People didn't always think of neurons as discrete units that communicated with each other via chemical and electrical signals. In 1873, Camillo Golgi, the creator of the silver staining technique now called the Golgi Stain, had a separate notion of the nervous system. He believed that the reticular theory was the correct way to understand the nervous system. The reticular theory stated that the nervous system was one continuous network, not a collection of individual cells. However, one of Golgi's colleague's, Ramon y Cajal, didn't accept this theory and worked to provide a more accurate picture of the nervous system.
Cajal's work illustrated that the nervous system, like the other parts of the body, was actually made up of cells and his neuro-anatomical drawings later supported the neuron doctrine which postulated that the nervous system was composed of discrete units. Today, we have much more information on the structure of neurons as well as how they communicate with each other.
An action potential propagates down the axons of a presynaptic neuron, triggering release of presynaptic vesicles filled with neurotransmitter into the synaptic cleft. Neurotransmitters bind to receptors on the postsynaptic cell, causing ions to flood into the cell, transmitting electrical information that can then propagate down that neuron!
This illustration from Khan Academy provides a great overview of how we currently believe synapses and neuron communication function. Different neurotransmitters are released from different neurons and subsequently have different effects. In this schematic, neurotransmitters from the presynaptic cell (the cell on top) causes a depolarization in the postsynaptic cell (the cell on the bottom).
Neuron communication is crucial to signal transduction all over the body. Our next blog post will explain neuronal communication and acetylcholine neurotransmitter at the neuromuscular junction!