Volume-minute equals Cardiac frequency (quantity of discharges per minute) times Systolic Volume (blood amount leaving the heart)
When we state volume-minute we refer to the amount of blood that leaves the heart every minute. If we take into account normal values, the cardiac frequency in normal physiology is 70 beats per minute. Systolic Volume: we had stated a 70 ml figure. 70 times 70 is 4900 (almost five liters and we had mentioned 5.5). These figures never match since each author publishes its own, but the normal volume-minute figure varies from 5 to 6. This is the accepted concept we have to deal with.
Diastole End Volume
Systolic Volume plus Residual Volume, which is what remains in the heart when diastole ends. When filling ends it will be equal to what ejected plus what is left.
Arterial Pressure: is equal to arterial tension. They are considered the same thing. Physically speaking, pressure equals strength against surface. That is pressure, a strength made in a normal direction, perpendicular to any surface. What is tension, then? Strength made not in a perpendicular way, but rather embracing that surface. That is the difference between pressure and tension. The “tension” concept is useful to comprehend that we are dealing with vessels, but in the daily chat there is no difference between them.
Properties of the Vessels and Pressure
Elasticity is the capacity to recover a former condition. I take something stretchable, I stretch it, then I loosen it up and the object recovers its former condition. Distensibility, on the other hand, is the capacity to modify a certain condition, its `physical conditions. I stretch a chewing gum and changes. Conceptually speaking, thus, elasticity and distensibility are opposite. Elasticity is the ability to recover a former condition, and distensibility the capacity to modify a physical condition. In general, when dealing with physiological concepts we are taken as equals. In order to make a first approach, however, we need to analyze both. When the heart ejection phase takes place, a great amount of blood is liberated towards the aorta, how will the vessels react? They will distend. They will modify their previous condition so they are able to receive blood. This also does not alter the vessel volume too much, avoiding its rupture. Finally they are not very oldstrong structures. They will reach this ability to distend themselves and adapt their volume capacity to the blood that might arrive. But this process takes place through a tension rise. In order to widen its volume, to receive this new content, pressure will necessarily rise.
If I take a spring and I distend it, I feel the tension that structure receives. Same thing happens with vessels. When the blood went through, during that second diastole took place, the vessel will recover its former condition. That is exactly what stretching ability means: the capacity to recover its former condition. Both concepts are equal to us since one affects the other. If a vessel is hard it is not able to distend nor can return to its former condition. However, we need to distinguish between distension and elasticity.
Now, arteriosclerosis is basically this: fat agglutinates (especially cholesterol) in the vessels’ walls, they harden up and they loose they elastic capacity. When blood arrives they are not able to distend. Therefore they will be more susceptible to ruptures (ischemia, internal hemorrhages). This is why people affected by arteriosclerosis suffer from pressure rises. Their vessels volume is unable to change thus provoking a rise in the arterial pressure. We are now able to comprehend why we have a minimum and a maximum pressure. The first movement will carry the blood of the ejection phase of the cardiac cycle. The vessels will distend in order to receive this tension but the last will be higher so that when we register it, we will find it in its maximums peak. Once the blood went through, the vessel will recover its former condition, its volume will diminish and pressure against its wall will also be lower. Thus, when we measure this pressure it will be lower (“minimum”) than before.
Let us write down the usual pressure figures. This is important.
Pressure equals strength against surface. That is the most usual one. Therefore we will find a diastolic and a systolic arterial pressure. I want everybody now to feel their own pressure. Are you able to feel how blood passes through? What are you measuring now? Is it Systolic or diastolic arterial pressure? It is important to point out which is the zero point. Differential pressure is systolic arterial pressure minus diastolic arterial pressure and that is why you are not measuring any of them. This happens because you do not have a zero point.
When blood arrives you feel systolic arterial pressure and when that blood impulse is not present you do not feel a zero value, what you then measure is diastolic arterial pressure which is what we normally consider as a zero value. Thus, when you measure that pressure you measure a pressure difference, systolic minus diastolic. A value frequently used is the medium arterial pressure and to reach it we use the diastolic arterial pressure plus a third of differential pressure. It looks like a complicated formula, but it is a simplified manner of expressing a planimetric integration of a somehow strange curve. The important thing to comprehend is that medium arterial pressure is not an average between the diastolic and the systolic arterial pressures. It is closer to the diastolic one, which is a lower figure and this is related to physical values. It is important to note that when you read medium arterial pressure do not think in a media between diastolic and systolic, is just a separate figure: diastolic arterial pressure plus a third of differential pressure.
Peripheral Vascular Resistance
Résistance is everything that impedes the blood stream, in this case, evidently related to the pressure concept. What is usually expressed is that since there are several vessels resistance is parallel. Evidently, total resistance will always be minor than every one of the individual resistances.
