Physio Cardio Intro/Mechanism (11/12)

• deoxygenated blood from the systemic circulation enters the Right Atrium through the Superior Vena Cava & the Inferior Vena Cava
• once in the Right Atrium, blood flows through the Tricuspid Valve into the Right Ventricle
• from the Right Ventricle blood is pumped through the Pulmonary Semilunar Valve, enters the pulmonary artery & is taken to the lungs
• oxygenated blood from the lungs flows through the pulmonary vein into the Left Atrium
• it's then pumped through the Mitral Valve into the Left Ventricle
• from the Left Ventricle it's pumped through the Aortic Semilunar Valve to the aorta & enters the systemic circulation

• separates the Right Atrium & the Right Ventricle
• prevents back-flow of blood back into the Right Atrium
• opens during diastole so blood can empty from the Right Atrium into the Right Ventricle

• lies between the Right Ventricle & the pulmonary artery
• opens in ventricular systole when the pressure in the Right Ventricle rises above the pressure in the pulmonary artery

• separates the Left Atrium & the Left Ventricle
• opens during diastole
• open during diastole

• separates the Left Ventricle & the aorta
• opens in ventricular systole when the pressure in the Left Ventricle rises above the pressure in the aorta

• when the tissues forming the valve leaflets become stiffer, narrowing the valve opening & reducing the amount of blood that can flow through it
• main cause: arteriosclerosis
• result: the body may not receive adequate blood flow

• cardiac muscle layers are oriented differently in comparison to each other
• innermost layer = longitudinal
• middle layer = circular
• 2 outside layers = oblique
• important so that the atria & ventricles can pump all blood they come in contact with into where they need to go

• L: 120/0 mm Hg
• R: 25/0 mm Hg
• the left ventricle needs to pump blood throughout the entire systemic circulation which the right ventricle need only pump it through the pulmonary system
• even though the SAME amount of blood is pumped through systemic & pulmonary systems, the pressure generated is difficult due to the fact that the L ventricle experiences more RESISTANCE to flow than the R

• the TOTAL volume of blood flow through the systemic or pulmonary circulation
• units = mL/min
• CO = heart rate X stroke volume
• typically 5L/min

• 1. heart rate
• 2. stroke volume: volume of blood ejected from a ventricle (~70 cc)

• volume/time; cm³ of blood per minute
• a snapshot of blood moving
• is kept in one direction by the presence of valves, between atria & ventricles (tricuspid & mitral) & between ventricles & pulmonary artery or aorta (pulmonic & aortic valves)

• distance blood moves/time; cm/min
• V (cm/min) = flow (Q) (cm³/min) / X-Sectional Area (cm²)
• how far a RBC moves per some time frame (can measure using doppler principle)

• a certain volume of blood flow will have a HIGHER velocity going through a vessel with a small cross sectional area than it will going through a vessel with a large cross sectional area
• 

• using an ultrasonic doppler flow meter
• it's placed over the ascending aorta & measures both its cross sectional area & the velocity of flow through the vessel
• Q (cm³/min) = V (cm/min) * A (cm²)
• Q = VA

• the flow always stays constant - it's determined by cardiac output, however blood velocity changes
• the aorta is branching into smaller vessels & the overall cross sectional area is INCREASING (capillary x-sectional A = > 40,000 cm2)

• fastest
• Aorta = Arteries
• Vena Cava (~same as arterioles)
• Arterioles (large variation)
• Veins
• Venules
• Capillaries
• slowest
• 

• because that's where exchange of nutrients, O₂, & CO₂ is happening - blood wants to move SLOWLY here to allow for thorough exchange to occur
• the entire point of the cardiovascular system is to get blood to the capillaries

• QR = P₁ - P₂
• (Flow)(Resistance) = Mean Pressure

• (SYSP - DIASP)/3 + DIASP
• 1/3(S - D) + D
• an average blood pressure in an individual; the average arterial pressure during a single cardiac cycle

• defines the effects of fluid viscosity, tube radius, & length on the relationship between pressure drop & flow
• Q = ΔPπr4/8ηL
• ΔP = Q * { 8ηL/πr4 } {} = resistance
• ΔP = QR, Q = ΔP/R

• because blood vessel walls can stretch - their radius can change
• has a profound effect on resistance
• constricting & dilating BVs is one of the main ways vessels direct blood flow throughout the body

• difficulty of blood to flow over other blood (viscosity)
• stays the same unless a person becomes very sick

via saline filled catheters of 2 basic types attached to electronic pressure transducers

• using echo-cardiographic imaging techniques or calculated from flow measurements
• echocardiography looks at chamber volume & how much blood they hold

• used to study the mechanical events of the cardiac cycle
• inserted into artery or vein & passed into chambers of the heart
• attached to electronic pressure transducers to measure pressure
• blood can be withdrawn through the catheters to obtain blood gas measurements

• used to catheterize the chambers & vessels of the right side of the heart
• measure pressures in the right side of the heart, pulmonary arteries, veins, & left atrium
• can be inserted into a (neck) vein & pushed forward to a position where the tip is at the junction of the vena cava & the right atrium
• here the catheter is swept along w/ venous return into the right atrium

