hello everyone we're back again we spent our last mini lecture talking about the conduction pathway and that conduction pathway made up of specialized cardiac muscle cells is acting as the heart's nervous system the heart's central nervous system this means the heart can literally take care of itself it runs on its own does not need any help for the most part to just do everyday types of functions even if blood flow coming into the heart changes because of the way this conduction pathway is set up inside of the heart it can adapt now it's adapting after the changes have occurred but it's adapt it can adapt to amounts of fluid moving into it we're going to take that information that we talked about with the conduction pathway and take it a step further the heart is working on its own but you know there are times that it may need help or at least in these bodies that we have evolved into it is found it beneficial to be able to kind of look ahead to anticipate what's happening in its environment that's where today's lecture comes into play we're going to talk about what are called autonomic inputs autonomic inputs these autonomic inputs you've heard a little bit about probably from other classes you've heard about the sympathetic and the parasympathetic nervous systems autonomic inputs are kind of large-scale reflexive actions or activity from the nervous system that kind of help feed information to different parts of the body to get it ready to do certain things ready to talk about this let's jump into this folks okay in this image here you've seen this before we use this image when we were talking just about the anatomy of the heart and the conduction pathway itself in this image again just to review what's in dark red is that conduction pathway remember the SA node the AV node AV bundle and the purkinje fibers as they course through the body or I should say the heart itself now remember the essay note can generate its own action potentials and the information or the action potentials that it generates will feed over by way of the internodal pathway that's these fibers that you see here over to the AV node which will translate over to the AV bundle which will translate over to the burkinje fibers and get different parts of the hard beating at different times Atria first ventricles next Atria ventricles Atria ventricles again the heart can work on its own we need to talk about how the heart though actually gets kind of added information to maybe start speeding up before it needs to or to slow down after it's already been working pretty hard on taking care of certain things let's go on to our next slide now we need to give you a definition of the autonomic nervous system we'll be looking at it more closely a little bit later in the semester but for now I want you to understand some of the basics associated with it so the autonomic nervous system is a component is a part of our nervous system part of the peripheral nervous system now this peripheral nervous system is involved in trying to make sure to take care of what I have listed here is involuntary physiological processes involuntary meaning it's trying to do it without you consciously paying attention to it everybody kind of got that autonomic nervous system so give you an idea an idea of what this is entailing um if you're walking you've been standing in class you're getting ready to leave you're going to run out to your car and get away from Lab because it's late at night it would be really advantageous that as soon as you started walking which is changing things around the body pressures fluid levels all this sort of thing because of Fighting Gravity and everything else that you don't have to consciously think about I need to increase my heart rate so that I can I'll have enough fluid blood coursing around the body getting to the muscles to get me out to the car because I have to go down the steps down the hill out to the parking lot to get there the autonomic nervous system is all about okay we've got to let the heart know you know what you may want to start changing your your pumping action we're just giving you a heads up that's what this is involved with because of this the autonomic nervous system at least from what we can see is kind of divided up into three pieces three parts there's a sympathetic nervous system that you've heard about there's a parasympathetic nervous system that you probably also have heard about and there's one that doesn't always get included in this group but I'm letting you know is actually a very integral part of all this and that's a part of this autonomic nervous system called the enteric nervous system enteric so let's define these three pieces here sympathetic nervous system is involved in elevating particular processes around the body to deal with a stressor to deal with the stressor so what are we calling a stressor a stressor is anything that takes the body away from what it normally does so if you're sitting and you decide to stand up that's a stressor if you're standing up and deciding to sit down that's a stressor got that it's not just what we may psychologically think of a stressor because that adds to this as well but it's anything that takes the body away from its baseline from its Baseline sympathetic nervous system the parasympathetic nervous system it's involved in well bringing things back to that Baseline so sympathetic getting the body ready to deal with whatever the stressor may be parasympathetic we've dealt with the stressor let's get