Psych 454 1st EditionExam 2 Study GuideLec. 14 I. IntroA. Anosmia – loss of smell; 1/5 of general populationB. Olfactory organ1. Olfactory epithelium – olfactory receptor cells (ORCs), supporting cells, basal cells2. Cribriform plate – a thin sheet of bone through which small clusters of axons penetrate, coursing to the olfactory bulbII. Signal transductionA. Odorants bind to specific receptors -> cAMP -> binds to cation channels -> influx of Na+ and Ca2+ -> Ca2+ activated Cl channelIII. Olfactory bolb (OB)A. Receives input from the olfactory nerveB. The first relay station in the olfactory pathwayC. Odorant concentration coding in ORCs and OBD. 1st relay station1. each odor is represented by the activity of a large population of neurons2. neurons responsive to particular odors may be organized into spatial maps3. the timing of action potentials may be an essential code for particular odorsE. summary of olfactory pathways1. frontal cortex – conscious perception of smell2. hypothalamus amygdala – motivational and emotional aspects of smell3. hippocampus – odor memoryIV. Characteristics of olfactionA. Most primitive sensory systemB. Olfactory sensory cells are true neuronsC. Only one relay station from the outside world to cortical tissueD. Olfactory fatigue (adaptation): the temporary, normal inability to distinguish a particular odor after a prolonged exposure to that airborne compoundV. Main and accessory olfactory system (MOS and AOS)A. Found in addition to the MOS in terrestrial vertebrates B. Initiated in vomeronasal organ (VNO) and is mainly used in the detection of pheromonesC. Does AOS exist in humans?1. Vistible vestigial human VNO2. Trpc2 is a pseudo gene in human 3. Absence of the VNA did not affect the detection of the putative human pheromone VI. PheromoneA. Chemical molecules released to elicit specific behavioral expressions or hormonal changes from other individuals of the same species B. Important signals:1. Reproductive behavior2. Territorial boundaries3. Identification4. AggressionC. Role in humans1. Pheromone communication in humans may be conveyed via the main olfactory system VII. SummaryA. Intro1. The role that olfaction played in everyday life – anosmiaB. Olfactory pathway1. Signal transduction2. Olfactory bulb3. Summary of olfactory pathwayC. Characteristics of olfactory systemD. Main and accessory olfactory pathway1. Accessory olfactory pathway2. Pheromone detection in humanLec. 15 I. 5 basic tastes: A. salty – tastes like salt; NaClB. sour – acids; HCLC. sweet – sugars and sucrose, some proteins, artificial sweetenersD. bitter – range of different substances; simple ions and complex organic molecules1. poisonous substances are often bitter 2. we can detect very low concentrations of bitter substances E. umami – savory; amino acids 1. eg. Glutamate or MSG2. MSG creates tingly sensation on tongue II. Anatomy of mouth:A. Taste is predominantly a function of the tongue, the pharynx, palate and epiglottis also contribute B. Nasal cavity, palate, tongue, pharynx, epiglottisC. Tongue: 1. ‘papillae’ visible to naked eye; each has from 1-100’s of taste budsa. papillae contain taste buds which are conglomeration of taste cells; range in number of taste buds 2. taste pore – on surface of tongue, exposed to mouth contentsa. where substances dissolved in saliva interact with taste cells b. any taste stimuli accesses taste cell through this pore 3. each taste bud has 50-150 taste cells a. taste cells have about 2 week lifespan4. a person typically has 2000-5000 taste buds 5. tongue isn’t divided into different regions that receive specific taste info; receptors are all over tongueIII. Taste cellsA. Taste stimuli depolarize taste cells1. The membrane potential of taste cells changes (depolarizes) when activated by appropriate substance2. >90% of taste cells respond to 2 or more basic tastes3. cells are broadly tuned, but some are more selective 4. depolarization  transmitter release, can fire APs under certain conditionsB. Salt and sour taste stimuli interact with ion channels on taste cells1. Salt pathway: Na2+ conc. must be high (>10mM) to taste ita. Salt sensitive cells have Na+ selective channelsb. Na+ channel is always open (voltage insensitive)c. Inc Na+ in mouth leads to inc Na+ influx through Na+ channeld. This depolarizes the cell causing Ca2+ influx through voltage-sensitive Ca2+ cells e. Transmitter is released2. Sour pathway: sour taste due to acidity (H+ ions)a. Acids dissolve in water producing H+ ionsb. Sour-sensitive cells have Na+ and K+ channelsc. H+ ions enter cells through Na+ channelsd. H+ binds to and blocks K+ channelse. Blocking K+ channels reduces K+ effluxf. H+ actions via Na+ and K+ channels depolarize cells g. Ca2+ influx through voltage-sensitive Ca2+ channelsh. Transmitter is released C. Bitter, sweet and umami substances bind to GPCRs1. GPCRs = G-protein-coupled receptors2. Binding to GPCRs initiates intracellular signaling effectsa. G-proteins stimulate enzyme called ‘phospholipase C’b. Phospholipase C produces inositol triphosphate (IP3)c. Leads to metabolic change within cell 3. Na+ influx into taste cells via Na+ channelsa. IP3 opens type of Na+ channels unique to taste cells b. Na+ influx depolarizes taste cells c. IP3: activates unique Na+ cells that only respond to IP3 and causes Ca+ release from intracellular storage sites4. Inc. Ca+ concentration inside taste cell a. Ca+ influx via voltage-sensitive Ca+ channels b. IP3 triggers release of Ca+ from intracellular Ca+ storage sites 5. Transmitter release stimulates axons in cranial nervesa. Both sources of calcium trigger transmitter releaseb. Transmitter is adenosine triphosphate (ATP)6. GPCRs made of one of more protein subunits a. T1R and T2R genes encode for taste protein subunitsb. Different genes encode for bitter, sweet, and umami GPCRsc. Bitter receptors i. 30 different typesii. these receptor types compromise the family of T2R proteinsiii. different once can detect poisonous substances d. Sweet receptorsi. Only one type ii. Two subunits; formed from two T1R proteins ie. T1R2 and T1R3e. Umami receptorsi. Formed from two T1R proteins ii. T1R1 and T1R3f. Bitter, sweet and umami proteins in different cells IV. Taste pathway to brainA. Taste information is carried by 3 cranial nerves to the brainstem1. Anterior 2/3 of tongue and palate send axons into cranial nerve VIIa. Cranial nerve VII – attached to tongue 2. Posterior 1/3 of