What neurotransmitter is released into the synaptic cleft at the neuromuscular junction to stimulate muscle contraction?

Correct Answer: C

Rationale: Acetylcholine (ACh) is the neurotransmitter released by motor neurons into the synaptic cleft at the neuromuscular junction. It binds to receptors on the muscle fiber, initiating an action potential that leads to contraction. Serotonin, GABA, and dopamine have other neural roles, making 'Acetylcholine (ACh)' 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.

Correct Answer: A

Rationale: A joint, or articulation, is the anatomical location where two bones connect, allowing for stability or movement (e.g., knee, shoulder). Tendons connect muscles to bones, ligaments connect bones to other bones, and muscles move bones but aren’t the meeting point, making 'joint' the correct answer.