us back to our Baseline let's get us back to our Baseline does that make sense folks so you've heard of this sympathetic parasympathetic setup you hear in other courses the fight or flight systems all these are pseudonyms for this autonomic nervous system an extension of both the sympathetic and parasympathetic is the enteric nervous system this enteric nervous system is involved strictly with the gastrointestinal system the gastrointestinal system and you'll see when we start moving into that area how it much like the heart has its own internal system and so the enteric system gets information from both sympathetic and parasympathetic now we're going to look at the conduction system of the heart and you're going to see it's getting input from both sympathetic over here and parasympathetic using that information to adjust what it's doing so that it can better respond to the environment better respond to the environment in this image you can see the heart over to the right and I want to make sure that you can see the essay node sitting up in the upper right hand corner of the uh the right Atria and the AV node which is sitting at the junction between the right Atria moving down into the ventricles SA node AV node over to your left we have sections through particular parts of the nervous system up here a section through the brain stem the medulla oblongata and down below a section through the spinal cord what we're trying to illustrate here are where sympathetic and parasympathetic neurons are located and where they send their axons so that they can innervate synonym send information over to the heart itself we're going to start with the sympathetic first that's what's here in green the sympathetic nervous system there are multiple neurons that are involved or multiple groups of neurons that are associated with gathering this information and they're linked this information is linked to all the senses as well so as as I mentioned earlier if you're starting to go out or the your brain is already thinking about okay you've got to walk to the car automatically sympathetic mechanisms are picking up that information sending it down from the brain stem down to the spinal cord out to a group of neurons that sits outside of the spinal cord called the sympathetic trunk and then sending those neurons sending their axons out to specific areas out in the tissues since we're talking about the heart trying to show you it will innervate specifically the SA node the AV node and most likely the purkinje fibers that are sitting in the walls of the ventricles this is classic for the sympathetic nervous system think of the sympathetic nervous system as kind of a firearm that fire alarm goes off and it's loud why because we want everybody to hear it now we don't want to have to send that information by Word of Mouth just one person at a time we need to have everybody hear it because we're dealing with a particular type of stressor that's what the sympathetic nervous system does it tries to alert everybody that hey something's happening we need to do this if the sympathetic nervous system is communicating with these different parts of the heart the job of that is to increase contraction increase the strength of contraction and increase the rate of contraction to help increase fluid moving around the body parasympathetic mainly coming from brain stem or from the base of the spinal cord extends out and you can see it's going to spend most of its time innervating SA node and AV node it really doesn't care about the purkinje fibers its job we're going to go to the two that are probably the leaders and tell that okay everything is good we've come to a point where we can start to relax slow down everybody slow down got that sympathetic increasing activity for the heart to increase pumping parasympathetic they're to slow down pumping when we don't need to have it at that point everybody got that good good let's review just real slowly here all right heart rate heart rate will be affected the contractility of the heart and the rate of its contraction will be dependent on sympathetic activity which will increase heart rate parasympathetic activity which will slow down heart rate slow down heart rate there's also another way we can change this heart rate as well the adrenal glands which are part of the sympathetic nervous system just to kind of make sure everybody's hearing the the siren literally condump neurotransmitters and hormones like epinephrine into the bloodstream which comes right through the heart and can activate the conduction pathway of the heart two start beating faster and harder faster and harder in this next image here we're going to concentrate on just the SA node do you remember us talking about the action potential that's generated by those specialized tissues like the SA node if you can remember back a few lectures this is what that action potential looked like for specialized tissues like the SA node you can see here in this Legend a is the control B during sympathetic stimulation C during parasympathetic stimulation a sitting here in the middle this is a normal action potential that we would see in the SA node remember it drops down to about um negative 55 but starts to slowly creep up because of the sodium channels or excuse me sodium leaking through the calcium channels we get through a threshold bam we get an action potential it repolarizes and then we start all over again so a in this greenish color that's the normal action potential for the SA node