heart muscle provides the vital functions of all tissues, cells and organs.Transport of substances in the body is carried out thanks to the constant circulation of the blood;It also provides and maintain homeostasis.
structure of the heart muscle
heart is represented by two halves - left and right, each of which consists of the atria and ventricles.The left half of the heart pumps the arterial blood, and the right - venous.Therefore, the left half of the heart muscle is much thicker than the right.The muscles of the atria and ventricles are separated by fibrous rings that have atrioventricular valves: DOUBLE (left half of the heart) and tricuspid (right half of the heart).These valves during a heartbeat warning return of blood in the atria.At the outlet of the aorta and pulmonary artery are placed fortnightly valves which prevent the return of blood to the ventricles during diastole total heart.
heart muscle belongs to the striated muscle tissue.Therefore, this muscle has the same properties as the skeletal muscle.Muscle fibers consist of myofibrils, sarcoplasm and the sarcolemma.
Through the heart pump blood through the blood vessels.The rhythmic contraction of the muscles of the atria and the ventricles (systole) alternates with its relaxation (diastole).The sequential change of systole and diastole of the heart cycle.The heart muscle is working rhythmically that provided by the system, conducting agitation in different parts of the heart
Physiological properties of cardiac muscle
excitability of the myocardium - is its ability to react to electrical, mechanical, thermal and chemical stimuli.Excitation and contraction of the heart muscle occurs when the stimulus reaches a threshold force.Irritation weaker threshold are not effective and do not change the suprathreshold force of myocardial contraction.
excitation of the heart muscle is accompanied by an action potential.He shortened with frequent and longer deceleration heartbeats.
excited heart muscle briefly loses its ability to respond to additional stimulation or impulses coming from the source of automaticity.This nonexcitability called refractory.Strong stimuli that act on the muscle in the relative refractory period, causing an extraordinary contraction of the heart - the so-called arrythmia.
myocardial has features in comparison to skeletal muscle tissue.The excitation and contraction in cardiac muscle last longer than skeletal.The heart muscle is dominated by aerobic processes of re-synthesis of energy-rich compounds.During diastole automatically change the membrane potential in several cells in different parts of the assembly.Hence the excitement spreads the muscles of the atria and reaches the atrioventricular node, which is considered the center of automaticity II order.If you turn off the sinoatrial node (ligation, cooling, poisons), then after a while the ventricles begin to contract in a rare rhythm under the influence of impulses arising in the atrioventricular node.
conduction of excitation in different parts of the heart varies.It should be noted that the rate of warm-blooded animals of excitation of the muscle fibers of the atria is about 1.0 m / s;in the conduction system of the ventricles to 4.2 m / s;in the ventricular myocardium to 0.9 m / s.
characteristic of conduction of excitation in the heart muscle is that the potential of action arising in one area of muscle tissue, spread to other areas.
