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See media help. The cardiac cycle is the performance of the human heart from the beginning of one heartbeat to the beginning of the next. [ 1] It consists of two periods: one during which the heart muscle relaxes and refills with blood, called diastole, following a period of robust contraction and pumping of blood, called systole. [ 1]
A circadian rhythm ( / sərˈkeɪdiən / ), or circadian cycle, is a natural oscillation that repeats roughly every 24 hours. Circadian rhythms can refer to any process that originates within an organism (i.e., endogenous) and responds to the environment (is entrained by the environment). Circadian rhythms are regulated by a circadian clock ...
Wave. Surface waves in water showing water ripples. In physics, mathematics, engineering, and related fields, a wave is a propagating dynamic disturbance (change from equilibrium) of one or more quantities. Periodic waves oscillate repeatedly about an equilibrium (resting) value at some frequency. When the entire waveform moves in one direction ...
Oscillation. An undamped spring–mass system is an oscillatory system. Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendulum and alternating current.
Amplitude. The amplitude of a periodic variable is a measure of its change in a single period (such as time or spatial period ). The amplitude of a non-periodic signal is its magnitude compared with a reference value. There are various definitions of amplitude (see below), which are all functions of the magnitude of the differences between the ...
Use of real time monitoring of the heart in an intensive care unit in a German hospital (2015), the monitoring screen above the patient displaying an electrocardiogram and various values of parameters of the heart like heart rate and blood pressure. Electrocardiography is the process of producing an electrocardiogram ( ECG or EKG[ a] ), a ...
The refractory period in cardiac physiology is related to the ion currents that, in cardiac cells as in nerve cells, flow into and out of the cell freely. The flow of ions translates into a change in the voltage of the inside of the cell relative to the extracellular space. As in nerve cells, this characteristic change in voltage is referred to ...
Cardiac systole is the contraction of the cardiac muscle in response to an electrochemical stimulus to the heart's cells ( cardiomyocytes ). Cardiac output is the volume of blood pumped by the ventricles in one minute. The ejection fraction is the volume of blood pumped divided by the total volume of blood in the left ventricle.