Podcast
Questions and Answers
What is the term for the maximum volume of blood in the left ventricle at the end of diastole?
What is the term for the maximum volume of blood in the left ventricle at the end of diastole?
What occurs during the phase known as systole?
What occurs during the phase known as systole?
What is referred to as the minimum volume of blood in the left ventricle at the end of systole?
What is referred to as the minimum volume of blood in the left ventricle at the end of systole?
How can end diastolic volume and end systolic volume be utilized in cardiac physiology?
How can end diastolic volume and end systolic volume be utilized in cardiac physiology?
Signup and view all the answers
What happens to the volume of blood in the left ventricle as it contracts during the cardiac cycle?
What happens to the volume of blood in the left ventricle as it contracts during the cardiac cycle?
Signup and view all the answers
What term describes the total blood volume ejected by the left ventricle during one contraction?
What term describes the total blood volume ejected by the left ventricle during one contraction?
Signup and view all the answers
During which phase does the left ventricle achieve its least volume?
During which phase does the left ventricle achieve its least volume?
Signup and view all the answers
Which statement best describes the relationship between end diastolic volume and end systolic volume?
Which statement best describes the relationship between end diastolic volume and end systolic volume?
Signup and view all the answers
What primarily determines the systolic blood pressure?
What primarily determines the systolic blood pressure?
Signup and view all the answers
Which equation defines stroke volume?
Which equation defines stroke volume?
Signup and view all the answers
How is mean arterial pressure calculated?
How is mean arterial pressure calculated?
Signup and view all the answers
What does an increase in total peripheral resistance (TPR) typically cause?
What does an increase in total peripheral resistance (TPR) typically cause?
Signup and view all the answers
What is the effect of vasodilation of arterioles on total peripheral resistance?
What is the effect of vasodilation of arterioles on total peripheral resistance?
Signup and view all the answers
In a patient with heart failure, how does the stroke volume and pulse pressure typically present?
In a patient with heart failure, how does the stroke volume and pulse pressure typically present?
Signup and view all the answers
Which of the following is true about end diastolic volume (EDV)?
Which of the following is true about end diastolic volume (EDV)?
Signup and view all the answers
If the end diastolic volume is 150 mL and the end systolic volume is 75 mL, what is the left ventricular ejection fraction?
If the end diastolic volume is 150 mL and the end systolic volume is 75 mL, what is the left ventricular ejection fraction?
Signup and view all the answers
Which term refers to the volume of blood returned to the heart during each cardiac cycle?
Which term refers to the volume of blood returned to the heart during each cardiac cycle?
Signup and view all the answers
How is pulse pressure defined?
How is pulse pressure defined?
Signup and view all the answers
What does a higher end systolic volume indicate?
What does a higher end systolic volume indicate?
Signup and view all the answers
What does the body spend more time in during the cardiac cycle?
What does the body spend more time in during the cardiac cycle?
Signup and view all the answers
If a patient exhibits high total peripheral resistance, what might be an expected effect on their blood pressure during diastole?
If a patient exhibits high total peripheral resistance, what might be an expected effect on their blood pressure during diastole?
Signup and view all the answers
Which factor is primarily responsible for the increase in preload?
Which factor is primarily responsible for the increase in preload?
Signup and view all the answers
What effect does raising heart rate have on preload?
What effect does raising heart rate have on preload?
Signup and view all the answers
How does nitroglycerin reduce preload in patients with angina?
How does nitroglycerin reduce preload in patients with angina?
Signup and view all the answers
What is the consequence of chronically high afterload on the left ventricle?
What is the consequence of chronically high afterload on the left ventricle?
Signup and view all the answers
What happens to stroke volume when afterload increases?
What happens to stroke volume when afterload increases?
Signup and view all the answers
What would lead to a decrease in LVEDV?
What would lead to a decrease in LVEDV?
Signup and view all the answers
How does aortic stenosis affect afterload?
How does aortic stenosis affect afterload?
