Cardiovascular system.pptx..............

Human Anatomy

1. The Cardiovascular System BY Dr.V.S . Neharkar, M.Pharm,Ph.D Dept. of Pharmacology, RMDIPER,Chinchwad,Pune

2. The Cardiovascular System A closed system of the heart and blood vessels The heart pumps blood Blood vessels allow blood to circulate to all parts of the body The function of the cardiovascular system is to deliver oxygen and nutrients and to remove carbon dioxide and other waste products

3. The Heart Location Thorax between the lungs Pointed apex directed toward left hip About the size of your fist

4. The Heart

5. MAIN FUNCTIONS OF THE CIRCULATORY SYSTEM Transport and distribute essential substances to the tissues. Remove metabolic byproducts. Adjustment of oxygen and nutrient supply in different physiologic states. Regulation of body temperature. Humoral communication.

6. Systemic Pulmonary Main circulatory paths Coronary

7. Aorta Arteries Arterioles Capillaries LV Veins Venules Venae cavae (inferior and superior) RA Systemic circulation

8. Systemic circulation

9. The heart is enclosed in a double-walled sac called the pericardium, which is anchored to the diaphragm below and to the connective tissue of the great vessels above the heart. The parietal pericardium (pericardial sac)consists of a tough fibrous layer of dense irregular connective tissue and a thin smooth serous layer. The serous layer turns inward at the base of the heart and forms the visceral pericardium covering the heart surface. Pericardial anatomy Fibrous pericardium Serous pericardium (separated by pericardial cavity) Epicardium (visceral layer) Heart Covering

10. Pericardium: sac of connective tissue surrounding the heart. Functions: a) It prevents friction between the wall of the heart and the surrounding structures. b) It prevents the over stretch (over dilatation) of the ventricles because of its inelasticity.

11. The Heart: Heart Wall Three layers Epicardium Outside layer This layer is the parietal pericardium Connective tissue layer Myocardium Middle layer Mostly cardiac muscle Endocardium Inner layer Endothelium

12. The Heart: Chambers Right and left side act as separate pumps Four chambers Atria Receiving chambers Right atrium Left atrium Ventricles Discharging chambers Right ventricle (pump for the pulmonary circulation) Left ventricle (pump for the systemic circulation)

13. The right and left  atria  are the top chambers of the  heart  and receive  blood  into the heart. The atria do not have inlet valves, but are separated from the  ventricles  by valves. The atria facilitate circulation by allowing uninterrupted  blood flow  into the heart during ventricular  systole . The right and left ventricles are the bottom chambers of the heart. They have thicker walls than the atria, and they create higher  blood pressures  to pump blood out of the heart into circulation to the body and the  lungs . Systole describes ventricular contraction, when blood is pumped from the heart into circulation. Diastole  describes ventricular relaxation, when blood moves from the atria to the ventricles, and the ventricles fill in preparation for systole.

14. The Heart: Valves Allow blood to flow in only one direction Four valves Atrioventricular valves – between atria and ventricles Bicuspid valve (left) Tricuspid valve (right) Semilunar valves - between ventricle and artery Pulmonary semilunar valve Aortic semilunar valve

15. Heart Valves: Lub*-Dub** *Tricuspid Valve: Right AV valve 3 Cusps (flaps) made of endocardium and Chordae Tendinae Cusps anchored in Rt. Ventricle by Chordae Tendinae Chordae Tendinae prevent inversion of cusps into atrium Flow of blood pushes cusps open When ventricle in diastole (relaxed), cusps hang limp in ventricle Ventricular contraction increases pressure and forces cusps closed *Bicuspid (Mitral) Valve: Left AV valve 2 cusps anchored in Lft. Ventricle by chordae tendinae Functions same as Rt. AV valve **Semilunar valves : prevents backflow in large arteries Pulmonary Semilunar Valve: Rt Ventricle and Pulmonary Trunk Aortic Semilunar Valve: Left Ventricle and Aorta 3 cusps (flaps):

16. Heart Sounds 1 st sound (“lub”) closing of the AV valves 2 nd sound (“dup”) closing of the semilunar valves

17. Cardiac valves Atrioventricular (AV) valves Semilunar (SL) valves Tricuspid v. Between Rt atrium & Rt ventricle Pulmonary v. Between pulmonary artery & Rt ventricle Mitral v. Between Lt atrium & Lt ventricle Aortic v. Between aorta & Lt ventricle

18. The cardiac valves allow the blood to flow in one direction only (from atria to ventricles and from ventricles to aorta or pulmonary artery). Cardiac valves open and close passively, according to pressure gradient .

