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233 Cards in this Set
- Front
- Back
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Blood volume in arteries is called
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stress volume
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Site of highest resistance in CVS?
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arterioles
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2 adrenergic receptors of arterioles?
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a1, b2
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a1 is found?
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skin, splanchnic, renal
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b2 is found?
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sk muscle
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Have largest total cross-sectional and surface area
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capillaries
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Highest proportion of blood in CVS found in
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veins
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blood volume in veins called
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unstress volume
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adrenergic receptor of veins?
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a1
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velocity eqn?
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V = Q/A (velocity = flow/cross-sectional area)
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blood flow eqn?
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Q = DP/R (CO = MAP-RAP/TPR)
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Poiseuille's resistance eqn?
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R = 8hl/pr^4
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Eqn for SV?
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EDV - ESV
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Eqn for CO?
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SV x HR
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Eqn for EF?
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EF = SV/EDV
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Eqn for SW?
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SV x Aortic pressure
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Eqn for O2 consumption?
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CO x ([O2] pulm vein - [O2] pulm artery)
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When a vessel is added in parallel, resistance
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dec
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Thus pressure
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incr
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When a vessel is added in series, resistance
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incr
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Thus pressure
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dec
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Reynolds number predicts if blood flow is
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laminar or turbulent
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Audible vibrations of turbulence are called
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bruits
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Shear force is highest
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at the wall of vessel
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2 words meaning the distensibility of a vessel
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capacitance, compliance
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Capacitance eqn?
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C = V/P (capacitance = volume/pressure)
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What is the fx of age?
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Compliance dec
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Explain why veins are more compliant than arteries?
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Less pressure
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Describe the pressure profile of large blood vessels
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Highest pressure in aorta; lowest in vena cavae
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What do arterioles have the largest dec in pressure?
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Highest resistance
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Is arterial pressure constant during cardiac cycle?
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No, it's pulsatile
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Systolic pressure is after
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the heart contracts
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Diastolic pressure is after
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the heart relaxes
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Pulse pressure defined as
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SBP - DBP
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Most important determinant of pulse pressure is
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stroke volume
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MAP (mean arterial pressure) is defined as?
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DBP + (SBP/3)
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LAP is estimated by?
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pulm wedge pressure
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P wave represents
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atrial depolarization
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Why isn't atrial repolarization shown
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buried in QRS
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PR interval defined as
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BEGINNING of P to BEGINNING of Q
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Varies with?
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Conduction of AV node
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Fx of SNS?
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dec PR
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Fx of PNS?
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Incr PR
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QRS represents?
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depolarization of ventricles
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QT interval defined as
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BEGINNING of Q to END of T
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Represents?
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ENTIRE depolarization & repolarization of ventricles
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ST segment defined as
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END of S to BEGINNING of T
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Should have what characteristic?
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Isoelectric
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Represents?
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when ventricles depolarized
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T wave represents
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ventricular repolarization
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Resting membrane potential determined by
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K conductance (I-K1)
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5 phases of atria, ventricles, Purkinje
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Phase 0-4
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Phase 0 is the
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Upstroke
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Caused by transient incr in
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Na conductance (I-Na)
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Phase 1 is the
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initial repolarization
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Determined by 2
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K flow out; dec Na conductance
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Phase 2 is the
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plateau
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Caused by transient incr in
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Ca conductance (I-Ca)
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Phase 3 is the
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repolarization
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Determined by 2
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K conductance incr (I-K); Ca conductance dec
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What makes the SA node the pacemaker?
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Phase 4 depolarization (automaticity)
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2 latent pacemakers if SA node is suppresed?
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AV node > His-Purkinje
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What 2 phases are not present in SA node?
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Phase 1, 2
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What defines phase 0 in SA node?
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Incr Ca conductance (I-Ca)
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How does this differ from other parts of heart?
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Not about Na conductance
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What phase is similar in the SA node and other parts of heart?
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Phase 3
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Phase 4 current is defined by
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Incr Na conductance (I-f)
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What is the action potential?
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Slow repolarization
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How is it activated?
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I-f turned on by repolarization of membrane potential
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How is the AV node similar to SA node?
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Phase 0 upstroke is also I-Ca
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Conduction velocity is determined by
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size of inward current during upstroke
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Fastest in
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Purkinje system
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Slowest in
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AV node (PR interval)
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Fx of faster AV conduction?
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Ventricular filling compromised
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Absolute refractory pd is
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when no AP can be initiated
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When does this occur?
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Beginning of upstroke to end of plateau
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Effective refractory pd is
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when CONDUCTED AP can't be elicited
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Relative refractory pd is
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AP is elicited with a higher inward current
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Chronotropic fx change
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HR
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Dromotropic fx change
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Conduction of AV node (affect PR)
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PNS innervates 3
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SA node, AV node, atria
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NT?
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Ach
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Acts on?
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Muscarinic R
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Fx? 3
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Neg chronotropic, neg dromotropic, dec contractility (atria only)
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Mech of neg chronotropic fx?
