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Wajid aBBas
United States
Приєднався 13 лис 2015
Videos are just to assist med students while learning. Having innocuous fun. Do watch and learn medicine and have a fun.
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BEST OF LUCK
Cardiac action Potential and Effects of Antiarrthymic Drugs
Myocardial action potential and action of antiarrhythmic drugs
CLASSIFICATION OF ANTIARRHYTHMIC DRUGS -
The different antiarrhythmic drugs often have several effects on action potential generation and propagation and may also affect the autonomic nervous system. Those drugs that act on ion channels may preferentially bind to the activated (open) or inactivated state . The classification of antiarrhythmic drugs according to the Harrison modification of the Vaughan-Williams classification was originally based upon their effects on the action potential and also assumes that individual drugs have a predominant mechanism of action . This distinction remains clinically useful even though it does not account for complicated electrophysiologic and autonomic interactions that may be present or for the action of certain antiarrhythmic drugs such as digitalis and adenosine .
**Class I** - The class I drugs act by modulating or blocking the sodium channels, thereby inhibiting phase 0 depolarization. They are all at least in part positively charged and presumably interact with specific amino acid residues in the internal pore of the sodium channel. Three different subgroups have been identified because their mechanism or duration of action is somewhat different due to variable rates of drug binding to and dissociation from the channel receptor :
●The class IC agents have the slowest binding and dissociation from the receptor.
●The class IB agents have the most rapid binding and dissociation from the receptor.
●The class IA agents are intermediate in terms of the speed of binding and dissociation from the receptor
During faster heart rates, less time exists for the drug to dissociate from the receptor, resulting in an increased number of blocked channels and enhanced blockade. These pharmacologic effects may cause a progressive decrease in impulse conduction velocity and a widening of the QRS complex. This property is known as "use-dependence" and is seen most frequently with the class IC agents, less frequently with the class IA drugs, and rarely with the class IB agents .
●**Class IA drugs (quinidine, procainamide, and disopyramide) depress phase 0 (sodium-dependent) depolarization, thereby slowing conduction. They also have moderate potassium channel blocking activity (which tends to slow the rate of repolarization and prolong action potential duration [APD]), anticholinergic activity, and tend to depress myocardial contractility. At slower heart rates, when use-dependent blockade of the sodium current is not significant, potassium channel blockade may become predominant (reverse use-dependence), leading to prolongation of the APD and QT interval and increased automaticity.
One difference between the drugs is that quinidine and procainamide generally decrease vascular resistance, whereas disopyramide increases vascular resistance. In addition, N-acetyl-procainamide (NAPA), a metabolite of procainamide, has little sodium current blocking activity, while retaining potassium current blocking activity. Thus, NAPA behaves like a class III drug.
●**The class IB drugs (lidocaine and mexiletine) have less prominent sodium channel blocking activity at rest, but effectively block the sodium channel in depolarized tissues. They tend to bind in the inactivated state (which is induced by depolarization) and dissociate from the sodium channel more rapidly than other class I drugs. As a result, they are more effective with tachyarrhythmias than with slow arrhythmias.
●Class IC drugs (flecainide and propafenone) primarily block open sodium channels and slow conduction. They dissociate slowly from the sodium channels during diastole, resulting in increased effect at more rapid rate (use-dependence). This characteristic is the basis for their antiarrhythmic efficacy, especially against supraventricular arrhythmias. Use-dependence may also contribute to the proarrhythmic activity of these drugs, especially in the diseased myocardium, resulting in incessant ventricular tachycardia.
****NO MORE SPACE TO MENTION OTHER 3 CLASSES OF DRUGS*****
CLASSIFICATION OF ANTIARRHYTHMIC DRUGS -
The different antiarrhythmic drugs often have several effects on action potential generation and propagation and may also affect the autonomic nervous system. Those drugs that act on ion channels may preferentially bind to the activated (open) or inactivated state . The classification of antiarrhythmic drugs according to the Harrison modification of the Vaughan-Williams classification was originally based upon their effects on the action potential and also assumes that individual drugs have a predominant mechanism of action . This distinction remains clinically useful even though it does not account for complicated electrophysiologic and autonomic interactions that may be present or for the action of certain antiarrhythmic drugs such as digitalis and adenosine .
**Class I** - The class I drugs act by modulating or blocking the sodium channels, thereby inhibiting phase 0 depolarization. They are all at least in part positively charged and presumably interact with specific amino acid residues in the internal pore of the sodium channel. Three different subgroups have been identified because their mechanism or duration of action is somewhat different due to variable rates of drug binding to and dissociation from the channel receptor :
●The class IC agents have the slowest binding and dissociation from the receptor.
●The class IB agents have the most rapid binding and dissociation from the receptor.
●The class IA agents are intermediate in terms of the speed of binding and dissociation from the receptor
During faster heart rates, less time exists for the drug to dissociate from the receptor, resulting in an increased number of blocked channels and enhanced blockade. These pharmacologic effects may cause a progressive decrease in impulse conduction velocity and a widening of the QRS complex. This property is known as "use-dependence" and is seen most frequently with the class IC agents, less frequently with the class IA drugs, and rarely with the class IB agents .
●**Class IA drugs (quinidine, procainamide, and disopyramide) depress phase 0 (sodium-dependent) depolarization, thereby slowing conduction. They also have moderate potassium channel blocking activity (which tends to slow the rate of repolarization and prolong action potential duration [APD]), anticholinergic activity, and tend to depress myocardial contractility. At slower heart rates, when use-dependent blockade of the sodium current is not significant, potassium channel blockade may become predominant (reverse use-dependence), leading to prolongation of the APD and QT interval and increased automaticity.
