What is the neurotransmitter responsible for transmitting signals from motor neurons to muscle fibers at the neuromuscular junction?

Correct Answer: B

Rationale: At the neuromuscular junction, motor neurons release acetylcholine (ACh) into the synaptic cleft to stimulate muscle fiber contraction. ACh binds to receptors on the muscle cell membrane, triggering an action potential that leads to contraction. Dopamine, serotonin, and GABA are neurotransmitters involved in other neural functions, not muscle contraction, making 'Acetylcholine (ACh)' the correct answer.

Correct Answer: B

Rationale: The appendicular skeleton, including limbs and girdles, is designed for movement and locomotion. Bones like the femur and humerus enable walking and arm motion, supported by the pelvic and pectoral girdles. Protection of organs is an axial skeleton role, making 'Facilitating movement and locomotion' the correct answer.

Correct Answer: C

Rationale: Acetylcholine (ACh) is released by the motor neuron at the neuromuscular junction, crossing the synaptic cleft to bind to muscle fiber receptors, triggering an action potential for contraction. It does not inhibit, relay sensory data, or degrade fibers, making 'Transmitting signals from the motor neuron to the muscle fiber' the correct answer.

Correct Answer: A

Rationale: Creatine phosphate stores high-energy phosphate bonds in muscle cells. During contraction, it transfers its phosphate to ADP, regenerating ATP to power myosin heads. Glycogen is a glucose store, myoglobin holds oxygen, and lactic acid is a byproduct, making 'Creatine phosphate' the correct answer.

Correct Answer: D

Rationale: The ribs, part of the axial skeleton’s thoracic cage, primarily protect thoracic organs like the heart and lungs by forming a bony enclosure. They don’t support lower limbs, protect the spinal cord (vertebral column’s role), or aid digestion, making 'Protecting the thoracic organs' correct.