The work of the heart ensures the functioning of all organs of the body. Due to its contractions, the blood constantly moves to biological tissues, where it gives off oxygen and removes metabolites, carbon dioxide. Returning through the veins, it goes to the lungs, where it is again saturated with oxygen. With each new systole, this cycle maintains a continuous blood supply, which can be disturbed by arrhythmia, a decrease or increase in the heart rate. And only the functional needs of the body will determine what the heartbeat should be at the current moment.
Differences in heart rate
The heart rate is one of the most important parameters of the human body. It depends on the current functional state, being at rest or physical activity, on the size of the heart and body. The smaller the organ, the higher the frequencyabbreviations.
That is why the heart rate in children is always higher than in adults, because in the process of growth of the organism and the body, morphological proportions change. In particular, the heart increases in size at first more slowly than the rest of the body, and then partially compensates for the lag. For this reason, the child's heart rate is initially higher than that of an adult, and later the rate gradually decreases.
Adult heart rate
A person at rest often experiences bradycardia, and at the peak of functional load, the heart rate reaches 160 beats per minute without loss of minute volume of blood supply. This is achieved by marked hypertrophy of the left ventricle, which ensures the ability to maintain effective expulsion of systolic volume.
But if you do not consider the extreme limit, then what should be the normal heartbeat? In reality, the rate is in the range of 60 to 90 ventricular contractions per minute. And this is not a strict biological constant, but just an average medical value. The constant is the level of the body's need for blood supply, and if there are any deviations from it, then the heart rate will be changed.
Baby heart rate
Children have a much higher heart rate than adults, which is associated with a discrepancy between the size of the heart cavities and the morphological parameters of the body. Because of this, to ensure effective blood supply to the bodyforced to force the heart to beat faster. In a fetus, the normal limits are at the level of 120-160 beats per minute, in a newborn - from 110 to 170, and at the age of 1 year, the heart rate is normally 100-160 beats per minute.
From the first to the second year of life, the limits of the norm are at the level of 96-150, and from 2 to 4 years - from 90 to 140 beats per minute. At the age of 4-6 years, the heart rate is 86-126 beats, at 6-8 years - 78-118 beats per minute. Upon reaching the age of 8-10 years, normal heart rate values drop to levels of 68-108, and from the age of 12, the child's heart rate corresponds to the norms of an adult.
Intensity of blood supply
Comfortable heart rate depends only on physical activity, the state of the body's humoral systems and morphological dimensions. These mechanisms determine what a normal heartbeat should be in a particular patient. The norms accepted in the medical community are not individually adapted for each person, but are average statistical indicators for the comfortable functioning of all body structures.
Effective heart rate is the number of contractions of the heart, which provides the intensity of blood supply to organs and tissues necessary for comfortable life. For example, the current rate is 70 beats per minute. And at rest, this is enough to provide the entire body with oxygen and nutrients. If the body goes into another functional state,for example, a person gets up and runs, the heart rate will increase, as the load requires an increase in the intensity of nutrition of the skeletal muscles.
In another situation, when the body goes from rest to sleep, the functional load becomes even lower, due to which the rate of blood supply intensity also decreases. Since the tissues work in the mode of minimal energy consumption, the intensity of the work of the heart to maintain their vital activity in this state should be minimal. This determines what the heartbeat should be at the current moment. And at rest, the frequency will be at the lower limits of the norm or fall even lower, provided that the most important electrophysiological constants (action potential and width of electrocardiographic intervals) are preserved.
Justification of the norms
Above it was indicated what kind of heartbeat a person should have, and on what factors it depends. However, why the norm is such, should be explained in more detail. So, the heart rate depends on the required level of blood supply intensity. If it is low, and the tissues experience oxygen starvation, then as a result of stimulation of the activity of the cardiovascular system, the number of contractions and the minute volume of blood supply will increase.
The norm of the heart rate is observed at the moment when the volume of systolic ejection sent to the circulation circles with each contraction is sufficient to supply the body structures with blood. If necessary, increase the intensityblood supply, the frequency will be increased to acceptable values, which are limited by the cessation of the increase in minute volume of blood circulation.
Functional dependence of heart rate
The increase in heart rate will only increase the intensity of blood supply to a certain limit, above which the effectiveness of this mechanism is greatly reduced. This is observed due to two mechanisms. The first is diastolic filling of the heart: the higher the heart rate, the less efficiently the heart cavities are filled. Therefore, less blood enters the ventricles, and instead of an increase in the minute volume of blood circulation, its significant decrease will be noted.
The second mechanism is efficient pushing. The higher the frequency and the less the filling of the ventricular cavity, the less effective will be the expulsion of a portion of blood from the ventricular cavity into the arteries. Therefore, an increase in heart rate leads to an increase in the intensity of blood supply only up to a certain functional limit.
The balance between these two mechanisms and the functional needs of the body determines what should be the heartbeat of an adult at a certain point in time. Above it, increasing the heart rate will not allow the electrophysiological system of the myocardium, failures and malfunctions of which occur only in pathology (arrhythmia).
