Which type of bone is characterized by its cylindrical shape and is found in the limbs?

Correct Answer: B

Rationale: Long bones are characterized by a cylindrical shape, with a shaft (diaphysis) and ends (epiphyses), and are primarily found in the limbs (e.g., femur, humerus). Short bones are cube-shaped (e.g., carpals), irregular bones have complex shapes (e.g., vertebrae), and flat bones are broad and thin (e.g., scapula), making 'Long bone' the correct answer.

Correct Answer: B

Rationale: In a relaxed muscle, tropomyosin covers the myosin-binding sites on actin filaments, preventing contraction. When calcium binds to troponin, it moves tropomyosin, exposing the sites for myosin attachment. Troponin regulates, myosin contracts, and collagen is structural, making 'Tropomyosin' the correct answer.

Correct Answer: B

Rationale: The metacarpal bones, found in the hand, are part of the appendicular skeleton, which includes the limbs and girdles. They are long bones but belong to the appendicular division, not axial (skull, spine, ribs). 'Long bones' is a type, not a division, making 'Appendicular skeleton' correct.

Correct Answer: C

Rationale: The humerus, an upper arm bone in the appendicular skeleton, facilitates arm movement by articulating with the scapula and forearm bones (radius, ulna). It doesn’t protect the heart (rib cage’s role) or support lower limbs, making 'Facilitating arm movement' the correct answer.

Correct Answer: B

Rationale: At the neuromuscular junction, the motor neuron releases acetylcholine into the synaptic cleft, stimulating the muscle fiber to contract. Calcium is stored in the sarcoplasmic reticulum, ATP is produced in mitochondria, and muscle fibers contract, not neurons, making 'Release acetylcholine' correct.