if the sympathetic nervous system feeds over to that SA node look at what happens this area here that we saw where the resting membrane potential was slowly moving up to the threshold here you can see it moves much more quickly that's because sympathetic stimulation is going to cause the channels those calcium channels to be even more leaky more sodium leaks across the membrane so you can see it is coming and hitting the threshold much more quickly bam we get an action potential it drops back down again bam it's going to come back up we have an increase in rate an increase in rate of contraction occur in purple this is the parasympathetic nervous system's effects it actually will hyperpolarize these specialized cardiac muscle cells and it slows down the leakiness of the channels those calcium channels to sodium meaning it's going to take longer to reach the threshold longer in between action potentials which means a slower rate a slower rate in this last image this one's an interesting one and it's a little more difficult to understand we're going to try to illustrate a little bit well about what's happening with sympathetic stimulation and I guess we could say parasympathetic over here to the left I wanted to make sure you remembered blood flow through the heart over here the right atrium with fluid blood coming from the superior and inferior vena cava into the right atrium right atrium to right ventricle right ventricle to pulmonary trunk into the lungs from the lungs into the left atrium left ventricle out through the aorta everybody got that remember that good the reason I'm going through this is because this graph is trying to illustrate how the sympathetic nervous system will affect fluid movement blood flow and what we called cardiac output you remember that cardiac output so cardiac output here on this axis on the bottom axis right atrial pressure this is why I wanted you to remember blood flow right atrial pressure that means right atrium here the pressure in that area so why are we concerned about that well pressure in the right Atria needs to be very very low the reason we want fluid to literally freely move into the right Atria so if there's pressure there a buildup of pressure or build up a fluid creating pressure fluid from the superior and inferior vena cava will not be able to move in there that could be a problem so normally in US pressure at the right atrium is usually sitting somewhere around zero on this graph zero here is referring to normal right atrial pressure everybody got that well it's zero pressure right atrial pressure if we were to calculate cardiac output remember that from a few lectures ago taking remember let's see here stroke volume is 70 milliliters per stroke and if your normal heart rate is sitting somewhere around 70 beats per minute that's about 4 900 leaders excuse 4 900 milliliters not liters milliliters and if we kind of uh take that and kind of manipulate the decimal point that's about five liters per minute so normal cardiac output for most of us is about five liters per minute now at 5 liters per minute or we can kind of check that right atrial pressure and no sympathetic stimulation we could say let's say there's no stressor you're just completely relaxed well I hate to tell you this even under relaxed situations there's still some sympathetic stimulation going on the body always likes to remain ready so where I have the star placed is probably fairly close to where we would have that's our normal cardiac output at zero pressure in the right atrium if we had a little more activity going on in the body you were coming into class and and kind of rushing in from from where you parked your car out in the parking lot well normal sympathetic stimulation then would increase cardiac output by increasing the rate and contractility of the heart makes sense so now instead of putting up five liters per minute to make sure your body was able to get here on time and do everything you normally do once you get into class it had to increase cardiac output up to about seven eight almost nine liters per minute just to take care of what you were doing just in that short period of time now let's say a fire alarm goes off in the hall or in the building and we got to get people out of here and I say okay I need everybody getting down those stairs getting out to our safe spot outside in the in the courtyard of the science building you're all rushing you're at heightened uh stimulation because this is a major stressor your cardiac output is going to be increased maximally as you can see here it's up to about 15 liters per minute now is that as much as the heart can do no you can see from this graph it can do quite a bit more but this should be sufficient for you to be able to handle the stressor that you're just now in now I'm going to be bringing this graph back a little bit later as we when we talk about the actual vascular Network outside of the heart and into the body and we will be bringing back this idea of right atrial pressure and what happens if that pressure increases you can see here all of these curves are so associated with the sympathetic nervous system flatten out that's not a good sign there's only so much the heart can pump and if it can't pump when all this fluid is being pushed back in pressure is just going to get worse and worse and worse all right folks we're going to end our cardiac lectures there and we'll see you next time when we start talking about the actual vascular Network see you later folks