Taste+and+Smell+P1+Paige,+James,+Helga

media type="custom" key="11771980" Final Script

Paige: Hi everyone! Today you will be learning about smell and taste and how they are closely connected, sending messages to the brain. Helga will now tell you all about the stimuli for smell and taste.

Helga: The stimuli for smell and taste are chemical substances. The substances are suspended in the air at high concentrations that enter the body at the nose. There is different stimuli for each taste: sweet, salty, sour, and bitter. Sour taste is caused by acid, a hydrogen ion concentration; salty taste is caused by ionized salts, mainly a sodium ion concentration; sweet taste is caused by sugars, alcohols and other chemicals and bitter taste is caused by long chains of organic substances.

Paige: That’s very interesting Helga. Our sense of smell is known as the olfactory system, which is brought together by specialized sensory cells in the nasal cavity. In the olfactory system, olfactory bulbs are located in the bottom-side area of the brain involved in the perception of odors, known as olfaction. When the chemicals that are floating in air enter the nasal passage, the olfactory bulb is activated and sends smell information from the nose to the brain. The smell information is sent to the hippocampus. The hippocampus is the area in your brain that accesses memory and emotions, therefore, people sometimes experience memories when they smell certain odors. Smell information is also sent to areas in the brain such as, the amygdala, neocortex, and hippocampus, where top-down information is recieved.

Our sense of taste is known as the gustatory system that allows humans to sense the difference between safe and harmful food. There are five different taste receptors: bitter, sour, salty, sweet, and savory. These tastes are sensed by specialized receptors in the mouth known as taste buds. For each different taste receptor, there is a way of sensory transduction that detects substances in the mouth. Salt is the simplest receptor found in the mouth, where an ion channel in the taste cell wall allows sodium ions to flood the cell, leading to neurotransmitter release. Sour taste signals the presence of acidic compounds in the mouth. There are three different receptor proteins that work in the mouth to transmit signals to the brain. Bitter taste is a very important part of survival because ingesting a bitter compound may lead to injury or death. When bitter compounds activate G protein-coupled receptors, gustducin is released. Sweet taste also involves G protein-coupled receptors, where they are activated and gustducin is released. Savory taste acts similar to bitter and sweet receptors because the G-protein is activated and neurotransmitters are released.

Helga: The sensation of flavor is actually a combination of sense and smell. 75% of what we perceive as taste actually comes from our sense of smell. Smell is our most primal sense. Animals need the sense of smell to survive, because it helps them find food. For humans, the sense of smell communicates many of the pleasures in life, but it can also signal danger, fear, or dread.

Paige: Thanks, Helga! James will now discuss absolute thresholds

James: Humans have an absolute threshold containing the ability to smell 1 drop of perfume in a 3 room apartment. there are studies that have shown that dogs can smell certain concentrations of chemicals up to 100 times less than humans can. There are some cases where dogs have the advantage up to a million times more than humans can. some dogs in the police force smell things way beyond the human absolute threshold like concealed narcotics and currency. The threshold for humans sense of taste is 1 teaspoon of sugar diffused in 2 gallons of water. Not only can we taste compounds at extremely low levels, we can also identify between compounds that are very related. For some molecules, we can distinguish between stereoisomers, molecules that are made of the same atoms, but are mirror images of eachother. For example, The artificial sweetener aspartame tastes sweet, but its stereoisomer does not.

-We have almost 10,000 taste buds in our mouths; we even have them on the roof of our mouth. -Insects have the most highly developed sense of taste including taste organs on their feet. -Fish can taste with their fins, tail, and mouth. -Dogs have 1 million smell cells in each nostril and their smell cells are 100 times larger than humans. -Humans use insect pheromones to keep away pesky insects!

Images: [|__http://leavingbio.net/THE%20SENSES_files/THE%20SENSES.htm__] [|__http://images.google.com/imgres?q=smell+and+taste&hl=en&biw=1603&bih=786&gbv=2&tbm=isch&tbnid=EVYtzfp0oYNmbM:&imgrefurl=http://www.harunyahya.com/books/science/smell_taste/smell_taste_02.php&docid=970B6ly7PzuU1M&imgurl=http://www.harunyahya.com/books/science/smell_taste/res/42.jpg&w=400&h=359&ei=2GneToz5HuHg0QGtl8HGBw&zoom=1&iact=rc&dur=387&sig=100806740481856875809&sqi=2&page=1&tbnh=128&tbnw=141&start=0&ndsp=36&ved=1t:429,r:16,s:0&tx=66&ty=48__]

Text Bibliography: <span style="background-color: transparent; color: #000099; font-family: Arial; font-size: 15px; vertical-align: baseline;">[|__http://www.sciencebuddies.org/science-fair-projects/project_ideas/HumBio_p013.shtml__] <span style="background-color: transparent; color: #000099; font-family: Arial; font-size: 16px; vertical-align: baseline;">[|__http://en.wikipedia.org/wiki/Gustatory_system#__] <span style="background-color: transparent; color: #000099; font-family: Arial; font-size: 16px; vertical-align: baseline;">[|__http://www.everythingsmells.com/smellyfacts.html__] <span style="background-color: transparent; color: #000099; font-family: Arial; font-size: 15px; vertical-align: baseline;">[|__http://en.wikipedia.org/wiki/Olfactory_bulb__] <span style="background-color: transparent; color: #000099; font-family: Arial; font-size: 15px; vertical-align: baseline;">__http://en.wikipedia.org/wiki/Olfaction__ <span style="background-color: transparent; color: #000099; font-family: Arial; font-size: 15px; vertical-align: baseline;">[|__http://www.reachoutmichigan.org/funexperiments/agesubject/lessons/newton/tstesmll.html__] <span style="background-color: transparent; color: #000099; font-family: Arial; font-size: 15px; vertical-align: baseline;">__http://www.scribd.com/doc/2668591/The-Chemical-Senses-Taste-and-Smell__ <span style="background-color: transparent; color: #000099; font-family: Arial; font-size: 15px; vertical-align: baseline;">__http://en.wikipedia.org/wiki/Odorant__