Muscle questions in general science are short and fixed — which muscle is the largest, which type is voluntary, what causes cramps, which proteins do the work. None of it changes. This post covers the three types of muscle, the named muscles exams ask about, how muscles actually move a bone, and the terms and conditions that come with them, followed by 15 previous year questions.
Key Points (Quick Revision)
- Three types — skeletal (voluntary), smooth (involuntary) and cardiac
- Gluteus maximus is the largest muscle; stapedius in the ear is the smallest
- Cardiac muscle is striated but involuntary — the exception that questions target
- Muscles work in antagonistic pairs: biceps contracts while triceps relaxes
- Actin and myosin are the contractile proteins; lactic acid causes muscle fatigue
1. The three types of muscle
| Type | Control | Appearance | Where |
|---|---|---|---|
| Skeletal or striated | Voluntary | Striated, with light and dark bands | Attached to bones — limbs, trunk, face |
| Smooth or unstriated | Involuntary | Not striated, spindle-shaped | Stomach, intestine, blood vessels, urinary bladder |
| Cardiac | Involuntary | Striated, branched, with intercalated discs | Only in the heart |
Cardiac muscle is the exception that nearly every paper tests. It looks striated like skeletal muscle but is involuntary like smooth muscle, and it exists nowhere except the heart. A question asking which muscle is striated yet involuntary has exactly one answer.
The other regularly asked distinction is fatigue. Skeletal muscle tires; cardiac muscle does not fatigue, which is why the heart beats continuously through life. Smooth muscle contracts slowly and can sustain contraction for long periods, which is what movement of food through the gut requires.
That gut movement has its own name, asked directly: peristalsis, the wave-like contraction of smooth muscle that pushes food along the alimentary canal.
2. Named muscles and superlatives
| Description | Muscle |
|---|---|
| Largest muscle in the body | Gluteus maximus, in the buttock |
| Smallest muscle in the body | Stapedius, in the middle ear |
| Strongest muscle by force for its size | Masseter, the jaw muscle used in chewing |
| Longest muscle | Sartorius, running across the thigh |
| Busiest muscles | The eye muscles, which move constantly |
| Main muscle of breathing | Diaphragm, a sheet of muscle below the lungs |
| Approximate number of muscles | Over 600 in the human body |
Gluteus maximus and stapedius are the pair asked most, as largest and smallest. Note that the smallest muscle and the smallest bone are both in the middle ear — stapedius is the muscle, stapes is the bone — and papers use one as a distractor for the other.
The diaphragm earns its place twice, since it is asked in the respiratory system as well: its contraction increases the volume of the chest cavity and draws air in.
3. How a muscle moves a bone
Muscles can only pull, never push. That single fact explains why they are arranged the way they are, and it is asked directly.
Because a muscle cannot push a bone back, muscles work in antagonistic pairs — one contracts while the other relaxes, and to reverse the movement the roles swap.
| Movement | Muscle that contracts | Muscle that relaxes |
|---|---|---|
| Bending the elbow | Biceps | Triceps |
| Straightening the elbow | Triceps | Biceps |
| Bending the knee | Hamstrings | Quadriceps |
| Straightening the knee | Quadriceps | Hamstrings |
Biceps and triceps at the elbow is the example every paper uses. The muscle that produces the movement is called the agonist or prime mover, and the one that relaxes is the antagonist.
Muscles are attached to bones by tendons, which are tough and inelastic so that the pull transfers fully to the bone. Ligaments, by contrast, join bone to bone. That pair is swapped in options constantly.
4. Muscle physiology and common conditions
| Term | What it means |
|---|---|
| Actin and myosin | The two contractile proteins; myosin filaments slide over actin to shorten the muscle |
| Sarcomere | The functional contracting unit of a muscle fibre |
| Lactic acid | Builds up during vigorous exercise when oxygen is short, causing muscle fatigue and cramps |
| Anaerobic respiration | Respiration without oxygen in muscle, producing lactic acid |
| Rigor mortis | Stiffening of muscles after death, as the chemical needed for relaxation runs out |
| Myoglobin | The oxygen-storing pigment that gives muscle its red colour |
| Tetanus | Sustained contraction; also the name of the bacterial disease causing muscle spasm |
| Muscular dystrophy | A group of inherited disorders causing progressive muscle weakening |
Lactic acid causing cramps is the single most asked item in this section, and it links to the respiration chapter: when oxygen cannot reach the muscle fast enough during hard exercise, glucose is broken down anaerobically and lactic acid accumulates.
Actin and myosin are asked as a pair, and the mechanism is described as the sliding filament theory — the filaments do not shorten themselves, they slide past one another.
5. Previous year questions
- How many types of muscle are there in the human body? — Three
- Which muscles are voluntary? — Skeletal or striated muscles
- Which muscle is striated but involuntary? — Cardiac muscle
- Where is cardiac muscle found? — Only in the heart
- Which is the largest muscle in the human body? — Gluteus maximus
- Which is the smallest muscle in the human body? — Stapedius
- Which muscle is the main muscle of breathing? — Diaphragm
- Muscles are attached to bones by what? — Tendons
- Which muscle contracts when the elbow is bent? — Biceps
- Muscles working in opposite pairs are called what? — Antagonistic muscles
- Which acid causes muscle fatigue and cramps? — Lactic acid
- Which two proteins are responsible for muscle contraction? — Actin and myosin
- Stiffening of muscles after death is called what? — Rigor mortis
- Which pigment gives muscle its red colour? — Myoglobin
- Wave-like contraction that moves food along the gut is called what? — Peristalsis
6. How to revise this topic
Start with the three-type table, because most questions come from it. For each type fix three things — voluntary or involuntary, striated or not, and where it is found. Once cardiac muscle is clear as the striated-but-involuntary exception, the rest follows.
Then learn the superlatives as pairs: gluteus maximus and stapedius for largest and smallest, and note that stapedius is a muscle while stapes is a bone, both in the middle ear. That pair is a favourite distractor.
Finally keep four physiology facts on their own card — actin and myosin, lactic acid, rigor mortis and myoglobin. Together with the biceps and triceps example, they cover almost everything asked beyond classification.
7. Frequently Asked Questions
Which muscle is striated but involuntary?
Cardiac muscle, found only in the heart. It looks striated like skeletal muscle but is not under conscious control, and unlike skeletal muscle it does not fatigue, which is why the heart beats continuously.
Which is the largest and which is the smallest muscle?
Gluteus maximus in the buttock is the largest, and stapedius in the middle ear is the smallest. Note that stapedius is a muscle while stapes is a bone, and papers use one as a distractor for the other.
What causes muscle cramps after exercise?
Lactic acid. During vigorous exercise oxygen cannot reach the muscle fast enough, so glucose is broken down anaerobically and lactic acid accumulates, causing fatigue and cramps.
Why do muscles work in pairs?
Because a muscle can only pull, never push. To reverse a movement a second muscle must pull the bone back, so they are arranged as antagonistic pairs such as the biceps and triceps at the elbow.
What is the difference between a tendon and a ligament?
A tendon attaches muscle to bone and transmits the pull of the muscle. A ligament joins bone to bone and stabilises a joint. The two are swapped in options constantly.
For more General Science topics in simple language, see our Human Skeletal System and Human Body Systems posts, or browse the General Science section. Preparing for a specific exam? Start with the SSC CGL guide or join the 100 Hour GS Course.