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Flashcards in Integration of Cardiac Function Deck (50)
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2 mechanisms to control CO

intrinsic - local to heart
-mechanical/muscular (Starling's law related to contractility)
-electrical/ionic (membrane potential; ionic concentrations)

extrinsic - extra-cardiac neuronal and hormonal signaling pathways
-baroreceptors and chemoreceptors related to sympathetic stimulation and parasympathetic inhibition


neurotransmitter, receptors, second messenger, and functional "results" for sympathetic stimulation of the heart

NE to beta1 (pacemakers and myocetes) that increase cAMP
-cause tachycardia and increased contractility


neurotransmitter, receptors, second messenger, and functional "results" for parasympathetic stimulation of the heart

ACh to M2 (pacemakers, minor myocete effect) that decrease cAMP
-cause bradycardia and decreased contractility


how does CO compare in the aorta and pulmonary artery?

CO is the same in both, b/c they are in series
-it is NOT the sum of flows into aorta and pulmonary arteries


how low does CO go to be defined as hypoxia?

falls below 1/3 normal


what is the relationship between CO, work, and O2 consumption during exercise?

positive linear relationship


how does mild inspiratory hypoxia change CO?

increases CO
-decreased O2 concentration in environment (like at high altitude)


how does chronic anemia change CO?

increases CO
-decreased O2 content in blood when RBC concentration is reduced


how does histotoxic hypoxia change CO?

increases CO
-tissue poisoning involves decreased ability of tissues to utilize O2 as occurs after cyanide ingestion


how does pulmonary disease change CO?

increases CO
-in general, resulting in hypoxemia (lowered O2 concentration in blood)


what are 4 compensatory diseases that increase CO?

-chronic anemia
-histotoxic hypoxia
-pulmonary disease with hypoxemia
-mild inspiratory hypoxia


how does hyperthyroidism change CO?

increases CO b/c increased metabolic rate


how does pregnancy change CO?

increases CO (by 8%) corresponding to increased metabolism


difference between mild anoxia and severe anoxia

mild anoxia: increases CO b/c decrease peripheral resistance
severe anoxia: decreases CO b/c O2 deprivation in heart


how does HTN change CO?

unaltered in most forms


what happens to CO during hemorrhage?

CO is less than 1/2 normal for a significant period of time
-can cause severe shock


what 3 heart diseases decrease CO?

acute myocardial infarction
rheumatic fever
congestive heart failure


effect of body size on CO

CO increases in proportion to size
-CO = k * W^(3/4)


cardiac index and equation

CI = CO/body surface area
-attempt to normalize CO to individuals of different sizes


how does CO change with age?

body metabolism slows with increasing age, as does CO, by about 30% between 20 to 45 years old
-drops from 6 to 5.25 L/min


effect of anxiety on CO

emotional factors increase CO


effect on posture on CO

if laying down to sitting up: CO decreases by 23%
if laying/sitting to standing up, CO increases b/c tensing muscles


effect of temperature on CO

during fever, CO rises due to effects of temperature on metabolic rates of tissue


4 phases of cardiac cycle

1. filling phase
2. isovolumetric contraction phase
3. ejection phase
4. isovolumetric relaxation phase


what does the P wave correspond to

atrial depolarization
-while the AV node, bundle of his, bundle branches, and Purkinje network are depolarized as well, they don't generate voltages large enough to be measured


what does the QRS complex correspond to?

ventricular depolarization (upstrokes)


what does the T-wave correspond to?

ventricular repolarization


what does the ST segment correspond to?

plateau phase (phase 2)


what does the TP segment correspond to?

ventricular diastole


ventricular volume changes in cardiac cycle

1. ejection: falls from 120 to 50 mL, corresponding to stroke volume of 70 mL, and EJ of 58%
2. filling: occurs during early diastole as mitral and tricuspid valves open
-atrial systole occurs at the end of diastole, with only a small rise in pressure for both right and left hearts, so responsible for only a small increase in ventricular volume

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