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Anatomy & Physiology: Cardiac System Key Concepts

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  • Atrioventricular (AV) valves

    Valves between atria and ventricles that prevent backflow of blood during ventricular contraction.

  • Arrhythmia

    An irregular heartbeat caused by abnormal electrical activity in the heart.

  • Atrioventricular (AV) bundle of His

    A bundle of specialized cardiac muscle fibers that conduct impulses from the AV node to the bundle branches.

  • Atrioventricular (AV) node

    A cluster of cells that delays the electrical impulse from the atria before passing it to the ventricles.

  • Atrium/atria

    The upper chambers of the heart that receive blood returning to the heart.

  • Bradycardia

    A heart rate that is slower than normal, typically below 60 beats per minute.

  • Bundle branches

    Pathways that conduct electrical impulses from the bundle of His to the Purkinje fibers in the ventricles.

  • Cardiac cycle

    The sequence of contraction (systole) and relaxation (diastole) of the heart chambers during one heartbeat.

  • Cardiac muscle contractions

    Involuntary contractions of the heart muscle that pump blood through the heart and circulatory system.

  • Cardiac output (CO)

    The volume of blood the heart pumps per minute, calculated as \(CO=HR \times SV\).

  • Cardiac pacemaker/autorhythmic cells

    Specialized heart cells that generate and conduct electrical impulses to regulate heartbeat.

  • Congestive heart failure (CHF)

    A condition where the heart cannot pump blood effectively, leading to fluid buildup in tissues.

  • Coronary circulation

    The flow of blood through the vessels that supply the heart muscle (myocardium) itself.

  • Deoxygenated blood

    Blood that is low in oxygen and high in carbon dioxide, returning to the heart from the body.

  • Diastole

    The phase of the cardiac cycle when the heart muscle relaxes and chambers fill with blood.

  • Electrocardiogram (ECG, EKG)

    A recording of the electrical activity of the heart used to detect heart abnormalities.

  • Endocardium

    The thin, smooth inner lining of the heart chambers and valves.

  • Epicardium/visceral layer of serous pericardium

    The outer layer of the heart wall that also forms part of the pericardium.

  • Fibrillation

    Rapid, irregular, and uncoordinated contractions of the heart muscle, impairing effective pumping.

  • Fibrous pericardium

    The tough, outermost layer of the pericardium that protects and anchors the heart.

  • Heart rate (HR)

    The number of heartbeats per minute.

  • Heart sounds

    Sounds produced by the closing of heart valves during the cardiac cycle, commonly described as "lub-dub."

  • Intrinsic cardiac conducting system

    A network of specialized cardiac cells that initiate and distribute electrical impulses to coordinate heartbeats.

  • Myocardial infarction

    Also known as a heart attack; occurs when blood flow to part of the heart muscle is blocked, causing tissue damage.

  • Myocardium

    The thick, muscular middle layer of the heart wall responsible for contraction.

  • Oxygenated blood

    Blood rich in oxygen, pumped from the lungs to the body by the heart.

  • P wave

    The ECG wave representing atrial depolarization, which triggers atrial contraction.

  • Pulmonary circuit

    The path of blood flow from the heart to the lungs and back, for oxygenation.

  • QRS complex

    The ECG wave representing ventricular depolarization, leading to ventricular contraction.

  • Sinoatrial (SA) node

    The heart's natural pacemaker located in the right atrium that initiates the heartbeat.

  • Stroke volume (SV)

    The amount of blood ejected by a ventricle with each heartbeat.

  • Subendocardial conducting network/Purkinje fibers

    Specialized fibers that rapidly conduct impulses throughout the ventricles to coordinate contraction.

  • Systemic circuit

    The path of blood flow from the heart to the body tissues and back.

  • Systole

    The phase of the cardiac cycle when the heart muscle contracts to pump blood out.

  • T wave

    The ECG wave representing ventricular repolarization, which precedes ventricular relaxation.

  • Tachycardia

    A heart rate that is faster than normal, typically above 100 beats per minute.

  • Ventricle

    The lower chambers of the heart that pump blood out to the lungs and body.