cardiac cycle


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Related to cardiac cycle: cardiac output, blood pressure, Heart sounds

cycle

 [si´k'l]
a succession or recurring series of events.
cardiac cycle a complete cardiac movement, or heart beat, including systole, diastole, and the intervening pause.
Cardiac cycle. From Applegate, 2000.
cell cycle the cycle of biochemical and morphological events occurring in a reproducing cell population; it consists of the S phase, occurring toward the end of interphase, in which DNA is synthesized; the G2 phase, a relatively quiescent period; the M phase, consisting of the four phases of mitosis; and the G1 phase of interphase, which lasts until the S phase of the next cycle.
citric acid cycle tricarboxylic acid cycle.
estrous cycle the recurring periods of estrus in adult females of most mammalian species and the correlated changes in the reproductive tract from one period to another.
hair cycle the successive phases of the production and then loss of hair, consisting of anagen, catagen, and telogen.
menstrual cycle see menstrual cycle.
ovarian cycle the sequence of physiologic changes in the ovary involved in ovulation; see also ovulation and reproduction.
reproductive cycle the cycle of physiologic changes in the reproductive organs, from the time of fertilization of the ovum through gestation and childbirth; see also reproduction.
sex cycle (sexual cycle)
1. the physiologic changes that recur regularly in the reproductive organs of nonpregnant female mammals.
2. the period of sexual reproduction in an organism that also reproduces asexually.
tricarboxylic acid cycle the cyclic metabolic mechanism by which the complete oxidation of the acetyl portion of acetyl-coenzyme A is effected; the process is the chief source of mammalian energy, during which carbon chains of sugars, fatty acids, and amino acids are metabolized to yield carbon dioxide, water, and high-energy phosphate bonds. Called also citric acid cycle, Krebs cycle, and TCA cycle.
 Central pathways of metabolism: How the body produces energy from the energy-containing nutrients using the tricarboxylic acid cycle. From Davis and Sherer, 1994.
urea cycle a cyclic series of reactions that produce urea; it is a major route for removal of the ammonia produced in the metabolism of amino acids in the liver and kidney.

car·di·ac cy·cle

the complete round of cardiac systole and diastole with the intervals between, or commencing with, any event in the heart's action to the moment when that same event is repeated.

cardiac cycle

Etymology: Gk, kardia + kyklos, circle
the cycle of events in the heart during which an electrical impulse is conducted from the sinus node to the atrioventricular (AV) node, to the AV bundle, to the bundle branches, and to the Purkinje fibers, causing depolarization of the atria followed by depolarization of the ventricles. Depolarization leads to contraction. The contractions of the left and the right atria are nearly simultaneous; they precede the nearly simultaneous contractions of the ventricles. Structural, chemical, or electrical abnormalities may cause a large variety of anomalies in the cardiac cycle.

cardiac cycle

Cardiology A cycle of pumping–systole and refilling–diastole. See Electrophysiology.

car·di·ac cy·cle

(kahr'dē-ak sī'kĕl)
The complete round of cardiac systole and diastole with the intervals between, commencing with any event in the heart's action and ending when same event is repeated.
Enlarge picture
CARDIAC CYCLE (ONE HEARTBEAT, PULSE 75): The outer circle represents the ventricles, the middle circle the atria, and the inner circle the movement of blood and its effect on the heart valves.

cardiac cycle

The period from the beginning of one heartbeat to the beginning of the succeeding beat, including systole and diastole. Normally, the atria contract immediately before the ventricles. The ordinary cycle lasts 0.8 sec with the heart beating approx. 60 to 85 times a minute in the adult at rest. Atrial systole lasts 0.1 sec, ventricular systole 0.3 sec, and diastole 0.4 sec. Although the heart seems to be working continuously, it actually rests for a good portion of each cardiac cycle.
A wart, typically found on the genitals, the perineum, the anus, or the mucosal surfaces of the vagina or mouth, usually spread by sexual contact. It is caused by various types of human papilloma virus and may be spread by physical contact with an area containing a wart. The spread of a wart from one labium to the other by autoinoculation is possible. The virus that causes the wart is usually transmitted sexually. Synonym: genital wart

Treatment

Topically applied liquid nitrogen, imiquimod cream, fluorouracil, or podophyllin may prove effective; multiple treatments are usually needed, including occasionally surgery, electrosurgery, or laser ablation. Extremely large lesions (Buschke-Lowenstein tumor) may need radical excision.