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Dec I-f (SA phase 4)
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Mech of neg dromotropic fx?
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Dec I-Ca and incr I-K in AV node
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NT of SNS?
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Norepi
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Acts on?
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b1-R
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Fx? 3
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Post chronotropic, pos dromotropic, incr contractility
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Mech of pos chronotropic fx?
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Incr I-f (SA phase 4)
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Mech of pos dromotropic fx?
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Incr I-Ca in AV node
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Fx on PR interval?
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PNS incr, SNS dec
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Purpose of intercalated disks? 2
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Maintain cell-cell cohesion; gap junciton to sync
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T tubles in cardiac muscle form
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dyads
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Purpose?
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Carry AP into cell interior
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Excitation-contraction coupling occur in which phase?
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Phase 2
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When Ca conductance incr, it travels thru?
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L-type Ca channels = dihydropyridine R
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What does this trigger?
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Release of Ca from SR
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What are the names of these channels
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RYR (ryanodine receptors)
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Magnitude of tension developed is proportional to
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Intracellular [Ca]
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Relaxation occurs by what mech?
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Ca-ATPase pump on SR
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Another name for contractility?
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inotropism
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Can be estimated by?
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EF (ejection fraction)
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What is a norm EF?
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55% (0.55)
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3 factors that incr contractility?
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Incr HR, SNS stim, cardiac glycosides
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Mech of incr HR?
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More AP/unit time -> more Ca enters -> more Ca release from SR
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What is the positive staircase?
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Incr HR stepwise incr contractilty as intracellular [Ca] accumulates
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What is postextrasystolic potentiation?
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Beat after extrasystolic beat has extra Ca enter cells during extrasystole -> stronger contraction
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Mech of SNS? 2
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Incr Ca current, phopholamban-P incr activity of SR pump
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Mech of cardiac glycosides?
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Inh Na/K ATPase -> incr intracellular [Na] -> incr [Ca] intracellular by Na/Ca exchange
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Factors that dec contractility? 1
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PNS stim
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Mech?
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Decr Ca current
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Preload of ventricular muscle is
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EDV (related to LAP)
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Afterload of ventricular muscle is
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Aortic pressure (LV), pulm artery pressure (RV)
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Sarcomere length determines 2
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max # cross-bridges; max tension (force of contraction)
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Velocity of contraction at fixed length determined by?
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AFTERLOAD
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What is the Frank-Starling relationship?
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Incr venous return (EDV) -> Incr SV & CO
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Mech?
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Incr EDV -> incr ventricular fiber length -> incr tension
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Pos inotropic effect shifts curve
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Up
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Neg inotropic effect shifts curve
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down
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In PV loop of LV, what is the x-axis? Y-axis?
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X = LV volume; Y = LV pressure
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R border is?
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Isovolumetric contraction
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L border is?
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Isovolumetric relaxation
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Superior border is?
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Ventricular ejection
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Inferior border is?
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Ventricular filling
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SV is represented by?
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Width of loop
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Stroke work represented by?
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Area of loop
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Incr preload shifts
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R border more R
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Hemodynamic fx?
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SV inc (EDV inc)
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Incr afterload shifts 2
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Superior border up, L border more R
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Hemodynamic fx?
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Incr ESV -> dec SV
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Incr contractility shifts 2
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Superior border up, L border more L
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Hemodynamic fx?
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Dec ESV -> incr SV
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CVS fxn curve: y-axes?
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CO and venous return
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CVS fxn curve: x-axes?
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RAP and EDV
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Which direction does venous return run?
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Top L to bottom R
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Which direction does CO run?
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Top R to bottom L
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X-intercept of Venous return represents?
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Mean systemic pressure
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What does that mean?
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MSP = RAP when no flow in CVS
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What incr MSP? 2
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Incr blood volume, dec venous compliance
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Which changes occur in the graph?
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venous return curve shifts R
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What fx does this have on CO?
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Incr
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What fx does this have on venous return?
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Incr
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What fx does this have on RAP?
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Incr
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Clockwise rotation of CO and counterclockwise rotation of venous returns represents
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Incr TPR
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What fx does this have on the RAP?
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NONE
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What fx does this have on CO?
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Dec
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What fx does this have on venous return?
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Dec
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What fx does this have on MSP?
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NONE
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How do pos inotropic agents change the graph?
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Shift CO counterclockwise
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What fx does this have on RAP?
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Dec
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What fx does this have on CO?
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Incr
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What fx does this have on venous return?
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Incr
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What fx does this have on MSP?
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NONE
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Atrial systole is preceded by what on EKG?
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P wave
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Incr atrial pressure (venous pressure) causes which wave on venous pulse curve?
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a wave
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What is the correlating heart sound?
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S4
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S1 correlates to what wave on EKG?
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QRS
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Which valves are closing?
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MV, TV
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Which of these close first?
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MV
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Most of the SV is ejected during?
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Rapid ventricular ejection
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What does this correlate with on EKG?
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ST segment
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During the onset of T wave, what is the status of LV?
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Slow ventricular ejection
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S2 correlates with what on EKG?
