Final answer:
The axon's neural impulse speed is increased with a myelin sheath, a lipid layer that allows nerve impulses to travel more rapidly and efficiently.
Step-by-step explanation:
The speed at which a neural impulse travels is increased when the axon is covered with a myelin sheath.
This myelin sheath acts like a layer of insulation, similar to the plastic that encases an electrical cord. It is a lipid layer produced by glial cells such as oligodendrocytes in the central nervous system (CNS) and Schwann cells in the peripheral nervous system (PNS). Myelination allows for the rapid transmission of nerve impulses down the axon by enabling the impulse to 'jump' across the regularly spaced gaps in the sheath known as nodes of Ranvier.
In the context of neural communication, synaptic vesicles are involved in storing neurotransmitters that are released into the synaptic cleft to transmit signals to another neuron. However, they do not affect the speed of impulse propagation along an axon. Dendrites receive signals, and neurotransmitters are the chemicals that transmit signals across synapses. Neither dendrites nor neurotransmitters play a role in the speed of impulse conduction along the axon.