1. The Cardiovascular System Dr. Mona Soliman, MBBS, MSc, PhD Dr. Mona Soliman, MBBS, MSc, PhD Department of Physiology College of Medicine KSU November 2012

2. Structure of the Heart

3. The Atria Thin walled Thin walled Receives blood from: Receives blood from: the systemic circulation (right atrium) the systemic circulation (right atrium) the pulmonary circulation (left atrium) the pulmonary circulation (left atrium) Open into the ventricles via the: Open into the ventricles via the: Atrioventricular valves Atrioventricular valves (AV valves) Structure of the Heart

4. The Ventricles Thick muscular walled (why?) Thick muscular walled (why?) Pump blood into: Pump blood into: Pulmonary trunk (right ventricle) Pulmonary trunk (right ventricle) Aorta (left ventricle) Aorta (left ventricle) A fibrous tissue ring separate the atria from the ventricles (importance: electrical activity, AV valve) A fibrous tissue ring separate the atria from the ventricles (importance: electrical activity, AV valve) Structure of the Heart

5. The Valves of the Heart The Atrioventricular Valves 1. The Tricuspid Valve… between the right atrium and the right ventricle, 3 cusps 2. The Mitral Valve (bicuspid valve) … between the left atrium and the left ventricle, 2 cusps

6. Prevent back flow of blood from the ventricles to the atria Prevent back flow of blood from the ventricles to the atria Held by chordae tendineae to papillary muscle Held by chordae tendineae to papillary muscle Contraction of papillary muscle… Contraction of papillary muscle… The Valves of the Heart The Atrioventricular Valves

9. The Valves of the Heart The Semilunar Valves Located at the origin of the pulmonary artery and aorta Located at the origin of the pulmonary artery and aorta Open during ventricular contraction…why? Open during ventricular contraction…why? Close during ventricular relaxation…why? Close during ventricular relaxation…why? 1. The Aortic Valve 2. The Pulmonary Valve

11. Cardiac muscle cell

12. Cardiac Muscle cell

13. Striated Striated Contain actin and myocin filaments arranged in sarcomeres…contract by sliding mechanism Contain actin and myocin filaments arranged in sarcomeres…contract by sliding mechanism Branch and interconnect Branch and interconnect Cardiac Muscle cell

14. Gap junctions Gap junctions Trans-membrane channel proteins, connecting the cytoplasm of the cells Trans-membrane channel proteins, connecting the cytoplasm of the cells Allow spreading of the action potential from one fiber to another Allow spreading of the action potential from one fiber to another Allow cardiac muscle to function as a syncytium “all or none law”: stimulation of a single muscle fiber results in contraction of all the muscle fibers Allow cardiac muscle to function as a syncytium “all or none law”: stimulation of a single muscle fiber results in contraction of all the muscle fibers Intercalated discs Intercalated discs Cardiac Muscle cell

16. Electrical Activity of the Heart

17. Automaticity: capable of originating action potential Automaticity: capable of originating action potential

18. Resting membrane potential in myocardial cells -90 mV Resting membrane potential in myocardial cells -90 mV Stimulation of myocardial cell Myocardial action potential

20. Phases of cardiac AP Ionic changes Rapid depolarization (+20 mV) Na + in Partial repolarization (5-10mV) K + out Action potential plateau (0 mV) Ca 2+ in (slow) Repolarization (back to RMP) K + out Myocardial action potential

21. Conduction of Impulses The sinoatrial node (SA node): Located in the right atrium Pacemaker of the heart Is capable of originating action potentials Highest frequency The atrioventricular (AV) node Located at the junction of the atria and the ventricles Delay in the conduction of impulses…why?

