Final answer:
The neuron is surrounded by a cell membrane which serves as a protective barrier for the cell. Myelin sheath provides insulation for the axon, not the entire cell, and a synapse is the junction for neuronal communication.
Step-by-step explanation:
The neuron, like all cells in the body, is surrounded by a cell membrane. The cell membrane is a fundamental component of all cells that acts as a barrier, controlling the entry and exit of substances, and maintaining the cell's integrity.
While the myelin sheath is associated with neurons, it is an insulating layer that surrounds the axon, enabling efficient transmission of nerve impulses. It is produced by glial cells, such as oligodendrocytes in the central nervous system or Schwann cells in the peripheral nervous system.
The axon itself is a long extension that conducts electrical signals away from the neuron's cell body to other cells, but it is not the surrounding structure. Lastly, a synapse is a junction between two neurons where neurotransmitters are released and received, facilitating communication between neurons, not the surrounding structure of a neuron.