The vessels which we call arteries branch inside the body, they form arterioles and then smaller structures and at a capillary level these vessels begin to acquire every time weaker structures, thinner walls finally easing the gaseous exchange tissues need. This means that next to the heart, if we are to analyze a vessel’s structure, we will observe that they have a great amount of elastic fibers, of muscular walls, whereas as you reach the capillary the structure will be much thinner. This is due to the gaseous exchange through which the capillary will yield Oxygen to the tissues and receive Carbon Dioxide and discarded elements from them. In order for this process to take place the vessels structure need to be small, thin and permeable to these gases. That is what we call capillary. Not always the organism keeps this model artery-capillary-vein. This very same thing happens in the lung: lung arteries which carry low oxygen saturation blood reach the alveolus and the capillary are finally created but in this case the capillary instead of yielding oxygen receive it and exactly the opposite takes place with carbon dioxide. It saturates with oxygen and returns as lung veins this time full of oxygen. However, this scheme of artery-capillary-vein continues, this time at a lung level.
Cardiac Innervations
Within the heart it is necessary to comprehend two systems: one is the vascular which we just have reviewed. There is a second one which we need to analyze which is the nervous system. We know that the heart is a pump which will contract in a synchronic, rhythmic way and that it will need some sort of nervous system able to regulate that type of contraction. If this fails to happen, pathologies appear. This system is denominated as cardio-connector system. It is an innervation’s intrinsic system which the heart possesses. When we study sympathetic and Para-sympathetic we learn that there exists an extrinsic influence, which means that this happens out of the heart thus enabling to regulate the stress situations and other physiological situations as well. The cardio-connector, however, is a heart intrinsic system which will regulate its contraction ability. We are going to find the Sino-auricular nodule and the auricle-ventricular nodule, which we will find on the floor of the right auricle within the separation between the auricle and the ventricle. We see haceks inter-nodules (its existence is still argued). We see the Has de hiss trunk with a left and a right branch. Because we assert that the left heart is the one that is in charge of carrying all this blood, the left ventricle’s size is larger than the right and besides will have greater and more profuse innervations at the pirkinje fiber level. It is notoriously larger, and that is why any pathology will concentrate at that level. The left ventricle’s wall is very important. The thickness will reach great importance in what is denominated cardiac hypertrophy and also regarding its contraction capacity. The cardio-connector will mainly gather the capacity of step-marker. Many organs in the body have that activity: within the digestive tube, the muscular fibers and also within some central structures. In the heart there is a type of fiber with a special regulation which will discharge before the others and will mark the beat of discharge for the rest of the neurons. Since its discharge rhythm is oldstronger, the rest will follow. This is the Sino-auricular nodule (san). And will mark the beat at a discharge frequency of 70 to a 100 discharges per minute. If san fails the rest of the cardiac system will follow the group of neurons which might have the second fastest rate: the auricular-ventricular nodule (avn) which will mark a frequency of 40 to 50 discharges per minute. A failure at this level will provoke that the Has de Hiss trunk will lead the frequency at a 35 to 40 level, almost a life compatibility one.
Generally, before reaching these values the step-marker inactivity is tried to be substituted by an electrical one, introducing within the heart a devise which might produce a discharge more similar to the san’s one. The important question here is to point out that each of the fibers will make its discharge in an independent fashion, with its own frequency, but will abandon that frequency to follow the one that might have a faster frequency. They will always mate that which might have a higher discharge speed. Any muscular cell, isolated, has its own discharge frequency, but when facing other cell stimulus it discharges sooner and produces a normal discharge cycle which would produce otherwise. However, it will mate in such a way that without getting into histological details we are going to comprehend the cells the same way we analyze the skeleton muscle ones, they are muscular cells, and conform the cardiac muscle. They have different characteristics but they will also develop as an outstanding particularity a high permeability between them because they are highly coordinated to one another since it is very important that the heart might contract in a synchronic and synergic manner in order to act as a pump and propel blood towards the periphery.
Bradycardia: Slow rhythm.
Tachycardia: fast rhythm-
Arrhythmia: the heart rhythm does not keep regular intervals but it continues contracting generally in a collective manner.
A pathology produced by imbalances is the fibrillation. This is linked with channels that allow information permeability regarding what is going on in the previous cell discharge.
nervous system able to regulate that type of contraction. If this fails to happen, pathologies appear. This system is denominated as cardio-connector system. It is an innervation’s intrinsic system which the heart possesses. When we study sympathetic and Para-sympathetic we learn that there exists an extrinsic influence, which means that this happens out of the heart thus enabling to regulate the stress situations and other physiological situations as well. The cardio-connector, however, is a heart intrinsic system which will regulate its contraction ability. We are going to find the Sino-auricular nodule and the auricle-ventricular nodule, which we will find on the floor of the right auricle within the separation between the auricle and the ventricle. We see haceks inter-nodules (its existence is still argued). We see the Has de hiss trunk with a left and a right branch. Because we assert that the left heart is the one that is in charge of carrying all this blood, the left ventricle’s size is larger than the right and besides will have greater and more profuse innervations at the pirkinje fiber level. It is notoriously larger, and that is why any pathology will concentrate at that level. The left ventricle’s wall is very important. The thickness will reach great importance in what is denominated cardiac hypertrophy and also regarding its contraction capacity. The cardio-connector will mainly gather the capacity of step-marker. Many organs in the body have that activity: within the digestive tube, the muscular fibers and also within some central structures. In the heart there is a type of fiber with a special regulation which will discharge before the others and will mark the beat of discharge for the rest of the neurons. Since its discharge rhythm is oldstronger, the rest will follow. This is the Sino-auricular nodule (san). And will mark the beat at a discharge frequency of 70 to a 100 discharges per minute. If san fails the rest of the cardiac system will follow the group of neurons which might have the second fastest rate: the auricular-ventricular nodule (avn) which will mark a frequency of 40 to 50 discharges per minute. A failure at this level will provoke that the Has de Hiss trunk will lead the frequency at a 35 to 40 level, almost a life compatibility one. 
fashion, with its own frequency, but will abandon that frequency to follow the one that might have a faster frequency. They will always mate that which might have a higher discharge speed. Any muscular cell, isolated, has its own discharge frequency, but when facing other cell stimulus it discharges sooner and produces a normal discharge cycle which would produce otherwise. However, it will mate in such a way that without getting into histological details we are going to comprehend the cells the same way we analyze the skeleton muscle ones, they are muscular cells, and conform the cardiac muscle. They have different characteristics but they will also develop as an outstanding particularity a high permeability between them because they are highly coordinated to one another since it is very important that the heart might contract in a synchronic and synergic manner in order to act as a pump and propel blood towards the periphery. 
