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USMLE
CV 3
| Question | Answer |
|---|---|
| when in the cardiac cycle is O2 consumption highest? | isovolumetric contraction |
| this is the period between mitral valve closing and aortic valve opening | isovolumetric contraction |
| this is the period between aortic valve opening and closing | systolic ejection |
| this is the period between aortic valve closing and mitral vale opening | isovolumetric relaxation |
| when does rapid filling occur? | just after mitral valve opens |
| when does slow filling occur? | just before mitral valve closes |
| when is JVD seen? | right heart failure |
| what is cardiac muscle contraction dependent on? | extracellular calcium, which enters the cells during plateau of action potential and stimulates calcium release from the sarcoplasmic reticulum (calcium-induced calcium release) |
| what is the plateau in the cardiac muscle action potential due to? | calcium influx |
| where does the pacemaker action potential occur? | SA and AV nodes |
| what accounts for the automaticity of the SA and AV nodes? | slow diastolic depolarization - membrane potential spontaneously depolarizes as Na+ conductance increases (funny channel) |
| what determines heart rate? | slope of phase 4 in the SA node |
| what are the peripheral chemoreceptors? what do they respond to? | carotid and aortic bodies - they respond to decreased (less than 60 mmHg)/increased PCO2, decreased pH of blood |
| what do central chemoreceptors respond to? | changes in pH and PCO2 of brain interstitial fluid, which in turn are influenced by arterial CO2 |
| what does the aortic arch respond to? how does it transmit and to where? | responds to increased BP; transmits via vagus to medulla |
| how and to where does the carotid sinus transmit information? | via glossopharyngeal to the medulla |
| how do the central chemoreceptors respond to increased intracranial pressure? | hypertension (sympathetic response) and bradycardia (parasympathetic response) |
| what organ receives the larges share of systemic cardiac output? | liver |
| what organ receivest eh highest blood flow per gramof tissue? | kidney |
| how does the heart meet increased O2 demand? | incrased coronary blood flow, not by increased extraction of O2 |
| hypoxia in the pulmonary vasculature causes what? | vasoconstriction (unique because in other organs hypoxia causes vasodilation) |
| what are the local factors in the heart that determine autoregulaton? | O2, adenosine, NO |
| what are the local factors in the brain that determine autoregulation? | CO2 (pH) |
| how do the kidneys determine autoregulation? | myogenic and tuboglomerular feedback |
| what local factors determine autoregulation in skeletal muscle? | lactate, adenosine, K+ |
| what is the most important mechanism for determining autoregulation in the skin? | sympathetic stimulation - temperature control |
| what is the effect of carotid massage? | incrases pressure on carotid artery - increasing stretch and leading to decreased HR |
| what is the ultimate consequence of baroreceptors sensing hypotension? | vasoconstriction, incrased HR, contractility, and BP - important in the response to severe hemorrhage |
| sound of mitral and tricuspid valve closure | S1 |
| sound of aortic and pulmonary valve closure | S2 |
| sound at end of rapid ventricular filling | S3 |
| sound from high atrial pressure/stiff ventricle | S4 |
| what is S3 associated with? | dilated CHF, mitral/tricuspid regurgitation |
| what is S4 (atrial kick) associated with? | hypertrophic ventricle |
| what is paradoxical splitting associated with? | aortic stenosis, LBBB |
| what is fixed splitting associated with? | ASD |
| holosystolic high pitched 'blowing murmur' loudest at apex | mitral regurg (tricuspid regurg) |
| cresecendo-decrescendo systolic ejection murmur following ejection click | aortic (pulmonic) stenosis |
| pulsus parvus et tardus | pulses weak compared to heart sounds; seen in aortic stenosis |
| holosystolic murmur | VSD |
| late systolic murmur with midsystolic click | mitral prolapse |
| immediate high-pitched blowing diastolic murmur; wide pulse pressure | aortic regurgitation |
| delayed rubbing late diastolic murmur that follows opening snap | mitral stenosis |
| how does the murmur in tricuspid stenosis differ from that of mitral stenosis? | tricuspid stenosis differs because it gets louder with inspiration |
| continuous machine-like murmur | PDA |
| when is the murmur associated with a PDA loudest? | S2 |
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Asclepius
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