heart muscle performs important functions for the human body as the ability to initiate, conduct agitation and decline.
may excites everything myocardial cells.But set the rhythm reductions body is the sinus node cells, since only they are able to be excited by a greater number of times per minute than others.There is typically 60-80 times in calm conditions.
electrochemical interaction between a cell provides a conduction excitement: it is distributed throughout the myocardium.Using the electrocardiograph this process can capture and analyze the performance of muscles.
And the ability of the heart to contract is performed, as is known, as a cycle consisting of several phases.Adjusts his nervous system activity.Cardiac cycle and its phases of diastole and systole make up the heart.
cardiac cycle begins from the moment of excitement in the sinus node.At this time, and the atria and ventricles are relaxed and filled with blood.When the signal is received, the atria are beginning to decline.As a result, the ventricles receive an additional portion of blood and is also excited.At the same time extends the first wave - the phase asynchronous reduction.The pressure in the ventricles becomes stronger pressure in the atria, and the wing flaps are closed immediately.With this second cardiac cycle enters a phase of isometric contraction.During this period, ventricular volume does not change, and the pressure in them continues to grow.When it becomes stronger than that which comes from the blood vessels of the heart, the semilunar valves open and ends phase of isometric contraction.Thereafter blood is pushed into the heart vessels.Isometric and asynchronous phases of the cardiac cycle of the heart systole.
Then the heart is relaxed.Cardiac cycle enters a phase of isometric relaxation.By the close of semilunar valves and further relaxation of the body is already with all valves closed resulting in pressure vessels.At this time in the atria gradually accumulated blood.As soon as its pressure becomes higher than the pressure in the ventricles, flap valves will open and ventricles are filled with blood.Then, the circle begins the next cardiac cycle.And the filling of the ventricles and atria, and the phase of isometric relaxation together make diastole of the heart.
At the time of release of the blood vessels in portions created pressure not exceeding 120 mm Hg.Art.In large vessels, it is not changed.During termination therein blood from the heart, it is decreased, but not less than 80 mm Hg.Art.Within one minute, there is a complete circuit of five or six liters of blood, which are available in the adult healthy person.If some body need more blood, first expand the lumen of arterioles, capillaries and the set will only last to increase the productivity of the heart itself.It will be the higher, the larger the volume of blood is ejected in a single reduction (volume per heart beat) and the more the body will be reduced.The amount of blood which the heart surpasses per minute (volume per minute), depends not only on the physical and emotional state, but also on the growth and weight of the person.Therefore, to evaluate the individual activity of the heart, expect the special cardiac index.
heart can also change the frequency of contractions and their strength, the speed at which the excitation is carried out under the influence of impulses, which are sent to the central nervous system.For example, the vagus nerve signals do reduce weak, their frequency is becoming rarer, the excitement goes down and is held much more slowly.But the impulses sent by the sympathetic nerves are just the opposite.
further way of blood ejected from the heart through the arteries continues.