Study Guide Exam 4 Olfaction What is the function of olfaction o Approach avoidance additional social role pheromones o Chemicals are detected in 2 ways floating in the air olfaction in solution gustation Dogs have more olfactory receptor neurons that humans and rats have more types of olfactory receptors than humans What are the functional consequences of these differences o Dogs need receptor neurons for better detection smell is a lot less important in humans than animals the more receptors means more sensitivity to certain odorants rats also have huge olfactory bulb What makes something an odorant Are there compounds that should be odorants but we cannot smell o Odorant volatile small hydrophobic o We can t smell natural gas carbon dioxide because we don t have receptors to detect them there was never any environmental pressure to detect these things so it didn t come up in evolution Anatomy of the olfactory system o What are turbinates ridges that add turbulence to incoming air to send some thru the olfactory cleft and onto the olfactory epithelium o What is the olfactory epithelium what types of cells does it contain where the olfactory receptor neurons are Supporting cells metabolic and physical support for olfactory cells Basal cells stem cells mature into new olfactory receptor cells Olfactory sensory neurons small sensory neurons with cilia receptor proteins are on cilia they die and are replaced every month or so project to glomeruli each sensory neuron has only one type of olfactory receptor Glomeruli clusters of dendrites neurons in olfactory bulb Metabotropic receptors 2nd messenger opens channels that flux Na and Ca2 also opens Cl channel o Olfactory bulb relays signals to olfactory tract o Cribriform plate bony plate axons go thru before olfactory bulb o Olfactory nerve all of the axon projections from OSNs CN1 Understand the anatomy of the olfactory receptor cells in olfactory epithelium cilia dendrites extend into mucosa and contain receptors axon travels thru cribriform plate as part of olfactory nerve and ends in olfactory bulb How is the olfactory information organized in the olfactory bulb especially w regard to glomeruli What is the projection neuron within the glomerulus that receives info from the olfactory nerve and sends info to the cortex What parts of cortex get olfactory info Where else in the brain does olfactory information go and what are the roles of each of those regions o OSNs in nasal epithelium axons go thru cribriform plate and end in olfactory bulb ipsilateral projection all the way to cortex all of these axons together create olfactory nerve o Axons from olfactory receptor cells synapse on glomeruli odorant activates pattern of glomeruli cross fiber patterning Glomeruli pattern of activation depends on experience preference for the odorant o mitral cells from olfactory bulb project directly to entorhinal cortex piriform cortex and amygdala entorhinal cortex piriform cortex conscious perception thin axons so slow AP spatially organizaed like olfactory bulb anterior piriform cortex important for detection thresholds similarity between odors adaption and cross adaptation posterior PC important for quality of odor what is it memory doesn t need to go to thalamus for further processing o entorhinal cortex hippocampus memory o pririform cortex orbitofrontal cortex assigning positive and negative value to odors flavor decision making o amygdala emotional memory approach avoidance behavior hypothalamus hormones feeding reproductive behavior What is shape pattern theory o Lock receptor and key odorant o Odorant molecules have different shapes olfactory receptors have different shapes o Different scents activate different arrays of olfactory receptors in epithelium various arrays produce specific firing patterns of neurons in olfactory bulb a pattern is generated across the glomeruli which determines what scent we perceive o The shape of the odorant is going to determine what receptors it binds to going to cause a pattern of activity in receptors and therefore in olfactory bulb Do we use labeled line or cross fiber patterning to identify odors Understand why o We detect odors by the pattern of activity across various receptor types one odorant molecule binds to a receptor dislodges binds to another receptor etc each receptor activates different part of olfactory bulb so we can start to understand odors based on this pattern of activity o Brain knows from what glomerulus axons have traveled which helps brain determine smell like labeled line coding What is anosmia and what can cause it What is specific anosmia and what is its most common cause o Inability to smell Causes fractured cribriform plate sinus infection medicals congenital los sense of smell more likely to be depressed o Specific anosmia the inability to smell a specific compound amid otherwise normal smell perception usually steroidal musk smells usually genetic also to androstenone the steroid in female sweat and urine What are some differences between men and women in olfaction o Women detect odors more readily at lower thresholds especially when ovulating brain responses to odors are stronger odor more important to women than men in choosing partners Child bearing age women sensitize to odors o Smell is synthetic sense don t perceive all molecules separately perceive them as a whole unless you go thru training and develop analytic ability How why do olfactory thresholds increase with age o Ability to replace olfactory sensory neurons decrease with age o 50 of elderly are anosmic What test is used to identify olfactory thresholds What test is used to study the ability to discriminate b t odorants o Staircase method similar to method of limits odor presented in increasing concentration increments then decreasing multiple times o Triangle test to determine if a person can discriminate between odorants one of these things is not like the other What are some functional consequences of the ipsilateral projection of the olfactory system together with the lateralization of language and emotion check out web essay 13 1 o Brain is lateralized right side is stronger in emotion left side is stronger in language o Smell goes to ipsilateral side of brain What is adaptation why does it occur Is there a psychological effect on adaptation o Adaptation stop perceiving a odorant while still in its presence enables us to filter out background odors happens about 10 15 mins of continuous exposure o
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