I'm Arman Hassoor, and I'm a biologist and medicine video. Please make sure to subscribe, join the forum and group for the latest videos. Please visit Facebook, I'm Arman Hassoor, and please like and you can also ask questions, answer questions, post some interesting things, including your artworks. And you can also change the quality settings to the highest one for good graphics. In this video, we're going to talk about the physiology of vomiting.
Now, vomiting refers to forceful expulsion of contents from stomach and intestines. It can act as a sort of defense mechanism to get rid of bad content or substances from the body. such as drinking excess amount of alcohol can cause us to vomit.
Vomiting is also related to many other things such as motion sickness, morning sickness, taking certain medications, suffering certain medical conditions, as well as receiving chemotherapy. Emesis is another word that means to vomit. And so emesis is sort of a medical terminology for vomiting. But how do we vomit?
Like what physiological mechanism you're in. causes us to vomit. Well, all the centers or areas related to initiating the act of vomiting comes from the central nervous system, particularly the brainstem, the area I am zooming into here.
There is a center or area known as the vomiting center here that initiates, regulates, and controls the act of vomiting. The vomiting center is located in a particular formation of the medulla oblongata. The vomiting center have predominantly muscarinic type receptors.
And so activation of these receptors will activate the vomiting center to send signals to the muscles that carry out the physical act of vomiting, the emetic reflux that is. Note emetic comes from emesis and emesis is a medical term to mean vomiting. So essentially it means vomiting reflux.
So the vomiting center is what essentially sends out the signals to cause us to vomit from the brain stem. Now, there are several ways that the vomiting center itself can be stimulated. One of the main ways is by the chemoreceptor trigger zone, which is located in the medulla here.
The chemoreceptor trigger zone have two types of... two main types of receptors. It has the dopamine type 2 receptor and the 5-hydroxytryptamine type 3 receptor.
Though the chemoreceptor trigger zone is located in the medulla, like the vomiting center, it is actually located conveniently outside the blood-brain barrier, which is a normal barrier to prevent circulating substances in the blood from making contact with the brain and areas of the brainstem. And so the chemoreceptor trigger zone lies outside the blood-brain barrier and is thus more permeable to circulating substances, such as toxins from chemotherapy that are circulating around or toxins from drugs, digitalis. So these toxins that are circulating around can conveniently activate the receptors of the chemoreceptor trigger zone.
Activation of the chemoreceptor trigger zone will then stimulate the vomiting center, which will then activate the emetic reflux, the physical act of vomiting. So essentially, chemoreceptor trigger zone is what's stimulated by toxins, circulating toxins, and this will cause us to vomit. Afferent impulses that activate the vomiting center to cause emesis, which is...
That also can be due to activity of the vestibular nucleus, which mediate nausea and vomiting of motion sickness. So motion sickness-related vomiting. How does motion sickness cause us to vomit? Let's have a look.
Well, here we have the human ear, the outer ear, middle ear, and inner ear. In the inner ear, we have what's called the labyrinth, where the cochlea is, where we have hair cells, which allow us to hear. Now, motion sickness will...
activate, abnormally activate the vestibular cochlear nerve, which connects the labyrinth to the vestibular nuclei here in the brain stem. Let's zoom into the vestibular nuclei. Now the vestibular nuclei have musculatic receptors as well, and also histamine type 1 receptors. And it is activation of these receptors by the vestibular cochlear nerve from the inner ear, will cause the vestibular nuclei to stimulate the chemoreceptor trigger zone which will then stimulate the vomiting center and thus the emetic reflux, the act of vomiting. Other impulses that can activate the vomiting center or stimulate the vomiting center are afferent impulses coming from the higher centers of the brain, so from around here.
They mediate the emetic response due to pain, foul smell, or putrid sight, and even memory, for example. So you know how some people see blood or some people... eat some types of food because and because of the foul smell and taste they would feel like vomiting well it's because of these higher centers that can actually stimulate the vomiting center to activate the emetic reflux finally of course here I am drawing the stomach and part of the where nerves from here as well as other parts of the gastrointestinal tract, including the esophagus, called the vagal sensory nerve fibers, can activate the vomiting center as well as the chemoreceptor trigger zone to cause the emetic reflux.
And this may be due to certain food that are consumed that may aggravate the stomach or the gastrointestinal lining. or possibly even due to chemotherapy, the toxins, will essentially send out signals from the vagal sensory nerve to the vomiting center that will cause us to vomit out. So the act of vomiting is, as we know, is initiated from the brainstem, from the vomiting center. However, the physical act of vomiting, from signals coming from the brainstem, is due to the contraction of abdominal muscles squeezing the duodenum and the stomach to cause the food to move upwards.
And following this food moving upwards, the gastrointestinal tract, particularly the esophagus, the muscles around this area, will relax to allow food to regurgitate back up, causing us to vomit. to spew up. Now I hope that makes sense.
Now there is a pharmacology part to this video which will be added soon that tells you what type of drugs can be used for treating vomiting type sicknesses like motion sickness or morning sickness or even to treat people receiving chemotherapy because vomiting is a side effect of people for people receiving chemotherapy. Now I hope you enjoyed this video. Thank you for watching.