• the “pulmonary wedge pressure”
• this is a good indicator of left atrial pressure, which otherwise can't be measured by a catheter
• records the back pressure pushing against the catheter coming from the L atrium
• 

• measures aortic pressure & L ventricular pressure
• the catheter must be inserted into a peripheral artery (femoral) & advanced against the direction of arterial blood flow
• it approaches the left ventricle is from the aorta
• used to get left ventricular pressure (NOT arterial)

by examining the pressure gradient between the “pulmonary wedge” pressure & the ventricular pressure during diastole (when the mitral valve is open)

• ventricular & atrial DIASTOLE happen simultaneously
• there is a time difference between atrial systole, which happens first, followed by ventricular systole
• atrial contraction is complete before the ventricle begins to contract

good website*

• when both L & R atria CONTRACT to push blood through mitral & tricuspid valves → this is the "topping off" of ventricles
• mitral & tricuspid valves are open facing ventricles nearly completely full of blood
• atrial systole is the final part of diastole (filling)
• causes an increase in endiastolic (ventricle) pressure

• in the beginning it's open & has been since rapid ventricular filling during ventricular diastole
• at the end the mitral valve CLOSES

occurs when the atrium contracts, increasing atrial pressure, during atrial systole

• NO atrial systole - ventricle don't get "topped off" but because the ventricle is mostly full, enough blood is pumped out to the systemic circulation
• causes a ~5-10% reduction in normal cardiac output

• both semilunar valves are open (aortic & pulmonary)
• the mitral & tricuspid valves are closed
• both ventricles CONTRACT to push blood through the semilunar valves
• includes Isovolumetric contraction, Rapid ejection, & Reduced Ejection
• (mitral valve closure tells you it starts, aortic valve closure tells you its over)

• signifies the beginning of Systo1e
• corresponds to closing of mitral (& tricuspid) valve
• noise made is actually caused by the eversion of the mitral valve slightly back into the left atria due to the large force generated by the L ventricle contracting

it triggers the start of ventricular contraction (systole)

• the ventricles contract, causing ventricular pressure to rise sharply, but there is no overall volume change b/c atrioventricular valves have just been shut (after atrial systole) & semilunar valves have not yet opened
• the 1st, short lived part of ventricular systole
• the beginning corresponds to the R peak seen on an EKG

• both are closed at the start
• both open at the end of isovolumetric contraction

• the semilunar (aortic & pulmonary) valves open at the beginning of this phase of ventricular systole
• ventricles continue contracting, the pressure in the ventricles exceeds pressure in the aorta & pulmonary arteries
• the semilunar valves open & blood exits the ventricles → causing the volume in the ventricles to decrease rapidly
• as more blood enters the arteries, pressure there builds until the flow of blood reaches a peak

• a small wave created by right ventricular contraction which pushes the tricuspid valve into the atrium & increases atrial pressure
• is normally simultaneous with the carotid pulse
• visible right between isovolumetric contraction & rapid ejection

• after the peak in ventricular & arterial pressures, blood flow out of the ventricles decreases & ventricular volume slowly decreases
• when the pressure in the ventricles falls below the pressure in the arteries, blood in the arteries begins to flow back toward the ventricles & causes the aortic & pulmonary valves to close, marking the end of ventricular systole

• mitral (bicuspid) valve open - into left ventricle
• tricuspid valve open - into right ventricle
• the ventricles fill during diastole (atrial pressure > ventricle pressure)
• includes Isovolumetric relaxation, Rapid ventricular filling, Reduced ventricular filling, & Atrial systole

• the beginning of ventricular diastole
• corresponds to closing of pulmonary & aortic valve
• is normally split b/c the aortic valve closes slightly before the pulmonary valve

• the beginning of diastole during which the atrioventricular valves are still closed
• throughout this & the previous two phases (rapid & reduced ejection) the atrium in diastole was filling w/ blood on top of the closed AV valves, causing atrial pressure to rise gradually
• the pressure in the ventricles continues to fall

• in isovolumetric relaxation during ventricular diastole
• at this point the ventricles are ready to be filled again w/ blood

a slow rise in atrial pressure due to the back flow of blood after it hits the closed AV valves

the AV valves open & blood that has accumulated in the atria flows rapidly into the ventricles causing a swift increase in ventricular volume

• ventricular volume increases more slowly now
• the ventricles continue to fill with blood until they are nearly full

• the volume of blood in the right & left ventricle at end diastole (when it's been almost completely filled)
• ~50% of it is ejected into the systemic or pulmonary circulation w/ each beat

• the volume of blood in a ventricle at the end of systole (contraction) or the beginning of diastole (filling)
• is the lowest volume of blood in the ventricle at any point in the cardiac cycle - NEVER 0

• stroke volume
• amount of blood pumped in each cardiac cycle

• mitral valve insufficiency (regurgitation, prolapse)
• aortic stenosis
• the direction of blood flow is out of the chamber

• mitral stenosis: softer murmur
• aortic insufficiency (regurgitation): more pronounced
• is softer b/c pressure behind them is lower