Peripheral Vascular Resistance: the cardiovascular system has the capacity to control and regulate the contraction at the arterioles level. The arterioles will be the body’s maximum resistance point. At that level the cardiovascular system will regulate the peripheral vascular resistance. Already knowing that the volume-minute is equal to the arterial pressure divided by the peripheral vascular resistance we will be able to comprehend its importance. The body, foe example, will regulate the arterial pressure through the arteriole’s resistance. Resistance is the resistance to blood pass. Volume-minute is the amount of blood which will leave the heart. If the peripheral vascular resistance raises then the blood able to leave the heart will lower. This will picture what’s going on. If resistances contract at a certain level, then the amount of blood able to pass will lower. Example: during an exercise there will be blood redistribution through the whole body and the sympathetic will guarantee that this blood reaches the places which will need it. In this case will be a certain muscle. There will then exist a rise in the peripheral vascular resistance in other organs (digestive, immunologic, renal too). Those organs do not need blood at that moment, certain muscles need it the most and their volume is important. How ensuring that blood does not reach the unwanted organs? This is done through the vessel-constriction and the vessel-dilatation which will regulate the peripheral vascular resistance. Its rise will be given by the vessel-constriction and, on the contrary, its diminution will be related to dilatation. Which system contracted the vessel, the sympathetic or the Para-sympathetic? The sympathetic. Generally speaking the sympathetic effect is vessel-contracting. When explanations are needed, simplified schemes are useful. Most of the processes will require sympathetic and Para-sympathetic. Thus sympathetic will produce vessel-constriction and a rise in the peripheral vascular resistance. Imagine a vessel: if you squeeze it resistance will rise and volume allowed to pass trough will lower. Vessel-dilatation, on the other hand, will be given by the Para-sympathetic. Peripheral vascular resistance will then diminish. This will acquire some importance when we analyze stress. And we also can perceive how these concepts are able to regulate arterial pressure. Example: In persons who suffer hypertension, very probably, the medicines they receive are inhibitors of vessel contraction. If we inhibit such contraction we do not allow the rise of the peripheral vascular resistance thus provoking a pressure lowering and maintaining the body’s activity. We will se how these three variables (arterial pressure, peripheral vascular resistance and volume-minute) interact between them and we will now use an old formula. Later on when we analyze stress we will perceive how these variables interact between themselves.
The same way we said there is a cardio-connector system, a nervous system that will intrinsically regulate the heart; we will also find an exogenous system, an outside system which will oldstrongly influence it and changes the scale, the scheme of this cardio-connector system. The sympathetic alters its base time. Following other base rhythm will change the scale, the fundamentals. The cardio-connector system will hierarchically place itself below this autonomous system in such a way that both the Para-sympathetic and the sympathetic will act at the heart’s level.
When we talked about the sympathetic we said that it uses acetylcholine as neuronal transmitter. The heart uses a receptor named M2, or better yet muspharinical 2. As for the sympathetic we have referred to noradrenalin and we found the receptors Beta 1 within the heart. The Para-sympathetic diminished the cardiac properties, it inhibits them and the sympathetic, on the contrary, rises and stimulates them. Now, in spite of the fact that the Para-sympathetic generally influences the vessels, once we refer to vessels we will talk about the sympathetic effects. I do not want to confuse you but that is the way it is. Some other thing I do want to explain to you. If this confuses you even more, just try to forget it buy for me it is very important to explain this concept. The sympathetic will act in a vessel level. Which will be the neuronal transmitter? Noradrenalin. At vessels level the last will have two basic receptors. Beta 2(vessel dilatation) and Alfa 1 (vessel constriction). What does this mean? Was not the sympathetic the one that provoked the vessel constriction? What are you saying to me right now? That the Para-sympathetic just makes the opposite than the sympathetic? Yes, of course, but they are just simplified schemes. This is the only thing I do want to explain to you. We are watching at a unified system that with the same neuronal transmitter provokes two effects: vessel constriction and dilatation. Why? What will decide which of the opposites will be the effect? The receptor. If noradrenalin interacts with Alfa 1 the effect will be constriction and if the receptor happens to be Beta 2 dilatation will take place. The same signal, when interacting with two different receptors will provoke two completely different signals. What is this saying to us? That the receptor chooses the effect and that if I introduce any other substance within the organism which may carry something that the receptor recognizes or provokes its interaction, then the receptor will follow its path towards constriction or dilatation. Anything that might correctly stimulate the receptor will produce an effect. This means that the effect depends upon the receptor, not the neuronal transmitter, the signal. That is the concept of drugs, medicines. How can we introduce substances that the body may have never been in touch with and produce any effect? Simple, we can copy the molecular composition of noradrenalin or any other substance. The last, new to the body, interacts with receptors. And these just have to follow the previewed plan.