22. Conduction of Impulses The atrioventricular (AV) bundle (Bundle of His) The atrioventricular (AV) bundle (Bundle of His) The right and left bundle branches The right and left bundle branches Purkinje fibers Purkinje fibers Spread within the muscle of the ventricular walls Spread within the muscle of the ventricular walls Highest speed of conduction Highest speed of conduction

23. Contractility Contractility is the ability of cardiac muscle to convert chemical energy into mechanical work Contractility is the ability of cardiac muscle to convert chemical energy into mechanical work

24. Depolarization of myocardial cell Opening of Ca 2+ channels Ca 2+ increase in the cytoplasm Ca 2+ binds to troponin Contraction Contractility

25. Repolarization of myocardial cell Ca 2+ OUT Ca 2+ decrease in the cytoplasm Relaxation Contractility

26. Absolute refractory period Absolute refractory period Cardiac muscle cannot be excited while it is contracting … benefit? Cardiac muscle cannot be excited while it is contracting … benefit? Long ARP Long ARP Time: depolarization & 2/3 of repolarization Time: depolarization & 2/3 of repolarization Relative refractory period Relative refractory period Time: last 1/3 repolarization Time: last 1/3 repolarization Strong stimulus can give rise to contraction Strong stimulus can give rise to contraction

27. The Cardiac Cycle

28. The repeating pattern of contraction (systole) and relaxation (diastole) of the heart The repeating pattern of contraction (systole) and relaxation (diastole) of the heart Duration of cardiac cycle = 0.8 seconds Duration of cardiac cycle = 0.8 seconds Diastole longer than systole Diastole longer than systole Ventricular contraction follows atrial contraction (0.1 to 0.2 second later)…why? Ventricular contraction follows atrial contraction (0.1 to 0.2 second later)…why?

29. The end diastolic volume: the total volume of blood in the ventricles at the end of diastole (120 ml) The end diastolic volume: the total volume of blood in the ventricles at the end of diastole (120 ml) Stroke volume is the volume of blood pumped by each ventricle per beat (70 ml) Stroke volume is the volume of blood pumped by each ventricle per beat (70 ml) Residual volume: amount of blood left in each ventricle at the end of systole (50 ml) Residual volume: amount of blood left in each ventricle at the end of systole (50 ml) The Cardiac Cycle

30. Ventricles contract Ventricles contract Ventricular pressure: increasing Ventricular pressure: increasing Ventricular volume: no change Ventricular volume: no change AV valves: closed.. prevent backflow of blood AV valves: closed.. prevent backflow of blood Semilunar valves: closed (P in ventricles < P in vessels) Semilunar valves: closed (P in ventricles < P in vessels) Heart sounds: 1 st heart sound Heart sounds: 1 st heart sound ECG: QRS complex ECG: QRS complex The Cardiac Cycle Isovolumetric ventricular contraction

32. Ventricular pressure: increasing > the pressure in the aortic and pulmonary vessels Ventricular pressure: increasing > the pressure in the aortic and pulmonary vessels Left ventricular pressure up to 120 mmHg Left ventricular pressure up to 120 mmHg Right ventricular pressure up to 25 mmHg Right ventricular pressure up to 25 mmHg Ventricular volume: decreasing Ventricular volume: decreasing Semilunar valves: open Semilunar valves: open AV valves: closed.. prevent backflow of blood AV valves: closed.. prevent backflow of blood The Cardiac Cycle Ejection phase

34. Ventricles relax Ventricles relax Ventricular pressure: decreasing Ventricular pressure: decreasing Ventricular volume: no change Ventricular volume: no change AV valves: closed AV valves: closed Semilunar valves: closed Semilunar valves: closed Heart sounds: 2 nd heart sound Heart sounds: 2 nd heart sound ECG: T wave ECG: T wave The Cardiac Cycle Isovolumetric relaxation

36. Ventricular pressure: below atrial pressure ( slightly above zero) Ventricular pressure: below atrial pressure ( slightly above zero) Ventricular volume: increasing Ventricular volume: increasing AV valves: open when pressure in the atria> the pressure in the ventricles AV valves: open when pressure in the atria> the pressure in the ventricles Semilunar valves: closed Semilunar valves: closed Passive ventricular filling via AV valves (80%) Passive ventricular filling via AV valves (80%) The Cardiac Cycle Rapid filling of the ventricles

38. Active filling of the ventricles (20%) Active filling of the ventricles (20%) Ventricular volume: slight rise Ventricular volume: slight rise Ventricular pressure: slight rise Ventricular pressure: slight rise Semilunar valves: closed Semilunar valves: closed AV valves: open AV valves: open ECG: P wave ECG: P wave The Cardiac Cycle Atrial systole

40. The Cardiac Cycle 1. Isovolumetric contraction 2. Ejection phase 3. Isovolumetric relaxation 4. Rapid filling of the ventricles 5. Atrial systole