Signup and view all the answers
Which condition would likely result in increased peripheral resistance and higher afterload?
Which condition would likely result in increased peripheral resistance and higher afterload?
Signup and view all the answers
What effect does decreased blood pressure have on the afterload experienced by the heart?
What effect does decreased blood pressure have on the afterload experienced by the heart?
Signup and view all the answers
What occurs to the left ventricle if there are heightened forces opposing outflow?
What occurs to the left ventricle if there are heightened forces opposing outflow?
Signup and view all the answers
Which of the following describes a characteristic of LVEDP?
Which of the following describes a characteristic of LVEDP?
Signup and view all the answers
Which statement best reflects the relationship between preload and afterload?
Which statement best reflects the relationship between preload and afterload?
Signup and view all the answers
In a state of dehydration, what will happen to the cardiac output?
In a state of dehydration, what will happen to the cardiac output?
Signup and view all the answers
What is the relationship between preload and cardiac output?
What is the relationship between preload and cardiac output?
Signup and view all the answers
Which of the following factors is NOT a determinant of cardiac output?
Which of the following factors is NOT a determinant of cardiac output?
Signup and view all the answers
How can one increase preload in a clinical setting?
How can one increase preload in a clinical setting?
Signup and view all the answers
What is the primary effect of increasing preload on the heart's workload?
What is the primary effect of increasing preload on the heart's workload?
Signup and view all the answers
Which of the following is a consequence of a decreased heart rate?
Which of the following is a consequence of a decreased heart rate?
Signup and view all the answers
Which physiological mechanism primarily facilitates the increase of preload during blood loss?
Which physiological mechanism primarily facilitates the increase of preload during blood loss?
Signup and view all the answers
What happens to stroke volume if preload decreases?
What happens to stroke volume if preload decreases?
Signup and view all the answers
Which statement best describes preload?
Which statement best describes preload?
Signup and view all the answers
How can stroke volume be calculated?
How can stroke volume be calculated?
Signup and view all the answers
When the heart is at rest, what generally happens to cardiac output?
When the heart is at rest, what generally happens to cardiac output?
Signup and view all the answers
What physiological parameter correlates with the volume of blood returning to the heart at the end of diastole?
What physiological parameter correlates with the volume of blood returning to the heart at the end of diastole?
Signup and view all the answers
Which of these options can lead to a decrease in end diastolic volume?
Which of these options can lead to a decrease in end diastolic volume?
Signup and view all the answers
Which factor is primarily affected when there is an increase in contractility?
Which factor is primarily affected when there is an increase in contractility?
Signup and view all the answers
What physiological state is described by the heart needing to work harder due to more cardiac output?
What physiological state is described by the heart needing to work harder due to more cardiac output?
Signup and view all the answers
What is the primary effect of the sympathetic nervous system on contractility?
What is the primary effect of the sympathetic nervous system on contractility?
Signup and view all the answers
Which condition is characterized by poor contractility?
Which condition is characterized by poor contractility?
Signup and view all the answers
What happens to the end diastolic volume (EDV) as heart rate increases?
What happens to the end diastolic volume (EDV) as heart rate increases?
Signup and view all the answers
What is the role of calcium channel blockers on contractility?
What is the role of calcium channel blockers on contractility?
Signup and view all the answers
How does increased contractility affect ejection fraction?
How does increased contractility affect ejection fraction?
Signup and view all the answers
What is a common response of the body to physiologic stress in terms of cardiac function?
What is a common response of the body to physiologic stress in terms of cardiac function?
Signup and view all the answers
What effect do sympathomimetic drugs have on the heart?
What effect do sympathomimetic drugs have on the heart?
Signup and view all the answers
In heart failure, what happens to stroke volume?
In heart failure, what happens to stroke volume?
Signup and view all the answers
What is a major consequence of increased contractility on oxygen demand?
What is a major consequence of increased contractility on oxygen demand?
Signup and view all the answers
What mechanism is primarily responsible for reducing contractility during cardiac events?
