1. Cardiovascular System
Unit 9 – The Heart
Cardiovascular System
The Heart

2. Functions of the Heart Generating blood pressure Routing blood
Heart separates pulmonary and systemic 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

3. The Closed Circulatory System
Humans have a closed circulatory system, typical of all vertebrates, in which blood is confined to vessels and is distinct from the interstitial fluid.
The heart pumps blood into large vessels that branch into smaller ones leading into the organs.
Materials are exchanged by diffusion between the blood and the interstitial fluid bathing the cells.

4. The Cardiovascular System
Three Major Elements – Heart, Blood Vessels, & Blood

5. Size, Shape, Location of the Heart
Size of a closed fist
Shape
Apex: Blunt rounded point of cone
Base: Flat part at opposite of end of cone
Located in thoracic cavity in mediastinum

6. Heart Cross Section

7. Pericardium

8. 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

9. Heart Wall

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

11. External Anatomy

12. Coronary Circulation

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

14. Heart Valves

15. Function of the Heart Valves

16. Let’s Practice….

17. Did you get them all correct?

18. Blood Flow Through Heart

20. Systemic and Pulmonary Circulation
Pulmonary circuit
The blood pathway between the right side of the heart, to the lungs, and back to the left side of the heart.
Systemic circuit
The pathway between the left and right sides of the heart.

21. 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

22. The Circulatory System
Blood Vessels -A network of tubes
Arteriesarterioles move away from the heart
Elastic Fibers
Circular Smooth Muscle
Capillaries – where gas exchange takes place.
One cell thick
Serves the Respiratory System
VeinsVenules moves towards the heart
Skeletal Muscles contract to force blood back from legs
One way values
When they break - varicose veins form

24. 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

25. Conducting System of Heart

26. Electrical Properties
Resting membrane potential (RMP) present
Action potentials
Rapid depolarization followed by rapid, partial early repolarization. Prolonged period of slow repolarization which is plateau phase and a rapid final repolarization phase
Voltage-gated channels

27. Action Potentials in Skeletal and Cardiac Muscle

28. SA Node Action Potential

29. 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

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
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

34. Cardiac Cycle

35. Events during Cardiac Cycle

36. 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

37. Location of Heart Valves

38. Mean Arterial Pressure (MAP)
Average blood pressure in aorta
MAP=CO x PR
CO is amount of blood pumped by heart per minute
CO=SV x HR
SV: Stroke volume of blood pumped during each heart beat
HR: Heart rate or number of times heart beats per minute
Cardiac reserve: Difference between CO at rest and maximum CO
PR is total resistance against which blood must be pumped

39. Factors Affecting MAP

40. Regulation of the Heart
Intrinsic regulation: Results from normal functional characteristics, not on neural or hormonal regulation
Starling’s law of the heart
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

41. 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

42. Baroreceptor and Chemoreceptor Reflexes

43. Baroreceptor Reflex

44. Chemoreceptor Reflex-pH

45. 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