Imperfect evolution (Introduction)
by David Turell 
, Monday, January 19, 2015, 15:27 (3385 days ago)
Heart rhythm disturbances in aquatic diving mammals:-http://www.sciencedaily.com/releases/2015/01/150116085554.htm-"Instead of a single level of reduced heart rate during dives, the researchers found that heart rates of diving animals varied with both depth and exercise intensity, sometimes alternating rapidly between periods of bradycardia and tachycardia. Cardiac arrhythmias occurred in more than 70 percent of deep dives.-"We tend to think of marine mammals as completely adapted to life in the water. However, in terms of the dive response and heart rate, it's not a perfect system," Williams said. "Even 50 million years of evolution hasn't been able to make that basic mammalian response impervious to problems."-"The conflict between dive-induced bradycardia and exercise-induced tachycardia involves two different neural circuits that regulate heart rate, she said. The sympathetic nervous system stimulates the heart during exercise, whereas the parasympathetic nervous system controls the slowing of the heart rate during the dive response."
Imperfect evolution
by Balance_Maintained , U.S.A., Monday, January 19, 2015, 21:40 (3385 days ago) @ David Turell
Heart rhythm disturbances in aquatic diving mammals: > > http://www.sciencedaily.com/releases/2015/01/150116085554.htm > > "Instead of a single level of reduced heart rate during dives, the researchers found that heart rates of diving animals varied with both depth and exercise intensity, sometimes alternating rapidly between periods of bradycardia and tachycardia. Cardiac arrhythmias occurred in more than 70 percent of deep dives. > > "We tend to think of marine mammals as completely adapted to life in the water. However, in terms of the dive response and heart rate, it's not a perfect system," Williams said. "Even 50 million years of evolution hasn't been able to make that basic mammalian response impervious to problems." > > "The conflict between dive-induced bradycardia and exercise-induced tachycardia involves two different neural circuits that regulate heart rate, she said. The sympathetic nervous system stimulates the heart during exercise, whereas the parasympathetic nervous system controls the slowing of the heart rate during the dive response."-Wouldn't this kind of be expected, though? I mean, to hold your breath for a long time, you have to slow your heart, to exercise, you have have increase your heart rate, so their bodies would have to be balancing the need for both things and under extreme pressure. To me, it would seem that what you would expect to see is that their heart rate would generally slow down and then when needed, for a burst of speed or to counter under water currents and such, that the heart rate would have to kick back up to give a fresh supply of oxygenated blood to the muscles, and then immediately drop back down to allow for continued long dives.-It reminds me of an electric hydraulic motor, or the motor for a pressure washer or generator. They don't run hard all the time. They cycle depending on load.
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What is the purpose of living? How about, 'to reduce needless suffering. It seems to me to be a worthy purpose.
Imperfect evolution
by David Turell , Monday, January 19, 2015, 22:03 (3385 days ago) @ Balance_Maintained
David: Heart rhythm disturbances in aquatic diving mammals: > > > > http://www.sciencedaily.com/releases/2015/01/150116085554.htm > > > > "Instead of a single level of reduced heart rate during dives, the researchers found that heart rates of diving animals varied with both depth and exercise intensity, sometimes alternating rapidly between periods of bradycardia and tachycardia. Cardiac arrhythmias occurred in more than 70 percent of deep dives. > > Wouldn't this kind of be expected, though? -No, they are talking about arrhythmias, in cardiologic parlance 'abnormal rhythm' What they were seeing was abnormally slow rhythms and abnormally fast ones, not fitting the activity. We humans have a dive reflex which slows your heart as you hit the water. In rare circumstances it has killed. > > Tony: It reminds me of an electric hydraulic motor, or the motor for a pressure washer or generator. They don't run hard all the time. They cycle depending on load.-Here you are describing normal cardiac activity related to exercise. There is a direct correlation between calorie work load and pulse rate different for each individual based on their state of fitness, with a maximal rate limited by advancing age.