What mechanism is primarily responsible for reducing contractility during cardiac events?
Signup and view all the answers
What is affected by aortic valve replacement in stenotic valves?
What is affected by aortic valve replacement in stenotic valves?
Signup and view all the answers
What is the relationship between stroke volume, end diastolic volume (EDV), and end systolic volume (ESV)?
What is the relationship between stroke volume, end diastolic volume (EDV), and end systolic volume (ESV)?
Signup and view all the answers
What physiological factor affects contractility during high levels of carbon dioxide in the blood?
What physiological factor affects contractility during high levels of carbon dioxide in the blood?
Signup and view all the answers
What is the outcome of increased heart rate with unchanged contractility, preload, and afterload?
What is the outcome of increased heart rate with unchanged contractility, preload, and afterload?
Signup and view all the answers
What effect does an increase in heart rate have on stroke volume under physiological conditions?
What effect does an increase in heart rate have on stroke volume under physiological conditions?
Signup and view all the answers
What primarily controls the relationship between heart rate and contractility?
What primarily controls the relationship between heart rate and contractility?
Signup and view all the answers
Under what conditions does a higher heart rate lead to reduced cardiac output?
Under what conditions does a higher heart rate lead to reduced cardiac output?
Signup and view all the answers
What happens to left ventricular filling time when the heart beats at pathological heart rates?
What happens to left ventricular filling time when the heart beats at pathological heart rates?
Signup and view all the answers
Which of the following represents the effect of stroke work related to heart physiology?
Which of the following represents the effect of stroke work related to heart physiology?
Signup and view all the answers
Why might a person experiencing ventricular tachycardia be at risk of losing consciousness?
Why might a person experiencing ventricular tachycardia be at risk of losing consciousness?
Signup and view all the answers
In what scenario does the relationship between cardiac output and heart rate appear linear?
In what scenario does the relationship between cardiac output and heart rate appear linear?
Signup and view all the answers
What physiological parameter reflects the demand placed upon the heart during increased activity?
What physiological parameter reflects the demand placed upon the heart during increased activity?
Signup and view all the answers
Why does elevated heart activity during exercise not reach pathological frequency levels?
Why does elevated heart activity during exercise not reach pathological frequency levels?
Signup and view all the answers
How does increased heart work relate to oxygen extraction in the blood?
How does increased heart work relate to oxygen extraction in the blood?
Signup and view all the answers
Which of the following correctly describes a consequence of higher afterload?
Which of the following correctly describes a consequence of higher afterload?
Signup and view all the answers
What situation exemplifies increased cardiac output at higher heart rates?
What situation exemplifies increased cardiac output at higher heart rates?
Signup and view all the answers
Which of the following best describes the relationship between oxygen extraction and heart workload?
Which of the following best describes the relationship between oxygen extraction and heart workload?
Signup and view all the answers
What is the primary reason cardiac output can decrease at high heart rates?
What is the primary reason cardiac output can decrease at high heart rates?
Signup and view all the answers
The amount of blood in the left ventricle at the end of diastole is called the end ______ volume.
The amount of blood in the left ventricle at the end of diastole is called the end ______ volume.
Signup and view all the answers
Systole is the phase when the left ventricle ______ and pushes blood out.
Systole is the phase when the left ventricle ______ and pushes blood out.
Signup and view all the answers
The smallest volume of blood the left ventricle holds during the cardiac cycle is called the end ______ volume.
The smallest volume of blood the left ventricle holds during the cardiac cycle is called the end ______ volume.
Signup and view all the answers
The left ventricle goes back and forth between the end diastolic volume and the end ______ volume.
The left ventricle goes back and forth between the end diastolic volume and the end ______ volume.
Signup and view all the answers
The amount of blood that the left ventricle can eject with each contraction is defined by the left ventricular ______ fraction.
The amount of blood that the left ventricle can eject with each contraction is defined by the left ventricular ______ fraction.