19. As the heart muscle contracts and relaxes, the valves open and shut, letting blood flow into the ventricles and atria at alternate times. The following is a step-by-step description of how the valves function normally in the left ventricle: - When the left ventricle relaxes, the aortic valve closes and the mitral valve opens, to allow blood to flow from the left atrium into the left ventricle. - The left atrium contracts, allowing even more blood to flow into the left ventricle. - When the left ventricle contracts again, the mitral valve closes and the aortic valve opens, so blood flows into the aorta. How do the heart valves function?

20. Coronary Circulation Blood in the heart chambers does not nourish the myocardium The heart has its own nourishing circulatory system Coronary arteries Cardiac veins Blood empties into the right atrium via the coronary sinus

21. The Heart: Conduction System Intrinsic conduction system (nodal system) Heart muscle cells contract, without nerve impulses, in a regular, continuous way

22. Cardiac muscle It is striated muscle and consists of two types of fibers: Actine & Myosin are primary structural proteins of cardiac muscle

23. Within the atria and ventricles myocardial cells are connected by gap junctions. Gap junctions allow the cardiac action potential to propagate from cell to cell through a low resistance pathway.

24. GAP JUNCTIONS

25. Types of cardiac muscle fibers : 1-Contractile fibers It is the major type of fibers (99%). They constitute the atrial and ventricular walls. This type is responsible for the pumping action of the heart. 2-Excitatory and conductive fibers (Auto rhythmic cells) It constitute (1%) of fibers. These fibers are responsible for the generation and conduction of the excitation wave to all parts of the cardiac muscle.

26. The contractile fibers Cardiac muscle to act as functional syncitium due to presence of junctions called intercalated discs These junctions include: 1- Gap junctions : It allow all the cardiac muscle fibers to act electrically as a one unit. 2- Tight junctions : It make all fibers to act mechanically as one unit.

27. Excitatory and conductive fibers : SA node AV node Bundle of His Bundle Branches Purkinje fibers

28. Autonomic Innervations of the Heart

29. The Heart: Conduction System Special tissue sets the pace Sinoatrial node (right atrium) Pacemaker Atrioventricular node (junction of r&l atria and ventricles) Atrioventricular bundle (Bundle of His) Bundle branches (right and left) Purkinje fibers

30. Intrinsic Cardiac Conduction System Approximately 1% of cardiac muscle cells are autorhythmic rather than contractile 75/min 40-60/min 30/min

31. Intrinsic Conduction System Function : initiate & distribute impulses so heart depolarizes & contracts in orderly manner from atria to ventricles. SA node AV node Bundle of His Bundle Branches Purkinje fibers

32. Sinoatrial Node Atrioventricular Node

33. RHYTHMICITY Definition: It is the ability of the cardiac muscle to initiate its own regular impulses (rhythm), independent of any nerve supply. Cause: The cardiac muscle has a specialized excitatory conductive system , which has the property of auto-rhythmicity. Rate of autorhythmicity : SA Node : 70-80 beats/min AV Node : 40-60 beats/min Bundle of His : 30 beats /min Purkinje fibers : 15 beats/min (incompatible with life)

34. HEART RATE is determined by pacemaker activity of the heart (70-80/min) Variations in heart rate: 1- Tachycardia (Increase HR) : sympathetic stimulation as in emotions, exercise, hyperthyroidism. 2- Bradycardia (decrease HR) : parasympathetic stimulation as in sleep, hypothyroidism.

35. Excitability (Irritability): = the ability of cardiac ms to respond to adequate stimuli by generating an action potential followed by a mechanical contraction.

36. Definition: It is the ability of cardiac muscle to conduct the excitation wave to all parts of the heart. Conductivity

37. Conductive system of the heart:

38. 1- The Sino-atrial node (SA node) Site: It is located in the posterior wall of the right atrium. Function: It acts as a pace maker for the heart . Rate of firing (discharge): - The spontaneous rate of firing is 100-120 impulses /minute. - Inside the body (with autonomic control) 60-90 impulses /minute. This decrease in the rate of firing is due to continues inhibition of the vagus nerve on the SA node activity which is called the Vagal tone.

39. PACEMAKER OF THE HEART The area which determines the pace or rhythm of the heart is called the pacemaker of the heart. The SA Node is the pacemaker of the heart because: 1- it has the highest rhythm 2- and the whole heart obeys it. If the SA Node is destroyed, the AV Node will be pacemaker. VAGAL TONE: It is the continuous impulses in the vagus nerve which decrease the inherent high rhythm of the SA Node from 100-120/min to 70-80/min (the normal heart rate)

40. Atrio-Ventricular Node (AVN) Site : Right atrium at lower part of interatrial septum. Functions: 1) Delay of conduction of cardiac impulse from atria to Ventricles . So: a- Atrial contraction occurs before ventricular contraction. b- Ventricles are protected from the abnormal high rhythms in atria (in case of atrial arrhythmia). 2) It becomes the pace maker of the heart in case of damage of SA node.

