Boron Cardiac Physio Review II Flashcards
sinus arrhythmia
normal - with respiration
re-entry
depolarization travels in circle
requires:
1 - closed conduction loop
2 - region of unidirectional block
3 - sufficiently slow conduction of APs around loop
**often with diverse tachyarrhythmias
unidirectional block
impulses travel in one direction but not in the opposite one
depolarization induced triggered activity
induced automaticity in non-pacemaer cells
I-Ca triggers slow positive deflection of Vm - early afterdepolarization
may trigger extrasystole
run of three or more ventricular extrasystoles
pathologic
-V-tach?? compare to dubin
long QT syndrome
prone to develop torsades de pointes
-hypokalemia, hypocalcemia, or medications
Ca overload
digitalis intox
- SR sequesters too much Ca
- transient inward current - delayed afterdepolarization
-can produce spontaneous action potential
ischemia and anoxia
decreased ATP
- ATP K channels more
- cells less excitable
- slow/blocks conduction
myocardial infarction
peaking of T waves followed by T wave inversion
-then elevation of ST segment
elevation of ST segment
myocytes at epicardium - become depolarized by cellular anoxic injury
- injured cell more positive resting potential
- but, has same plateau as uninjured cells
- difference in voltage is depressed everywhere but at the ST segment (elevates it)
coronary artery spasm
also produce ST elevation
ST segment depression and T wave inversion
ischemia
-anginal episodes
deep Q waves
irreversible cell death (necrosis)
AV valves
tricuspid (right)
mitral (left)
semilunar valves
pulmonary (right)
aortic (left)
four phases of cardiac cycle
1 inflow phase
2 isovolumetric contraction
3 outflow phase
4 isovolumetric relaxation
systole
phase 2 and 3
isovolumetric contraction and outflow
diastole
phase 4 and 1
isovolumetric relaxation and inflow
dicrotic notch
when aortic valve closes
-dip in aortic pressure
S1 heart sound
closure of AV valves
S2 heart sound
closure of aortic and pulmonary valves
S3 heart sound
diastolic filling gallop
S4 heart sound
artial sound - presystolic gallop
stroke volume = ?
EDV - ESV
ejection fraction = ?
SV / EDV
pressure-volume loop
plot of ventricular pressure and volume against time
starlings law
longer muscle fiber causes more mechanical energy
-muscle length proportional to EDV
contractility mesures
rate of pressure development
velocity of ejection
enhanced contractility
increases stroke volume
positive inotropic agents
increase Ca
- sympathetics
- cardiac glycosides (digitalis)
- high extracellular Ca
- low extracellular Na
- increased HR
negative inotropic agents
decreased Ca
- Ca channel blockers
- low extracellular Ca
- high extracellular Na
increased baroreceptor activity
inhibits the cardioacceleratory areas of medulla
sympathetics to heart
increased heart rate and contractility
SA node, atria, and ventricles
**at rest - more PS
parasympathetics to heart
decreases heart rate at SA
inhibit conduction through AV
also decreases contractility to some extent
sympathetics in blood vessels
kidney and skin - vasoconstriction
parasympathetics to blood vessels
sailvary and GI glands, erectile tissue
indirect vasodilation - NO
sympathetics to blood vessels in skeletal m
vasodilation - cholinergic
vasoconstriction - adrenergic
chromaffin cells
in adrenal medulla
-release epinephrine
sympathetics in pacemaker cells
beta1
- stimulate If
- stimulate Ca current
- increased rate of diastolic depolarization and negative shift in threshold
- increased HR
sympathetics in myocardial cells
beta1
- positive inotropic - contractility
- increased Ca channels
parasympathetics in pacemaker cells
- M2 - open K channels - more negative max diastolic potential
- decreases I-f
- decreases I-Ca - reduced rate of diastolic depolarization
reduced heart rate
parasympathetics in myocardial cells
minor negative inotropic effect
- counter adrenergic
- raising Ca - NO - inhibit L-type channels - decreased Ca influx
alpha1
vasoconstriction
beta2
vasodilation
afterload
force against which ventricles eject blood
preload
end-diastolic volume
heart rate increases
diastole shortens greater extent than systole
-decreased EDV
