3 24 S P Olfaction Ppt 1 Pheromones a Chemical compound produced by one animal that elicits a specific behavioral or physiological effect in another animal of the same species b Different from odorants that stimulate olfactory receptors c Purposes of pheromonal communication 1 Tiger rubs tree with glands from its 2 Your cat rubs you with its eyebrows i Territory cheek and rump ii Mating 1 Female tells male she is fertile receptive 2 Male tells female to initiate sexual behavior iii Defense 1 Chemical released from stinger of honeybee when it stings tells other bees to join in 2 Olfaction and Pheromones a 2 olfactory systems i Main olfactory bulb what we have ii Accessory olfactory bulb what projects on to the main olfactory bulb and the amygdala and hypothalamus 1 Humans don t have this 2 Added on in back of MOB 3 No connection with main olfactory bulb 4 Activated by vomeronasal organ iii Vomeronasal organ 1 Amphibians reptiles many mammals not birds or humans 2 Fewer types of receptors compared to regular olfactory receptors 3 Each receptor responds to only 1 pheromone 4 Receptors are very sensitive 5 No adaption 6 Responds to pheromones 3 Pheromonal communication in humans a McClintock Effect i Synchronization of womens menstrual cycles when they live together ii As long as they are not on hormonal contraceptive iii Can also happen with other species b AND androstadienone i Made in adrenal glands and gonads as part of step for making testosterone and estrogen ii Increases alertness and positive mood in women iii Decrease positive mood in men iiii Hypothalamus activation in women and homosexual men not hetero 1 EST activates hypothalamus in men not women c Major histocompatibility complex MHC i Large gene family chromosome 6 in humans ii Genes make the molecules that enable immune system to recognize invaders iii More diverse MHC of parents stronger immune system of offspring iiii Women prefer odor of men with dissimilar MHCs to their own 1 Preference reversed if taking oral contraceptives 2 Preference seen in male mice and fish too d Humans have no functional VNO or AOB so if there is pheromonal communication between humans it is unclear how it is occurring Study Questions for Olfaction ppt 1 What is the function of olfaction To detect chemicals that are floating in the air Similar to taste in function The sense of smell 2 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 It affects the sensitivity to certain odorants and if an animal has more receptors they are more sensitive to odors 3 What makes something an odorant Are there compounds that should be odorants but we cannot smell Something is an odorant if it is volatile meaning it can float through air it is small hydrophobic Yes compounds such as natural gases like methane and CO carbon monoxide 4 Anatomy of the olfactory system What are turbinates What is the olfactory epithelium what types of cells does it contain Olfactory bulb Cribriform plate Glomeruli Olfactory nerve 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 Turbinates are ridges that add turbulence to incoming air to send some thru the olfactory cleft and onto the olfactory epithelium The olfactory epithelium is a secretory mucous membrane in the human nose whose primary function is to detect odorants in inhaled air It contains three types of cells olfactory sensory neurons basal cells and supporting cells Olfactory bulb a blueberry sized extension of the brain just above the nose where olfactory information is first processed There are two olfactory bulbs one in each brain hemisphere corresponding to the right and left nostrils Cribiform Plate a bony structure riddled with tiny holes at the level of the eyebrows that separates the nose from the brain The axons from the olfactory sensory neurons pass through the tiny holes of the cribiform plate to enter the brain Glomeruli any of the spherical conglomerates containing the incoming axons of the olfactory sensory neurons Each olfactory sensory neuron converges onto two glomeruli Olfactory nerve the first pair of cranial nerves The axons of the olfactory sensory neurons bundle together after passing through the cribiform plate to form the olfactory nerve which conducts impulses from the olfactory epithelia in the nose to the olfactory bulb 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 Information in the olfactory bulb is organized by personal experience Glomeruli may receive axons from several different receptor types Our personal experience with an odor can change the pattern of activity that is produced by the glomeruli in the olfactory bulb There is no fixed code for odor perception What is the projection neuron within the glomerulus that receives info from the olfactory nerve and sends info to the cortex Trigeminal nerve The limbic system also receives olfactory information which is involved in many aspects of emotion and memory Olfactory bulb projects directly to Enthorial cortex Hippocampus memory Piriform cortex Orbitofrontal cortex assigning value to things and flavor Amygdala Emotional memory Hypothalamus hormones feeding and reproductive behavior 5 What is shape pattern theory Shape pattern theory is the current dominant biochemical theory for how chemicals come to be perceived as specific odors It contends that different scents activate different arrays of olfactory receptors in the olfactory epithelia These various arrays produce specific firing patterns of neurons in the olfactory bulb which then determine the particular scent we perceive It contends that odorant molecules have different
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