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Questions and Answers
What initiates the process of ventricular systole?
What initiates the process of ventricular systole?
What happens during the diastole phase of the cardiac cycle?
What happens during the diastole phase of the cardiac cycle?
What happens to the residual volume as the force of contraction increases?
What happens to the residual volume as the force of contraction increases?
What effect does a lower resting heart rate in trained athletes have on cardiac output during exercise?
What effect does a lower resting heart rate in trained athletes have on cardiac output during exercise?
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When does aortic valve closure occur in relation to left ventricular pressure?
When does aortic valve closure occur in relation to left ventricular pressure?
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During isovolumetric relaxation, what happens to the atrial pressure?
During isovolumetric relaxation, what happens to the atrial pressure?
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What is the relationship between heart rate and end-diastolic volume?
What is the relationship between heart rate and end-diastolic volume?
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Which phase occurs first during the ventricular systole process?
Which phase occurs first during the ventricular systole process?
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What causes the closure of the sigmoid valves?
What causes the closure of the sigmoid valves?
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What characterizes prolonged tachycardia?
What characterizes prolonged tachycardia?
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What does the aortic pressure rebound indicate about the aorta?
What does the aortic pressure rebound indicate about the aorta?
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What occurs during iso-volumetric relaxation?
What occurs during iso-volumetric relaxation?
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How do cardiac pressures vary during the cardiac cycle?
How do cardiac pressures vary during the cardiac cycle?
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What condition produces the dicrotic wave seen in aortic pressure?
What condition produces the dicrotic wave seen in aortic pressure?
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What primarily regulates the SV/DV variation?
What primarily regulates the SV/DV variation?
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What characterizes the pulmonary pressure curve compared to the aortic pressure curve?
What characterizes the pulmonary pressure curve compared to the aortic pressure curve?
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What heart sound is produced by the closure of the A-V valves?
What heart sound is produced by the closure of the A-V valves?
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Which of the following heart sounds is not audible through auscultation?
Which of the following heart sounds is not audible through auscultation?
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What is the primary cause of cardiac work (W) as described in the content?
What is the primary cause of cardiac work (W) as described in the content?
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During which condition does cardiac output increase significantly?
During which condition does cardiac output increase significantly?
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What does the term 'pre-load' refer to in the context of cardiac physiology?
What does the term 'pre-load' refer to in the context of cardiac physiology?
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What is a characteristic feature of heart murmurs?
What is a characteristic feature of heart murmurs?
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What physiological event generates the B2 heart sound?
What physiological event generates the B2 heart sound?
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What does the Frank-Starling mechanism indicate about the relationship between cardiac muscle fiber length and contraction force?
What does the Frank-Starling mechanism indicate about the relationship between cardiac muscle fiber length and contraction force?
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What is the formula for Stroke Volume (SV)?
What is the formula for Stroke Volume (SV)?
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Which factor does NOT directly affect end systolic volume (ESV)?
Which factor does NOT directly affect end systolic volume (ESV)?
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During which physiological condition is cardiac output (Qc) expected to increase the most?
During which physiological condition is cardiac output (Qc) expected to increase the most?
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What relationship exists between preload (VTD) and contractility in terms of intracellular Ca2+ availability?
What relationship exists between preload (VTD) and contractility in terms of intracellular Ca2+ availability?
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What is the normal cardiac output (Qc) for an adult male at rest?
What is the normal cardiac output (Qc) for an adult male at rest?
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Which statement accurately describes the role of afterload in cardiac function?
Which statement accurately describes the role of afterload in cardiac function?
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What does the cardiac index measure?
What does the cardiac index measure?
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Which condition is NOT a cause of low cardiac output of cardiac origin?
Which condition is NOT a cause of low cardiac output of cardiac origin?
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What is primarily measured using the Fick method?
What is primarily measured using the Fick method?
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Which factor is responsible for high cardiac output in cases of anemia?
Which factor is responsible for high cardiac output in cases of anemia?
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What does the term 'arterio-venous difference' refer to in the context of the Fick method?
What does the term 'arterio-venous difference' refer to in the context of the Fick method?