One difference between the drugs is that quinidine and procainamide generally decrease vascular resistance, whereas disopyramide increases vascular resistance. In addition, N-acetyl-procainamide (NAPA), a metabolite of procainamide, has little sodium current blocking activity, while retaining potassium current blocking activity. Thus, NAPA behaves like a class III drug.
●**The class IB drugs (lidocaine and mexiletine) have less prominent sodium channel blocking activity at rest, but effectively block the sodium channel in depolarized tissues. They tend to bind in the inactivated state (which is induced by depolarization) and dissociate from the sodium channel more rapidly than other class I drugs. As a result, they are more effective with tachyarrhythmias than with slow arrhythmias.
●Class IC drugs (flecainide and propafenone) primarily block open sodium channels and slow conduction. They dissociate slowly from the sodium channels during diastole, resulting in increased effect at more rapid rate (use-dependence). This characteristic is the basis for their antiarrhythmic efficacy, especially against supraventricular arrhythmias. Use-dependence may also contribute to the proarrhythmic activity of these drugs, especially in the diseased myocardium, resulting in incessant ventricular tachycardia.
****NO MORE SPACE TO MENTION OTHER 3 CLASSES OF DRUGS*****
Переглядів: 2 026
Відео
visual pathway and Visual Field Defects
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This Demonstrates the following 1. Normal Eye Anatomy 2. Visual pathway 3. Visual Defects 4. Normal Swinging flashlight Test 5. Accommodation Convergence Reaction 6. Argyll Robertson pupil 7. Marcus Gunn Pupil 8. Adie's Pupil
Heme Synthesis and Degradation (Metabolism)
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You ll learn the reason behind the porphyria, which are group of disorders that result from a buildup of natural chemicals that produce porphyrin in your body. Porphyrins are essential for the function of hemoglobin - a protein in your red blood cells that links to porphyrin, binds iron, and carries oxygen to your organs and tissues. High levels of porphyrins can cause significant problems. The...
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Magnifique
Зрители этого видео из Германии есть?
thank you😊
Oonhuuuuu okay 👍 and yes you iiiiijj in uuuuuuiuiiiiu mmm npnil I’ll orderhhgghvvhi
powerful
Brilliant ❤❤❤❤❤❤
This is such a great explanation for this topic 😁
1:03
Muy buena información sobre cómo funciona el pet, muchas gracias
Feel spread goodness
good❤ amazing! 😊😊
omg amazing! 😍🔥🔥
Thanks❤
I was struggling trying to understand the explanation in my textbook, but the animation with the narration together make it way more understandable to me. Thanks! :D
Congratulations. Excellent presentation.
مكانش وحدة مدبلجة باه منقعدش عام باه نفهم
Amazing!!
🙏🥹
Very helpful and easy to understand, thank you!
wow that's so ez to understand !
Thanks
`This is the best and clearest explanation about the process of phototransduction. Thank you.
But how does a stronger stimulus create a stronger response then?
Hello, thank you for making this video. I have a question, on 0:29, why the light enters from the inner segment first?
Because this is how it evolved…
How can this be used or prescribed for chronic pain imaging using FDG or a CgRp tracer ?
This was sensational
0:20 these pats were so dry but very wholesome.
Amazing! Thanks!
Amazing!!!!! Thank you
this video explained more than my professor did in 60 lectures
AapkaAedrsKhaPrHgi
SirapkaContacn
تم الدعس ،شكرا..
hands down the best video on this topic.
Thank you so much. I am using this for my bio project this is so cool thank you!
Our main ambition : propagating Meditation and Buddhism via science based tactics . You may have seen, new born cubs starting to walk and loving it's mother , would It be possible just upon probability ? What about S. P. Infusion of norepinephrine and it's carbon rings ! What is the combination behind it and carbon rings of serotonin ? Every chemical compound has it's endemic rethum or wave generated according to variations of ionization energy when excited , and so it's a matter of short circuit , through electro-negativity which executes commands, responding to the rays and waves from environment , inducing Ca+ waves , catalyzed by enzymes and powered by cAMP. Memory retention ; micro-tubules in pyramidal cells of dentategyruss = a memory chip of your PC or smart phone !
Amazing!!!! Thanks!!!❤
Is this bio, chem, or just plain old mix of everything research
Need to know this as a human
This 9 minutes video was clearer than a University professor.
Estaria bueno en español
Excellent way of presentation. Thanks Dr
Isn't it a little farfetched to state that the inside-out recording allows for single-channel recordings? It would be quite impossible to make sure that the excised piece of membrane only contains one channel. Otherwise, thanks for the video, very instructive and clear
this is a wonderful video, so clear
i am still not getting the right videos, but class b ones
Very clear and instructive!
thankyou for helping
probably one of the worst animations and explanations for this process, sorry. straight to the point for people who already know what is going on....
The video is actually very enlightening. If you don’t find it okay, you can just move on instead of dropping your irrelevant comment. Effort was put into making the video you know
@@aminamusabob the comment is about the quality of the teaching in the video, how's it irrelevant? Just because knowledge and effort was put into the video doesn't mean it's a good video. I appreciate the effort, I'm commenting on the execution and the teaching, it's not good. My comment wasn't meant to be mean, it was critical.
Then why don't you explain about this
@@checkle1?
great for review for my medical imaging class
Arab