Signup and view all the answers
Diastole is the phase in which the left ventricle ______ with blood.
Diastole is the phase in which the left ventricle ______ with blood.
Signup and view all the answers
The cardiac cycle consists of alternating phases known as ______ and diastole.
The cardiac cycle consists of alternating phases known as ______ and diastole.
Signup and view all the answers
The maximum volume of blood in the left ventricle during the cardiac cycle is known as the end diastolic ______.
The maximum volume of blood in the left ventricle during the cardiac cycle is known as the end diastolic ______.
Signup and view all the answers
The sympathetic nervous system is the major controller of heart rate and ______.
The sympathetic nervous system is the major controller of heart rate and ______.
Signup and view all the answers
In real life, when heart rate increases, it is usually accompanied by an increase in ______.
In real life, when heart rate increases, it is usually accompanied by an increase in ______.
Signup and view all the answers
At pathologic heart rates, there is very short ______, leading to decreased filling time.
At pathologic heart rates, there is very short ______, leading to decreased filling time.
Signup and view all the answers
Ventricular tachycardia is an example of a condition where the heart rate can exceed ______ beats per minute.
Ventricular tachycardia is an example of a condition where the heart rate can exceed ______ beats per minute.
Signup and view all the answers
The amount of work the heart has to do is controlled by preload, afterload, ______, and heart rate.
The amount of work the heart has to do is controlled by preload, afterload, ______, and heart rate.
Signup and view all the answers
Stroke work is proportional to stroke volume times the mean ______.
Stroke work is proportional to stroke volume times the mean ______.
Signup and view all the answers
If the heart generates more stroke volume, that means there is more ______ work.
If the heart generates more stroke volume, that means there is more ______ work.
Signup and view all the answers
When the heart works harder, the blood that enters the coronary sinus has ______ oxygen.
When the heart works harder, the blood that enters the coronary sinus has ______ oxygen.
Signup and view all the answers
A rise in cardiac output when heart rate increases is primarily due to changes in ______ and contractility.
A rise in cardiac output when heart rate increases is primarily due to changes in ______ and contractility.
Signup and view all the answers
The only time a higher heart rate leads to a fall in cardiac output is at ______ heart rates.
The only time a higher heart rate leads to a fall in cardiac output is at ______ heart rates.
Signup and view all the answers
The classic example of a situation where the heart doesn't fill properly due to rapid beating is ______ tachycardia.
The classic example of a situation where the heart doesn't fill properly due to rapid beating is ______ tachycardia.
Signup and view all the answers
The relationship between cardiac output and heart rate has a linear increasing ______.
The relationship between cardiac output and heart rate has a linear increasing ______.
Signup and view all the answers
More oxygen is used when the work of the heart ______.
More oxygen is used when the work of the heart ______.
Signup and view all the answers
A higher heart rate leads to more cardiac output, which is essential during ______.
A higher heart rate leads to more cardiac output, which is essential during ______.
Signup and view all the answers
The heart's contractility can be represented by the ______ fraction.
The heart's contractility can be represented by the ______ fraction.
Signup and view all the answers
The main way to increase contractility in the human body is through the ______ nervous system.
The main way to increase contractility in the human body is through the ______ nervous system.
Signup and view all the answers
Patients with heart failure typically exhibit ______ contractility.
Patients with heart failure typically exhibit ______ contractility.
Signup and view all the answers
Ejection fraction is an index of ______.
Ejection fraction is an index of ______.
Signup and view all the answers
Drugs like dopamine and epinephrine are classified as ______ drugs.
Drugs like dopamine and epinephrine are classified as ______ drugs.
Signup and view all the answers
When contractility rises, there is a lower end systolic ______.
When contractility rises, there is a lower end systolic ______.
Signup and view all the answers
Increased heart rate can lead to a decrease in end diastolic ______.
Increased heart rate can lead to a decrease in end diastolic ______.
Signup and view all the answers
Calcium channel blockers, such as verapamil, are used to ______ contractility.
