Final answer:
The synaptic knob, or axon terminal, of a neuron contacts another neuron at the synapse to transmit signals through neurotransmitters. The axon conducts electrical signals, and a bundle of axons in the peripheral nervous system is called a nerve.
Step-by-step explanation:
The part of a neuron that directly contacts another neuron at the synapse is the synaptic knob (also known as the axon terminal). At the synapse, the synaptic knob of the presynaptic neuron releases neurotransmitters that cross the synaptic cleft and bind to the receptors on the dendrites of the postsynaptic neuron, thereby transmitting the signal.
In terms of an electrical signal being transmitted to a target cell, it is the axon that conducts this signal. When the signal reaches the axon terminal, neurotransmitters are released into the synapse. In the peripheral nervous system, a bundle of axons is known as a nerve.