@@fareshejazi2297 perhaps 'pat brewer' meant that, through 15 years of lectures/classes, this video had the clearest explanation (compared to pat's lecturer/textbook explanations)
+Crist Gord hi guys, the best results that I have ever had was by using the Anatomy Blueprint Pro (just google it) definately the no.1 course that I've followed.
Adding onto his notes in more specificity: The unstable membrane potential for which these pacemaker fibers start is known as a pacemaker potential since the fibers never truly rest at a constant value. This would be the beginning of his stage 4 at about -60mV. These pacemaker fibers contain channels known as I-funny channels, that are different from other excitatory tissues in that they allow Na ions and K ions to both pass. When these channels open at negative values, they allow for a greater influx of Na+ than an efflux of K+. This influx of Na+ slowly begins to depolarize the fibers, which can be seen in his slow incline along phase 4. As the fibers become more inside positive, the I-funny channels slowly start to close. It is at this point, right before the sudden inclination, that a specific set of Ca2+ channels open, allows Ca2+ to move into the fibers and continues to make the auto-rhythmic fibers more inside positive. When the pacemaker potential reaches threshold, a different group of Ca2+ channels open, allowing a sudden rush of Ca2+ into the cell and creating the steep 0 phase. The steep depolarization due to Ca2+ is a key characteristic of pacemaker cells. In other cells, the steep depolarization phase is due to a net influx of Na+. At the peak, these Ca2+ channels close, and slow K+ channels open. The rapid efflux of K+ is responsible for repolarization (his phase 3). This phase is similar to other excitatory cells. Similarly, the small "under shoot" at the end of the steep decline signifies the closure of K+ channels. Among other things, the time it takes for depolarization of pacemaker cells determines the heart rate.
Armando, I am truly grateful for your videos. Your videos have help breakdown complexing subjects into bite size clear information. You have an amazing way of teaching the material and thanks to your videos I made it through my Pathophysiology course. Thank you again for taking the time to help me and so many who struggle with reading words on a textbook. Thank you again and God bless !
you can't imagine how thankful I am... my exam is tomorrow and I was crying cause I didn't understand it till I found your video and it appears clear like water... thanks you so so much!!!!!!❤❤❤❤❤❤❤❤❤❤❤
The videos are just amazing and so to the point..also Please post some detailed videos on CARDIAC ARRTHYMIAS and ANGINA PECTORIS..and if it has already been made..please provide the link..unable to find it..
if you look into the period of the cardiac cycle, there is about 0.3 sec when four chambers are all relaxed and waiting for blood coming into the atrium.I think that area should be shown longer. thank you!
This is probably a minor and inconsequential point, but at ~8:50, Armando mentions phase 0 (the steep upward curve) and states that the influx of sodium is the contraction of the ventricles. While this phase of the action potential is the depolarization of the membrane, the voltage-gated influx of calcium (Ca) ions (via the L-type channels) starts at about -40 mV and is more prolonged than sodium influx (lasting throughout phase 2). The Ca ions which influx during this phase trigger a massive release of Ca ion storage from the sarcoplasmic reticulum, which is responsible for ventricular contraction. Therefore, I believe it would be more precise to say contraction of the ventricles happen during phase 2. Source: Pathophysiology of Heart Disease, L. Lilly.
Cmiiw : SA node -> AV node -> Bundle of Hiss -> Purkinjae Fibers Location, SA : Crista Terminalis - Atrium Dextra Posterior AV : Trigonum Koch - near A-V Valve Bundle of Hiss : Interventriculare Ceptum Purkinjae Fibers : spread in Miocard Ventricle
Hi, good catch when you said atrial diastole instead of ventricular diastole. But if you want to add in, the S4 sound should be heard right before the QRS complex. Also when you drew the cardiac myocyte action potential on top of the EKG, shouldn't phase 3 include the T wave instead of ending at the T wave, since the T wave represents ventricular repolarization.
Thank you for this amazing video but i want to point out about the action potential of the SA node, the action potential peak reaches +10 not 0, otherwise there will be potential difference between the charges if it stops at 0
ok...one question right,,,for the ventricle graph..first depolarization means filling the with positive charge..so how is phase0 systolic when there is rapid depolarization....could you kindly explain that as soon as possible
very very very very ......... Great work , u have a genius creative mind (prefrontal cortex :P ) that connects all things together in a simple way ,,, I really love this way of looking at things thanks very much man , u are a hero :D
thaaaanx it made alot of sense now..ive been looking for the video next to this one but i couldnt find it could u please tell me how to find it..many thanx
I am a Biology Higher level teacher, your videos and teaching skills have really advanced my teaching approaches and bettered learners' understanding and good approach to the most challenging questions. thank you very much, may God bless you.
Mr. Richard Adetoye, there's no reply option to your comment so I'll just answer you question here. When you mean systolic, there is contraction of ventricular muscles to push the blood from the ventricles to the pulmonary artery or to the aorta. Depolarization means making the membrane potential to become more positive to make muscle contraction possible. Phase 0 means depolarization of the ventricular muscles thus is part of the systolic phase. Hope this helps.
hey man great video. I just have a quick note about the SA node phases. In phase 4, it is true that the L and T types open up channels but they do so after it reaches -40 mV. From -55 to -40 mV is produced by something called a funny channel which is activated by negative membrane potential and this channel bring in Na +. Just wanted to add detail but great video, love your stuff please keep doing what youre doing!