Calcium channel blockers, such as verapamil, are used to ______ contractility.
Signup and view all the answers
The heart's workload increases with higher heart ______.
The heart's workload increases with higher heart ______.
Signup and view all the answers
Conditions such as hypoxia and hypercapnia can ______ contractility.
Conditions such as hypoxia and hypercapnia can ______ contractility.
Signup and view all the answers
The sympathetic nervous system activates ______ receptors on heart muscle cells to increase contractility.
The sympathetic nervous system activates ______ receptors on heart muscle cells to increase contractility.
Signup and view all the answers
In patients exercising, high contractility results in a very high ______ fraction.
In patients exercising, high contractility results in a very high ______ fraction.
Signup and view all the answers
Myocytes release more calcium from the ______ reticulum to increase contractility.
Myocytes release more calcium from the ______ reticulum to increase contractility.
Signup and view all the answers
Drugs that block the sympathetic nervous system, like ______ blockers, lower contractility.
Drugs that block the sympathetic nervous system, like ______ blockers, lower contractility.
Signup and view all the answers
Physiological stress activates the sympathetic nervous system, leading to increased ______.
Physiological stress activates the sympathetic nervous system, leading to increased ______.
Signup and view all the answers
The left ventricular ______ fraction is the percentage of blood ejected with each squeeze of the chamber.
The left ventricular ______ fraction is the percentage of blood ejected with each squeeze of the chamber.
Signup and view all the answers
Stroke volume is calculated by subtracting the end systolic volume from the end ______ volume.
Stroke volume is calculated by subtracting the end systolic volume from the end ______ volume.
Signup and view all the answers
The volume of blood pushed out of the left ventricle during each cardiac cycle is called ______ output.
The volume of blood pushed out of the left ventricle during each cardiac cycle is called ______ output.
Signup and view all the answers
Total peripheral resistance (TPR) is the resistance to blood flow from ______ structures.
Total peripheral resistance (TPR) is the resistance to blood flow from ______ structures.
Signup and view all the answers
The difference between systolic and diastolic blood pressure is called ______ pressure.
The difference between systolic and diastolic blood pressure is called ______ pressure.
Signup and view all the answers
The lowest blood pressure in the central aorta is referred to as the ______ blood pressure.
The lowest blood pressure in the central aorta is referred to as the ______ blood pressure.
Signup and view all the answers
Vasoconstriction of arterioles tends to raise the total peripheral ______.
Vasoconstriction of arterioles tends to raise the total peripheral ______.
Signup and view all the answers
A normal left ventricular ejection fraction for a healthy heart is about ______% or 60%.
A normal left ventricular ejection fraction for a healthy heart is about ______% or 60%.
Signup and view all the answers
The major vessels that determine the total peripheral resistance are the ______.
The major vessels that determine the total peripheral resistance are the ______.
Signup and view all the answers
Mean arterial pressure (MAP) can be calculated using diastolic blood pressure plus one third of the ______ pressure.
Mean arterial pressure (MAP) can be calculated using diastolic blood pressure plus one third of the ______ pressure.
Signup and view all the answers
An important mechanism affecting diastolic pressure is the total ______ resistance.
An important mechanism affecting diastolic pressure is the total ______ resistance.
Signup and view all the answers
With each cardiac cycle, the amount of ______ returned to the left ventricle should equal the cardiac output.
With each cardiac cycle, the amount of ______ returned to the left ventricle should equal the cardiac output.
Signup and view all the answers
Patients with heart failure tend to have a very low stroke volume and a very low ______ pressure.
Patients with heart failure tend to have a very low stroke volume and a very low ______ pressure.
Signup and view all the answers
As blood leaves the left ventricle, it drives up the blood pressure in the central ______.
As blood leaves the left ventricle, it drives up the blood pressure in the central ______.
Signup and view all the answers
The formula for determining the mean arterial pressure involves adding 80 plus one third of the difference of ______.
The formula for determining the mean arterial pressure involves adding 80 plus one third of the difference of ______.
