Butmotropic effect in cardiac physiology
The heart is a muscular organ with its own rhythm regulation system. It is represented by pacemaker cells that regulate the activity of the heart muscle. It is influenced by drugs and mediators produced by the adrenal glands. This action is described as a positive or negative inotropic, chronotopic, dromotropic or batmotropic effect.
Batmotropia and chronotropy of the heart
Batmotropia is the influence of a certain factor on cardiac activity in such a way that the excitability of pacemaker cells changes as a result. The term "excitability" is the ability to generate an action potential. The suppression of excitability is an increase in the threshold, after which the action potential is formed. Stimulation of the excitability of the heart is a decrease in the threshold value of the membrane potential, above which rapid depolarization occurs. This process is called the appearance of an action potential. In general, the term "batmotropic effect" means a change in the excitability of the myocardium.
Chronotropic effect in the electrophysiology of the myocardium is the frequency with which the heart rhythm is formed. A positive chronotropic effect mediates the increase in the frequency of pulse generation, that is, the action potential. Negative chronotropy - a decrease in the frequency of the rhythm. Pulse generation is the process of formation of an action potential that forms an "order" to reduce. This means that the rhythm frequency on a healthy heart means the same as the frequency of contractions.
Differences between the concepts of
The terms "chronotropic" and "batmotropic effect" at first seem almost identical. But there is a fundamental difference between them, which should be explained by two theses. The essence of the first is that the increase in the frequency of cardiac contractions can be achieved without reducing the threshold of excitability of the pacemaker. Similarly, slowing down the cut does not at all mean that it is necessary to increase the threshold of excitability, that is, to provide a negative butmotropic effect.
The second thesis boils down to the fact that a decrease in the excitability of the heart always means a decrease in the rhythm. The increase in the excitability of the heart also means that the rhythm frequency will increase significantly. Excitability( batmotropia) is only the ability to generate action potential. And the frequency, that is, the chronotropy of the heart, is a measure of quantitative determination in the generation of rhythm. In the physiology of the heart, the frequency follows excitability. The higher the excitability of the myocardium, the higher the frequency of the rhythm.
Inotropy and dromotrocopy of the heart
In physiology of the myocardium there are such concepts as inotropic and dromotropic effects. Inotropy is the power of contraction of the muscle cell, and dromotropic is the conductivity, that is, the speed of the pulse propagation through the conducting system or the non-vascular contacts between the myocardial cells. The physiology of the heart is such that the higher the force of contraction of the heart, the greater the volume of blood ejected from the left ventricle. The higher the frequency of full-fledged contractions, the more often the body receives portions of oxygenated blood.
Physiology of cardiac activity
Conditions for stimulation of cardiac activity are created due to the presence of batmotropic and dromotropic effects. That is, with an increase in the excitability of the myocardium and with accelerated conduction, an increase in the frequency of heart contractions and their strength can be achieved. In a situation where the body needs to quickly mobilize its functionality, for example, before physical activity and during it, the physiological processes of regulation of cardiac activity are strengthened. It all starts with a positive dromotropic and butmotropic effect, immediately after which the chronotropic effect of the mediators increases. The last one is the inotropic mechanism. The extinction of effects after cessation of stimulation by catecholamines occurs in the reverse order.
Positive Batmothropia
Positive batmotropia is an effect on the heart cells in which their excitability rises. That is, the threshold for generating the action potential is reduced. In other words, a positive butmotropic effect is a decrease in the membrane potential necessary for rapid depolarization of the plasmolemma of the cardiomyocyte. Sympathetic neurotransmitters( adrenaline, norepinephrine), as well as xenobiotics( cocaine and amphetamine), are distinguished by this action.
As drugs, atropine, epinephrine, noradrenaline, dopamine are used, which are used to achieve positive cell death, inotropy, chronotropy and dromotropy. This is necessary for resuscitation of patients with cardiac arrest. Dopamine and atropine can also be used to stimulate the cardiovascular system in intensive care to maintain acceptable blood flow.
Negative Batmothropia
In the human body, a negative butmotropic effect in the human body is exerted by the parasympathetic nervous system through activation of the vagus nerve. Its influence raises the threshold of excitability of pacemakers and contractile myocardium, thereby reducing the likelihood of generating an action potential at a time when it is not required to ensure the functional needs of the organism.
Negative batmotropy is typical for poisoning OPF, and beta-blockers, some antiarrhythmics. In the narrow sense, the negative butmotropic effect should be considered as a process of increasing the threshold value of the membrane potential, at which the fast sodium channels open. This interpretation is appropriate for analyzing the molecular mechanisms of rhythm generation.