Final answer:
The neuromuscular junction (NMJ) can only transmit impulses in one direction, from the neuron to the muscle, initiated by the release of acetylcholine which triggers muscle fiber contraction.
Step-by-step explanation:
The anatomical component of the neuromuscular system that can only transmit impulses in one direction is the neuromuscular junction (NMJ). The NMJ is where the axon of a motor neuron communicates with a muscle fiber, and this junction ensures that action potentials are transmitted only from the neuron to the muscle, not in reverse. This one-way communication is facilitated by the release of acetylcholine from the synaptic end bulbs of the motor neurons, which binds to receptors on the muscle fiber's sarcolemma. Ligand-gated ion channels then open, allowing cations to move across the sarcolemma, depolarizing it and initiating muscle contraction. The process of muscle contraction is dependent on the frequency of motor neuron impulses, which influences the strength and number of fibers contracting.