Signup and view all the answers
Cardiac output is equal to the heart rate times the ______.
Cardiac output is equal to the heart rate times the ______.
Signup and view all the answers
An increase in heart rate means more ______ for the heart.
An increase in heart rate means more ______ for the heart.
Signup and view all the answers
The four determinants of cardiac output are preload, afterload, ______, and heart rate.
The four determinants of cardiac output are preload, afterload, ______, and heart rate.
Signup and view all the answers
Preload refers to the volume of blood that fills the left ventricle during ______.
Preload refers to the volume of blood that fills the left ventricle during ______.
Signup and view all the answers
An increase in preload leads to an increase in ______, and subsequently, cardiac output.
An increase in preload leads to an increase in ______, and subsequently, cardiac output.
Signup and view all the answers
One way to increase preload is to infuse a unit of ______ into a patient.
One way to increase preload is to infuse a unit of ______ into a patient.
Signup and view all the answers
Constricting veins can push more blood back into the heart and increase ______.
Constricting veins can push more blood back into the heart and increase ______.
Signup and view all the answers
When the heart rate slows, it allows for more filling of the left ventricle, which results in increased ______.
When the heart rate slows, it allows for more filling of the left ventricle, which results in increased ______.
Signup and view all the answers
The degree of stretch on the myocardial fibers before contraction is referred to as ______.
The degree of stretch on the myocardial fibers before contraction is referred to as ______.
Signup and view all the answers
Increased preload raises the end diastolic ______ returning to the left ventricle.
Increased preload raises the end diastolic ______ returning to the left ventricle.
Signup and view all the answers
During exercise, the body naturally responds by increasing cardiac ______.
During exercise, the body naturally responds by increasing cardiac ______.
Signup and view all the answers
Any time there's more preload in the left ventricle, it generates more cardiac ______.
Any time there's more preload in the left ventricle, it generates more cardiac ______.
Signup and view all the answers
The sympathetic nervous system causes vein ______ as a response to blood loss.
The sympathetic nervous system causes vein ______ as a response to blood loss.
Signup and view all the answers
Venous tone determines how much ______ will be pushed out of the venous system and into the heart.
Venous tone determines how much ______ will be pushed out of the venous system and into the heart.
Signup and view all the answers
Pooling blood in the veins is the mechanism of action of ______ drugs like nitroglycerin.
Pooling blood in the veins is the mechanism of action of ______ drugs like nitroglycerin.
Signup and view all the answers
When preload decreases, there is less work for the ______.
When preload decreases, there is less work for the ______.
Signup and view all the answers
The LVEDV is the volume of blood in the left ventricle when it has completed filling at the end of ______.
The LVEDV is the volume of blood in the left ventricle when it has completed filling at the end of ______.
Signup and view all the answers
Afterload refers to forces that resist the flow of blood out of the left ______.
Afterload refers to forces that resist the flow of blood out of the left ______.
Signup and view all the answers
If the aortic valve is ______, it can generate high afterload making it hard for blood to exit the left ventricle.
If the aortic valve is ______, it can generate high afterload making it hard for blood to exit the left ventricle.
Signup and view all the answers
Chronically high afterload can lead to hypertrophy of the left ______.
Chronically high afterload can lead to hypertrophy of the left ______.
Signup and view all the answers
When afterload increases, stroke ______ tends to decrease.
When afterload increases, stroke ______ tends to decrease.
Signup and view all the answers
One way to increase afterload is if the mean blood ______ goes up.
One way to increase afterload is if the mean blood ______ goes up.
Signup and view all the answers
Obstruction to outflow from the left ventricle can also significantly increase ______.
Obstruction to outflow from the left ventricle can also significantly increase ______.
Signup and view all the answers
In cases of dehydration, patients will experience low LVEDV and low ______.
In cases of dehydration, patients will experience low LVEDV and low ______.
Signup and view all the answers
More afterload results in the heart requiring more ______ to push blood out to the body.
