1. The Heart
Chapter 20

2. Interesting Facts
At rest, the heart pumps 30xs its own weight each minute.
There are 60,000 miles of blood vessels.
In one day, the heart can pump 7000 L.
In one year, the heart pumps about 5 million L.
The average body contains about 5 L of blood volume.

3. Functions of the Heart Generating blood pressure Routing blood
Heart separates pulmonary (lungs to left side) and systemic (O2 & nutrients) circulations
Ensuring one-way blood flow
Heart valves ensure one-way flow
Regulating blood supply
Changes in contraction rate and force match blood delivery to changing metabolic needs

4. Size, Shape, Location of the Heart
Size of a closed fist
Shape
Apex: Blunt rounded point of cone (pointed bottom)
Base: Flat part at opposite of end of cone (rounded top)
Located in thoracic cavity in mediastinum (b/w the lungs; 2/3 to left of center)

5. Pericardium Encloses the heart and holds it in place Two layers:
Outer, fibrous pericardium prevents the heart from overstretching
The inner, serous pericardium contains pericardial fluid to prevent friction

6. Heart Wall Three layers: Epicardium—thin, transparent outer layer
Myocardium—cardiac muscle tissue; bulk of the heart
Endocardium—lines the inside of the myocardium and covers the valves

7. Heart Chambers Two upper chambers: Atria
Receiving chambers
Separated by interatrial septum
Two lower chambers: Ventricles
Pumping chambers
Separated by interventricular septum

8. Thickness of Heart Chambers
Vary according to each chambers functions.
Atria—thin walls because they only pump blood to ventricles
Right ventricle—pumps blood to lungs; slightly bigger than atria
Left ventricle—pump blood to entire body and keep up with the other chambers; thickest of the four chambers

9. Concept Check What are the functions of the heart?
Blood pressure, routing blood, one-way blood flow, regulating blood supply
Name and describe the 3 layers of the heart.
Epicardium (thin/transparent outer layer), myocardium (cardiac muscle tisssue; bulk), endocardium (lines inside of myocardium & covers valves)
What is the difference between atria and ventricles?
Atria receives blood; ventricles pumps blood

10. Blood Vessel Structure
Arteries
Elastic, muscular, arterioles
Capillaries
Blood flows from arterioles to capillaries
Most of exchange between blood and interstitial spaces occurs across the walls
Blood flows from capillaries to venous system
Veins
Venules, small veins, medium or
large veins

11. Valves of the Heart Four valves one for each chamber
They keep blood from flowing back to where it came from
They open and close in response to the pressure of blood against them

12. Valves of the Heart Atrioventricular (cuspid) valves
Tricuspid valve —between right atrium and right ventricle; 3 flaps or cusps
Chordae tendinae —tendon-like cords that prevent the cusps from being pushed back
Bicuspid valve —between left atrium and left ventricle; two cusps

13. Path of Blood Right atrium receives deoxygenated blood from 3 veins:
Superior Vena Cava—blood from above the heart
Inferior Vena Cava—blood from below the heart
Coronary Sinus—blood from the heart wall

14. Vessels of the Heart

15. Right Ventricle Blood goes from to the pulmonary trunk
Pulmonary trunk divides into left and right pulmonary arteries
Pulmonary arteries lead to the lungs

16. From the Lungs
Oxygenated blood enters the left atrium via four pulmonary veins

17. From the Left Ventricle
Blood enters the ascending aorta
To the coronary arteries
To the arch of the aorta
To the thoracic aorta
To the abdominal aorta

18. Valves of the Heart Semilunar Valves
Pulmonary semilunar valve— between right ventricle and pulmonary artery
Aortic semilunar valve— between left ventricle and the aorta

19. Blood Supply of the Heart
Coronary Circulation—blood flow through the myocardium
Left and right coronary arteries bring blood to the tissue
Coronary sinus take deoxygenated blood from the tissue

20. Blood Flow Through Heart

21. Concept Check What are the 3 types of blood vessels?
Arteries, veins, capillaries
Describe the flow of blood through the heart starting w/ the body.
Body, (SVC, IVC, CS), R Atrium, Tricuspid Valve, Chordae Tendinae, R Ventricle, Pulmonary SLV, Pulmonary Trunck, Pulmonary Arteries, Lungs, Pulmonary Veins, L Atrium, Bicuspid Valve, Chordae Tendinae, L Ventricle, Aortic SLV, Aorta, Body

22. Disorders 
Ischemia —faulty circulation weakens cells due to lack of oxygen, but the cells don’t die
Angina Pectoris —chest pain resulting from ischemia; also from stress, over exertion, high blood pressure, or narrow arteries

23. Disorders  Myocardial Infarction (MI) —heart attack
Infarction is the death of an area due to interrupted blood supply; usually from a clot
Tissue beyond the clot will die and become scar tissue
Location of the infarction area is key to how serious it is

24. Conduction System of the Heart
This is an intrinsic regulating system
It does not need a stimulus from the nervous system
All cardiac muscle is capable of self-excitation
Cardiac muscle generates its own action potential

