We will now name four or five heart properties. Traditionally only four properties were mentioned but relaxation became very fashionable in the last 20 years and it was included among them.
- Automatism or Cronotropism
- Excitability or Batomotropism
- Conductivity or Dromotropism
- Contractility or Inotropism
- Relaxation or Lusitropism
It is interesting to note that these five properties as simple phases within a normal contraction cycle. The muscular fibers have an automatic property. We have already stated that they have the ability to possess an endogenous rhythm so each of them could potentially contract in an autonomous fashion. They are automatic; excitable (this autonomous rhythm will produce in them an excitation, an electric charge), they are able to conduct this charge , they are able to contract themselves because of fibers such as the skeleton muscle and can also relax; which means they are simple phases. These five characteristics are going to be modulated by the Autonomous Nervous System (ANS), and the sympathetic and Para-sympathetic nervous systems.
Which are the effects of the sympathetic and the Para-sympathetic on the cardiac properties?
The sympathetic system is going to stimulate the five cardiac properties whereas the Para-sympathetic system will inhibit them. We link it to the concept of exercise. In the exercise is activated the sympathetic system and we link it with the tachycardia, or the rise of the cardiac frequency.
Useful Values:
Volume per minute 5.5 liters
Fin de Diastole Volume: 130 ml
Residual Volume: 70/80 ml (these are variable data from the book)
Systolic Volume: 50 ml
Ejection Fraction: Systolic Volume / Diastole End Volume: 0.5 (relationship)
Cardiac Cycle
We are going to use these words on a trigger bases: what is diastole and what is systole?
Diastole is a period of relaxation which will allow the filling.
Systole is a contraction which produces blood ejection in the heart.
At the same time there is a rhythm of filling and emptying given by the san, which is of 70 to 100 hundred contractions per minute. This will generate a volume-minute of 5.6/6 liters which means that the blood volume that goes through the organism per minute is 5.5 liters.
Diastole End Volume: how much is there within each ventricle, in this filling relaxation phase, when the diastole ends? Be careful, within each ventricle!! We draw our figure thinking in the left ventricle. The left ventricle, when the diastole ends, when this filling phase ends will have some 130 ml inside. Afterwards, the contraction takes place (the systole) a 50 ml volume is going to be expelled from the ventricle. The residual volume is what remains within the heart after the systole. This means that we have to change the systole concept. Systole is a contraction which will not produce a total emptying of the ventricle, only a partial one. There is a small blood volume which will remain in the heart and it will have its consequences. According to this analysis the diastole end volume (which means all the blood we find at the end of this process) is going to be equal to the volume expelled minus what is left: in other words, systolic volume plus residual volume. The ejection fraction shows clearly this relation, since 70 are more or less half of 130. What the heart ejects is more or less half of the volume there is when it is full. If a person has low contractility, if it has cardiac insufficiency, if someone has a small ejection capacity, the ejection fraction diminishes (minus 0.5). The cardiac frequency rises in all individuals when making exercise, in sportsman trained in aerobic activities. They will have a minor frequency and a major volume, and that major volume, depending on the activity they might develop, will correspond to a diastole end major volume or to a smaller residual volume. Very interesting is to analyze how a person can, modifying the activity also alter the cardiac properties. If you and your grandmother climb some steps, she will end puffing and blowing and you will not, and you won’t understand why. Since she does not make any physical activity her cardiac frequency will rise up a whole lot when making this exercise, whereas a person who is trained or practices any sport is much more used to effort. Thus, regarding that same effort his cardiac frequency is smaller. Probably his volume-minute is also higher depending upon the type and intensity of the exercise. The cardiac frequency, however, is the value in which this phenomenon can be better analyzed.
Let us study in a deeper way the cardiac cycle. Let us analyze -starting from the anatomy we have just seen- what the diastole and the systole are all about. Let us see some details about them. The chart we use to integrate the cycle with pressure normal values at the heart cavities’ level. We call it Pressure Curve Volume. We first are going to comprehend this curve and then will understand its physiological variations. This is a Chart where pressure is expressed in mmhg as regarding volume measured in ml. We have already expressed that the residual volume was of 50 ml. This is the smaller volume that the ventricle should carry. The diastole end volume is 130 ml, which is the maximum possibility for the ventricle. And 120-125 is the maximum we reviewed that systolic pressures can reach in the left ventricle as well the aorta. We will choose the 0.50 coordinates, which we will denominate Point One. At this “point one” the auricular-ventricular valves are going to open and the filling phase will start. We have to locate ourselves within the cycle: they are then in the second part of the diastole.
