Myosin filaments (primary filaments)

Actinfilaments (secondary filaments)

1.

Found only in A-band of sarcomere.

1.

Found in both A and I-bands.

2.

Thicker (0.01 mm) but longer (4.5 mm) than actin filaments.

2.

Thinner (0.005 mm) but shorter (2-2.6 mm)

than myosin filaments.

3.

More molecular weight.

3.

Less, molecular weight.

4.

Cross bridges present, hence have rough

4.

Cross bridges absent, hence have smooth

surface.

surface.

5.

Fewer than actin filaments.

5.

More numerous than myosin filaments, six of

6.

Free at both the ends.

6.

them surround each myosin filament.

Free at one end and are joined to Z-line by other end.

7.

Consist of 2 proteins: myosin and meromysm.

7.

Consist of 3 proteins: actin, tropomyosin and troponin.

8.

Do not slide during muscle contraction.

8.

Slide into H-zone during muscle contraction.