How many tarsals are there in the tarsus?

Correct Answer: A

Rationale: The tarsus (ankle) contains 7 tarsal bones: talus, calcaneus, navicular, cuboid, and three cuneiforms (medial, intermediate, lateral), forming the foot’s proximal structure.

Correct Answer: B

Rationale: The appendicular skeleton includes the bones of the limbs and the girdles (pectoral and pelvic) that attach them to the axial skeleton. The femur, a long bone in the thigh, is part of the lower limb and thus belongs to the appendicular skeleton. The sternum (breastbone), occipital bone (skull), and vertebrae (vertebral column) are all components of the axial skeleton, making 'Femur' the correct choice.

Correct Answer: A

Rationale: The axial skeleton, including the skull, vertebral column, and rib cage, is designed to support and protect major organs. The rib cage shields the heart and lungs, the skull protects the brain, and the vertebral column encases the spinal cord. The appendicular skeleton focuses on movement, while irregular and long bones are types, not divisions, making 'Axial skeleton' the correct answer.

Correct Answer: C

Rationale: The neuromuscular junction is the specific site where a motor neuron’s axon terminal connects to a muscle fiber’s membrane. Here, acetylcholine is released to trigger contraction. The synaptic cleft is the gap within this junction, the axon terminal is part of the neuron, and the sarcomere is within the muscle, making 'Neuromuscular junction' the correct answer.

Correct Answer: A

Rationale: In the sliding filament theory, calcium ions trigger myosin binding to actin. Released from the sarcoplasmic reticulum, calcium binds to troponin, shifting tropomyosin to expose actin’s binding sites, allowing myosin heads to attach. Sodium and potassium regulate nerve signals, not this process, making 'Calcium ions' the correct answer.