Health and medicine
Created by Ronald Sahyouni.
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- For those who had a hard time understanding his Mouse's nasal path drawing at3:49, Found this picture much more helpful to go along with this lecture:
- Is there any way to improve the audio quality in this recording? Ronald's voice is quite muffled and hard to hear(11 votes)
- I found that it can be helpful to use closed caption or the transcript tab and read what the person is saying when the audio is poor or the person has an accent I do not understand. Hope this helps.(5 votes)
- at the end you mention that humans do not have an accessory olfactory bulb but still have vomeronasal system/cells- are these vomeronasal cells still able to send a signal to the amygdala?(11 votes)
- It is still debatable whether humans can detect pheromones or not. Though there are studies that show some evidence of humans detecting pheromones under some contexts, it has not been well elucidated. Though if these cells do project to the amygdala, it would be interesting.(4 votes)
- can't understand half these words as he says them with the sound quality(7 votes)
- Good news, look below the video and you will see the tab "transcript", click on that tab and read along with the video. It is not always a perfect transcription, but it is better than most. Cheers.(6 votes)
- at2:05what did he say when the subtitles showed "[unintelligable]"(2 votes)
- He says "Bees use pheromones, dogs use pheromones, bears use pheromones"(6 votes)
- Why our own pheromones don't have effect on ourselves? Or is it due to sensory adaptation?(3 votes)
- Pheromones differ slightly from individual to individual. A dog recognizes if it's its own pee or not, it's as accurate if not even more accurate than identification through fingerprints.
"Pheromones function to communicate one’s species, sex, and perhaps most importantly one’s genetic identity. "See this experiment, it still works more or less in humans:https://en.wikipedia.org/wiki/Major_histocompatibility_complex_and_sexual_selection(3 votes)
- For clarification, at6:17he says the cell will "send and axon" does he mean is sending an action potential down an axon or is the cell creating an axon and sending it through the pathway? The former makes more sense to me. Is it a common way to describe sending an action potential like this?(1 vote)
- This is a difficult video because the teacher states things that are imprecise at best and the audio is garbled. Neurons have axons that are extensions that are already in place or 'wired into the brain'. Take a look at the next question and the answer which gives a better picture of the anatomy. He is trying to describe the anatomy of the neurons and explain the axon goes to the amygdala, an area of memories and emotions. This 'arm' or extension of the neuron, the axon, 'carries' the action potential. The analogy typically given is that it is like electricity carried on a wire. When the action potential reaches the end of the neuron, the axon terminals release the neurotransmitter there. And he said the smell would affect the animal's behavior. He stated that humans are less affected by smells compared to other animals and this is likely true. However, smell is one sense that is NOT filtered by the thalamus and it immediately evokes memories and emotions in people too, although they may not be as obvious as changes in animals' behaviors. Holiday smells, food smells, perfumes and cologne s evoke strong memories. And pheromones do play a part in human attraction and reproduction. We are animals. The scent business is a thriving multi million dollar business, we pay a lot of money for scents so I would argue it is more important then we realize.(4 votes)
- Why are animals' sense of smell better than humans?(2 votes)
- As Bob said, humans have less olfactory neurons than mice or dogs. Also, since humans are bipedal, we've evolved so that we don't put our noses to the ground. But, we're actually much better at smelling things than most people think. In one nature paper, humans who were blindfolded were actually able to follow a scent trail as well as dogs if they put their noses to the ground.
