1. The Cardiovascular system: Heart
Chapter 15

2. Thoracic cavity between two lungs surrounded by pericardium:
Location
Thoracic cavity between two lungs
~2/3 to left of midline
surrounded by pericardium:
Fibrous pericardium-
Inelastic and anchors heart in place
Inside is serous pericardium- double layer around heart
Parietal layer fused to fibrous pericardium
Inner visceral layer adheres tightly to heart
Filled with pericardial fluid- reduces friction during beat.

3. Figure 15.1

4. Epicardium- outer layer Myocardium- cardiac muscle
Heart Wall
Epicardium- outer layer
Myocardium- cardiac muscle
Two separate networks via gap junctions in intercalated discs- atrial & ventricular
Networks- contract as a unit
Endocardium- Squamous epithelium
lines inside of myocardium

5. Figure 15.2a

6. Figure 15.2b

7. Figure 15.2c

8. 2 lower chambers = ventricles Wall thickness depends on work load
2 upper chambers= Atria
Between is interatrial septum
Contains fossa ovalis- remnant of foramen ovalis
2 lower chambers = ventricles
Between is interventricular septum
Wall thickness depends on work load
Atria thinnest
Right ventricle pumps to lungs & thinner than left

9. Great Vessels Of Heart- Right
Superior & inferior Vena Cavae
Delivers deoxygenated blood to R. atrium from body
Coronary sinus drains heart muscle veins
R. Atrium  R. Ventricle
pumps through Pulmonary Trunk
R & L pulmonary arteries
 lungs

10. Great Vessels Of Heart-Left
Pulmonary Veins from lungs
oxygenated blood
L. atrium Left ventricle
ascending aorta body
Between pulmonary trunk & aortic arch is ligamentum arteriosum
fetal ductus arteriosum remnant

11. Figure 15.3a

12. Figure 15.3b

13. Figure 15.3c

14. Designed to prevent back flow in response to pressure changes
Valves
Designed to prevent back flow in response to pressure changes
Atrioventricular (AV) valves
Between atria and ventricles
Right = tricuspid valve (3 cusps)
Left = bicuspid or mitral valve
Semilunar valves near origin of aorta & pulmonary trunk
Aortic & pulmonary valves respectively

15. Figure 15.4ab

16. Figure 15.4c

17. Figure 15.4d

18. Figure 15.5a

19. Figure 15.5b

20. Blood flow through vessels in myocardium = coronary circulation
Blood Supply Of Heart
Blood flow through vessels in myocardium = coronary circulation
L. & Right coronary arteries
branch from aorta
branch to carry blood throughout muscle
Deoxygenated blood collected by Coronary Sinus (posterior)
Empties into R. Atrium

21. Conduction System
1% of cardiac muscle generate action potentials= Pacemaker & Conduction system Normally begins at sinoatrial (SA) node Atria & atria contract AV node -slows AV bundle (Bundle of His) bundle branches Purkinje fibers  apex and up- then ventricles contract

22. Pacemaker
Depolarize spontaneously sinoatrial node ~100times /min also AV node ~40-60 times/min in ventricle ~20-35 /min Fastest one run runs the heart = pacemaker Normally the sinoatrial node

23. Figure 15.6

24. P wave= atrial depolarization QRS complex= Ventricular depolarization
Electrocardiogram
Recording of currents from cardiac conduction on skin = electrocardiogram (EKG or ECG)
P wave= atrial depolarization
Contraction begins right after peak
Repolarization is masked in QRS
QRS complex= Ventricular depolarization
Contraction of ventricle
T-wave = ventricular repolarization
Just after ventricles relax

25. Figure 15.7

26. after T-wave ventricular diastole After P-wave atrial systole
Cardiac Cycle
after T-wave ventricular diastole
Ventricular pressure drops below atrial & AV valves open  ventricular filling occurs
After P-wave atrial systole
Finishes filling ventricle (`25%)
After QRS ventricular systole
Pressure pushes AV valves closed
Pushes semilunar valves open and ejection occurs
Ejection until ventricle relaxes enough for arterial pressure to close semilunar valves

27. Action Potential
Review muscle Heart has addition of External Ca2+ creates a plateau prolonged depolarized period. Can not go into tetanus.

28. Figure 15.8

29. Flow Terms
Cardiac Output (CO) = liters/min pumped Heart Rate (HR) = beats/minute (bpm) Stroke volume (SV) = volume/beat CO = HR x SV

30. Controls- Stroke Volume (S.V.)
Degree of stretch = Frank-Starling law
Increase diastolic Volume increases strength of contraction increased S.V.
Increased venous return  increased S.V.
increased sympathetic activity
High back pressure in artery  decreased S.V.
Slows semilunar valve opening

31. Pacemaker adjusted by nerves parasympathetic- ACh slows
Controls- Heart Rate
Pacemaker adjusted by nerves
Cardiovascular center in Medulla
parasympathetic- ACh slows
Via vagus nerve
Sympathetic - norepinephrine speeds
Sensory input for control:
baroreceptors (aortic arch & carotid sinus)- B.P.
Chemoreceptors- O2, CO2, pH

32. Epinephrine & norepinephrine increase H.R.
Other Controls
Hormones:
Epinephrine & norepinephrine increase H.R.
Thyroid hormones stimulate H.R.
Called tachycardia
Ions
Increased Na+ or K+ decrease H.R. & contraction force
Increased Ca2+ increases H.R. & contraction force

33. Figure 15.9

34. Well trained athlete doubles maximum C.O.
Exercise
Aerobic exercise (longer than 20 min) strengthens cardiovascular system
Well trained athlete doubles maximum C.O.
Resting C.O. about the same but resting H.R. decreased

35. Figure 15.10