+filling systolic iso-volumetric contraction ejection diastolic iso-volumetric relaxation Active tension curve Passive tension curve or distension ability
We are dealing with values of the left ventricle since from a physiological point of view they are more interesting to analyze. In the same way, when the auricular-ventricular valves close it is called medical clinic S1, and then the sigmoid ones close it is called S2. This is important regarding the blow diagnosis. There has to be a fixed time between S1 and S2 and also between S2 and S1. If we find any alteration between those periods cardiac failures appear.
- Filling
- Passive Tension or Dis-sensibility
- Systolic Iso-volumetric contraction
- Ejection
- Active Tension
- Diastolic Iso-volumetric relaxation
We analyze pressure in mmHg over volume in ml. 50 is the residual volume, which is the blood volume remaining in the heart after the systole, and after the ejection and the diastole end volume is of 130 ml which is equal to the blood total volume which the ventricle embraces before ejection takes place. Then, the diastole ends. Maximum volume is reached just before the systole begins.
We will review each point in this curve. We are now in point one; we will start with the ventricular filling. The auricle-ventricular valves need to open. Blood begins to enter the ventricle and its volume starts to rise, as we see, and its pressure also rises. The curve describes this trajectory up to point two. At point two a pressure of 10 is reached, equaling and surpassing the auricle’s pressure. What happened? The auricular-ventricular valves closed because the ventricle’s pressure surpassed the auricular one. That way begins the systolic iso-volumetric contraction phase. We should remember that the auricular-ventricular valve just happened to close. After the ejection ended the sigmoid valves closed down. Since both valves are closed, it will be iso-volumetric, in such a way that the trajectory is going to be parallel to the axis. And no volume variation will be perceived. There is, nevertheless, a pressure rise due to the ventricle’s muscular fiber contractions. An enormous pressure rise (10 to 80) will take place. The ventricle’s pressure rises up a lot during this stage. Point Three: The pressure rises up so much that the sigmoid valves open up. There is an opening of the aortic valve because the ventricular pressure was so high that surpassed the aorta’s pressure in diastole (which means before the ejection, 80-120, and an average aorta’s pressure during diastole). When reaching the ventricle, this pressure of eighty will allow the opening of the aortic valves. They open and the contraction continues to take place. In the beginning the pressure rise continues. We have already said that the ventricle’s pressure rises up to 120-125 which is the maximum figure that the ejection reaches during this first phase, really too fast. Then the diminishing phase starts, the ejection lowers which in turn also diminishes the ventricle’s pressure. We see that during the ejection phase we go backwards, when analyzing this process, why? It is because the volume will be lowering. The ventricle’s volume if it is ejecting any blood then it will be diminishing. We finally reach the “point four”: the ventricle’s pressure diminishes so much that it will reach a point below the aortic pressure thus provoking the shut down of the aortic valves. At the ejection phase it lost volume in such a way, that its pressure lowered. When ejection begun, it was high, there existed a high pressure, and also a great difference which needed to be equilibrated. When we reach a certain stage, however, that strength reaches a maximum point, and that gap disappears and therefore the exit speed will lower, the ventricle’s pressure lowers and starts a reduced ejection phase. At point four, then, there is a close down of the aortic valves because the aortic pressure is larger than the ventricle’s pressure which went down a whole lot. We now find a very interesting data. We had seen that the aorta’s pressure was 80 but here is closing at 100. Why is that so? Why is there a difference of 20 mmHg? At this point, the ventricle’s pressure (80 mm Hg) had surpassed the aorta’s one. The valves opened, it surpassed it, but when it lowered down to 100 then the aortic valves did close. Why did this take place? This takes place because the ventricle is emptying towards the aorta in such a way that at the same time the ventricle’s pressure lowers the aorta’s rises. We should remember that not only the heart has a diastolic and systolic pressure (or a relaxation and contraction pressure). Also the vessels (in this case the aorta) will register a diastolic and systolic pressure as well. We have already stated that the aorta has a diastolic pressure of 80, which means that before receiving the heart blood flow its diastolic pressure almost reached 120. At approximately 100 equilibrium and closing take place. One more clue: when you measure your arterial pressure, two figures are given to you. These figures correspond to a diastolic and a systolic value. The same way the heart will carry on this biphasic cycle of diastole and systole, retaining or freeing blood towards the vessels, which in a certain way are elastic, distensible, they in turn will respond to this diastole and systole process. At a moment they do not receive anything and all of a sudden they do receive. When we measure a person’s pressure, then, it will reflect this alteration of the cardiac cycle. When we reach 100 mmHg the aortic valves close down. What stage is left? The diastolic iso-volumetric relaxation. Relaxation: the ejection has just taken place and the ventricle is relaxing. Iso-volumetric: the aortic valve is closed and the auricular-ventricular valves are closed two stages behind. This blood inflow and outflow ceases and thus, during relaxation pressures diminishes and its volume remains unaltered. During this stage, as we see, the residual volume is the same. Residual volume does not change since the auricular-ventricular valves shut down. And we reach again the Phase Number One where pressures lowers and reaches a point where the auricle and ventricle pressure difference is zero and once again the opening of the auricular-ventricular valves and the filling process takes place. This means that the heart is always changing between this residual volume and the diastole end volume. We always find it between these two stages, or in the iso-volumetric one or going into the other one. The heart is constantly equaling, surpassing or just below the pressures of the surrounding compartments (auricles or vessels). And that is how the cardiac cycle regulates. Thus, physical processes, time coordination are involved and we will understand the importance of this cardio-connector system we referred to before. If this system is not perfectly coordinated this cycle does not work out. And we now comprehend how steps coordinate one another.
