Term
| What are the 3 primary independent determinants of force of contraction and stroke volume? |
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Definition
| Preload, Afterload, and Contractility |
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Term
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Definition
| The amount of passive tension that is formed on the walls from the volume of blood in the chamber just prior to ejection. |
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Term
| What is Cardiac Afterload? |
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Definition
| The force that the ventricle is working against after the onset of the contraction. |
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Term
| What is Cardiac Contractility? |
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Definition
| It is the contractile force developed by the ventricle at a given preload and afterload. |
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Term
What is Cardiac Output? What is the equation for cardiac output? |
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Definition
Cardiac output is the functional output of the cardiovascular system and is the amount of blood that is pumped by the ventricle each minute. CO = (HR)(SV) |
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Term
What is the Cardiac Index? What is the equation for the Cardiac Index |
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Definition
Cardiac Index is Cardiac Output that is adjusted for the size of the individual Cardiac Index = CO/Body Surface Area |
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Term
What is the cardiac output at rest? What is the cardiac output during exercise? |
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Definition
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Term
| How do you calculate the Ejection Fraction |
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Definition
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Term
| What is Fick's Principle? |
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Definition
| The quantity of oxygen of pulmonary arterial blood, plus the quantity of oxygen added to blood in the pulmonary capillary blood as it passes through the lung must be equal to the quantity of oxygen in the pulmonary venous blood. |
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Term
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Definition
| An indicator dilution technique that involves measuring the temperature change in saline that is injected into the right atrium as it passes through the right ventricle and into the pulmonary artery. By understanding the area under the thermdilution curve, one can measure the cardiac output. |
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Term
| What are the advantages of the thermodilution technique? |
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Definition
1. Arterial puncture is not necessary 2. Several measurements can be taken without changing the status of the patient 3. There is no recirculation of the indicator like other techniques |
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Term
| What are two other ways to measure Cardiac Output? |
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Definition
Echocardiography Gated Radionucleotide imaging |
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Term
1. What is the normal range of resting HR? 2. What is maximum HR in a young individual? 3. What is Tachycardia? 4. What is Bradycardia? |
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Definition
1. 60 - 90 BPM 2. 180 - 200 BPM 3. HR > 100 BPM 4. HR < 60 BPM |
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Term
| How does a faster HR affect filling during diastole? |
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Definition
| There is less time for filling so the volume of blood that enters into the ventricles decreases. Thus, the preload is decreased. |
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Term
| How does an increase in preload affect stroke volume? |
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Definition
| An increase in preload will increase the the stroke volume |
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Term
| What is the Left Ventricular End Diastolic Pressure (LVEDP)? |
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Definition
| This is the effective "preload" pressure that represents the passive pressure on the walls just prior to onset of contraction. |
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Term
| What is the Left Ventricular End Diastolic Volume? |
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Definition
| This is the end volume just prior to contraction. Thus increased LVEDV will lead to a higher stroke volume. |
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Term
| What is the Frank Starling Law of the Heart or The Length-Tension Relationship? |
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Definition
The relationship between the active contractile force and and extent to which passive length determines it. It is an intrinsic mechanical property of the heart, and does not depend on nerves or hormones. Increased Filling -> Increased Preload -> Increased Force of Contraction -> Increased Stroke Volume -> Increased CO |
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Term
What determines preload in the right ventricle? In the left ventricle? |
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Definition
Central Venous Pressure Pulmonary Vein Pressure These, increased, will increase the volume that the ventricles will recieve during diastole. |
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Term
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Definition
| This is the availability of the ventricles to increase SV via increasing preload activity above normal physiological levels. |
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Term
| How does Smooth Muscle Tone contribute to CVP and thus Preload? |
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Definition
| Increased smooth muscle tone -> Increased CVP -> Increased Preload |
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Term
| What is the major determinant of cardiac preload? |
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Definition
| Arterial Pressure that is determined via Central Venous Pressure. |
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Term
| How does Blood Volume affect Preload? |
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Definition
Since 60 - 70% of blood volume is in the venous system changes in blood volume have a tremendous effect on CVP and thus Preload. Decreased Blood Volume -> Decreased Preload -> Decreased SV |
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Term
| How does Body Position affect CVP and Preload? |
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Definition
Lying down = Increased CVP = Increased Preload = Increased SV Standing = Pooling of blood in lower extremity = Decreased CVP = Decreased Preload = Decreased SV |
