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Anatomy & Physiology: The Cardiovascular System I - The Heart

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  • Layers of the pericardium

    The pericardium has two parts: the fibrous pericardium and the serous pericardium. The serous pericardium has two layers: parietal and visceral (epicardium), with pericardial fluid between them.

  • Location of the heart

    The heart is located in the mediastinum, anterior to the vertebral column, posterior to the sternum, and superior to the diaphragm, with about two-thirds of its mass to the left of the midline.

  • Function of the right and left coronary arteries

    The right and left coronary arteries branch off the aorta and supply oxygen-rich blood to the heart muscle tissue.

  • Role of the coronary sinus

    The coronary sinus collects oxygen-poor blood from the cardiac veins and returns it to the right atrium.

  • Major chambers of the heart

    The heart has four chambers: two atria (right and left) that receive blood, and two ventricles (right and left) that pump blood out.

  • Function of atrioventricular (AV) valves

    AV valves (tricuspid on right, bicuspid/mitral on left) separate atria from ventricles and prevent backflow during ventricular contraction.

  • Function of semilunar (SL) valves

    SL valves (pulmonary on right, aortic on left) separate ventricles from arteries and prevent backflow after blood is ejected.

  • Pathway of blood through the heart

    Blood flows: body → right atrium → tricuspid valve → right ventricle → pulmonary semilunar valve → pulmonary trunk → lungs → left atrium → bicuspid valve → left ventricle → aortic semilunar valve → aorta → body.

  • Difference between pulmonary and systemic circuits

    The pulmonary circuit carries blood between the heart and lungs; the systemic circuit carries blood between the heart and the rest of the body.

  • Structure of cardiac muscle tissue

    Cardiac muscle is striated, involuntary, with branched cells containing one nucleus, abundant mitochondria, and intercalated discs with gap junctions and desmosomes.

  • Autorhythmic cardiac cells

    About 1% of cardiac muscle cells are autorhythmic pacemaker cells that generate spontaneous action potentials due to Na+ leakiness.

  • Cardiac conduction system components

    Includes the sinoatrial (SA) node, atrioventricular (AV) node, AV bundle (Bundle of His), and Purkinje fibers, which coordinate heart rhythm.

  • ECG waveforms and their significance

    P wave: atrial depolarization; QRS complex: atrial repolarization and ventricular depolarization; T wave: ventricular repolarization.

  • Common ECG abnormalities

    Bradycardia (slow HR), tachycardia (fast HR), AV block (slow conduction), atrial fibrillation (no P wave), ventricular fibrillation (no organized waves, fatal).

  • Phases of the cardiac cycle

    Atrial systole (atria contract), ventricular systole (ventricles contract), and relaxation (diastole) with corresponding valve openings and closings.

  • Heart sounds and their causes

    Lubb (1st sound) caused by closing of AV valves at ventricular systole start; Dupp (2nd sound) caused by closing of semilunar valves at ventricular systole end.

  • Definition and formula for cardiac output (CO)

    CO is the volume of blood pumped by a ventricle per minute. Formula: CO = HR × SV, where HR is heart rate and SV is stroke volume.

  • Frank-Starling law of the heart

    Increased preload (ventricular stretch) leads to increased force of contraction and stroke volume.

  • Factors affecting stroke volume

    Preload (stretch), afterload (arterial pressure to overcome), and contractility influence stroke volume.

  • Autonomic regulation of heart rate

    Sympathetic stimulation increases HR and contractility; parasympathetic (vagus nerve) decreases HR.

  • Chemical and non-chemical factors influencing heart rate

    Hormones (epinephrine, norepinephrine, thyroid), electrolytes (Ca++, Na+, K+), body temperature, age, and fitness affect heart rate.

  • Congestive heart failure (CHF)

    CHF is reduced cardiac output due to diseased heart muscle, causing pulmonary and peripheral edema; treatment includes activity, drugs, pacemakers, stents, or transplant.