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50 Cards in this Set

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  • Back
What is cardiac output?
stroke volume x heart rate
What is cardiac index?
cardiac output / body surface area
What is venous return?
volume returning to heart each minute
What causes the dicrotic notch in arterial pressure?
The closing of the aortic valve causes the blood to backflow temporarily, increasing arterial pressure.
When is end diastolic volume measured?
isovolumetric contraction
When is end systolic volume measured?
isovolumetric relaxation
When does the a wave in the atrial pressure occur?
during atrial filling
What event corresponds with the c wave in atrial pressure?
onset of right ventricular systole
What mechanical and electrical activity is correlated with S1?
-mechanical: mitral valve closes followed by tricuspid valve
-electrical: QRS complex
What mechanical and electrical activity is correlated with S2?
-mechanical: aortic valve closes follwed by pulmonic valve
-electrical: return to baseline from T wave
What is the difference between "pressure work" and "volume work" of the heart?
-pressure work = afterload (resistance to ejection)
-volume work = preload (filling volume)
How does the length of systole and diastole change with increase in heart rate?
systole decreases slightly, diastole decreases drastically
What are the mechanical events of systole?
-atrial systole
-isovolumetric contraction
-ventricular ejection
What are the mechanical events of diastole?
-isovolumetric relaxation
-ventricular filling
How is force controlled in skeletal muscle?
-number of fibers stimulated varies
-frequency of action potentials varies
How is force controlled in cardiac muscle?
amount of Ca2+ released can vary
What triggers the influx of extracellular (activator) calcium?
voltage-sensitive L-type Ca2+ channels in the sarcolemma open in response to depolarization
What triggers the influx of intracellular (storehouse) calcium?
Ca2+ sensitive Ca-release channels in the sarcoplasmic reticulum open in response to influx of activator calcium
How is intracellular Ca2+ removed?
-Na/Ca exchanger in the sarcolemma
-Ca-ATPase in the sarcoplasmic reticulum
What are the two ways that the force at which the heart contracts can be changed?
-change initial fiber length (Frank-Starling mechanism)
-change contractility
How does increasing initial fiber length change the force of contraction?
-overlap of thick and thin filaments increases (total tension increases)
-greater sensitivity to [Ca2+]
-sarcoplasmic reticulum releases more Ca2+
What is the Frank-Starling law of the heart?
Within physiological limits, the tension generated by the contracting heart becomes greater as the heart muscle is stretched.
How does a change in preload affect stroke volume?
increase in preload causes increase in stroke volume
How does a change in afterload affect stroke volume?
increase in afterload causes decrease in stroke volume
How does a change in contractility affect stroke volume?
increase in contractility causes increase in stroke volume
How does norepinephrine increase contractility?
NE activates a G-protein receptor, and the Gαs subunit increases the open probability of the L-type Ca2+ channel.
How does digitalis increase contractility?
Inhibits the Na/K pump, increasing the intracellular [Na+]. This inhibits the Na/Ca exchanger and increases intracellular [Ca2+].
What heart conditions could be treated by blocking L-type Ca2+ channels?
-heart failure (decrease workload of the heart)
-arrhythmia (slow AV conduction)
What is the source population (in biomedical studies)?
-group of persons eligible for inclusion in study
-criteria: personal, temporal, and geographic
What is the base population (in biomedical studies)?
-broader than the source population
-group from which the cases arose
What is the target population (in biomedical studies)?
-broader than the base population
-group to which the study results will be applied
What factors directly affect stroke volume?
-end diastolic volume (preload)
-end systolic volume
stroke volume = EDV - ESV
What factors directly affect end diastolic volume?
-central venous pressure
-ventricular compliance
What factors directly affect end systolic volume?
-ventricular contractility (inversely affects ESV)
-arterial pressure (afterload)
What factors directly affect central venous pressure (or right atrial pressure, jugular venous pressure)?
-atrial kick
-blood volume
-venous capacity
What is a normal central venous pressure (in mmHg)?
1-2 mmHg
How does cardiac output affect central venous pressure?
as cardiac output increases, central venous pressure decreases, and eventually becomes negative when a suction is created
How does central venous pressure affect cardiac output?
As central venous pressure increases, cardiac output increases.
What are the coordinated responses to hemmorhage?
-sudden hypovolumia
-sympathetic stimulation of heart (contractility ↑)
-sympathetic venoconstriction
How does breathing affect venous return?
-inspiration accelerates venous return by increasing intraabdominal pressure and decreasing intrathoracic pressure
-expiration slows venous return
What is the purpose of venous valves?
Break the large vessels into segments to decrease the effect of gravity.
What is the formula for Reynold's number?
density x diameter x velocity / viscosity
What conditions can increase Reynold's number?
-anemia
-valve stenosis
-atherosclerosis
-pressure cuff
Where in the circulation is Reynold's number the greatest?
-branch points
-aorta
How are systemic vascular resistance, mean arterial pressure, and cardiac output?
MAP increases CO and SVR decreases it. CO = MAP / SVR
How is mean arterial pressure estimated?
diastolic pressure + 1/3 (systolic - diastolic)
How is flow velocity related to bulk flow and cross-sectional area?
velocity = flow / area
What is the Fahraeus-Lindqvist effect?
reduced viscosity when erythrocytes pass in single file through narrow vessels (axial streaming)
What are the 4 control systems that govern regional blood flow?
-metabolic control
-nervous control (sympathetic fibers)
-hormonal control (renin, ADH, etc.)
-long term control (angiogenesis)
What factors contribute to metabolic hyperemia?
-K+
-hyperosmolarity
-↓pO2
-adenosine