Elasticity is the capacity to recover a former condition. I take something stretchable, I stretch it, then I loosen it up and the object recovers its former condition. Distensibility, on the other hand, is the capacity to modify a certain condition, its `physical conditions. I stretch a chewing gum and changes. Conceptually speaking, thus, elasticity and distensibility are opposite. Elasticity is the ability to recover a former condition, and distensibility the capacity to modify a physical condition. In general, when dealing with physiological concepts we are taken as equals. In order to make a first approach, however, we need to analyze both. When the heart ejection phase takes place, a great amount of blood is liberated towards the aorta, how will the vessels react? They will distend. They will modify their previous condition so they are able to receive blood. This also does not alter the vessel volume too much, avoiding its rupture. Finally they are not very oldstrong structures. They will reach this ability to distend themselves and adapt their volume capacity to the blood that might arrive. But this process takes place through a tension rise. In order to widen its volume, to receive this new content, pressure will necessarily rise.
the cardiovascular system will regulate the peripheral vascular resistance. Already knowing that the volume-minute is equal to the arterial pressure divided by the peripheral vascular resistance we will be able to comprehend its importance. The body, foe example, will regulate the arterial pressure through the arteriole’s resistance. Resistance is the resistance to blood pass. Volume-minute is the amount of blood which will leave the heart. If the peripheral vascular resistance raises then the blood able to leave the heart will lower. This will picture what’s going on. If resistances contract at a certain level, then the amount of blood able to pass will lower. Example: during an exercise there will be blood redistribution through the whole body and the sympathetic will guarantee that this blood reaches the places which will need it. In this case will be a certain muscle. There will then exist a rise in the peripheral vascular resistance in other organs (digestive, immunologic, renal too). Those organs do not need blood at that moment, certain muscles need it the most and their volume is important. How ensuring that blood does not reach the unwanted organs? This is done through the vessel-constriction and the vessel-dilatation which will regulate the peripheral vascular resistance. Its rise will be given by the vessel-constriction and, on the contrary, its diminution will be related to dilatation. Which system contracted the vessel, the sympathetic or the Para-sympathetic? The sympathetic. Generally speaking the sympathetic effect is vessel-contracting. When explanations are needed, simplified schemes are useful. Most of the processes will require sympathetic and Para-sympathetic. Thus sympathetic will produce vessel-constriction and a rise in the peripheral vascular resistance. Imagine a vessel: if you squeeze it resistance will rise and volume allowed to pass trough will lower. Vessel-dilatation, on the other hand, will be given by the Para-sympathetic. Peripheral vascular resistance will then diminish. This will acquire some importance when we analyze stress. And we also can perceive how these concepts are able to regulate arterial pressure. Example: In persons who suffer hypertension, very probably, the medicines they receive are inhibitors of vessel contraction. If we inhibit such contraction we do not allow the rise of the peripheral vascular resistance thus provoking a pressure lowering and maintaining the body’s activity. We will se how these three variables (arterial pressure, peripheral vascular resistance and volume-minute) interact between them and we will now use an old formula. Later on when we analyze stress we will perceive how these variables interact between themselves. 
When we talked about the sympathetic we said that it uses acetylcholine as neuronal transmitter. The heart uses a receptor named M2, or better yet muspharinical 2. As for the sympathetic we have referred to noradrenalin and we found the receptors Beta 1 within the heart. The Para-sympathetic diminished the cardiac properties, it inhibits them and the sympathetic, on the contrary, rises and stimulates them. Now, in spite of the fact that the Para-sympathetic generally influences the vessels, once we refer to vessels we will talk about the sympathetic effects. I do not want to confuse you but that is the way it is. Some other thing I do want to explain to you. If this confuses you even more, just try to forget it buy for me it is very important to explain this concept. The sympathetic will act in a vessel level. Which will be the neuronal transmitter? Noradrenalin. At vessels level the last will have two basic receptors. Beta 2(vessel dilatation) and Alfa 1 (vessel constriction). What does this mean? Was not the sympathetic the one that provoked the vessel constriction? What are you saying to me right now? That the Para-sympathetic just makes the opposite than the sympathetic? Yes, of course, but they are just simplified schemes. This is the only thing I do want to explain to you. We are watching at a unified system that with the same neuronal transmitter provokes two effects: vessel constriction and dilatation. Why? What will decide which of the opposites will be the effect? The receptor. If noradrenalin interacts with Alfa 1 the effect will be constriction and if the receptor happens to be Beta 2 dilatation will take place. The same signal, when interacting with two different receptors will provoke two completely different signals. What is this saying to us? That the receptor chooses the effect and that if I introduce any other substance within the organism which may carry something that the receptor recognizes or provokes its interaction, then the receptor will follow its path towards constriction or dilatation. Anything that might correctly stimulate the receptor will produce an effect. This means that the effect depends upon the receptor, not the neuronal transmitter, the signal. That is the concept of drugs, medicines. How can we introduce substances that the body may have never been in touch with and produce any effect? Simple, we can copy the molecular composition of noradrenalin or any other substance. The last, new to the body, interacts with receptors. And these just have to follow the previewed plan.
