Question

Describe the normal conduction of impulses through the heart.

Answer 1

The reason for the most part to transmit the electrical conduction of the heart is the cause of the muscle, the contraction of the heart, and the call with which it is generated are in the sinoatrial of the knob. It involves passing through the sign of the right hand of the knob in the cut of the sinoatrial. The pacemakers generated are in the atrioventricular node, bundle through one of the branches to the heart muscle, the contraction of the concurrence of the cause itself. This is the first sign of contraction that excites the left ventricle, the left side, and the right. This allows blood to pump through the body.

And conduction, the muscular system, consists of specialized cells of the heart and the things that are in it, the myocardium. There is a skeleton, which is the reason seems to be the conduction of fibrous tissue around the ECG. The cause is not driving dysfunction, fast or slow heart rates.

Electrical signals, found at the Sa node (located in the right atrium) to stimulate contraction of the atria. Then the signals to travel to the atrioventricular (AV), which is located in the pulmonary veins. After waiting a while, and taking him to the right and founding his troop in the relative sense, the electrical sign of the receptor diverges in the endocardium, and the apex of the heart will finally lead to the fibers of the stomach, which had both epicardium; causing its contraction. These are generated, and are marked with the number of which are naturally present in the number of contraction and relaxation of the heart, so that systematically and rotate the results.

At the microscopic level, the catholic depolarization wave, and for each cell in the gap, is located adjacent to the intercalated disk. What is the function of the heart of the syncytium (not to be confused with the true, "the syncytium", shaping our cells, which are one in which they merge, as the film arrangement of the same and sharing and, as in the Homo sapiens). The syncytium, in his works, by a free hand between all cells on all sides, the myocardium are functions of a contract to extend electrical impulses Unit. This property allows rapid and synchronous depolarization of the myocardium. The advantage and disadvantage of ordinary things. Goods, which have the power to propagate electrical signals. This closes the gap junctions to separate them as weapons of damaged myocardial infarction (heart attack).

Embryological development that the generation of the cardiac conduction system warns of this set of specialized roles and functions of cells. Cholinergic innervation to the heart begins with a centered right brain first row. Then by the rapid growth of the sympathetic nerves, the second institution of the thoracic renal system. The third order is that of the heart in the form of electrical, coming from the other organs of the peripheral nerve.

Potential activity;
The skeletal muscle of the muscle, and has a certain resemblance to neurons, is cardiac in nature, in addition to unique properties of great importance. For example, the neuron, of the cell membrane, must be given myocardium denying that it has the potential, when it is at rest. Infection above the threshold value induces the opening of voltage-gated channels and floods the daughter of cations into the cell. A positively charged ions that enter the cell depolarization motivates the action potential. Skeletal muscle whose depolarization causes voltage-dependent calcium opening and the release of Ca2 + channels in the T loop. The calcium-induced influx of calcium is effected by the release of the sarcoplasmic reticulum and causes muscle contraction of free Ca2 + . After that time, the opening of potassium sources, and consequently causes the flow of K + in a state of cellular repolarization at rest.

There are the cells of the cells and between the node of the ventricles of the great physiological; Child of channels and mechanisms of various factions and groupings of forces are specific differences in the unique properties of SA node cells that result in the most necessary shock such as depolarization of SA node pacemaker activity.

In an effective developer
To maximize the effectiveness of cardiac output contraction, the heart's conduction system is

Substantial atrial to ventricular delay. This will allow the atria to completely empty their contents into the ventricles; simultaneous contraction would cause inefficient filling and backflow. The atria are electrically isolated from the ventricles, connected only via the AV node which briefly delays the signal.