More afterload results in the heart requiring more ______ to push blood out to the body.
Signup and view all the answers
Drugs that lower blood pressure help to ______ afterload.
Drugs that lower blood pressure help to ______ afterload.
Signup and view all the answers
The terms LVEDV and LVEDP are critical markers of ______.
The terms LVEDV and LVEDP are critical markers of ______.
Signup and view all the answers
Study Notes
Cardiac Cycle Volumes and Ejection Fraction
- End Diastolic Volume (EDV): Maximum volume of blood in the left ventricle during filling (diastole).
- End Systolic Volume (ESV): Minimum volume of blood in the left ventricle after contraction (systole).
- Left Ventricular Ejection Fraction (LVEF): Percentage of blood ejected from the left ventricle with each contraction. Calculated as [(EDV - ESV) / EDV] * 100. Normal range is approximately 55-60%.
Stroke Volume and Cardiac Output
- Stroke Volume (SV): Volume of blood ejected from the left ventricle per heartbeat. Calculated as EDV - ESV.
- Cardiac Output (CO): Volume of blood pumped by the heart per minute. Calculated as SV x Heart Rate.
- Venous Return: Blood returning to the heart; should equal cardiac output.
- Total Peripheral Resistance (TPR) / Systemic Vascular Resistance (SVR): Resistance to blood flow in the peripheral vessels, mainly determined by arteriolar constriction/dilation.
Blood Pressure
- Systolic Blood Pressure: Highest pressure in the central aorta during ventricular contraction. Largely determined by stroke volume.
- Diastolic Blood Pressure: Lowest pressure in the central aorta during ventricular relaxation. Largely determined by total peripheral resistance.
- Pulse Pressure: Difference between systolic and diastolic pressure (systolic - diastolic). Proportional to stroke volume.
- Mean Arterial Pressure (MAP): Average pressure in the arterial system over a cardiac cycle. Calculated as diastolic pressure + [1/3 * (systolic – diastolic)].
Determinants of Cardiac Output
-
Preload: Volume of blood in the left ventricle at the end of diastole, stretching the myocardial fibers. Increased preload = increased EDV = increased SV = increased CO. Increased preload requires more heart work and oxygen.
- Increased preload causes: Increased intravascular volume, venous constriction, slower heart rate.
- Decreased preload causes: Blood loss, dehydration, nitrate drugs (dilate veins).
-
Afterload: Forces opposing blood ejection out of the left ventricle. Increased afterload = increased ESV = decreased SV = decreased CO. Increased afterload requires more work and oxygen use.
- Increased afterload causes: High blood pressure, aortic stenosis, hypertrophic cardiomyopathy.
- Decreased afterload causes: Lowering blood pressure, treating aortic stenosis or hypertrophic cardiomyopathy
-
Contractility: Strength of ventricular contraction. Increased contractility = decreased ESV = increased SV = increased CO. Increased contractility requires more work and oxygen.
- Increased contractility caused by: Sympathetic nervous system (beta 1 receptors), sympathomimetic drugs like dobutamine, epinephrine, digoxin.
- Decreased contractility caused by: Beta blockers, calcium channel blockers, hypoxia, acidosis.
- Heart Rate: Number of heartbeats per minute. Increased heart rate = potentially increased CO, especially in the physiological range. Increased heart rate in isolation, without change in other parameters, decreases EDV and thereby SV at very high rates, leading to decreased CO.
Heart Rate and Cardiac Output Relationship
- Physiological heart rates increase cardiac output by increasing both heart rate and contractility.
- Pathological heart rates (e.g., >250 bpm) decrease cardiac output due to insufficient filling time in diastole.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Test your knowledge on the cardiac cycle, including important concepts such as End Diastolic Volume, End Systolic Volume, and Left Ventricular Ejection Fraction. Understand stroke volume and cardiac output, as well as the factors that affect venous return and vascular resistance. This quiz will help reinforce your understanding of cardiovascular physiology.