25. Sinoatrial (SA) Node
Located in the right atrial wall just below the superior vena cava
Known as the pacemaker of the heart
Rate of self-excitation is faster than all other heart fibers
Its impulses are spread to all the other areas thus setting the rhythm of the heart
Both atria will contract at the same time
This will then depolarize the AV node (ventricles contract)

26. Atrioventricular (AV) Node
Located in the interatrial septum
Last part of atria to depolarize
This impulse will depolarize fibers in the interventricular septum— bundle of His
This is the only electrical connection between the atria and ventricles

27. Atrioventricular (AV) Node
The impulse passes toward the apex through left and right bundle branches to the ventricles
The actual contraction of the ventricles is done by the Purkinje fibers

28. Conducting System of Heart

29. Electrocardiogram (ECG)
A record of the electrical changes that accompany the heartbeat.

30. Electrocardiogram
Action potentials through myocardium during cardiac cycle produces electric currents than can be measured
Pattern
P wave
Atria depolarization
QRS complex
Ventricle depolarization
Atria repolarization
T wave:
Ventricle repolarization

31. Cardiac Arrhythmias Tachycardia: Heart rate in excess of 100bpm
Bradycardia: Heart rate less than 60 bpm
Sinus arrhythmia: Heart rate varies 5% during respiratory cycle and up to 30% during deep respiration
Premature atrial contractions: Occasional shortened intervals between one contraction and succeeding, frequently occurs in healthy people

32. Alterations in Electrocardiogram

33. Cardiac Cycle

34. Cardiac Cycle
Heart is two pumps that work together, right and left half
Repetitive contraction (systole) and relaxation (diastole) of heart chambers
Blood moves through circulatory system from areas of higher to lower pressure.
Contraction of heart produces the pressure

35. Concept Check Why does the SA node act as the pacemaker?
Impulses are spread to other areas setting the rhythm of the heart
How does the heart contract without an impulse from the brain?
Intrinsic regulation / Self-excitation / Cardiac muscle generates own action potentials
What actually contracts the myocardium of the ventricles?
Purkinje fibers
What is an infarct?
Death of an area due to interrupted blood supply; usually a clot

36. Concept Check What does an EKG measure? Why is QRS bigger than P?
Electrical changes in the heart that accompany heart beat
Why is QRS bigger than P?
QRS = contraction of ventricles
P = contraction of atria
What is a fibrillation or arrhythmia?
Fibrillation = heart’s electrical activity has become disordered; contraction rapid, unsynchronized; flutter rather than beat; heart pumps little or no blood

37. Heart Rate
Cardiac Output —amount of blood ejected from the left ventricle into the aorta per minute
Stroke volume —amount of blood ejected from the left ventricle per contraction

38. Factors Affecting Heart Rate
Autonomic control —baroreceptors—neurons sensitive to blood pressure changes
Chemicals —too much or too little K+, Na+, or Ca+ either increases or decreases heart rate; oxygen demands
Temperature —increase temperature, increase heart rate; lower temperature, decrease heart rate
Emotions —fear, anxiety, anger all increase heart rate while depression and grief lower heart rate
Sex and age —faster in females; fastest at birth but slows as one gets older

39. More Disorders 
Arteriosclerosis - thickening of the walls of the arteries and loss of elasticity
Atherosclerosis - Deposition of plaque on walls
Congenital defects—a defect that exists at birth
Interventricular septal defect—hole in septum
Valvular stenosis—narrowing of a valve
Arrthymia—any irregularity in heart rhythm

40. Effects of Aging on the Heart
Gradual changes in heart function, minor under resting condition, more significant during exercise
Hypertrophy of left ventricle
Maximum heart rate decreases
Increased tendency for valves to function abnormally and arrhythmias to occur
Increased oxygen consumption required to pump same amount of blood

41. Heart Sounds First heart sound or “lubb” Second heart sound or “dupp”
Atrioventricular valves and surrounding fluid vibrations as valves close at beginning of ventricular systole
Second heart sound or “dupp”
Results from closure of aortic and pulmonary semilunar valves at beginning of ventricular diastole, lasts longer
Third heart sound (occasional)
Caused by turbulent blood flow into ventricles and detected near end of first one-third of diastole

42. Blood Pressure Measure of force exerted by blood against the wall
Blood moves through vessels because of blood pressure
Measured by listening for Korotkoff sounds produced by turbulent flow in arteries as pressure released from blood pressure cuff

43. Pulse Pressure
Difference between systolic (contraction of ventricles) and diastolic (relaxation of ventricles) pressures
Increases when stroke volume increases or vascular compliance decreases
Pulse pressure can be used to take a pulse to determine heart rate and rhythmicity

44. Concept Check
What types of things would increase your heart rate? Decrease?
What is a congenital disorder? Describe the problems with interventricular septal defect.
What is the difference between systole and diastole if they both measure on the arteries?
What causes the heart sounds?