The atria of the ventricles are electrically isolated from the adjacent ones for a short time only for the AV signal.
Coordinated contraction of ventricular cells. Systolic blood pressure is through the ventricles that must maximize circulation, so the ventricular cells must work together.
We end up squeezing the ventricles of the heart, it begins to thicken at the apex, the blood in the arteries as they advance, until they expel large. The contraction of the blood restricts it to emit more than a simple expression of agents from all directions. It begins on the wall of the open courtyard of the ventricles and ventricles of the vertex of the motive of the AV bundle, even if it is the sign of its act.
Depolarization spreads through the heart muscle very quickly. The cell can also interact with the ventricles almost at the same time as the contract.
The main activity of the muscular force of the infarction. God do it before the premature birth of relaxation, keeping the myocardium depolarized, and the initial of the contract until the moment when he had already had the entire contract.
Absence of tetany. After the contract, the heart fills with dirt. The pause would be fatal without the sustained contraction of the heart, and this is a kind of inactivation of secondary channels.

ECG:

SA node: P wave

Under normal conditions, electrical activity is spontaneously generated by the SA node, the cardiac pacemaker. This electrical impulse is propagated throughout the right atrium, and through Bachmann's bundle to the left atrium, stimulating the myocardium of the atria to contract. The conduction of the electrical impulses throughout the atria is seen on the ECG as the P wave.

As the electrical activity is spreading throughout the atria, it travels via specialized pathways, known as internodal tracts, from the SA node to the AV node.

AV node and bundles: PR interval

The AV node functions as a critical delay in the conduction system. Without this delay, the atria and ventricles would contract at the same time, and blood wouldn't flow effectively from the atria to the ventricles. The delay in the AV node forms much of the PR segment on the ECG, and part of atrial repolarization can be represented by the PR segment.

The distal portion of the AV node is known as the bundle of His.The bundle of His splits into two branches in the interventricular septum: the left bundle branch and the right bundle branch. The left bundle branch activates the left ventricle, while the right bundle branch activates the right ventricle.

The left bundle branch is short, splitting into the left anterior fascicle and the left posterior fascicle. The left posterior fascicle is relatively short and broad, with dual blood supply, making it particularly resistant to ischemic damage. The left posterior fascicle transmits impulses to the papillary muscles, leading to mitral valve closure. As the left posterior fascicle is shorter and broader than the right, impulses reach the papillary muscles just prior to depolarization, and therefore contraction, of the left ventricle myocardium. This allows pre-tensioning of the chordae tendinae, increasing the resistance to flow through the mitral valve during left ventricular contraction. This mechanism works in the same manner as pre-tensioning of car seatbelts.

Purkinje fibers/ventricular myocardium: QRS complex

The two bundle branches taper out to produce numerous Purkinje fibers, which stimulate individual groups of myocardial cells to contract.

The spread of electrical activity through the ventricular myocardium produces the QRS complex on the ECG.

Atrial repolarization occurs and is masked during the QRS complex by ventricular depolarization on the ECG.

Ventricular repolarization:

The last event of the cycle is the repolarization of the ventricles. It is the restoring of the resting state. In the ECG, repolarization includes the J point, ST segment, and T and U waves.

The transthoracically measured PQRS portion of an electrocardiogram is chiefly influenced by the sympathetic nervous system. The T (and occasionally U) waves are chiefly influenced by the parasympathetic nervous system guided by integrated brainstem control from the vagus nerve and the thoracic spinal accessory ganglia.

An impulse (action potential) that originates from the SA node at a relative rate of 60-100bpm is known as normal sinus rhythm. If SA nodal impulses occur at a rate less than 60bpm, the heart rhythm is known as sinus bradycardia. If SA nodal impulses occur at a rate exceeding 100bpm, the consequent rapid heart rate is sinus tachycardia. These conditions are not necessarily bad symptoms, however. Trained athletes, for example, usually show heart rates slower than 60bpm when not exercising. If the SA node fails to initialize, the AV junction can take over as the main pacemaker of the heart. The AV junction consists of the AV node, the bundle of His, and the surrounding area; it has a regular rate of 40 to 60bpm. These "junctional" rhythms are characterized by a missing or inverted P wave. If both the SA node and the AV junction fail to initialize the electrical impulse, the ventricles can fire the electrical impulses themselves at a rate of 20 to 40bpm and will have a QRS complex of greater than 120 ms. This is necessary for the heart to be in good function.