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Course: Stanford School of Medicine > Unit 1
Lesson 4: AsthmaAsthma
Take a glimpse into your lungs to understand what happens when you have an asthma attack.
These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video. Created by Stanford School of Medicine.
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- Asthma can sometimes be triggered by non chemical factors such as environmental temperature, stress or exercise and by non-inhaled, digested substances such as aspirin or other medications. Are these stimuli also activating the alpha receptors?(15 votes)
- Most of these factors won't trigger the alpha-1-receptor, but will iritate the cells in de walls of the bronchioli. For example when you exercise, you have to breath with your mouth to keep up with the amount of air needed in your lungs, but when you breath through your mouth the air you inhale will be colder and dryer then when you breath through your nose. This colder and dryer air will iritate the walls and more blood will flow through them which leads to edema, the irritation also causes more mucus production.(17 votes)
- what are the benifits of histamine?(8 votes)
- Histamine is produced by basophils and mast cells (types of white blood cells). It increases the permeability of the capillaries to white bloods cells to allow them to engage pathogens. In laymen's terms, histamine makes the blood vessels big to allow white blood cells (infection fighting cells) attack anything that can be harmful to the body.(12 votes)
- What is the difference between HFA and CFC inhalers and why do CFC inhalers work better?(5 votes)
- I'm not aware of any medical studies showing CFC inhalers work better. Many patients believe they work better because they could feel the mist of CFC inhalers in their mouths upon inhalation; however, HFA inhalers don't produce that same sensation in the mouth, sometimes making the patient believe they're not getting any medication.(2 votes)
- asthma is sometimes a genetic factor.In those people is beta agonist absent?(7 votes)
- Asthma is over sensitivity to the triggers, whereas those people who do not have asthma, get a similar but extremely toned down reaction that doesn't cause the same respiratory stress that an asthmatic reaction causes. Beta agonist is any compound/medicine that can be administered from a fast acting inhaler and/or nebulizer, but not exactly body created. So to answer your question, yes, beta agonist is absent in those people, but it is also absent in non-asthmatics as well.(7 votes)
- I do not understand what an "edema" is.(5 votes)
- an abnormal accumulation of fluid in the interstitium, which are locations beneath the skin or in one or more cavities of the body. It is clinically shown as swelling. Generally, the amount of interstitial fluid is determined by the balance of fluid homeostasis, and increased secretion of fluid into the interstitium or impaired removal of this fluid may cause edema.(5 votes)
- If you're asthmatic, why is your weight such a big factor in keeping your asthma under control?(4 votes)
- The heaver you are, it takes more energy for normal breathing. The effect of weight gain on asthma has been examined in several epidemiological studies in adults and children. Majority of these studies have shown an increased risk of incident asthma with an increase in body mass index (BMI). Importantly, obesity antedates asthma. Experimental data from studies in obese also support the causal relationship in asthma.(5 votes)
- Is it possible to rid Asthma from a human being permanently? Is it possible people with Asthma can take a pill to add extra protection to histamine so that it does not spill and swell the muscle?(3 votes)
- Asthma is a very complex disease. There's no pill at this time that can completely eradicate the disease. At this point, there's only symptom control. Sometimes, asthma goes away on its own though.(4 votes)
- At4:28, the presenter mentions that edema is a factor in the narrowing of the bronchioles in an asthma attack. What is edema, and how is it caused?(1 vote)
- Edema is just another word for swelling or inflammation. Simply put, it's an accumulation of fluid in and/or around the cells of tissue. There are many causes, but in the case of asthma, it's a histamine reaction not unlike when someone with a peanut allergy eats one and their tissue swells up. Edema/swelling/inflammation is a defense mechanism that we all have, but when someone who has an allergy to something is exposed to whatever it is they're allergic to, their body's defense goes too far like in the case of asthma.(5 votes)
- So what DOES cause asthma? Does it occur when you're born, or is it developed throughout life? Like, let's say, when you're little, you don't have asthma, but then when you grow up you do. So would this have been caused by poor quality of the air, or the different air particles... ?(3 votes)
- is there a import difference between Inhalers w/ and wo/ cortison?(2 votes)
- mostly cortisone inhalers used for prophylactic asthmatic attack because it has slow onset with long duration of action so you can't use it in emergency situation.(3 votes)
Video transcript
Voiceover: In our last video we saw a
cross section through a bronchiole ... Bronchioles remember are those tubes
that allow air to pass into the lungs and they're the ones that
branch off of the bronchi. These guys are no longer
held open at a fixed diameter by the rings of cartilage but these guys have smooth
muscle in their walls so they're able to change diameter. We also saw that lining these tubes there was a little bit of
mucus and that that mucus was good for trapping particles that
might enter with the inhaled air. One thing that I didn't mention
is that there are also cells in these bronchiolar walls that
contain a chemical called histamine. Histamine is a chemical that
if it's released in the tissues it causes swelling of the tissues. Okay, now let's look at the
way in which we can understand what happens to somebody
who suffers from asthma during an asthma attack. This is a bit of a simplification but it's a good way to
understand what's going on. There are some receptors in these walls and this type of receptor is
called an alpha 1-receptor. The alpha 1-receptors send
messages to the smooth muscle in the walls of the bronchioles
and tell them to constrict. Alpha 1-receptors can be turned on
in people with asthma by triggers and these are things like cigarette smoke or dust
or pollen or pet dander. Whatever triggers that
person's asthma attack that will basically turn
on the alpha 1-receptor. What's going to happen then
is that the smooth muscle in the wall of that bronchiole
is going to shorten or contract and because it's contracting or shortening it's going to reduce the
diameter of the tube. Another thing that's going
to happen in response to a trigger binding to those receptors is that the histamine in the
histamine-containing cells is going to spill out into
the wall of the bronchiole and the result of that is
going to be edema or swelling of the bronchiolar wall. You can see that this wall is quite
a bit thicker than the original wall. The third thing that's going to
happen during an acute asthma attack is that there is going to be
increased secretion of mucus into the lumen or the hole of this tube. That's simply an attempt to try and
trap more of these offending particles. But the problem you can see is
that if we compare the diameter of this tube during the asthma attack and the diameter of
the original bronchiole you can see that there's not
much space here for air to pass. Airflow is severely restricted
during an asthma attack like this. Luckily there's another kind of receptor. I'm going to draw it as
the circle so you can see that it's different from
the alpha 1-receptor. This receptor is called a beta-2 receptor. It basically tells the smooth muscle
in the walls of the bronchioles to do the opposite. It tells the smooth muscle here to relax and to return to the original
relaxed open state of the bronchiole. The thing that binds to that
receptor is called a beta agonist. Beta agonists are the
medicine that's contained in the fast-acting inhalers that a
person with asthma will carry with them so that if they're in
a situation like this they can quickly inhale
the beta agonist medicine and get back to a relaxed state
where they can breathe more easily. If we had to summarize, the three
factors that cause narrowing of the bronchioles during
an asthma attack are: number one muscular constriction of
the smooth muscle cells in the walls. The second one is edema of the
walls that's mediated by histamine. And the third thing is the
increased mucus secretion that also reduces the size of the lumen or the pathway for air going
into and out of the lung.