Thanks for the comments guys. In regards to ionotropes I spelt that wrong, didn't look at how it's spelt before hand. And also I do also question how hypoxia decreases heart rate. I think it also increases it, but different books tell me different things. One thing is for sure though that when there is a decrease in blood levels and oxygen we tend to increase heart rate as the first compensatory mechanism. How long does this last? Not sure. So maybe hypoxia causes bradycardia in the long run. Don't quote me though. Cheers
hi man, great vid. As far as I know, hypoxia doesn't cause bradycardia...until the cardiorespiratory centre in the brain is starved of oxygen and then starts shutting down. By then though...the person is pretty much dead... or will need serious resuscitation. The body is really quite good at maintaining cardiac function under "normal" conditions, even in conditions of hypoxaemia. When the paO2 drops to around 8 kPa, (normally >10.6 kPa) the carotid chemoreceptors detect this fall and start ramping up cardiorespiratory rates (breathing and HR). Even if someone is chronically hypoxic, like someone with COPD, they can maintain a good enough cardiac output to not really notice until they exercise.
well let's see if that benefits, I studied that mild hypoxia causes tachycardia due to stimulation of CAC and CIC, but severe hypoxia causes bradycardia due to damage of medullary center and nodal tissues of the heart (end in death)
I think I finally am starting to understand preload and afterload. You have an amazing ability to explain difficult material in a manner that is understandable! I look forward to future videos :D
Great Job, nice and clear. I'm glad you mentioned the positive and negative chronotropic & ionotropic determinants in HR and Contractility, I had overlooked them and thanks to you I'm good on them! Again keep it up. God Bless!
Excellent video! I passed my final histology exam thanks to one of your drawings of the skin layers! And now I am taking physiology. Great video. Helped me organize what I learnt in class.
Hi Armando Thanks so much for your videos they are helping me greatly through my health degree. You explain things so clearly and your drawings are fantastic. Awesome.
You make some incredible videos! Very helpful study tools. The only thing that I could suggest is showing one final screen shot of everything all at once. That way you could test yourself using that image. Thanks again for these amazingly helpful videos. I hope to see you illustrating anatomy text books one day.
i disagree with regards to the equivalence between preload and end diastolic volume. there is what we call ejection fraction, which is a percentage of volume being ejected from the ventricles. this means not all the end diastolic volume is being ejected per pump. it's only a percentage. great visual presentation though. i like it
in the video you stated that hypocalcemia is a + ionotropic effect, and then at the end you said that hypErcalcemia is a + ionotropic effect, which one is it and why?
You say at <a href="#" class="seekto" data-time="315">5:15</a> that preaload is the volume entering the heart, but preload is the total volume of all the blood in the heart at the end of diastole (including direct flow, retained flow, delayed ejection flow and residual volume).
At ~6:00 you also say that the amount of blood entering the heart is about equal to the amount leaving the heart and that is true. But directly after you say that that "end diastolic volume ~ stroke volume", and that is not correct. The end diastolic volume is ~120ml for a normal person. At the end of each heart stroke there is about 50 ml left in the heart (the residual volume). The normal stroke volume is 70ml (120-50=70). This can be seen in a pressure-volume-loop.
Did you ever upload the video about the cardiac cycle ? I'm talking about the graph you mention at the very end. Can't seem to find the video about the subject.