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B/t T & P
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Which valves are closing?
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AV, PV
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Which of these close first?
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AV
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What resp manuever splits S2?
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Inspiration
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Blip in aortic pressure tracing during isovolumetric relaxation is called
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Dicrotic notch/incisura
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Rapid filling of LV correlates with which heart sound?
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S3
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Is this sound pathological?
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Not in children, but in adults
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Longest phase of cardiac cycle
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diastasis (reduce vent filling)
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When LVP matches LAP, which valve changes?
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MV
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When LVP matches Aortic P, which valve changes?
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AV
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Cardiac cycle graph
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Fast mech?
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Neuronal (Baroreceptor)
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Slow mech?
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Hormonal (RAAS)
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Baroreceptors located 2
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Bifurcation of common carotid, aortic arch
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What's the difference
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Aortic arch only sense incr; bifurcation both
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Afferent limb is which nerve
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CN IX
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Where does this information transmit to?
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Vasomotor center of medulla
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How does the Valsalva maneuver test the baroreceptor mech? 4
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Incr intrathoracic pressure -> dec venous return -> dec CO -> SNS response: incr HR
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Where is renin produced?
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Juxtaglomerular cells of afferent arteriole
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Role of renin?
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Angiotensinogen -> angiotensin
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ACE conversion occurs in which organ?
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lungs
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2 Rx that interfere with angiotensin?
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ACE-I (captopril), ARB (losartan)
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What is the other fxn of ACE that causes the side fx of ACE-I?
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Cleave bradykinin; promote cough
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4 fxn of AII
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Stim aldosterone,
Inc Na/H exchange in PCT, Inc thirst, Vasoconstrion of arterioles |
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Cushing rxn is
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response to cerebral ischemia
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Mech? 7
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Incr ICP -> vessel compression -> ischemia -> incr PCO2 -> vasomotor chemoreceptor -> incr SNS -> incr arterial pressure
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Peripheral chemoreceptors located
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Carotid bifuration, aortic arch
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What chemical do these detect?
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PO2
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2 fx of vasopressin (ADH)?
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Incr TPR, reabsorb H2O
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Which receptors facilitate this?
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V1R on arterioles, V2 on DCT and collecting duct
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3 fx of ANP?
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Dec TPR, incr H2O excretion by Na, inh renin
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Blood flow thru cap regulated by
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precapillary sphincters
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Lipid cross cap wall by
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simple diffusion
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Small hydrophilic substances cross cap wall by
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water filled clefts (exceptionally small in brain; big in liver/intestine)
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Large hydrophilic susbstances cross cap wall by
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pinocytosis
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Starling eqn?
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Jv = Kf (Pc -Pi) - (pc -pi)
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Jv positive correlates with
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Filtration; net fluid movement OUT of cap
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Jv negative correlates with
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Absorption; net fluid movement INTO cap
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Which 2 forces promote filtration?
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Pc, pi
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Which 2 forces promote absorption?
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Pi, pc
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Why is lymph flow unidirectional?
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one-way flap valves
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What force aids lymphatic flow?
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Skeletal muscle contraction
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How do burns induce edema?
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Incr Kf (constant)
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What else does this?
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Infl (Histamine, cytokines)
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Mech of EDRF?
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EDRF -> incr cGMP -> SM relaxation
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What's the most popular EDRF?
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NO
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3 organs that exert autoregulation of blood flow
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heart, brain, kidney
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What is active hyperemia?
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Incr blood flow b/c of metabolic activity
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What is reactive hyperemia?
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Incr blood flow after pd of occlusion
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Myogenic mech of local ctrl?
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Vasc SM contracts when it is stretched
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Metabolic mech of local ctrl?
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Vasodilating metabolites: CO2, H, K, lactate, adenosine
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What 2 chemicals cause vasodilation and venous constriction?
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Histamine, bradykinin
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What causes arteriolar constriction, implicating it in migraines?
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5HT
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Which PG are vasodilators?
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PGI2, PGE2
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Which PG are vasoconstrictors?
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PGF2, TXA2
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Coronary flow is primarily regulated by
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metabolic factors
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The most important of which are
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hypoxia, adenosine
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How does reactive hyperemia help coronary flow?
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Vessels compressed in systole -> fill during diastole
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Cerebral flow is primarily regulated by
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metabolic factors
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The most important of which is
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CO2
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Skeletal muscle is regulated by 2
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Sympathetics, metabolic factors
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Main metabolic factors?
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latate, adenosine, K
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Skin is regulated primarily by
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sympathetics
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What is the main fxn?
|
Temperature control
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Mech of ortho hypotension? 6
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Venous pooling -> dec venous return -> dec SV -> dec CO -> dec BP -> baroreceptor
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Norm P wave
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0.08-0.1 s = 2-2.5 little boxes
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Norm QRS
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0.06-0.1s = 1.5-2.5 little boxes
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Norm PR
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0.12-0.2s = 3-5 little boxes
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Norm QTc
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<0.44s = <11 little boxes
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QTc eqn?
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QT/√RR
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