1. Cardiovascular System
Chapter 20
Cardiovascular System
The Heart

2. The Heart The Heart is two pumps. Pulmonary circulation
Carries blood to lungs
Returns to the left side of heart
Systemic circulation
Delivers oxygen and nutrients to the body
Returns to the right side of the heart

3. Functions of the Heart Generating blood pressure Routing blood
Heart separates pulmonary and systemic circulations
Ensures oxygenation of blood flowing to tissues.
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: rounded tip of heart
Base: Flat part at opposite of end of cone
Located in thoracic cavity within the mediastinum

5. Heart Cross Section

6. Pericardium

7. Heart Wall Three layers of tissue
Epicardium: This serous membrane of smooth outer surface of heart
Myocardium: Middle layer composed of cardiac muscle cell and responsibility for heart contracting
Endocardium: Smooth inner surface of heart chambers

8. Heart Wall

9. External Anatomy Four chambers Auricles Major veins Major arteries
2 atria
2 ventricles
Auricles
Major veins
Superior vena cava
Inferior vena cava
Pulmonary veins
Major arteries
Aorta
Pulmonary trunk

10. External Anatomy

11. Coronary Circulation

12. Heart Valves Atrioventricular Semilunar
Tricuspid
Bicuspid or mitral
Semilunar
Aortic
Pulmonary
Prevent blood from flowing back

13. Heart Valves

14. Function of the Heart Valves

15. Blood Flow Through Heart

16. Systemic and Pulmonary Circulation

17. Heart Skeleton
Consists of plate of fibrous connective tissue between atria and ventricles
Fibrous rings around valves to support
Serves as electrical insulation between atria and ventricles
Provides site for muscle attachment

18. Cardiac Muscle
Elongated, branching cells containing 1-2 centrally located nuclei
Contains actin and myosin myofilaments
Intercalated disks: Specialized cell-cell contacts
Desmosomes hold cells together and gap junctions allow action potentials
Electrically, cardiac muscle behaves as single unit

19. Conducting System of Heart

20. Electrical Properties
Resting membrane potential (RMP) present
Depends on low permiability to Na+ and Ca++ and high permiability to K+.
Action potential
Depolarization (Fast voltage gated Na+ channels)
Early partial repolarization (Voltage gated Na+ channels close and a small number of K+ channels open.)
Plateau phase - Prolonged period of slow repolarization (Slow Ca++ channels are open)
Rapid final repolarization phase (Voltage gated Ca++ channels close and more K+ channels open)

21. Action Potentials in Skeletal and Cardiac Muscle

22. SA Node Action Potential
Permiability changes in the pacemaker cells (Autorhythmicity):
Prepotential
Small number of Na+ channels open
Voltage-gated K+ channels are closing
Voltage-gated Ca++ channels begin to open
Depolarization Phase
Voltage-gated Ca++ channels are open
Voltage-gated K+ channels are closed.
Repolarization phase
Voltage-gated Ca++ channels close.
Voltage-gated K+ channels open.
Note: Ca++ channel blockers like verapamil are used to treat tachycardia and arrhythmias.

23. Refractory Period
Absolute: Cardiac muscle cell completely insensitive to further stimulation
Relative: Cell exhibits reduced sensitivity to additional stimulation
Long refractory period prevents tetanic contractions

24. 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

25. 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

26. Alterations in Electrocardiogram

27. 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

28. Cardiac Cycle

29. Cardiac Cycle

30. 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
Clinical considerations:
Murmurs: abnormal heart sounds
Incompetent valve - leaks excessively (gurguling,swishing)
Stenosis: abnormally small valve openings (rushing sound before valve closes.
Causes: genetic or due to rhematic fever scaring or myocardial infarction affecting the papillary muscles.

31. Location of Heart Valves

32. Mean Arterial Blood Pressure
Stroke volume
Volume of blood pumped during each cardiac cycle
at rest ~70 ml
can increase to ~200 ml during exercise
Heart Rate
~72 BPM and can increase to over 120 BPM during exercise.
Cardiac Output =stroke volume X heart rate
Resting: 72 beats/min X 70 ml/beat = 5040 ml / min
Exercise: 120 beats/min X 200 ml/beat = 24,000 ml/min.
Cardiac reserve
max cardiac output - resting cardiac output
= 24, ml /min = ml
C.O. is the major factor in determining blood pressure.
Blood pressure
Blood pressure reflects pressure changes in the aorta not the ventricle
Normal BP 120 systolic / 80 diastolic

33. Factors Affecting MAP

34. Regulation of the Heart
Intrinsic regulation: Results from normal functional characteristics, not on neural or hormonal regulation
Starling’s law of the heart
Stretching of the SA node.
Extrinsic regulation: Involves neural and hormonal control
Parasympathetic stimulation
Supplied by vagus nerve, decreases heart rate, acetylcholine secreted
Sympathetic stimulation
Supplied by cardiac nerves, increases heart rate and force of contraction, epinephrine and norepinephrine released

35. Heart Homeostasis Effect of blood pressure
Baroreceptors monitor blood pressure
Effect of pH, carbon dioxide, oxygen
Chemoreceptors monitor
Effect of extracellular ion concentration
Increase or decrease in extracellular K+ decreases heart rate
Effect of body temperature
Heart rate increases when body temperature increases, heart rate decreases when body temperature decreases

36. Baroreceptor and Chemoreceptor Reflexes

37. Baroreceptor Reflex

38. Chemoreceptor Reflex-pH

39. 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