Regulation of Cardiac Output Flashcards
what can affect CO?
age
body size (cardiac index)
basal metabolic rate
rest/exercise
oxygen consumption?
parallels cardiac output with increasing work output during exercise
two determinants of CO?
heart rate and stroke volume
CO = HR x SV
phase 0
inward Ca2+ influx
phase 3
outward K+ efflux
phase 4
funny current
outward K+ decreasing
sodium (funny) increasing
calcium increasing influx
three ways to change pacemaker potential?
1 change in slope of phase 4 (slow depolarization)
2 change in the maximum diastolic potential
3 change in threshold potential
parasympathetic input?
ACh on M2 receptors
results in negative chronotrophy (decreased HR)
sympathetic input?
NE on beta-1 receptors
resultsin positive chronotrophy (increased HR)
sympathetic effect on HR?
beta-1 agonists (NE)
changes:
increased funny current (sodium)
-more steepness
increased I-Ca (calcium)
- more steepness
- threshold more negative
changes in funny current with sympathetics results in ?
more steepness
faster rate
changes in I-Ca with sympathetics results in?
more steepness AND threshold more negative
faster rate
parasympathetic effect on HR?
M2 muscarinic agonist (ACh)
increased K + permeability
-hyperpolarize - more negative max diastolic potential
decreased funny current
-decreased slow depolarization rate
decreased I-Ca
- decreased slow depolarization rate
- more positive threshold
increased potassium permeability in PS results in?
more negative maximum diastolic potential
slows heart rate
decreased funny current in PS results in?
decreases slow depolarization phase
decreased I-Ca in PS results in?
decreases slow depolarization rate AND threshold more positive
effects of ACh on HR?
1 change in slope
2 negative shift in maximum diastolic potential (K+)
3 threshold is more positive
hyperthyroidism?
increases heart rate
hypothyroidism?
decreases heart rate
catecholamines?
increase heart rate
hyperkalemia
decrease heart rate
more K+ in ECF, effects concentration gradient that normally promotes efflux
- repolarization phase, efflux is slowed phase 3
- longer AP
hypokalemia
increases heart rate
nodal ischemia/hypoxia
decreased heart rate
drugs that influence HR?
antiarrhythmic drugs
calcium channel blockers
beta-1 adrenoreceptor agonists/antagonists
how to change conduction velocity?
aka dromotropy**
amplitude of action potential
rate of membrane potential change (depolarization)
extrinsic factors increasing conduction velocity?
sympathetic muscarinic antagonist beta agonist catecholamines hypokalemia hyperthyroidism
extrinsic factors decreasing conduction velocity?
parasympathetic muscarinic agonist beta antagonist (beta-blocker) ischemia hyperkalemia Na/Ca channel blocker
SV?
stroke volume = HR x SV = EDV - ESV
end diastolic volume - end systolic volume