Which structure of the nervous system carries action potential in the direction of a synapse?

The cell body, or soma, contains the nucleus and organelles of the neuron but does not conduct action potentials. Instead, it integrates incoming signals from the dendrites and generates action potentials that are then transmitted down the axon. Thus, it is not involved in directly carrying the action potential toward the synapse.

A neuron is a complete nerve cell that includes the cell body, axon, and dendrites. While it is the overall structure that transmits signals, the term "neuron" does not specify the part responsible for carrying action potentials toward the synapse. Therefore, it is too broad to be the correct answer.

Myelin is a fatty substance that insulates the axon, enhancing the speed of action potential conduction. However, myelin itself does not carry action potentials; it merely supports the axon in this function. Thus, while it plays a crucial role in the process, it is not the structure that directly carries action potentials.