بسم الله الرحمن الرحيم

1. بسم الله الرحمن الرحيم

2. Cardiovascular system

3. CVS consists of the heart & a closed system of vessels called arteries, veins & capillaries • Vital role of CVS is controlling movement of blood through vessels to reach every cell in the body • The heart consists of: • 4 chambers (Right & left atria, Right & left ventricles) • 2 types of valves 1. Atrioventricular ---- Tricuspid & Bicuspid 2. Semilunar ---- Aortic & Pulmonary

6. De-oxygenated blood passes to the heart through veins after circulating in the body, it will enter right atrium ---- Blood passes to right ventricle through tricuspid valve ---- Right ventricle pumps the blood through pulmonary valve into pulmonary artery ---- The blood will go to the lung where it gets fresh oxygen ---- Then oxygenated blood will return through pulmonary veins to the left atrium ---- Then it will pass through mitral valve & enters left ventricle ---- The left ventricle pumps the oxygenated blood to the body’s circulation through the aorta

8. Cardiac properties The body consists of 3 types of muscles: • Smooth muscles: Are involuntary, found within walls of veins, arteries • Skeletal muscles: Are voluntary, controlled by somatic nervous system ---- These muscles contract & relax to help the body perform external movements • Cardiac muscles: Which cause the heart to beat

9. Cardiac cells have four properties: • Excitability: • Is the ability of cardiac cells to respond to stimuli that produces an electrical impulse ---- This impulse spreads across the heart causing it to beat • A single heart beat consists of 2 components: 1. Systole: Refers to contraction of the heart 2. Diastole: Refers to relaxation of the heart Both systole & diastole combine together to help the heart pump the blood to the body

10. 2. Conductivity: • Is the ability of cardiac cells to transfer the impulse generated at the sino-atrial node (SAD) from cell to another • The impulse moves at a rate of 1 meter per second 3. Contractility: • Is the ability of cardiac cells to transform the electrical impulse originating at SAN into mechanical action • Cardiac cells are present in the form of branches acting as one unit • The heart’s pumping ability is determined by the strength with which the cardiac cells contract

11. 4. Rhythmicity: • Is the ability of cardiac muscle to contract regularly without the involvement of any nerves • The action potential originate in SAN & moves through the entire heart without any neural involvement

12. Cardiac conduction system • It is the system that controls the heart rate • It generates electrical impulses & conducts them throughout the heart muscle stimulating it to contract & pump blood • It includes: 1. Sinoatrial node (SAN) 4. Purkinje fibers 2. Atrioventricular node (AVN) 3. AV bundle

13. Sinoatrial node (SAN) • In the upper part of the right atrium of the heart is a specialized bundle of neurons known as SAN • SAN is the natural pacemaker of the heart • It sends out regular electrical impulses causing the atrium to contract & pump blood into ventricles ---- the electrical impulses then pass to the ventricles through the atrioventricular node (AVN)

14. Atrioventricular node (AVN) • It is the electrical relay station between the upper & lower chambers of the heart • It slows the electrical current sent by SAN before the signal is permitted to pass down through the ventricles ---- This delay ensures that the atria have an opportunity to fully contract before the ventricles are stimulated ---- After passing the AVN, the electrical current travels to the ventricles, along special fibers embedded in their walls (Purkinje fibers)

15. AV bundle • The impulses are then sent down AV bundle (It is a bundle of fibers) ---- This bundle branches into two bundles & the impulses are carried down through them to the left & right ventricles • At the base of the heart AV bundles start to divide further into Purkinje fibers ---- When the impulses reach these fibers they cause ventricles’ contraction Purkinje fibers

16. How SAN sends electrical impulse??? • Normally, sodium is present outside the cell & potassium inside • The cells in SAN are permeable to sodium more than potassium & so the amount of sodium entering the cells will be more than potassium leaving ---- & so more positive charge inside the cell ---- Depolarization ---- Then calcium channels will open & calcium will rush inside the cell leading to rapid depolarization (Action potential)

17. Then potassium channels will open causing potassium to rush outside the cell ---- Causing membrane repolarization ---- & then process is repeated

18. Systolic blood pressure When the heart beats it will contract & pushes the blood through the arteries to the rest of the body, this force creates a pressure on the arteries known as Systolic blood pressure Is the pressure in the arteries when the heart rests between beats Diastolic blood pressure

19. Stroke volume It is the volume of blood (in ml) pumped by the left ventricle of the heart in each beat It is the filling pressure of the heart at the end of diastole ---- left atrial pressure (LAP) at the end of diastole will determine the preload Preload

20. Contractility Is the strength of the heart contraction during systole It is the pressure against which the heart must work to eject blood during systole (Aortic pressure) Afterload

21. Starling’s law of the heart It states that: The heart will eject a greater stroke volume if it is filled to a greater volume at the end of diastole (Volume of the heart at the end of diastole is related to preload which is determined by left atrial pressure) So, it is a relation between stroke volume & preload

22. Factors affecting Starling’s law 1. Contractility • For any filling pressure, the stroke volume will be greater if the contractility of the heart is greater 2. Afterload • The lower the afterload, the more blood the heart will eject in each contraction

23. Cardiac output It is the volume of blood pumped by the heart through the circulatory system per minute • Stroke volume & heart rate determine the cardiac output • Increasing either heart rate or stroke volume ---- will increase the cardiac output Cardiac output in ml/min = Heart rate (Beats/min) X Stroke volume (ml/beat)

