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Current time:0:00Total duration:8:57

Video transcript

some point in time you've seen someone walking their dog and your dog decides to pee on a fire hydrant now this is my attempt to draw up 500 but you see the dog can keep keys on this fire hydrant so here's the pee it's come in and splashed all over the place so why is the dog peeing on the fire hydrant well you might have heard that dogs pee on fire hydrants in order to mark their territory and how exactly is it that they're able to mark their territory well there are particular molecules that are released in the urine and these molecules can be scented can be sensed by other animals through their nose so these molecules are known as pheromones their loans pheromones now we can think of pheromones as specialized olfactory cues so in a previous video we spoke about how we're able to smell things well pheromones not only are we able to smell them and animals in particular able to smell them but they also cause some sort of response in the other animal that's smelling them so basically we can think of a pheromone as a chemical signal so a chemical signal that is released by one member of a species so for example the dog and is sensed another member of the species and it triggers an innate response response so pheromones are this really important in animals particularly insects and in insects they have been linked to mating to fighting and also in chemical communication so please use pheromones dogs use pheromones their uses with pheromones to mark their territories and basically communicate with other members of the species so this is where pheromones are in nutshell so now I'm going to go into a little bit of the anatomy and also how at a molecular level pheromones work so in a previous video we went into the olfactory system and we talked about a olfactory epithelium so let me just go ahead and let's imagine that this is the skull of a mouse to the mouse Cole here it's T okay and here is its you know so this is just a skull so this is the nose normally there via little bit of flesh here but these figures and there is an air comes in and it moves through the nasal passage and there is a part of the nasal passage that is known as the L factory epithelium so the factory at the field and the olfactory epithelium is sensitive to various wakile's and there is a specialized part of the olfactory epithelium which is up here in a mouse and this is known as an accessory olfactory epithelium so accessory olfactory factory epithelium and the accessory olfactory epithelium actually sends projections to a accessory olfactory bulb so this is the accessory olfactory foam that's refold so the olfactory epithelium sends information to control the normal factory archegonium sends its information to the olfactory bulb which is a factory cold but the accessory olfactory of the join sends information to the accessory olfactory bulb so let's look at the particular cells in the accessory olfactory epithelium that are responsive to their points so let's look a little bit more closely at the accessory olfactory episode in the accessory olfactory epithelium we have a structure known as a bone marrow nasal system so got this one zone over here and then we have beneath it another zone so this let's imagine that this part up here is the nasal passage so this is the nasal passage of passage and then over here are all the axons of the various sensory cells that will eventually go to the brain via the accessory olfactory bulb so within this Romero nasal system which I will label state blue Murrow nasal system there are different cells so there are some cells that are situated down here and they actually send a projection all the way up to this top zone over here so we've got these cells released since they're situated underneath this bottom zone are known as basal cells and there are other cells that are over here and they destructured little projections and these are known as apical size so apical cells are anillos this is integral and this over here is a basal cell and these cells similar to regular olfactory neurons will have little receptors at the very tips of their projections and these receptors will be sensitive to different molecules or pheromones so let's imagine that in the urine of that dog that peed on the fire hydrant there is a little molecule will draw it in a little triangle that triangle will come in and it might activate a receptor on this basal cell over here and when it does activate itself this basal cell will send a axon through the accessory olfactory epithelium and then eventually to the accessory olfactory bulb so accessory olfactory foam and then from there it will synapse onto a glomerulus and then to a microwave tufted cell and then that micro tuff itself will send a axon to the brain so there are many or these vomeronasal systems throughout the accessory olfactory bulb here I just drew one but basically again what we have is we have specialized cells that are responsible in one particular type of molecule that will send little axons that eventually go to the accessory olfactory bulb all the axons will synapse into one particular location known as a glomerulus so once these cells reach the accessory olfactory bulb and synapse on to the glomerulus they will then synapse on to a mitral tuck itself now mitral tuck and so will actually send a hex on to a part of the brain known as the amygdala they go up and they make the letters responsible for a host of things but particularly no importa involvement in emotion and aggression and mating and things like that so basically by having various cells respond to various pheromones in the environment you're able an animal is able to control its behavior via this pathway to the amygdala based on these extracellular cues of the environment so based on these foreign pheromones a pheromone will bind it will cause some kind of cell to fire and that cell will eventually reach the amygdala cause a behavioral response in the animal now signal transduction so this part right here this is where the receptor the molecule binds cell receptor this is causes a signal to be transduced in the particular sensory neuron and this signal transduction is exactly the same as what happens in regular olfaction where there's a receptor the receptor is a g-protein coupled receptor and when that receptor is activated it causes the cell to depolarize and fire an action potential now interestingly in humans we have evolved to to rely very little on pheromones so we do have a glimmer of nasal organ however we do not have an accessory olfactory bulb so we rely very little on pheromones