Heart

1. Heart • Considered to be a duel pump because the both sides work independently of one another. • The right side pumps blood to the lungs. • (pulmonary circulation) • The left side pumps blood to all of the other organs of the body • (systemic circulation)

2. Pathway of Blood Through the Heart and Lungs

3. Major Vessels of the Heart • Vessels returning blood to the heart include: • Superior and inferior venae cavae • Right and left pulmonary veins • Vessels carrying blood away from the heart include: • Pulmonary trunk, which splits into right and left pulmonary arteries • Ascending aorta (three branches) –, left common carotid, and subclavian arteries

4. Figure 19.5a

5. Figure 19.5b

7. Ventricles of the Heart • Ventricles eject blood from the heart • Right ventricle pumps blood into the pulmonary trunk which will go to the lungs. • Left ventricle pumps blood into the aorta which will go to the rest of the body

8. Atrioventricular Heart Valves • Heart valves ensure unidirectional blood flow through the heart. • Atrioventricular (AV) valves lie between the atria and the ventricles. • Tricuspid Right • Bicuspid (Mitral) Left • AV valves prevent backflow of blood into the atria when ventricles contract. • Chordae tendineae anchor AV valves to papillary muscles • First heart sound (LUB) when valves close

9. During diastole there is less pressure in the in ventricle. AV Valves open and filling the ventricle. • During systole the AV valves prevent the back flow of blood into the atrium. • Failure to prevent the blood from going back into the atria (systolic heart murmur)

10. Semilunar Heart Valves • Aortic semilunar valve lies between the left ventricle and the aorta. • Pulmonary semilunar valve lies between the right ventricle and pulmonary trunk • Semilunar valves prevent backflow of blood into the ventricles. • Second heart sound (DUB) when valves close.

11. Figure 19.9b • During ventricular systole the semilunar valves allow blood to be ejected from the ventricles into the aorta and pulmonary trunk. • During diastole they prevent the back flow of blood back into the ventricles. • Failure to prevent the backflow of blood into the ventricles. (diastolic murmur)

12. Coronary Arteries • Left coronary artery (LCA) • anterior interventricular branch • supplies blood to interventricular septum and anterior walls of ventricles • circumflex branch • passes around left side of heart in coronary sulcus, supplies left atrium and posterior wall of left ventricle • Right coronary artery (RCA) • right marginal branch • supplies lateral R atrium and ventricle • posterior interventricular branch • supplies posterior walls of ventricles

13. Cardiac muscle is short and striated. • Ability to beat independent of stimulation from the nervous system. • ANS • Functional syncytium: • intercalated discs connect cardiac cells which allow free passage of ions. • This allows the spread of action potentials from one myocyte to another. • The result is a coordinated contraction that moves the blood out of the heart.

14. Major Vessels

15. Figure 20.23a

16. Figure 20.27

17. Figure 20.28a

18. Mesenteric Vessels

20. Blood Pressure (BP) • Force per unit area exerted on the wall of a blood vessel by its contained blood. • Expressed in millimeters of mercury (mm Hg) • Measured in reference to systemic arterial BP in large arteries near the heart. • The differences in BP within the vascular system provide the driving force that keeps blood moving from higher to lower pressure areas.

21. Resistance • Resistance – opposition to flow • Measure of the amount of friction blood encounters as it passes through vessels. • Generally encountered in the systemic circulation. • Referred to as peripheral resistance (PR) • The three important sources of resistance are blood viscosity, total blood vessel length, and blood vessel diameter.

22. Resistance Factors: Viscosity and Vessel Length • Resistance factors that remain relatively constant are: • Blood viscosity – thickness or “stickiness” of the blood the greater the resistance. • Blood vessel length – the longer the vessel, the greater the resistance encountered. • Diameter- Smaller diameter arterioles are the major determinants of peripheral resistance • Fatty plaques from atherosclerosis: decreases both diameter and elasticity of vessel which results in: • Cause turbulent blood flow • Dramatically increase resistance due to turbulence

23. Blood Flow, Blood Pressure, and Resistance • Blood flow (F) is directly proportional to the difference in blood pressure • If P increases, blood flow speeds up; if P decreases, blood flow declines • Blood flow is inversely proportional to resistance (R) • If R increases, blood flow decreases • R is more important than P in influencing local blood pressure.

24. EKG

25. Why Get an EKG • Unexplained chest pain, or reduced blood flow to the heart (ischemia), shortness of breath, dizziness, fainting, or rapid and irregular heartbeats (palpitations). • Identify ventricle hypertrophy and other changes of the myocardium. • Check how well mechanical devices, such as pacemakers or defibrillators implanted in the heart, are working to control a normal heartbeat.

26. Electrocardiography • Electrical activity is recorded by electrocardiogram (ECG) • P wave corresponds to depolarization of SA node resulting in atrial systole • QRS complex corresponds to ventricular depolarization resulting in Ventricular contraction and blood being ejected from the heart. • Atrial repolarization is hidden with in QRS complex • ST segment - ventricular systole • T wave corresponds to ventricular repolarization

27. EKG

28. Normal Sinus Rhythm • The heart is being paced by the SA node. There is a degree of regularity between all components of EKG • Normal heart rate ranges between 60-100bpm. • 75bpm( average) dependent on activity. • Find a QRS that falls on a solid black line. • Then count 300-150-100-75-60-50-43 for each successive black line. Distance between QRS complexes are 5 black lines =60 Beats per minute

29. Sinus Bradycardia (SB) is defined as a sinus rhythm with a rate below 60 bpm. • Normally found in well trained persons and during sleep. • May also be found in patients post myocardial infarction • Beta Blockers reduce sympathetic input to the heart reducing both cardiac workload and blood pressure. • If on this medication heart rate is not a valid measure of exertion.

30. Tachycardia • Defined as a heart rate greater than 100bpm • This is a perfectly normal rhythm if you are exercising. • Heart beats faster under the influence of the SNS in order to meet the bodies increased demand of oxygen. • Stress, anxiety, or underline pathology may result in an elevated HR. • Context is important.

31. Atrial Fibrillation • Multiple ectopic foci fire chaotically in the atrium • This diminished the atriums ability to contract and results in pooling in the atrium. • (High risk of blood clot formation =need blood thinners) • Loss of atrial kick = reduced SV • May lead to a more severe arrhythmia.

33. Premature Ventricular Contraction (PVC) Ventricles contract before the atria in a cardiac cycle The SA node is not pacing the heart here. • typically caused by emotional stress, lack of sleep, smoking or stimulants (caffeine) which initiate an AP in the ventricles

34. Ventricular Tachycardia( V-Tach) • Heart rate greater then 150 that originates from an irritable foci in the ventricle. • It is a regular rhythm but is hemo-dynamically inefficient. The heart CO will be very poor due to reduced ventricular filling. • Reduced CO leads to poor coronary perfusion. • Will lead to Ventricular Fibrillation

35. Ventricular Fibrillation( V-FIB) • This is the most dangerous rhythm. There is no discernable pattern. • Multiple areas of the ventricles are initiating impulses at the same time resulting in a quivering heart instead of a contracting heart. • The heart will not efficiently fill up with blood. • Oxygen will not be delivered to the tissues. • Toe tag is eminent unless a defibrillator ( AED) is near.