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20 Cards in this Set
- Front
- Back
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What is the cardiac output, heart rate, and stroke volume in an average adult?
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Cardiac output: 5L/min
Heart rate: 70 beats/min Stroke volume: 70mL |
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What controls the heart rate? How is it increased and decreased?
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Controlled by ANS, increased by sympathetic branch through beta1-adrenergic receptors in the SA node and decreased by parasympathetic branch through muscarinic receptors in the SA node.
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What determines stroke volume?
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1. myocardial contractility
2. cardiac afterload 3. cardiac preload |
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What is preload, and how does it affect stroke volume?
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preload is the amount of tension or stretch applied to a muscle prior to contraction. An increase in preload will increase stroke volume and a decrease will decrease stroke volume.
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What is afterload, and how does it affect stroke volume?
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Afterload is the load against which a muscle exerts its force (the arterial pressure the l. ventricle must overcome to eject blood). If afterload increases, stroke volume decreases and if afterload decreases, stroke volume increases.
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What happens to stroke volume when arterioles constrict?
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Peripheral resistance rises, causing afterload to rise, causing stroke volume to decrease.
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What is Starling's Law of the Heart?
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the force of ventricular contraction is proportional to muscle fiber length. Accordingly, as ventricular diameter (fiber length) increases there is a corresponding increase in contractile force. When more blood enters the heart, more is pumped out.
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What is the normal systemic filling pressure?
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7 - 17 mm Hg
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What factors determine venous return?
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1. Systemic filling pressure
2. auxiliary muscle pumps 3. resistance to flow between peripheral vessels and the right atrium 4. right atrial pressure |
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Can the factors that determine venous return by influenced directly with drugs?
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No
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Under normal circumstances, how is arterial pressure regulated?
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1. the ANS
2. the renin-angiotensin-aldosterone system (RAAS) 3. the kidneys |
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Which of the AP regulators works fastest? What is responsible for this speed?
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The ANS. The baroreceptor reflex in the aortic arch and carotid sinus send messages to the brain, which in turn sends instructions to the vessels to either constrict or dilate as necessary.
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Is the baroreceptor reflex a good long-term regulator for arterial pressure? Why or why not?
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No, because after one or two days it adapts and perceives the new pressure as normal and no longer responds.
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In which ways does the RAAS support arterial pressure?
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1. constricts arterioles and veins (angiotensin II)
2. retains water via the kidneys (aldosterone) |
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Why does a reduction in arterial pressure cause the kidneys to retain water?
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Low AP reduces renal blood flow, which in turn reduces glomerular filtration rate, producing less urine. Low AP also activates the RAAS, causing angiotensin II and aldosterone levels to rise, constricting blood vessels and retaining sodium in the kidneys.
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What kind of drugs prolong and intensify orthostatic hypotension?
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vasodilators
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How do natriuretic peptides protect the cardiovascular system in the even of volume overload?
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1. by reducing blood volume
2. by promoting dilation of arterioles and veins |
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When are ANP, BNP and CNP released?
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When blood volume is excessive
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What is the job of ANP and BNP?
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reduce blood volume, increase venous capacitance and reduce cardiac output.
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What is the job of CNP?
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Vasodilation
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