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What is a disadvantage of the Echo-Doppler method for measuring cardiac output?
What is a disadvantage of the Echo-Doppler method for measuring cardiac output?
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What is the principle behind thermodilution as a method for measuring cardiac output?
What is the principle behind thermodilution as a method for measuring cardiac output?
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Which of the following substances is commonly used for dilution indicators in cardiac output measurement?
Which of the following substances is commonly used for dilution indicators in cardiac output measurement?
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In acute venous vasodilatation leading to low cardiac output, what is primarily affected?
In acute venous vasodilatation leading to low cardiac output, what is primarily affected?
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Study Notes
Cardiac Revolution Overview
- The heart functions as a pump through two phases: systole (contraction) and diastole (relaxation).
- A cardiac cycle consists of electrical and mechanical phenomena.
- Systole: Involves the contraction of ventricles and ejection of blood.
- Diastole: Involves relaxation and filling of the ventricles.
- The cardiac revolution is the time between successive heart contractions.
- Under normal heart rates, ventricular diastole lasts longer than ventricular systole.
- Flow increases with increasing heart rate, peaking at a maximum age-dependent frequency (220 - age).
- Trained athletes adapt better to exercise with lowered resting heart rates.
Ventricular Systole
- Initiates with closure of the atrioventricular (A-V) valves.
- Comprises two parts:
- Iso-volumetric contraction: Ventricles contract without changing volume.
- Systolic ejection: Blood is expelled into the aorta and pulmonary artery, concluding when the sigmoid valves close.
Ventricular and General Diastole
- Begins with the closure of the sigmoid valves; consists of four stages:
- Iso-volumetric relaxation: Valves closed, cardiac muscle relaxes, and residual volume is impacted by contraction strength.
- Aortic valve closes when left ventricular (LV) pressure falls below aortic pressure (approximately 80 mmHg).
- During this phase, mitral atrial pressure rises due to venous return.
Cardiac Pressures
- There is variability in cardiac pressures throughout the cycle:
- Systolic pressure in ventricles and aorta reach approximately 120 mmHg during contraction.
- Diastolic pressure in the aorta ranges between 70-80 mmHg.
Heart Sounds
- Heart sounds are detected via auscultation; produced by valve closures.
-
Audible Sounds:
- B1: Closure of A-V valves.
- B2: Closure of sigmoid valves.
-
Non-audible Sounds:
- B3: Rapid ventricular filling.
- B4: Atrial contraction.
- Abnormal heart sounds could indicate valve lesions, such as aortic insufficiency.
Cardiac Work and Function
- Cardiac work is the energy used for blood ejection per heartbeat.
- Defined as: Cardiac Work (W) = Pressure Difference (PD) × Volume Difference (VD).
- The heart has limited energy reserves, but can efficiently use various substrates, such as fatty acids and lactates.
Preload and Afterload
- Preload: Muscle tension at the start of contraction, dependent on LV blood volume at diastole.
- Afterload: Load the heart must overcome for contraction, correlated with systolic pressure in the aorta.
Frank-Starling Mechanism
- Suggests contraction energy relates to the initial length of cardiac muscle fibers.
- Increased venous return enhances filling and subsequently increases ejection volume (VES).
Cardiac Output (Qc)
- Defined as the volume of blood ejected by the ventricle per minute (average 5-6 l/min in adults).
- Regulated according to body needs, adaptable during physiologic changes:
- Increases significantly during pregnancy, stress, or physical exercise.
Measurement of Cardiac Output
- Fick Principle: Measures oxygen consumption related to arteriovenous oxygen difference and cardiac output.
- Other methods include:
- Echo-Doppler: Common but less precise.
- Thermodilution: Utilizes temperature change for cardiac output estimation.
Clinical Relevance
- Low cardiac output can result from conditions like myocardial infarction or hypovolemia.
- High cardiac output may occur in anemia or reduced afterload conditions.
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Description
Explore the mechanisms of the cardiac revolution, which includes the phases of systole and diastole. Understand the dynamics of the cardiac cycle as it relates to heart contractions, blood ejection, and the significant differences in duration between systole and diastole. Learn how heart rates affect these phases, especially in trained athletes.
