Taste (Gustation) & Smell (Olfaction) - - 1. 2. 3. 4. 5. 1. 2. 3. - Pheromones: Pheromones are secreted or excreted chemical factor that triggers a social response in members of the same species Basically a chemical signal that ends up triggering an innate response Very important in animals, specifically insects Has been linked to mating, fighting, The olfactory epithelium is sensitive to specific molecules and has an area in it known as an accessory olfactory epithelium (send projections to an accessory olfactory bulb) These all end up sending information to the amygdala, which is important for its involvement in emotion, aggression, and mating As humans, we rely very little on pheromones because we lack an accessory olfactory bulb Olfaction - Structure & Function: When you eat and break apart food in your mouth, small molecules will actually break off and enter your nose through the back of your mouth (makes things taste better) Flavor is a combination of taste and smell (smell can often enhance taste) The cribriform plate separates the olfactory epithelium from the brain The olfactory bulb is an extension from the bottom of the brain that is a bundle of nerves that sends projections through little holes in the cribriform plate to the olfactory epithelium There are receptors specifically designed to smell certain compounds From the glomerulus (specific towards different molecular signals), it will synapse to a mitral cell (also specific towards different molecular signals) which will transmit the information to the brain On the cell receptor, it's actually a GPCR, which will then get activated and cause a G Protein to open an ion channel, which then triggers an AP, leading to stimulation of the brain Gustation - Structure & Function: 5 main tastes, depending on the particular receptor: Sour Salty Sweet Bitter Umami (“savory”) and is associated with our ability to taste glutamate The first two rely on ion channels, where something like NaCl will bind to the ion channel, and let in positive ions in order to depolarize the cell and generate an AP The last three above have similar receptors (GPCR’s) which then goes on and opens ion channels to depolarize the cell and fire an AP Taste buds are mostly localized to the anterior portion of the tongue Fungiform Taste Buds are the ones mostly found in the anterior part of the tongue (this is where most of the taste buds are found) Foliate Taste Buds are typically found in the posterior, lateral sides of the tongue Circumvallate Taste Buds are typically found in the posterior portion of the time Each taste bud can differentiate between the 5 tastes shown above (they contain all of the taste cells necessary for this) The axons coming from these different taste cells actually remain separate all the way to the brain Each taste will go to a specific region in the gustatory cortex (i think it's in the insular cortex?) Extra Notes: Taste is largely perceived as ipsilateral The Orbitofrontal cortex is the first place that the signals from the olfactory system and the taste system are integrated