Exam 2- Cardio Flashcards
rate at which blood is pumped from either ventricle
cardiac output/afterload
rate at which blood is returned to the atria
venous return/preload
blood vessels with thick walls, elastic tissue, highest pressure, and stressed volume
arteries
site of highest resistance to blood flow
arterioles
single layer of endothelial cells that serve as site of exchange of nutrients, gases, water, and solutes between blood and tissues
capillaries
contain unstressed volume, have large capacitance
veins/venules
velocity is directly proportional to (blank); inversely proportional to (blank)
blood flow; cross sectional area
blood flow is directly proportional to (blank) and inversely proportional to (blank)
pressure gradient; resistance
resistance depends on
diameter and blood viscosity
resistance directly proportional to (2 things)
velocity and vessel length
formula for series resistance
Rtotal = R1 + R2 + R3….
formula for parallel series
1/ Rtotal = (1/R1) +(1/R2) + (1/R3)…….
streamlined parabolic profile of velocity within a blood vessel in which velocity is greatest in the center and 0 at the walls
laminar flow
disrupted flow that occurs at valves or site of blood clot or in vessels of high velocity
turbulent flow
predicts if flow will be laminar or turbulent; greater number = greater tendency for turbulence
Reynold’s Number
distensibility of blood vessels, inversely relate to elasticity
compliance
pressure in the artery during ventricular relaxation; lowest arterial pressure
diastolic pressure
pressure in the artery during ventricular contraction; highest arterial pressure
systolic pressure
difference between systolic and diastolic pressure, relates to stroke volume
pulse pressure
average pressure in a complete cardiac cycle
mean arterial pressure
causes an increase in systolic pressure, ouse pressure, and mean arterial pressure
arteriosclerosis
causes a decrease in systolic pressure, pulse pressure, and mean arterial pressure
aortic stenosis
incompetent aortic valve disrupts blood flow into the aorta, resulting in retrograde flow
aortic regurgitation
where are conducting cells found
SA node, atrial internodal tracts, AV node, bundle of His, purkinje fibers
normal sinus rhythm range depends on
action potential must originate in SA node
SA node impulses must occur regularly at 60-100 impulses/min
activation of the myocardium must occur in the correct timing and delays
Phase 0 of cardiac action potential
rapid depolarization caused by transient increase in Na conduction
Phase 1 of cardiac action potential
brief period of repolarization, net outward current
inactivation gates on Na channels close, outward current of K
Phase 2 of cardiac action potential
“plateau” - long period of stable depolarized membrane potential, no net current flow across membrane
inward Ca current (slow) balanced by outward K current
Phase 3 of cardiac action potential
repolarization; outward currents > inward currents
Phase 4 of cardiac action potential
resting membrane potential/electrical diastole
membrane potential stable again
inward and outward currents are equal (inward Na and Ca balance out outward K)
Phase 0 of SA node action potential
slow upstroke caused by inward Ca current
Phase 3 of SA node action potential
repolarization; increase in outward K current
Phase 4 of SA node action potential
longest part of SA action potential
slow upstroke due to inward Na current
conducts Na, K and Ca
inward Na turned on by repolarization of preceding AP
accounts for automaticity of SA nodal cells, rate of phase 4 determines heart rate
speed at which APs are propagated in the tissue
slowest in Av node to allow for ventricular filling; fastest in Purkinje fibers
conduction velocity
prevents conduction directly from atria to ventricles
antrioventricular ring
rate of conduction depends on (2 things)
size of inward current (# of ion channels)
more negative threshold
ability of cells to initiate an AP in response to inward depolarizing current; reflects recovery of channels that carry inward current during upstroke
excitability
period during which another AP cannot be elicited regardless of current; begins with upstroke and ends after plateau
absolute refractory period
period during which a generated AP cannot be conducted, Na+ channels begin to recover; inward current not enough to conduct to next site
effective refractory period
AP can be elicited if greater than usual current; occurs immediately after ARP when repolarization is almost complete
relative refractory period
period during which cell is more excitable than normal
supranormal period
chronotropic effects
effects of ANS on heart rate via SA node
positive=increase HR
negative = decrease HR
dromotropic effects
effects of ANS on conduction velocity via AV node
positive = increase conduction (symp B1)
negative = decrease conduction (parasymp)
p wave of EKG represents
atrial depolarization
PR interval of EKG
initial ventricular depolarization
QRS complex of EKG
ventricular depolarization
T wave
ventricular repolarization
QT interval
entire period of depolarization and repolarization of ventricles
ST segment
ventricular repolarization
maintain cell - cell cohesion, have gap junctions for cardiac muscle synctium
intercalated disk
ability of myocardial cells to develop force at a given muscle length
ionotropism
amount of Ca released from SR depends on… (2 things)
size of inward Ca current during plateau
amount of Ca previously stored in SR for release
contractility depends most on
intracellular Ca concentration
positive ionotropic effect
increase contractility,
increase rate of tension development/peak tension, increase rate of relaxation
mediated by B1 receptors
positive staircase effect
as intracellular Ca increases, HR increases and force of contraction increases in stepwise fashion
post extrasystolic potentiation
during an extra beat further release of Ca causes extra beat to have stronger force of contraction
used to treat CHF, inhibit Na-K ATPase to increase intracellular Na and Ca
positive ionotropic agents such as Digoxin
equivalent to end-diastolic volume; related to right atrial pressure
preload
volume of blood ejected by a ventricle on each beat
stroke volume
fraction of the end diastolic volume in each stroke volume, measures ventricular efficiency
ejection fraction
