Is there an interosseous membrane between tibia and fibula?

Correct Answer: A

Rationale: Yes, an interosseous membrane connects the tibia and fibula along their lengths, similar to the forearm, providing stability and a surface for muscle attachment.

Correct Answer: B

Rationale: Long bones (e.g., femur, humerus) have a hollow shaft (diaphysis) and expanded ends (epiphyses), designed for weight-bearing and movement in the limbs. Flat bones (e.g., sternum) are thin, short bones (e.g., carpals) are cuboidal, and irregular bones (e.g., vertebrae) have complex shapes.

Correct Answer: C

Rationale: The axial skeleton, comprising the skull, vertebral column, and rib cage, primarily serves to protect vital organs. The skull safeguards the brain, the vertebral column shields the spinal cord, and the rib cage encases the heart and lungs. While it does provide some support and attachment for muscles, its defining role is protection, distinguishing it from the appendicular skeleton, which is more involved in locomotion. Thus, 'Protecting vital organs' is the most accurate answer.

Correct Answer: C

Rationale: The neuromuscular junction is the specialized synapse where a motor neuron communicates with a skeletal muscle fiber. The motor neuron releases acetylcholine to stimulate the muscle fiber, initiating contraction. It does not involve muscle-to-muscle, muscle-to-tendon, or bone-to-bone connections, making 'A motor neuron and a muscle fiber' the correct answer.

Correct Answer: A

Rationale: In the sarcomere, myosin heads bind to actin filaments during contraction, as per the sliding filament theory. This interaction pulls actin toward the sarcomere center, shortening it. Troponin and tropomyosin regulate access to actin’s binding sites, while collagen is not involved, making 'Actin' the correct answer.