"Mechanisms of scent-tracking in humans"
And in the Smithsonian magazine: "In Some Ways, Your Sense of Smell Is Actually Better Than a Dog’s"
- How is it possible to have Vomeronasal organ without the accessory olfactory bulb if it is part of it? and what is the difference between Accessory olfactory bulb and just olfactory bulb?(2 votes)
- Crazy how every video has this man saying some wrong information(1 vote)
Voiceover: At some point in time, you've seen someone walking their dog, and their dog decides to pee on a fire hydrant. Now, this is my attempt to draw a fire hydrant, but you see the dog, and he pees on this fire hydrant. Here's the pee, it's coming, and it splashed all over the place. Why is the dog peeing on the fire hydrant? You might have heard that dogs pee on fire hydrants in order to mark their territory. How exactly is it that they're able to mark their territory? 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. These molecules are known as pheromones, pheromones. Now, we can think of pheromones as specialized olfactory cues. 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 are able to smell them, but they also cause some sort of response in the other animal that's smelling them. Basically, we could think of a pheromone as a chemical signal, 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. Pheromones are really important in animals, particularly insects. In insects, they have been linked to mating, to fighting, and also in chemical communications. Bees use pheromones, dogs use pheromones, [unintelligible] use pheromones to mark their territories and basically communicate with other members of the species. This is what pheromones are in a nutshell. Now we're going to go into a little bit of the anatomy and also how, at a molecular level, pheromones work. In a previous video, we went into the olfactory system, and we talked about the olfactory epithelium. Let me just go ahead, and let's imagine that this is the skull of a mouse. Here is a mouse skull, here are its teeth, and here is its nose. This is just the skull. This is the nose. Normally, there would be a little bit of flesh here, but basically, here is the nose, and air comes in, and it moves through the nasal passage, and there is a part of the nasal passage that is known as the olfactory epithelium, so olfactory epithelium. The olfactory epithelium is sensitive to various molecules. There is a specialized part of the olfactory epithelium which is up here in the mouse, and this is known as an accessory olfactory epithelium, accessory olfactory epithelium. The accessory olfactory epithelium actually sends projections to a accessory olfactory bulb. This is the accessory olfactory bulb. The olfactory epithelium sends information to ... [unintelligible] Normal olfactory epithelium sends its information to the olfactory bulb, which is olfactory bulb, but the accessory olfactory epithelium sends information to the accessory olfactory bulb. Let's look at the particular cells in the accessory olfactory epithelium that are responsive to pheromones. Let's look a little bit more closely at the accessory olfactory epithelium. Within the accessory olfactory epithelium, we have a structure known as a vomeronasal system. We got this one zone over here, and then we have beneath it another zone. Let's imagine that this part up here is the nasal passage, so this is the nasal 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. Within this vomeronasal system, which I will label, vomeronasal system, there are different cells. 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. We got these cells in this, since they're situated underneath this bottom zone, are known as basal cells. There are other cells that are over here, and they just have short little projections, and these are known as apical cells. Apical cells are in yellow. This is apical, and this over here is a basal cell. 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. Let's imagine that in the urine of that dog that peed on the fire hydrant, there is a little molecule. We'll draw it as a little triangle. That triangle will come in, and it might activate a receptor on this basal cell over here. When it does activate this cell, this basal cell will send a axon through the accessory olfactory epithelium and then eventually to the accessory olfactory bulb, so accessory olfactory bulb, and then from there, it will synapse onto a glomerulus and then to a mitral or tufted cell, and then that mitral or tufted cell will send a axon to the brain. There are many of 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 with 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. Once these cells reach the accessory olfactory bulb and synapse onto a glomerulus, they will then synapse onto a mitral or tufted cell, and that mitral or tufted cell will actually send a axon to a part of the brain known as the amygdala, amygdala. The amygdala is responsible for a host of things, but it's particularly known for its involvement in emotion and aggression and mating and things like that. So basically, by having various cells respond to various pheromones in the environment, an animal is able to control its behavior via this pathway to the amygdala based on these extracellular cues in the environment. Based on these pheromones, a pheromone will bind, they will cause some kind of cell to fire, and that cell will eventually reach the amygdala to cause a behavioral response in the animal. Now signal transduction, so this part right here, this is where the receptor, the molecule binds to the receptor. This causes a signal to be transduced in the particular sensory neuron. This signal transduction is exactly the same as what happens in regular olfaction, where there is a receptor. The receptor is a G-protein-coupled receptor. When that receptor is activated, it causes this cell to de-polarize and fire [unintelligible]. Now interestingly, in humans, we have evolved to, to rely very little on pheromones. We do have a vomeronasal organ. However, we do not have an accessory olfactory bulb, so we rely very little on pheromones.