Striated muscles are voluntary muscles with alternate light and dark bands, mostly attached to the bones of the skeleton.
Important points
- Also known as skeletal muscles.
- Muscle fibres are cylindrical and unbranched.
- The fibres of skeletal muscles are arranged in bundles.
- Alternate light and dark bands called striations are present.
- Fibres are multinucleate.
- Contractions are fast.
- Striated muscles are voluntary.
- Striated muscles get fatigued.
- Location – most skeletal muscles are attached to the skeleton, except the diaphragm and tongue muscles.
The striations come from the arrangement of two proteins: the dark A band (anisotropic) contains myosin, and the light I band (isotropic) contains actin. The unit between two Z lines is called a sarcomere, the functional unit of contraction. NCERT’s example of skeletal muscle is the biceps.
Smooth, skeletal and cardiac muscles
Skeletal (striated) muscles are one of the three types of muscles, along with smooth muscles and cardiac muscles.
| Feature | Smooth | Skeletal | Cardiac |
|---|---|---|---|
| Shape of fibres | Spindle-shaped | Long, cylindrical | Cylindrical, branched |
| Striations | Absent | Present | Present |
| Nuclei | One, central | Many, peripheral | One or two, central |
| Control | Involuntary | Voluntary | Involuntary |
| Fatigue | Does not fatigue | Fatigues quickly | Does not fatigue |
| Location | Walls of gut, blood vessels, urinary bladder | Attached to bones | Heart wall |
Skeletal muscle fibres are multinucleate because each fibre forms by the fusion of many cells, so it is a syncytium. Both skeletal and cardiac muscles are striated, but only skeletal muscle is voluntary.