41. Atrio-Ventricular bundle This consit of specializes fibres oroginating in Av node. Crosses the fibrous ring that separates atria & ventricles. at upper end Purkinje Fibers : The branches of Av bundles break up into fine fibres within the ventricular myocardium called Purkinje Fibers

42. Purkinje fibers Atrium Ventricle

43. Action potential of cardiac muscle * These are 2 types of action potential in the cardiac muscle fibers: Slow response AP Occurs in: SA node - AV node Fast response AP Occurs in : -Atria -Ventricles -Purkinje fibers

44. Fast response action potential *This type of action potential occurs in the muscle fibers of atria, ventricles and Purkinje fibers. A- Depolarization = phase (0) Caused by Na+ influx . B- Repolarization : (Triphasic) 1- Phase (1): It is a short rapid phase caused by K+ out flux 2- Phase (2) = Plateau caused by Ca++ + Na+ influx which balance the outflow of K+. 3- Phase (3): It is a rapid repolarization caused by rapid outflow of K+.

45. Action potential of ventricular muscle ■ Ventricular ms has a RMP of –90 mV. (  –85 to –95mV). ■ The trans-membranous AP overshoots to a potential of (  +20mV).

46. AP of ventricular muscle (continued ) Phase 0 = Rapid depolarization. Phase 1 = Rapid repolarization/ 1 st rapid repolarization. Phase 2 = A plateau. Phase 3 = Slow repolarization/ 2 nd rapid repolarization. Phase 4 = Complete repolarization. ■ Trans-membranous AP of ventricular ms is characterized by presence of 5 phases.

47. Phase 0 = Rapid depolarization. ■ op fast Na + channels   Na + influx. Phase 1 = Rapid repolarization/ 1 st rapid repolarization. ■ cls Na + channels,  K + permeability, w Cl - influx. Phase 2 = A plateau. ■ op slow Ca 2+ channels (slow Ca 2+ Na + channels)   Ca 2+ influx, w slow op K + channels. Phase 3 = Slow repolarization/ 2 nd rapid repolarization. ■ cls slow Ca 2+ channels, w  K + permeability   K + efflux. Phase 4 = Complete repolarization. ■ actv Na + K + pump  2K + in/ 3Na + out. AP of ventricular muscle (continued) 1 2 3 4

48. IONIC BASIS OF VENTRICULAR ACTION POTENTIAL Phase 0: Initial rapid depolarization: due to Na+ inflow due to opening of fast Na+ channels. Phase 1: Brief initial repolarization: due to opening of transient K+ channels. Phase 2: Prolonged plateau: due to opening of slow Ca ++ & Na+ channels.( A balance is created between influx of Na+ and Ca ++ and outflux of K+) Phase 3 : Late rapid repolarization: due to delayed opening of K+ channels. Phase 4: Resting membrane potential ( -100 mv)

49. ■ The mechanical response consists of contraction (systole) & relaxation (diastole). ■ Cardiac ms begins to contract few milliseconds after the AP begins, & continues to contract until few milliseconds after the AP ends. ■ Duration of contraction:  0.2 sec in arial muscle, &  0.3 sec in ventricular muscle . Relation between the action potential & the mechanical response

50. Excitability changes during the action potential: ■ Passes through 3 periods: 1. Absolute refractory period (ARP) 2. Relative refractory period (RRP) 3. Dangerous period (supranormal period)

51. Definition: * It is the ability of cardiac muscle to respond to adequate stimulus by contraction. Excitability = irritability Stages of excitability: Absolute refractory period (ARP): It is longer than that of skeletal muscle. Due to presence of plateau phase. So, (unlike the skeletal muscle), the cardiac muscles cannot undergo summation of contractions. i.e. Tetanus can not occur in the heart. 2- Relative refractory period (RRP) 3- Normal excitability

52. Refractory Periods

53. 1. Absolute refractory period (ARP): ■ The excitability of cardiac ms is completely lost during this period, i.e. doesn’t respond to 2 nd stimulus. ■ V. long . ■ Occupies the whole period of systole. ■ Corresponds to the period of depolarization (phase 0), & the first 2 phases of repolarization. ■ Ht can ’ t be tetanized (continuous contraction), as its ARP occupies the whole contraction phase.

54. ■ The excitability of cardiac ms is partially recovered during this period , i.e. stronger stimuli than normal are required to excite the ms. ■ Occupies the time of diastole. ■ Corresponds to the 3 rd phase of repolarization. ■ Can be affected by the HR, temp., bacterial toxins, vagal stimulation, sympathetic stimulation & drugs. Relative Refractory Period (RRP):