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Understanding Heart Structure and Function: From Chambers to Cardiac Cycle

This comprehensive overview explores the intricate structure and function of the heart, detailing its four chambers—right and left atria, and right and left ventricles—along with the role of the myocardium and pericardium. It delves into the cardiac cycle, highlighting systole and diastole phases, and explains heart rate regulation by the SA and AV nodes. The significance of ECG readings, normal and abnormal heart sounds, and the role of valves in blood flow are also examined. Gain insight into the essential mechanics of this vital organ.

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Understanding Heart Structure and Function: From Chambers to Cardiac Cycle

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Presentation Transcript

  1. Circulatory System

  2. Heart Structure • Surrounded by pericardium • Composed of heart muscle • Myocardium • 4 compartments • Right and left ventricles, right and left atria • Left ventricle  systemic • Right ventricle  pulmonary • Two sides separated by the septum

  3. Heart Structure • AV and semilunar valves • tricuspid valve – between right atrium and ventricle • mitral valve – between left atrium and ventricle • pulmonary valve – between the right ventricle and the pulmonary artery • aortic valve – outflow tract of the left ventricle (controls flow to the aorta)

  4. The Cardiac Cycle • Period between start one heartbeat to the beginning of another • Systole – contraction • Increase in pressure • Diastole – relaxation of all chambers followed by contraction of the atria • Decrease in pressure

  5. The Cardiac Cycle • Beginning – all 4 chambers relaxed and patr

  6. The Heartbeat • Heart rate determined by the SA node • Propagated by conducting system • Rate of propagation slows as it enters the AV node • Important delay allows atria to contract before ventricles • Other influences on heart rate • Parasympathetic nervous system • Sympathetic nervous system • Hormones

  7. SA Node • crescent shape, 15 mm long, and 5 mm wide • self-excitatory, pacemaker cells • generate an action potential at the rate of about 80 to 100 beats per minute • Abnormal pacemaker • Brachycardia • tachycardia

  8. AV Node • intrinsic frequency of about 40 – 60 pulses per min • if the AV node is triggered with a higher pulse frequency, it follows this higher frequency • the AV node provides the only conducting path from the atria to the ventricles • under normal conditions, the ventricles can only be excited by pulses that propagate through the AV node

  9. ECG/EKG • Records electrical events in heart • Small P wave • Depolarization of atria • QRS complex • Ventricles depolarize • Small T wave • P-R interval • Start of atrial depolarization to start of QRS complex • Q-T interval • Time for ventricle to polarize and depolarize

  10. ECG Abnormalities • Large QRS complex • Altered size and shape of T wave • Extension of P-R interval • Lengthened Q-T interval • Cardiac arrhythmias

  11. Heart Sounds • 4 heart sounds • S1 (lubb): AV valves close • S2 (dupp): semilunar valves close • S3 and S4: very faint sounds • S4 atrial contraction • S3 blood flowing into ventricles • Heart murmers • Valves do not close properly

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