Diastole End Volume: how much is there within each ventricle, in this filling relaxation phase, when the diastole ends? Be careful, within each ventricle!! We draw our figure thinking in the left ventricle. The left ventricle, when the diastole ends, when this filling phase ends will have some 130 ml inside. Afterwards, the contraction takes place (the systole) a 50 ml volume is going to be expelled from the ventricle. The residual volume is what remains within the heart after the systole. This means that we have to change the systole concept. Systole is a contraction which will not produce a total emptying of the ventricle, only a partial one. There is a small blood volume which will remain in the heart and it will have its consequences. According to this analysis the diastole end volume (which means all the blood we find at the end of this process) is going to be equal to the volume expelled minus what is left: in other words, systolic volume plus residual volume. The ejection fraction shows clearly this relation, since 70 are more or less half of 130. What the heart ejects is more or less half of the volume there is when it is full. If a person has low contractility, if it has cardiac insufficiency, if someone has a small ejection capacity, the ejection fraction diminishes (minus 0.5). The cardiac frequency rises in all individuals when making exercise, in sportsman trained in aerobic activities. They will have a minor frequency and a major volume, and that major volume, depending on the activity they might develop, will correspond to a diastole end major volume or to a smaller residual volume. Very interesting is to analyze how a person can, modifying the activity also alter the cardiac properties. If you and your grandmother climb some steps, she will end puffing and blowing and you will not, and you won’t understand why. Since she does not make any physical activity her cardiac frequency will rise up a whole lot when making this exercise, whereas a person who is trained or practices any sport is much more used to effort. Thus, regarding that same effort his cardiac frequency is smaller. Probably his volume-minute is also higher depending upon the type and intensity of the exercise. The cardiac frequency, however, is the value in which this phenomenon can be better analyzed.
pressure (80 mm Hg) had surpassed the aorta’s one. The valves opened, it surpassed it, but when it lowered down to 100 then the aortic valves did close. Why did this take place? This takes place because the ventricle is emptying towards the aorta in such a way that at the same time the ventricle’s pressure lowers the aorta’s rises. We should remember that not only the heart has a diastolic and systolic pressure (or a relaxation and contraction pressure). Also the vessels (in this case the aorta) will register a diastolic and systolic pressure as well. We have already stated that the aorta has a diastolic pressure of 80, which means that before receiving the heart blood flow its diastolic pressure almost reached 120. At approximately 100 equilibrium and closing take place. One more clue: when you measure your arterial pressure, two figures are given to you. These figures correspond to a diastolic and a systolic value. The same way the heart will carry on this biphasic cycle of diastole and systole, retaining or freeing blood towards the vessels, which in a certain way are elastic, distensible, they in turn will respond to this diastole and systole process. At a moment they do not receive anything and all of a sudden they do receive. When we measure a person’s pressure, then, it will reflect this alteration of the cardiac cycle. When we reach 100 mmHg the aortic valves close down. What stage is left? The diastolic iso-volumetric relaxation. Relaxation: the ejection has just taken place and the ventricle is relaxing. Iso-volumetric: the aortic valve is closed and the auricular-ventricular valves are closed two stages behind. This blood inflow and outflow ceases and thus, during relaxation pressures diminishes and its volume remains unaltered. During this stage, as we see, the residual volume is the same. Residual volume does not change since the auricular-ventricular valves shut down. And we reach again the Phase Number One where pressures lowers and reaches a point where the auricle and ventricle pressure difference is zero and once again the opening of the auricular-ventricular valves and the filling process takes place. This means that the heart is always changing between this residual volume and the diastole end volume. We always find it between these two stages, or in the iso-volumetric one or going into the other one. The heart is constantly equaling, surpassing or just below the pressures of the surrounding compartments (auricles or vessels). And that is how the cardiac cycle regulates. Thus, physical processes, time coordination are involved and we will understand the importance of this cardio-connector system we referred to before. If this system is not perfectly coordinated this cycle does not work out. And we now comprehend how steps coordinate one another