Imperfect evolution
by Balance_Maintained , U.S.A., Tuesday, January 20, 2015, 08:25 (3385 days ago) @ David Turell
Wouldn't this kind of be expected, though? > >David: No, they are talking about arrhythmias, in cardiologic parlance 'abnormal rhythm' What they were seeing was abnormally slow rhythms and abnormally fast ones, not fitting the activity. We humans have a dive reflex which slows your heart as you hit the water. In rare circumstances it has killed.-Yeah, um, of course their heart rate is abnormal then. I hate to sound like this is a DUH moment, but it kind of is. Ok, put your blindfold on and forget the article. As a cardiologist, tell me what YOU would expect in this scenario:-You hold your breath for 10 minutes. When you start the ten minutes, you are submerged in water that is about 62°. Assume minimal physical exertion, hold on to a brick and sink down 300m (deep dolphin dives). What's happening? The water temperature drops ten to twenty degrees to between 40-50°F, the pressure increases more than 30 atmospheres, and your blood is slowly deoxygenating while nitrogen bubbles form in your body. To compensate, your heart rate slows like a yogi, taking you down to a minimalist state. Now that you are under the water, you can float with minimal effort, so the slow heart rate doesn't hamper you too much. At this point, you have a challenge. Catch something before you drowned while fighting localized currents that buffet you with forces in excess of 4 tons per square meter, and make it back to the surface without getting the bends. What do you, as a cardiologist, predict would happen under these circumstances? Do you think "normal" even applies under these conditions? - > > > > Tony: It reminds me of an electric hydraulic motor, or the motor for a pressure washer or generator. They don't run hard all the time. They cycle depending on load. > > David: Here you are describing normal cardiac activity related to exercise. There is a direct correlation between calorie work load and pulse rate different for each individual based on their state of fitness, with a maximal rate limited by advancing age.-Yes, but doesn't that also depend on other conditions, temperature, oxygen in the blood vs. muscular demand, etc?
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What is the purpose of living? How about, 'to reduce needless suffering. It seems to me to be a worthy purpose.
Imperfect evolution
by David Turell , Tuesday, January 20, 2015, 14:59 (3384 days ago) @ Balance_Maintained
edited by David Turell, Tuesday, January 20, 2015, 15:15
> Tony; What do you, as a cardiologist, predict would happen under these circumstances? Do you think "normal" even applies under these conditions?-I have no idea. I've only worked with humans in factory settings, and in the lab, and I know exactly what exercising humans do in work responses. I can predict yours. The researchers said there were arrhythmias. I take them at their word. It is normal activity for the dolphin. > > > > David: Here you are describing normal cardiac activity related to exercise. There is a direct correlation between calorie work load and pulse rate different for each individual based on their state of fitness, with a maximal rate limited by advancing age. > > Tony: Yes, but doesn't that also depend on other conditions, temperature, oxygen in the blood vs. muscular demand, etc?-Of course it does. The relationships I described must take all of that in account.
Imperfect evolution
by Balance_Maintained , U.S.A., Tuesday, January 20, 2015, 19:25 (3384 days ago) @ David Turell
Yes, but arrhythmias are simply abnormalities, correct? And they are happening regularly, at specific points (during specific activities) during the dives, correct? The article mentions that it happened when starting their ascent and when chasing prey or during heightened activity. So, if it is normal for it to happen under those specific conditions, and not others, is it actually an abnormality, or simply a normal that we have not yet recognized? I was merely trying to point out that there are a LOT of things that go on under the water, particularly for warm blooded creatures in colder water, and even more particularly at depth where pressure and currents also play an increasingly large role. I think classifying something that is poorly understood as abnormal prior to trying to discern if there is in fact a very valid reason for what is happening might actually impede the progress of their research and lead to false assumptions.
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What is the purpose of living? How about, 'to reduce needless suffering. It seems to me to be a worthy purpose.
Imperfect evolution
by David Turell , Tuesday, January 20, 2015, 19:56 (3384 days ago) @ Balance_Maintained
Tony: I was merely trying to point out that there are a LOT of things that go on under the water, particularly for warm blooded creatures in colder water, and even more particularly at depth where pressure and currents also play an increasingly large role. I think classifying something that is poorly understood as abnormal prior to trying to discern if there is in fact a very valid reason for what is happening might actually impede the progress of their research and lead to false assumptions.-Not having read the article itself, I can't comment on their assumptions, but they should know an arrhythmia when they see it, with any cardiology experience. An arrhythmia has an abrupt onset and turn off, whereas in exercise one sees a gradual increase or decrease in heart rate. The arrhythmia may even have a different axis or vector indicating the rhythm is coming from an irritated focus in the heart.