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Circulatory System

Circulatory System. 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. Heart Structure.

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Circulatory System

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  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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