Search results
Results From The WOW.Com Content Network
This occurs due to a net flow of positive charge into the cell. In non-pacemaker cells (i.e. ventricular cells), this is produced predominantly by the activation of Na + channels, which increases the membrane conductance (flow) of Na + (g Na). These channels are activated when an action potential arrives from a neighbouring cell, through gap ...
The conduction system consists of specialized heart muscle cells, situated within the myocardium. [3] There is a skeleton of fibrous tissue that surrounds the conduction system which can be seen on an ECG. Dysfunction of the conduction system can cause irregular heart rhythms including rhythms that are too fast or too slow.
Cardiac physiology or heart function is the study of healthy, unimpaired function of the heart: involving blood flow; myocardium structure; the electrical conduction system of the heart; the cardiac cycle and cardiac output and how these interact and depend on one another.
These cells produce an electrical impulse known as a cardiac action potential that travels through the electrical conduction system of the heart, causing it to contract. In a healthy heart, the SA node continuously produces action potentials, setting the rhythm of the heart (sinus rhythm), and so is known as the heart's natural pacemaker.
The cardiac pacemaker is the heart's natural rhythm generator. It employs pacemaker cells that generate electrical impulses, known as cardiac action potentials.These potentials cause the cardiac muscle to contract, and the rate of which these muscles contract determines the heart rate.
Ventricular escape beats occur when the rate of electrical discharge reaching the ventricles (normally initiated by the heart's sinoatrial node (SA node), transmitted to the atrioventricular node (AV node), and then further transmitted to the ventricles) falls below the base rate determined by the rate of Phase 4 spontaneous depolarisation of ventricular pacemaker cells. [1]
These generate an electric current that causes the heart to contract, traveling through the atrioventricular node and along the conduction system of the heart. In humans, deoxygenated blood enters the heart through the right atrium from the superior and inferior venae cavae and passes to the right ventricle.
Cardioplegia solution protects the heart by arresting, or stopping the heart. This then decreases the heart's metabolic demand. There are multiple types of cardioplegia solutions, but most work by inhibiting fast sodium currents in the heart, which prevent conduction of the action potential.