Biology · Locomotion and Movement · NEET
Skeletal muscle (also called striated or voluntary muscle), smooth muscle (also called visceral or non-striated muscle), and cardiac muscle (the muscle of the heart). NCERT names them as Skeletal, Visceral and Cardiac. NEET often tests these three names in order, so learn them exactly.
Striation (the stripe pattern) comes from the ordered arrangement of actin and myosin. Voluntary control is a separate thing: it depends on whether the brain controls the muscle by will. Cardiac muscle has striations but the nervous system does not control it directly, so it is striated AND involuntary. This mix confuses many students, so remember: striation is about looks, voluntary is about control.
Only cardiac muscle has intercalated discs. These are special junctions between branched cardiac cells that let them communicate and contract together as one unit. Smooth and skeletal muscle do NOT have intercalated discs. NEET has directly asked which statement wrongly links smooth muscle with intercalated discs, so this is a high-value fact.
Smooth (visceral) muscles are involuntary. You cannot control them by will. They are found in the inner walls of hollow organs like the stomach, intestine and blood vessels, and they work automatically to move food, blood and other contents. They are also non-striated (no stripes) and spindle-shaped.
Under a microscope skeletal muscle shows alternate dark and light bands, giving a striped or striated look. These bands come from the pattern of two proteins, actin (light I-band) and myosin (dark A-band). Because these stripes are so clear, skeletal muscle is also called striated muscle. It is attached to skeletal bones, is voluntary, and its fibres are long, cylindrical and multinucleate.
Look at three things: shape, striations, and nuclei. Skeletal = long cylindrical fibres, striped, many nuclei at the edge (peripheral). Smooth = spindle-shaped (tapering) cells, no stripes, one central nucleus. Cardiac = branched fibres joined by intercalated discs, faintly striped, central nucleus. NEET 2024 gave exactly this microscope-based identification question.
Three types of muscle tissue are shown as (a), (b) and (c): (a) Long, parallel, cylindrical striated fibres with peripheral nuclei; (b) Spindle-shaped (fusiform) non-striated cells with a single central nucleus; (c) Striated, branched fibres joined end-to-end with central nuclei. Identify the correct matching pair along with their location in the human body.
Smooth muscles are:
Which of the following statements wrongly represents the nature of smooth muscle?
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Skeletal muscle is attached to skeletal bones (e.g. biceps, triceps of the limbs). Smooth muscle is in the inner walls of hollow visceral organs such as the stomach, intestine, urinary bladder and blood vessels. Cardiac muscle is found only in the wall of the heart.
Skeletal and cardiac muscle are striated (they show bands under a microscope). Smooth muscle is non-striated. So two of the three types have stripes, but only skeletal muscle is both striated and voluntary.
Cardiac muscle is highly resistant to fatigue because it works continuously throughout life without rest. Skeletal muscle can fatigue after heavy use due to lactic acid build-up. This fatigue contrast is a common NEET link between muscle types and the topic of muscle fatigue.
Skeletal muscle fibre is multinucleate (syncytium) with many nuclei placed at the edge (peripheral). Smooth muscle cell has a single central nucleus. Cardiac muscle fibre typically has a central nucleus. Nucleus position and number are quick clues in diagram-based questions.
Cardiac muscle is branched, with fibres joined end-to-end by intercalated discs. Skeletal muscle fibres are long and unbranched (cylindrical). Smooth muscle cells are unbranched and spindle-shaped. Branching plus intercalated discs is unique to cardiac muscle.