See: Cardiac Cycle illustration
See also: cycle

cardiac cycle

see HEART, CARDIAC CYCLE.

cardiac cycle

the events in the heart over the period from the beginning of the generation of one heart beat to the beginning of the next. The electrical cycle begins with discharge from the sinoatrial node, spreading excitation through the atrial muscle then via the atrioventricular node to the ventricular muscle; after this an isoelectric phase precedes the next cycle. The mechanical cycle begins with simultaneous contraction of the right and left atria (assisting filling of the ventricles); contraction of the ventricles (systole), raising pressure within them, which closes the atrioventricular and opens the aortic and pulmonary valves; ejection of blood; then relaxation (diastole) and refilling. See also blood pressure, cardiac output, electrocardiogram (ECG).

cardiac cycle

sequence of events that manifests as the 'heart beat' (Table 1)
Table 1: The cardiac cycle
Cardiac eventElectrocardiogram event
Atrial depolarization
Right and left atrial contraction
P wave
PR interval
Ventricular activation
Left and right ventricular contraction
QRS complex
Closure of mitral valve
Closure of tricuspid valve
Continued ventricular contraction
Pulmonary valve opens
Aortic valve opens
Ventricular ejection
Aortic valve closure
Pulmonary valve closure
Ventricular relaxation
Mitral valve opens
Tricuspid valve opens

cycle

a succession or recurring series of events.

cardiac cycle
a complete cardiac movement, or heartbeat, including systole, diastole, and the intervening pause.
The cycle includes eight separate phases: (1) isovolumetric contraction; (2) maximum ejection; (3) reduced ejection; (4) protodiastole (onset of ventricular relaxation); (5) isovolumetric relaxation; (6) rapid flow; (7) diastasis (onset of atrial contraction); (8) atrial systole.
cell cycle
the cycle of biochemical and morphological events occurring in a dividing cell population; it consists of the S phase, occurring toward the end of interphase, in which DNA is synthesized; the G2 phase, for gap 2, the interval between S and M; the M phase, for mitosis, consisting of the four phases of mitosis; and the G1 phase, which lasts from the end of M until the start of S phase of the next cycle. Fully differentiated cells are nondividing and are said to be in G0.
Enlarge picture
Cell cycle. By permission from Booth DM, Small Animal Clinical Pharmacology and Therapeutics, Saunders, 2000
citric acid cycle
estrus cycle
see estrous cycle.
Krebs cycle
ovarian cycle
the sequence of physiological changes in the ovary involved in ovulation. See also ovulation and reproduction.
reproductive cycle
the cycle of physiological changes in the reproductive organs, from the time of fertilization of the ovum through gestation and parturition. See also reproduction.
sex cycle, sexual cycle
1. the physiological changes recurring regularly in the reproductive organs of female mammals when pregnancy does not supervene.
2. the period of sexual reproduction in an organism that also reproduces asexually.
tricarboxylic acid cycle
urea cycle
a cyclic series of reactions that produce urea, a major route for removal of the ammonia produced in the metabolism of amino acids in the liver and kidney. See also urea.
References in periodicals archive ?
Net flow during the cardiac cycle is zero (Figs 2a - d and 3a - d).
Data acquisition with this technique is limited to a predefined phase of the cardiac cycle and is prospectively triggered with the ECG signal (QRS complex), which is simultaneously monitored.
MCP" selectively stimulates a patient's muscle groups electrically and affects their contraction in synchronization with the early diastole cardiac cycle, which acts to relieve the heart from workload and improve blood flow.
orientation during the cardiac cycle and adjustment for types of physical activity and irregular heartbeats have become the requirement by the medical community.
MR is the most common type of heart valve insufficiency,(2) occurring when the leaflets of the mitral valve do not close completely, causing blood to flow backwards and leak into the left atrium of the heart during the cardiac cycle.
The MRI shows oscillation of the atrial septum into both atria throughout the cardiac cycle (Figure 1).
In prospective gating, the acquisition is triggered by the QRS complex, and usually only 90% of the cardiac cycle is acquired.
Mitral valve regurgitation or MR is a condition in which the mitral valve, one of the valves in the heart, does not close tightly during the cardiac cycle, allowing the blood to flow backward.
The phaseXact component was designed to select the optimal phase within the cardiac cycle to use for reconstruction of the images.