- System, cardiac conduction
- The electrical conduction system that controls the heart rate. This system generates electrical impulses and conducts them throughout the muscle of the heart, stimulating the heart to contract and pump blood. Among the major elements in the cardiac conduction system are the sinus node, atrioventricular node, and the autonomic nervous system. The sinus node is the heart's natural pacemaker. The sinus node is a cluster of cells situated in the upper part of the wall of the right atrium. The electrical impulses are generated there. (The sinus node is also called the sinoatrial node.) The electrical signal generated by the sinus node moves from cell to cell down through the heart until it reaches the atrioventricular node (the AV node), a cluster of cells situated in the center of the heart between the atria and ventricles. The AV node serves as a gate that slows the electrical current before the signal is permitted to pass down through to the ventricles. This delay ensures that the atria have a chance to fully contract before the ventricles are stimulated. After passing the AV node, the electrical current travels to the ventricles along special fibers embedded in the walls of the lower part of the heart. The autonomic nervous system (the same part of the nervous system as controls the blood pressure) controls the firing of the sinus node to trigger the start of the cardiac cycle. The autonomic nervous system can transmit a message quickly to the sinus node so it in turn can increase the heart rate to twice normal within only 3 to 5 seconds. This quick response is important during exercise when the heart has to increase its beating speed to keep up with the body's increased demand for oxygen.
Medical dictionary. 2011.
Look at other dictionaries:
Cardiac conduction system — The electrical conduction system that controls the heart rate. This system generates electrical impulses and conducts them throughout the muscle of the heart, stimulating the heart to contract and pump blood. Among the major elements in the… … Medical dictionary
Conduction system, cardiac — The electrical conduction system that controls the heart rate. This system generates electrical impulses and conducts them throughout the muscle of the heart, stimulating the heart to contract and pump blood. Among the major elements in the… … Medical dictionary
Cardiac cycle — Cardiac events occurring in the cardiac cycle. Two complete cycles are illustrated. The cardiac cycle is a term referring to all or any of the events related to the flow or blood pressure that occurs from the beginning of one heartbeat to the… … Wikipedia
Cardiac output — (Q or or CO ) is the volume of blood being pumped by the heart, in particular by a left or right ventricle in the time interval of one minute. CO may be measured in many ways, for example dm3/min (1 dm3 equals 1000 cm3 or 1 litre). Q is… … Wikipedia
Cardiac muscle — Dog Cardiac Muscl … Wikipedia
Cardiac pacemaker — The contractions of the heart are controlled by chemical impulses, which fire at a rate which controls the beat of the heart.The cells that create these rhythmical impulses are called pacemaker cells, and they directly control the heart rate.… … Wikipedia
Cardiac amyloidosis — Infobox Disease Name = PAGENAME Caption = DiseasesDB = ICD10 = ICD9 = ICD9|277.3 ICDO = OMIM = MedlinePlus = eMedicineSubj = med eMedicineTopic = 3365 MeshID = Cardiac amyloidosis is a medical disorder, a type of amyloidosis, caused by deposits… … Wikipedia
System, autonomic nervous — Part of the nervous system that was once thought to be functionally independent of the brain. The autonomic nervous system regulates key functions of the body including the activity of the heart muscle (see below), the smooth muscles (e.g., the… … Medical dictionary
Cardiac asthma — Classification and external resources ICD 10 I50.1 ICD 9 428.1 … Wikipedia
Cardiac surgery — Intervention Two cardiac surgeons performing a cardiac surgery known as coronary artery bypass surgery. Note the use of a steel retractor to forcefully maintain the exposure of the patient s heart … Wikipedia