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believed that a neuron was the only cell able to signal and communicate. As we can see by the confusing nature of the “planet” Pluto, it is difficult to unclassify the classified. Neuron comes from the Greek for sinew or tendon, and synapse is Greek for clasp, although they all sound like they were coined by an extraterrestrial techno group. The word tomato’s origins come from the Aztec dialect of Nahautl in central Mexico, but almost everybody, including the author, doesn’t know whether it should be called a fruit or a vegetable.
    Of course, things change over time, and that is why the terms “glia” and “neuron” are preferable to some uniform naming procedure that modern biology and astronomy try to force upon us. And really, who knows glia means “glue” anyway? Our brains like to create.
    In evolutionary biology, it is not completely understood why life started. It is believed that carbon excluded sodium in the ocean at some point, thus creating a cell. Energy was then required to maintain the electrical gradient created by electrolyte exclusion. Eventually cells aggregated with other cells and worked together for energy. Then plants and animals split, with animals evolving so some of the cells were sensory units that knew where to find the food. Then, more defined motor cellular units developed to help the animal move more efficiently to attain the food.
    Neurons are the cells that developed for sensory and motor function and have their roots in the evolutionary reflex to procreate and get food. The higher-level thoughts of imagination and creation could have evolved separately and maybe even before the neuron.
    The classical neuron, as described by Cajal, is actually best represented by the cell located in the cerebellum first discovered by Jan Purkinje (1787–1869). The Purkinje cells of this area located in the posterior base of the brain have amazing aesthetic structure. The dendrites look like an elaborate magnolia tree. The cell body is a perfect bulb like a teardrop. And the axons are so long, they extend out of the cerebellum into the pons, a structure next to the medulla at the base of the brain.
    However, many other types of neurons exist with different characteristics. Functionally, they are mainly classified based on what connections they make: sensory neurons, motor neurons, and interneurons. In the patellar reflex or “knee jerk” reflex described by Sherrington in the early twentieth century, the tap of the patellar tendon of the knee causes sensory firing to the spinal cord, and the connection of motor neurons there creates contractions in your quadriceps, which causes the leg to jerk. No one who was tapped on the knee would argue that they controlled the reflex with their thoughts.
    Because of this reflex, people who rashly respond to something without thinking are derogatorily told not to have a “knee-jerk” reaction and to think before they talk. Someone who punches another person in the face for being called a “sheep lover” is likely not thinking before acting and having a “knee-jerk” reaction. Similarly, if someone’s father says hehates the St. Louis Cardinals, and then his child says he hates the St. Louis Cardinals, too, the kid is probably not thinking about why he hates the St. Louis Cardinals (although this may be a reasonable sentiment) and just copying an authority figure. This is another “knee-jerk” reaction. These reactions are completely neuronal and an occurrence by which nothing happens between the sensory stimulus and motor output.
    Sensory neurons are stimulated by the receptors that correspond to our five senses. For instance, the sensory neurons in our tongue respond to different molecules and pH levels in food to tell us whether we taste something sweet, sour, salty, bitter, or one recently discovered by Japanese researchers in the last five years, umami, which is a savory, meat-like flavor.
    In our ears, minute hair cell receptors at the end of our