Biology · Structural Organisation in Animals · NEET
| Striations | Skeletal & Cardiac: present (striated) | Smooth: absent (non-striated) |
| Control | Skeletal: voluntary | Smooth & Cardiac: involuntary |
| Shape | Skeletal: long cylindrical; Cardiac: branched | Smooth: spindle-shaped (fusiform) |
| Nuclei | Skeletal: many (multinucleate); Cardiac: usually one, central | Smooth: single, central |
| Intercalated discs | Cardiac: present | Skeletal & Smooth: absent |
| Location | Skeletal: attached to bones; Cardiac: heart only | Smooth: walls of internal organs, blood vessels |
Cardiac muscle IS striated. Students confuse it because it is involuntary, and they wrongly link 'involuntary' with 'non-striated'. NCERT clearly states cardiac muscles are striated but involuntary and branched. So striation and voluntary control are separate criteria: skeletal = striated + voluntary; cardiac = striated + involuntary; smooth = non-striated + involuntary.
Only cardiac muscle has intercalated discs. These are special junctions where branched cardiac cells join, allowing fast communication so the heart contracts as one unit. This is a top NTA trap: intercalated discs are NOT found in smooth muscle. NEET 2021 tested exactly this.
Smooth (visceral) muscles are involuntary. The nervous system does not control them by your will. They line the walls of internal hollow organs like the stomach, intestine, blood vessels and bladder, where they work automatically.
Because voluntary control depends on nervous control, not on striations. NCERT says the nervous system does not directly control cardiac activity; the heart beats on its own through nodal tissue (myogenic). So even though it looks striped like skeletal muscle, you cannot control your heartbeat by will, making it involuntary.
A skeletal muscle fibre is multinucleate (many nuclei) because it is a syncytium, its sarcoplasm contains many nuclei placed at the periphery. In contrast, a smooth muscle cell has a single central nucleus, and cardiac muscle cells are usually uninucleate with central nuclei.
Skeletal fibres are long, unbranched and cylindrical. Smooth muscle cells are spindle-shaped (fusiform), tapering at both ends. Cardiac fibres are branched (Y-shaped) and joined by intercalated discs. Shape is a quick way to identify a muscle from a diagram in image-based NEET questions.
Smooth muscles are
Which of the following statements wrongly represents the nature of smooth muscle? (a) Communication among the cells is performed by intercalated discs (b) These muscles are present in the wall of blood vessels (c) These muscles have no striations (d) They are involuntary muscles
Three types of muscles are given as a, b and c. Identify the correct matching pair along with their location in the human body.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Skeletal (striated) muscle, smooth (visceral, non-striated) muscle and cardiac muscle. All three arise from the mesoderm and share the properties excitability, contractility, extensibility and elasticity.
Cardiac muscle. It is striated in appearance, branched in structure, joined by intercalated discs and involuntary because the nervous system does not control it directly.
In the walls of internal hollow organs, the alimentary canal (stomach, intestine), blood vessels, urinary bladder, uterus (myometrium) and reproductive tracts. It is involuntary and non-striated.
About 40 to 50 per cent of the body weight of a human adult is contributed by muscles, according to NCERT. Muscle is a specialised tissue of mesodermal origin.
NEET repeatedly asks match-the-type-with-location and identify-from-diagram questions (2016, 2021, 2024). Confusing striation with voluntary control, or attaching intercalated discs to smooth muscle, are the common ways students lose easy marks here.
