cardiac cycle

(noun)

The term used to describe the relaxation and contraction that occur as a heart works to pump blood through the body.

Related Terms

Examples of cardiac cycle in the following topics:

  • Cardiac Cycle

    • The cardiac cycle describes the heart's phases of contraction and relaxation that drive blood flow throughout the body.
    • The cardiac cycle is the term used to describe the relaxation and contraction that occur as the heart works to pump blood through the body.
    • Heart rate is a term used to describe the frequency of the cardiac cycle.
    • Throughout the cardiac cycle, the arterial blood pressure increases during the phases of active ventricular contraction and decreases during ventricular filling and atrial systole.
    • Blood pressure is a regulated variable that is directly related to blood volume, based on cardiac output during the cardiac cycle.

  • The Cardiac Cycle

    • The cardiac cycle uses mechanical actions and electrical signals to push blood in and out of the heart.
    • The main purpose of the heart is to pump blood through the body; it does so in a repeating sequence called the cardiac cycle.
    • The cardiac cycle is the coordination of the filling and emptying of blood by electrical signals that cause the heart muscles to contract and relax.
    • In each cardiac cycle, the heart contracts (systole), pushing out the blood and pumping it through the body.
    • The final part of the ECG cycle prepares the heart for the next beat.

  • Blood Pressure

    • Blood pressure is the pressure of blood against the blood vessel walls during the cardiac cycle; it is influenced by a variety of factors.
    • The systolic pressure is defined as the peak pressure in the arteries during the cardiac cycle; the diastolic pressure is the lowest pressure at the resting phase of the cardiac cycle.
    • Throughout the cardiac cycle, the blood continues to empty into the arterioles at a relatively even rate.
    • Cardiac output is the volume of blood pumped by the heart in one minute.
    • Therefore, cardiac output can be increased by increasing heart rate, as when exercising.

  • Pumps and the Heart

    • The human heart will undergo over 3 billion contraction cycles during a normal lifetime.
    • A complete cardiac cycle is one round of the heart pumping blood and consists of two parts: systole (contraction of the heart muscle) and diastole (relaxation of the heart muscle).
    • During the cycle, the top half of the heart works as one unit, while the bottom half of the heart works as one unit.

  • Pressure in the Body

    • The mean arterial pressure (MAP) is the average pressure over a cardiac cycle and is determined by , where CO is the cardiac outputs, SVR is the systemic vascular resistance, and CVP is the central venous pressure (CVP).
    • The cycle repeats itself, resulting in the respiration which as discussed is mechanically due to pressure changes.
    • The mean arterial pressure (MAP) is the average pressure over a cardiac cycle and is determined this equation, where CO is the cardiac outputs, SVR is the systemic vascular resistance, and CVP is the central venous pressure (CVP).

  • Electric Activity in the Heart

    • The human heart provides continuous blood circulation through the cardiac cycle and is unsurprisingly one of the most vital organs in the human body.
    • These cells are specialized cardiomycetes (cardiac muscle cells).
    • Although all of the heart's cells have the ability to generate the electrical impulses (or action potentials) that trigger cardiac contraction, the sinoatrial node normally initiates it, simply because it generates impulses slightly faster than the other areas with pacemaker potential .
    • These fibers consist of specialized cardiomyocytes that are able to conduct cardiac action potentials more quickly and efficiently than any other cells in the heart.
    • During the ventricular contraction portion of the cardiac cycle, the Purkinje fibers carry the contraction impulse from both the left and right bundle branch to the myocardium of the ventricles.

  • Functions of the Brain Stem

    • The brainstem regulates vital cardiac and respiratory functions and acts as a vehicle for sensory information.
    • The brain stem also plays an important role in the regulation of cardiac and respiratory function.
    • It regulates the central nervous system (CNS) and is pivotal in maintaining consciousness and regulating the sleep cycle.
    • The medulla contains the cardiac, respiratory, vomiting, and vasomotor centers regulating heart rate, breathing, and blood pressure.
    • The midbrain (mesencephalon) is associated with vision, hearing, motor control, sleep and wake cycles, alertness, and temperature regulation.

  • Energy Requirements

    • Cardiac cells contain numerous mitochondria, which enable continuous aerobic respiration and production of adenosine triphosphate (ATP) for cardiac function.
    • Cardiac muscle tissue has among the highest energy requirements in the human body (along with the brain) and has a high level of mitochondria and a constant, rich, blood supply to support its metabolic activity.
    • Cardiac muscle cells contain larger amounts of mitochondria than other cells in the body, enabling higher ATP production.
    • Lactate, created from lactic acid fermentation, accounts for the anaerobic component of cardiac metabolism.
    • The produced pyruvate can then be burned aerobically in the citric acid cycle (also known as the tricarboxylic acid cycle or Krebs cycle), liberating a significant amount of energy.

  • African Trypanosomiasis

    • The entire life cycle of African trypanosomes is represented by extracellular stages.
    • The epimastigotes reach the fly's salivary glands and continue multiplication by binary fission.The entire life cycle of the fly takes about three weeks.
    • If left untreated, the disease overcomes the host's defenses and can cause more extensive damage, broadening symptoms to include anemia, endocrine, cardiac, and kidney dysfunctions.
    • Here is an outline of the life cycle of the protozoa Trypanosoma brucei, the parasite responsible for African trypanosomiasis (sleeping sickness).
    • Outline the life cycle of Trypanosoma brucei and its route of transmission that causes African trypanosomiasis

  • Stages of Sleep

    • Sleep proceeds through multiple cycles of non-REM (3 stages) and REM per night, with each full cycle lasting between 90 and 110 minutes.
    • These cycles typically last between 90 and 110 minutes.
    • slowed bodily functions (e.g., lower blood pressure; decreased cardiac and metabolic activity).
    • However, for each successive sleep cycle, the proportion of the cycle spent in REM sleep increases, up to an hour long in later cycles.
    • This sample hypnogram (EEG of sleep) shows how the proportion of the sleep cycle spent in REM sleep increases with each subsequent cycle over the course of a night.