24. Regulation of Cardiac output COP = HR x SV • COP depends on heart rate & stroke volume Regulation of heart rate: • By Sympathetic & Parasympathetic effects 1. Parasympathetic ---- Decreases heart rate 2. Sympathetic ---- Increases heart rate

25. Regulation of Stroke volume: • Sympathetic effect: Norepinephrine released by sympathetic nerves increases the force with which ventricular muscle contracts ---- & so, increases stroke volume 2. Afterload If the aortic pressure increases, this pressure will reduce the volume of blood that flows into the aorta during systole 3. Frank Starling mechanism As end diastolic volume increases, ventricles will contract more powerfully, ejecting greater stroke volume

27. Venous return It is how much blood returned to the heart by veins Factors affecting venous return: • Skeletal muscles pumps: • Muscles cause pressure to the veins, allowing more blood to go to the heart • Veins have only one way valves, so when muscles perform pressure on veins ---- blood will only be squeezed towards the heart

28. 2. Sympathetic nervous system: • It causes vasoconstriction ---- allowing more blood to return to heart 3. Blood volume Increase in blood volume ---- Causes EDV to increase 4. Respiration: • During inhalation ---- Diaphragm contracts, thoracic cavity becomes bigger & pressure decreases • During exhalation ---- Diaphragm relaxes, thoracic cavity pressure increases & so, helps blood to move through veins & back to heart

29. Cardiovascular reflexes • Intrinsic reflexes • Extrinsic reflexes • They aim to minimize fluctuations in the mean arterial blood pressure (MABP) & to maintain adequate perfusion to each organ

30. Intrinsic CV reflexes

32. Extrinsic reflexes Stimuli that are external to CVS also exert effect on the heart Example: Moderate pain causes tachycardia & increase in MABP Cold causes cutaneous & coronary vasoconstriction

33. Arterial blood pressure (ABP) Is the pressure exerted by circulating blood upon the walls of blood vessels • Systemic ABP • Usually BPs are categorized into: Low (90/60 or lower), Normal (Between 90/60 – 139/80) & High (140/90 or higher) Classification

34. ABP varies from person to person & in one person from moment to another & varies according to age & sex • The risk of CV diseases increase above 115/75 mmHg 2. Mean ABP Is the average BP over a cardiac cycle MABP = Pdia + 1/3 (Psys – Pdia)

35. 3. Pulmonary pressure • Is the pressure in pulmonary artery • Increase in pulmonary pressure ---- Causes pulmonary hypertension

36. Disorders of blood pressure High Persistent hypertension is one of risk factors for strokes, heart attacks, heart failure, chronic renal failure Isolated systolic hypertension Is the elevation of systolic blood pressure (>140) with a normal diastolic blood pressure

37. Low Hypotension causes symptoms as: dizziness, fainting or in extreme cases: Shock Orthostatic hypotension: It is the blood pressure drop when a patient stands up from sitting

38. Physical factors that influence ABP 1. Blood volume The more blood present in the body ---- The higher the rate of blood return to the heart & the resulting cardiac output ---- Resulting in increased ABP 2. Resistance The higher the resistance inside blood vessels ---- The higher the ABP Resistance is related to --vessel radius (↑↓) --vessel length (↑↑) 3. Blood viscosity (Thick blood ---- Increase in ABP)

39. Hydrostatic pressure It is the pressure that the fluid exerts on the wall of it’s container It is the pressure required to prevent the flow of water across a semi-permeable membrane via osmosis (Results from the proteins present inside the vessels) Osmotic pressure

40. Oncotic pressure Is a form of osmotic pressure exerted by proteins (Albumin) in a blood vessel’s plasma usually tends to pull water into the circulatory system • In conditions where plasma proteins are reduced (Such as: Lost in urine ---- proteinuria, Malnutrition) ---- There will be reduction in oncotic pressure & increase in filtration across the capillaries resulting in excess fluids in tissues (Oedema)

41. Oedema Is the abnormal accumulation of fluid in the interstitium beneath the skin ---- It is clinically shown as swelling

42. Causes of Oedema • Increased hydrostatic pressure • Reduced oncotic pressure within blood vessels • Increased tissue oncotic pressure • Increased blood vessel wall permeability (Inflammation) • Obstruction of fluid clearance in lymphatic system

43. Circulation & blood vessels • The heart & blood vessels makeup the overall blood circulatory system • Blood circulatory system is made of 4 subsystems: • Arterial circulation4. Pulmonary circulation • Venous circulation • Capillary circulation • It is the part of circulatory system where oxygen, nutrients & wastes pass between the blood & other parts of the body

44. Capillaries are very small blood vessels which connect the arterial & venous circulatory subsystems • The importance of capillaries lies in their very thin walls which allow oxygen & nutrients to pass from blood to parts of the body & waste products like CO2 to pass from the organs into the blood How this occurs????

46. Capillary walls contain small pores that allow certain substances to pass into & out of the blood vessel • Fluid exchange is controlled by hydrostatic pressure & osmotic pressure within the vessel • In the arteriole end of the vessel →→→ Hydrostatic pressure > Osmotic pressure Inside the vessel Net result: Fluid moves from the vessel to the body tissue

47. At the middle of the vessel →→→ Hydrostatic pressure = Osmotic pressure Inside the vessel Net result: Fluid passes equally between the vessel & the body tissue • In the venous end of the vessel →→→ Hydrostatic pressure < Osmotic pressure Inside the vessel Net result: Fluid, CO2 & wastes are drawn from the tissue into the capillaries

48. Thank you