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Heart 2 online
- 1. ANATOMY OF A HEART BEAT Copyright ยฉ 2011 Pearson Education, Inc.
- 2. Cardiac Muscle Cells โข The myocardium is composed of cardiac myocytes โข They contract similar to skeletal muscle cells. Copyright ยฉ 2011 Pearson Education, Inc.
- 3. Cardiac Muscle Cells โข Features: โข Striations โข Intercalated disks โข Gap junctions โข Cell communications โข Branched โข Anchored to endomysium โข desmosomes Copyright ยฉ 2011 Pearson Education, Inc.
- 4. Cardiac Muscle Contraction โข Contraction of the heart is rhythmic and spontaneous โข Similar to skeletal muscle cells, an action potential is generated Copyright ยฉ 2011 Pearson Education, Inc.
- 5. Steps of an Action Potential (REVIEW) Copyright ยฉ 2011 Pearson Education, Inc.
- 6. Role of the Sodium-Potassium Pump 1. Resting state โข Gates closed 1. Depolarization โข Stimulus causes Na+ gates to open 1. Repolarization โข Na+ gates close / K+ gates open 1. Hyperpolarization โข K+ gates close / Sodium-Potassium pumps activate Copyright ยฉ 2011 Pearson Education, Inc.
- 7. Cardiac Muscle Contraction โข Two chambers contract at different times โข Both generate action potentials 1. Atrium โข Contraction initiated by sinoarterial node (SA node) 1. Ventricles โข Contraction initiated when signal from SA node reaches atrioventricular node (AV node) Copyright ยฉ 2011 Pearson Education, Inc.
- 8. Electrocardiography โข Electrocardiogram (ECG or EKG): a composite of all the action potentials generated by the heart โข Three waves 1. P wave: depolarization of SA node 2. QRS complex: ventricular depolarization 3. T wave: ventricular repolarization Copyright ยฉ 2011 Pearson Education, Inc.
- 9. QRS complex Sinoatrial node Atrial depolarization Ventricular depolarization Ventricular repolarization Atrioventricular node P-Q Interval S-T Segment Q-T Interval Copyright ยฉ 2011 Pearson Education, Inc. Figure 17.16
- 10. SA node Depolarization R Repolarization R T P Q S 1 Atrial depolarization, initiated by the SA node, causes the P wave. R AV node T P Q S 4 Ventricular depolarization is complete. R T P T P Q S 2 With atrial depolarization complete, the impulse is delayed at the AV node. R Q S 5 Ventricular repolarization begins at apex, causing the T wave. R T P T P Q S 3 Ventricular depolarization begins at apex, causing the QRS complex. Atrial repolarization occurs. Copyright ยฉ 2011 Pearson Education, Inc. Q S 6 Ventricular repolarization is complete. Figure 17.17
- 11. (a) Normal sinus rhythm. (b) Junctional rhythm. The SA node is nonfunctional, P waves are absent, and heart is paced by the AV node at 40 - 60 beats/min. (c) Second-degree heart block. (d) Ventricular fibrillation. These chaotic, grossly irregular ECG Some P waves are not conducted deflections are seen in acute through the AV node; hence more heart attack and electrical shock. P than QRS waves are seen. In this tracing, the ratio of P waves to QRS waves is mostly 2:1. Copyright ยฉ 2011 Pearson Education, Inc. Figure 17.18
- 12. Heart Physiology: Sequence of Excitation 1. Sinoatrial (SA) node (pacemaker) โข Generates impulse 1. Atrioventricular (AV) node 2. Atrioventricular bundle โข Connects atria to ventricles 1. Bundle branches โข Connects the ventricles 1. Purkinji fibers Copyright ยฉ 2011 Pearson Education, Inc.
- 13. Superior vena cava Right atrium 1 The sinoatrial (SA) node (pacemaker) generates impulses. Internodal pathway 2 The impulses pause (0.1 s) at the atrioventricular (AV) node. 3 The atrioventricular (AV) bundle connects the atria to the ventricles. 4 The bundle branches conduct the impulses through the interventricular septum. 5 The Purkinje fibers Left atrium Purkinje fibers Interventricular septum depolarize the contractile cells of both ventricles. (a) Anatomy of the intrinsic conduction system showing the sequence of electrical excitation Copyright ยฉ 2011 Pearson Education, Inc. Figure 17.14a
- 14. Heart Sounds โข Two sounds (lub-dup) โข closing of heart valves 1. AV valves close โข Beginning of systole 1. SL valves close โข Beginning of diastole โข Heart murmurs: abnormal heart sounds โข Valve problems Copyright ยฉ 2011 Pearson Education, Inc.
- 15. Mechanical Events: The Cardiac Cycle โข Cardiac cycle: blood flow through the heart during one heartbeat โข Systole โcontraction โข Diastole โrelaxation โข Generally refers to activity of ventricles Copyright ยฉ 2011 Pearson Education, Inc.
- 16. Steps of the Cardiac Cycle 1. Ventricles fill โ mid diastole โข AV valves are open 1. Ventricular systole - contraction โข AV valves close โข SL valves open 1. Ventricles relax โbegin diastole โข SL valves close Copyright ยฉ 2011 Pearson Education, Inc.
- 17. Steps of the Cardiac Cycle Copyright ยฉ 2011 Pearson Education, Inc.
- 18. Cardiac Output (CO) โข Volume of blood pumped by each ventricle in one minute โข CO = heart rate (HR) x stroke volume (SV) โข HR = beats / minute โข SV = volume of blood pumped per beat Copyright ยฉ 2011 Pearson Education, Inc.
- 19. Regulation of HR โข Sympathetic nervous system โข emotional or physical stress โข Increases HR โข Parasympathetic nervous system โข Depresses HR โข Utilizes vagus nerve โข Hormones โข Epinephrine increases heart rate Copyright ยฉ 2011 Pearson Education, Inc.
- 20. Other Factors that Influence Heart Rate โข Age โข Gender โข Exercise โข Body temperature Copyright ยฉ 2011 Pearson Education, Inc.
- 21. HEART DISEASES Copyright ยฉ 2011 Pearson Education, Inc.
- 22. Homeostatic Defects Defects in contractions: 1.Arrhythmias: โข irregular heart rhythms 1.Fibrillation: โข rapid, irregular contractions โข cannot pump blood Copyright ยฉ 2011 Pearson Education, Inc.
- 23. Heart Disease โข Angina pectoris โข Chest pain โข Low coronary blood flow โข Myocardial infarction (heart attack) โข Prolonged coronary blockage โข Cardiac cell death โข repaired with scar tissue โข (not cardiac myocytes) Copyright ยฉ 2011 Pearson Education, Inc.
- 24. Abnormal Heart Rate โข Tachycardia: โข fast heart rate (>100 bpm) โข may lead to fibrillation โข Bradycardia: โข slow heart rate (< 60 bpm) โข Inadequate blood flow โข endurance training Copyright ยฉ 2011 Pearson Education, Inc.
- 25. Congestive Heart Failure (CHF) โข Cardiac output too low โข Caused by: โข Coronary atherosclerosis โข high blood pressure โข myocardial infarcts โข Dilated cardiomyopathy (DCM) Copyright ยฉ 2011 Pearson Education, Inc.