Free Support and Movement MCQs with Answers

1. The number of bones in the skeleton of a normal adult human is

• A. 200
• B. 206
• C. 213
• D. 306

Explanation: An adult has 206 bones, 80 in the axial skeleton and 126 in the appendicular skeleton. A newborn has roughly 300 separate bones, and the number falls as several of them fuse during growth, for example the ilium, ischium and pubis into one hip bone and the five sacral vertebrae into the sacrum. That fusion is why the infant figure is the standard distractor.

2. Which of the following bones belongs to the axial skeleton?

• A. Femur
• B. Clavicle
• C. Sternum
• D. Scapula

Explanation: The axial skeleton is the central supporting column: skull, vertebral column, ribs and sternum. The clavicle and scapula are tempting because they lie in the trunk, but they form the pectoral girdle, which attaches the arms and so belongs to the appendicular skeleton along with the femur and all other limb bones.

3. The number of cervical vertebrae in the human vertebral column is

• A. 5
• B. 12
• C. 4
• D. 7

Explanation: There are seven cervical vertebrae, and the number is seven in almost all mammals, including the giraffe, whose neck is long because each vertebra is long. The full adult column has 33 vertebrae in total: 7 cervical, 12 thoracic, 5 lumbar, 5 fused as the sacrum and 4 fused as the coccyx. Twelve is the thoracic count, which is the usual mix up.

4. The longest and strongest bone of the human body is the

• A. humerus
• B. tibia
• C. femur
• D. fibula

Explanation: The femur is the thigh bone, roughly a quarter of a person's height, and it carries the whole body weight during walking, so its shaft is built to resist very large compressive loads. The tibia is the next longest and also weight bearing, which makes it the closest distractor. The fibula lies beside the tibia but bears almost no weight and mainly gives muscle attachment.

5. Which type of muscle is striated but under involuntary control?

• A. Cardiac muscle
• B. Skeletal muscle
• C. Smooth muscle
• D. None of the three

Explanation: Cardiac muscle has the cross striations of skeletal muscle because it uses the same actin and myosin arrangement, but it contracts rhythmically on its own without conscious control and its fibres are branched and joined by intercalated discs. Skeletal muscle is striated and voluntary, and smooth muscle is involuntary but has no striations, so cardiac muscle is the only combination of both features.

6. The functional contractile unit of a myofibril is the

• A. myofilament
• B. sarcomere
• C. sarcolemma
• D. sarcoplasmic reticulum

Explanation: A sarcomere is the region between two Z lines, containing overlapping thick and thin filaments, and the whole muscle shortens because thousands of sarcomeres in series each shorten a little. A myofilament is a single actin or myosin strand, so it is a component rather than the unit. The sarcolemma is the cell membrane and the sarcoplasmic reticulum is the calcium store.

7. During the contraction of a skeletal muscle, which of the following does NOT change in length?

• A. I band
• B. H zone
• C. Sarcomere
• D. A band

Explanation: The A band is the full length of the thick myosin filaments, and since the filaments themselves do not shorten, the A band stays the same width throughout contraction. The I band and the H zone both narrow because the thin filaments are pulled inwards over the thick ones, and the sarcomere as a whole therefore shortens. This constant A band is the strongest single piece of evidence for the sliding filament model.

8. According to the sliding filament theory, a muscle shortens because

• A. actin filaments slide inwards over the myosin filaments
• B. both actin and myosin filaments themselves shorten
• C. the sarcomere is stretched by the load
• D. the Z lines dissolve and reform further apart

Explanation: Myosin heads bind actin, swivel, and drag the thin filaments towards the centre of the sarcomere, then detach and repeat, so the filaments overlap more without any of them changing length. The idea that the filaments contract is the older, wrong picture the theory replaced, and the unchanged A band disproves it. Each cycle of attachment and release needs one molecule of ATP.

9. Calcium ions start muscle contraction by binding to

• A. the myosin heads
• B. tropomyosin directly
• C. troponin, which moves tropomyosin off the binding sites on actin
• D. ATP, activating it

Explanation: In a relaxed fibre tropomyosin lies across the myosin binding sites of actin. Calcium released from the sarcoplasmic reticulum binds troponin, troponin changes shape and pulls tropomyosin aside, and only then can cross bridges form. Calcium therefore acts as the switch rather than as the energy source, and pumping it back into the reticulum is what causes relaxation.

10. Rigor mortis, the stiffening of muscles after death, occurs because

• A. calcium ions disappear from the sarcoplasm
• B. ATP is no longer available to detach the myosin heads from actin
• C. the muscle proteins are denatured by the fall in body temperature
• D. acetylcholine continues to be released at the neuromuscular junction

Explanation: ATP is needed not to form a cross bridge but to break one, so when respiration stops and ATP runs out the myosin heads stay locked on actin and the muscle cannot relax. Calcium in fact leaks out of the sarcoplasmic reticulum after death and floods the sarcoplasm, which is the opposite of the first option and is what allows the bridges to form in the first place.