1. Lesson 11.2 Regulation of the Heart Chapter 11: The Cardiovascular System

2. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Section Overview 1. internal control of the heart 2. external control 3. the conduction system Regulation of the Heart

3. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Sinoatrial node –pacemaker –sends electrical impulse –tells heart to beat 60–100 bpm Internal Control of the Heart

4. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. The cardiac center –sympathetic nerve system speeds up –parasympathetic nerve system slows down The endocrine system –some hormones speed up External Control of the Heart

5. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. SA node AV node bundle of His bundle branches– right and left Purkinje fibers The Conduction System

6. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. ECG or EKG –electrical activity of the heart –depolarize – contract –repolarize – relax Electrocardiogram

7. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. normal contractility condition –sinus rhythm – normal beating of the heart = SA node is contracting normally and bpm is between 60 - 100 abnormal contractility condition –arrhythmia abnormal beating of the heart, too fast or too slow ventricle or atria contraction is not normal Cardiac Arrhythmias

8. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. bradycardia –slow heart beat – rate below 60 bpm (athletes) tachycardia –fast heart beat – rate above 100 bpm premature atrial contraction (PACs) –Irritable piece of atria contracts before SA node (caffeine, stress, stimulants – red bull) Cardiac Arrhythmias

9. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. atrial fibrillation (Afib) –atria contract faster than 350 bpm –atria are not coordinated, they “quiver” –If severe, may need a pacemaker premature ventricular contractions (PVCs) –ventricles contract too soon –Purkinje fibers fire before SA node ventricular tachycardia (VT) –ventricles, rather than SA node, cause beat = lifethreating Cardiac Arrhythmias

10. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. ventricular fibrillation (VF) –ventricles “quiver”, contract faster than 350 bpm –No cardiac output heart block –impulse from SA node to AV node first – impulse delayed second – intermittently blocked third – completely blocked Cardiac Arrhythmias

11. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. automatic external defibrillator (AED) –electric shock –stops heart –allows heart to start normal rhythm –anyone can use one Defibrillators and Life-Threatening Arrhythmias