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Taste and Smell

Introduction Smell and taste are the two senses most closely connected. The two work together to deliver aromas and flavors to our brain to be processed and experienced. Although taste and smell are often underrated compared to sight and hearing, these senses are crucial to survival as they are linked to memory, emotion, and even reproduction processes. Stimuli The stimuli for both smell and taste are chemical substances. Substances can be smelled when chemicals enter the nasal passage. There are more than 40,000 different smells in the world, but they can be categorized into camphoric, musky, floral, pepperminty, etheral, pungent, and putrid.  Chemicals can be tasted when they are dissolved in fluid, like the saliva in the mouth. Taste is also divided into different categories and different parts of the tongue are more sensitive to certain types of taste: salty taste buds are found in the front of the tongue, sweet is in the front behind salty, sour taste buds are on both sides, and bitter is most sensitive at the very back of the tongue. Sensory Processing The process of smelling and tasting begins first when when molecules released by the substances around us stimulate special nerve cells found in the nose, mouth, or throat. These cells then transmit messages to the brain, where specific smells or tastes are identified. In order to smell something, volatile chemical substances enter the nose. The molecules stimulate olfactory receptors in the upper nasal passage. Neurons from the receptors group together to form the olfactory nerve, which travels to the olfactory bulb in the brain where the information is processed. In terms of tasting, the Gustatory or taste nerve cells are clustered in the taste buds of the mouth and throat. The chemicals are initially processed by some of the 10,000 taste buds that are located on the bumps of the tongue, known as papillae. The taste buds send information through sensory nerves to the thalamus and other areas of the cortex.These surface cells send taste information to nearby nerve fibers, which send messages to the brain. Thresholds Absolute thresholds are the minimal amount of energy needed to stimulate receptors. For smell, a human’s absolute threshold is one drop of perfume diffused into a three room apartment. For taste, a human’s absolute threshold is one teaspoon of sugar diffused into two gallons of water. Dogs have about two hundred and twenty million scent receptors in their nose while humans have only about five million scent receptors, demonstrating dogs have a much better sense of smell. For many animals, taste is described as being pleasant, unpleasant or neutral while humans have different thresholds for taste sensations that are sour, sweet, bitter and salty. Survival Smell and taste are vital for survival. Flavors and aromas often work together and according to scientists, “most of what we call flavor actually comes from the odors that reach nerves via nasal passages at the back of the throat.” Both of these senses are directly connected to certain brain areas that help control emotions, regulate food and water intake, and even form memories. Interestingly, your sense of smell is the sense most directly connected to your memory. For example, the smell of bad milk could remind you of a time you were sick after drinking similar milk in the past. During times of hunters and gatherers, this memory would be crucial to survival as humans encountered many dangerous substances in the wild. Reproduction is even linked to a sense of smell, because of pheromones. Pheromones are chemicals that are released from one’s body and that induce social attraction to another of the same species. This reaction is why humans are attracted to one another and somewhat explains the phrase “love at first sight.” This is key for survival of all species because it leads the species to reproduce and further their species for survival. Fun Facts There are many interesting facts about smelling and tasting. For example, for taste:
 * Insects have the most highly developed sense of taste. They have taste organs on their feet, antennae, and mouth parts.
 * In general, girls have more taste buds than boys.
 * <span style="background-color: transparent; color: #000000; font-family: Arial; font-size: 15px; text-decoration: none; vertical-align: baseline;">Additionally, taste is the weakest of the five senses.

<span style="background-color: transparent; color: #000000; font-family: Arial; font-size: 15px; text-decoration: none; vertical-align: baseline;">For smell:
 * <span style="background-color: transparent; color: #000000; font-family: Arial; font-size: 15px; text-decoration: none; vertical-align: baseline;">A woman’s sense of smell is keener than a man’s.
 * <span style="background-color: transparent; color: #000000; font-family: Arial; font-size: 15px; text-decoration: none; vertical-align: baseline;">People recall smells with a 65% accuracy after a year, while the visual recall of photos sinks to about 50% after only three months.
 * <span style="background-color: transparent; color: #000000; font-family: Arial; font-size: 15px; text-decoration: none; vertical-align: baseline;">Your sense of smell is least acute in the morning; our ability to perceive odors increases as the day wears on.