41. Heart Sounds The first heart sound: The first heart sound: Cause: closure of the AV valves Cause: closure of the AV valves The second heart sound: The second heart sound: Cause: closure of the semilunar valves Cause: closure of the semilunar valves

42. Cardiac Output

43. Cardiac output is the volume of blood pumped by each ventricle per minute Cardiac output is the volume of blood pumped by each ventricle per minute CO= Stroke volume x Heart rate CO= Stroke volume x Heart rate (L/min)(ml/beat) (beat/min) = 70 X 70 = 4900 ml/min = 5 L/min Normal cardiac output (CO) = 5 L/min Normal cardiac output (CO) = 5 L/min

44. Cardiac Output

45. Sympathetic stimulation Sympathetic stimulation  HR (positive chronotropic effect)  HR (positive chronotropic effect)  CO  CO Parasympathetic stimulation Parasympathetic stimulation  HR  HR  CO  CO Cardiac centers in the medulla oblangata Cardiac centers in the medulla oblangata Cardiac Output Regulation of Heart Rate

46. End Diastolic Volume (EDV) Frank- Starling Law of the Heart Frank- Starling Law of the Heart  venous return   EDV   length of cardiac muscle (stretch)   force of contraction   stroke volume   cardiac output Cardiac Output Regulation of Stroke Volume

47. Positive ionotropic effect  strength of contraction Positive ionotropic effect  strength of contraction Sympathetic stimulation Sympathetic stimulation Adrenaline Adrenaline Negative ionotropic effect   strength of contraction Negative ionotropic effect   strength of contraction Parasympathetic stimulation Parasympathetic stimulation Acetylcholine Acetylcholine Vagal stimulation Vagal stimulation Cardiac Output Regulation of Stroke Volume

49. Blood Pressure

50. Blood pressure The blood pressure is the pressure the blood exerts against the inner walls of the blood vessels The blood pressure is the pressure the blood exerts against the inner walls of the blood vessels Arterial blood pressure (BP) = Arterial blood pressure (BP) = cardiac output (CO) x peripheral resistance Heart Stroke Ratevolume Vasoconstriction Normal BP = 120/80 mmHg Normal BP = 120/80 mmHg

51. Sympathetic stimulation  vasoconstriction   Peripheral resistance   BP Sympathetic stimulation  vasoconstriction   Peripheral resistance   BP Parasympathetic stimulation  less important b/c of limited vasodilatation in the GIT, external genitalia and salivary glands Parasympathetic stimulation  less important b/c of limited vasodilatation in the GIT, external genitalia and salivary glands Arterial blood pressure Peripheral resistance

52. Sympathetic stimulation Sympathetic stimulation  HR (positive chronotropic effect)  HR (positive chronotropic effect)  CO  CO  BP  BP Parasympathetic stimulation Parasympathetic stimulation  HR  HR  CO  CO  BP  BP Arterial blood pressure Heart rate

53. Short term regulation Short term regulation Baroreceptor reflex Baroreceptor reflex Long term regulation Long term regulation 1. Renin- Angiotensin system 2. Aldosterone 3. Antidiuretic hormone 4. ANP Blood pressure Regulation of blood pressure

54. Arterial blood pressure Baroreceptor reflex Stretch receptors Located in: Stretch receptors Located in: 1. The aortic arch 2. The carotid sinus (at the bifurcation of the common carotid artery) Sensory nerve activity via the vagus and glossopharyngeal nerves Sensory nerve activity via the vagus and glossopharyngeal nerves Cardiac centers in the medulla oblangata Cardiac centers in the medulla oblangata The baroreceptor reflex is activated by changes in the BP The baroreceptor reflex is activated by changes in the BP

57. Blood pressure Regulation of blood pressure Long term regulation Long term regulation 1. Renin- Angiotensin system 2. Antidiuretic hormone 3. Aldosterone

58. Factors affecting blood pressure 1. Age: blood pressure increases with age 2. Sex: males have higher BP than females till the age of menopause (effect of estrogen) 3. Exercise: increases BP 4. Stress: increases BP due to sympathetic stimulation 5. Hormones: adrenaline, noradrenaline and thyroid hormones increase BP