Flashcards in Integration of Cardiac Function Deck (50)
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?
-decreased O2 concentration in environment (like at high altitude)
how does chronic anemia change CO?
-decreased O2 content in blood when RBC concentration is reduced
how does histotoxic hypoxia change CO?
-tissue poisoning involves decreased ability of tissues to utilize O2 as occurs after cyanide ingestion
how does pulmonary disease change CO?
-in general, resulting in hypoxemia (lowered O2 concentration in blood)
what are 4 compensatory diseases that increase CO?
-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
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
-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?
what does the ST segment correspond to?
plateau phase (phase 2)
what does the TP segment correspond to?