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Current time:0:00Total duration:6:16

Video transcript

sometimes in medicine you'll see that words get used a lot and sometimes their meaning is pretty simple or straightforward and and you know can be understood but the words themselves end up being kind of tricky and confusing and I think some of that has to do with the fact that these words and medicine often come from Latin and so we haven't really changed the word and so because Latin is not a language that any of us are really familiar with ends up being that the terms become confusing so what I'm going to do is I'm actually going to lay out four words for you and put out four words start with chrono trophy and we're going to go through them one by one basically kind of describing what they mean so chrono trophy refers to the heart rate now I actually put in kind of in parentheses a simpler way to maybe think about these terms so chrono drippy has to do with heart rate a second term is drama trophy drama trophy and drama trophy has to do with conduction velocity conduction velocity how fast a signal is going from one cell to the next conduction velocity and then we have inotropy inotropy and inotropy has to do with contractility contractility how hard the muscle is contracting the force of contraction you can think of it as the force of contraction and Lusa trophy lucid trophy oh there we go and lousã trophy has to do with the relaxation how fast it's relaxing so let's go through these one at a time and talk about the effects of the sympathetic and the parasympathetic s-- on this so actually the other thing i'm going to do maybe even white i'm going to write out where where these things are primarily being affected right where and then we'll talk about sympathetics and paris impacts okay so where is the first one happening so we talked about chrono trophy and of course it's not just one cell that's gonna be affected but in general what what cluster of cells are we thinking of you're you're right if you think about the SA node right the SA node and this is where the heart rate is usually set instead of the sympathetics we're going to basically make the SA node go in fire faster because you're going to allow more sodium into those cells so it's going to get up to the threshold for an action potential more quickly and parasympathetics basically do the opposite right they're going to allow less sodium to kind of flow in and it's going to take longer to get to the threshold potential so what about drama trophy this is a word that's maybe less commonly used and that's what I wanted to throw it up just so that you're at least familiar with the fact that it exists but drama trophy has to do with conduction velocity so how fast is the signal being conducted through the heart remember for this the major delay ends up being in the AV node right the huge delay sometimes we say it's a tenth of a second is in the AV node so what happens in the AV node if with sympathetic stimulation well you remember when you have sympathetic surround they allow the calcium to come into the cell more quickly so you actually have a faster conduction velocity so actually there's less of a delay with sympathetics and with parasympathetics there's a longer delay right again it's slower the AV node because you have less calcium coming in during the action potential of the AV node so the slope of the action potentials is slower is lower in parasympathetics now what about these last two inotropy and lousã tropi well both have to do with the ventricles right contractility and the force of contraction and then relaxation is how quickly are the ventricles relaxing so I'm going to write for both of them ventricles and I'm putting both ventricles left and right because it's not just one or the other same rules apply in both sides so ventricles and already I can tell you that pair of synthetics are going to have little effect here right because we said that really sympathetics affect your ventricles in in the parasympathetic simply don't have a similar effect to counterbalance it so I'm just going to put a little white line there to imply there's no major parasympathetic effect on either inotropy or Lusa trophy from a ventricle standpoint alright so sympathetics what do they do for inotropy or in terms of inotropy well you remember contractility is related to the amount of calcium that's going to come in during the action potential so what's going to happen if you have sympathetic stimulation or you're going to get more calcium in there so you're going to have a harder contraction or a stronger force I'll just put harder contraction meaning the muscles are going to squeeze down more forcefully than they than they would otherwise and what about relaxation well this is the the interesting thing we talked about with the sarcoplasmic reticulum right that's what's going to mop up all the calcium and allow our heart to get back into a state of relaxing and it's going to happen much quicker with sympathetics because they stimulate those ATP channels or ATP pumps to get calcium pumped back into the sarcoplasmic reticulum and away or sequestered from the cell itself so they basically create a faster relaxation so these are kind of the quick and dirty oh this is a kind of a quick and dirty overview of these four words and again you may or may not hear these words but at least you're familiar with them chrono drum oh I know and Lucy these four words describe the major functions of the sympathetic and parasympathetic nerves on the heart