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Term
| What is the effect of Intrathoracic Pressure on Preload? |
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Definition
| Increased respiration and depth (ex. during exercise) increases venous return and thus Preload. |
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Term
| What is the effect of Ventricular Compliance on Preload? |
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Definition
| Decreased compliance will limit preload or passive stretching in the ventricles. |
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Term
| At a given Preload and Contractility, an increase in afterload will ______________ Stroke Volume. |
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Definition
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Term
| As the force that the muscle contracts against increases, the amount and velocity of muscle fiber (cell) shortening will ____________. |
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Definition
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Term
| Under what conditions does maximal velocity of shortening of muscle cells occur? |
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Definition
| Under zero afterload. This is unphysiologically impossible. |
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Term
| What is the cellular basis of Afterload? |
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Definition
| The rate of actin-myosin cross bridge cycling, and thus rate and amount of cardiac cell shortening and chamber size reduction, are inversely related to the afterload. |
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Term
| What are the 3 Determinants of Cardiac Afterload? |
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Definition
1. Aortic Arterial Diastolic Pressure 2. Aortic Compliance 3. Aortic Valve Resistance |
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Term
Give the effect of Afterload based on these conditions: 1. Stenosis of Aortic Valve 2. Increased Aortic Compliance 3. Hypertension 4. Arteriosclerosis |
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Definition
1. Increased 2. Decreased 3. Increased 4. Increased |
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Term
| Increased Afterload will ____________ necessary oxygen consumption of the heart. |
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Definition
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Term
| At a given preload and contractility, an increase in afterload will _____________ stroke volume. |
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Definition
| Decrease (Converse is also true) |
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Term
| What is the relationship between Contractility and Stroke Volume? |
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Definition
| It is a direct relationship. Thus, an increase in contractility will increase stroke volume. |
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Term
| What is the difference between "Contractility" and "Contractile Force"? |
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Definition
Contractility refers specifically to the force achieved at a given pre- and afterload. Contractile force is the generic force of contraction or tension developed during contraction. |
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Term
| What are the 4 main Cellular Basis for Contractility? |
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Definition
1. Calcium Kinetics 2. Myosin ATPase activity 3. ATP levels 4. Number of cross-bridges |
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Term
| What effect does Calcium Kinetics have on Contractility? |
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Definition
| The rate and absolute increase in cytoplasmic calcium that occurs during depolarization determines the level of CTY. |
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Term
| What effect do Catecholamines have on Calcium Kinetics and correspondingly to Contractility? |
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Definition
| Catecholamines bind to β1 adrenergic receptors and increase cAMP and increase all 3 calcium determinants: Increased Ca2+ influx and release from SR during depolarization; Increased removal from cytoplasm during repolarization |
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Term
| How does Myosin ATPase activity affect Contractility? |
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Definition
| Increased activity will increase corresponding Contractility. |
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Term
| How do ATP levels affect Contractility? |
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Definition
| ATP levels have a direct correlation to Contractility. Thus lower ATP levels will decrease Contractility. |
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Term
How do each of these affect Contractility? 1. Norepinephrine 2. Acetylcholine 3. Increase Ca2+ influx 4. Decreased number of cross-bridges |
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Definition
1. Increase CTY 2. NO EFFECT - Vagal changes only affect the HR and NOT CTY 3. Increased CTY 4. Decreased CTY |
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Term
| What is the most pure, direct measure of contractility, but can only be derived experimentally (in an isolated heart with no afterload on it). |
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Definition
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Term
| In the intact heart, what is the best measure of Contractility? |
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Definition
| CTY is best indicated by the pressure-volume point at aortic valve closure. This point is shifted up and to the left with an increase in CTY and down and to the right with a decrease in CTY. |
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Term
| What does ∂P/∂tmax measure? |
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Definition
| This indirectly measures Contractility by measuring the maximal rate of ventricular pressure rise during the isovolumetric period. |
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Term
| What are some factors that promote venous return? |
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Definition
| Contraction of muscles surrounding veins will increase the extraluminal pressure compressing the vein and thus increase return of the blood to the heart. Backflow is also prevented by valves. |
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Term
| How does respiratory inspiration increase venous return from abdomen to thorax? |
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Definition
| The pressure in the thorax is normally negative. During inspiration, thoracic pressure becomes more negative and abdominal pressure increases slightly. This increase in pressure gradient increases the venous return from abdomen to thorax. |
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