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Questions and Answers
What is the resting adult heart rate typically around?
What is the resting adult heart rate typically around?
Which of the following conditions is associated with a heart rate of less than 60 beats per minute?
Which of the following conditions is associated with a heart rate of less than 60 beats per minute?
Which component of the autonomic nervous system increases the heart rate by stimulating the sino-atrial node?
Which component of the autonomic nervous system increases the heart rate by stimulating the sino-atrial node?
What physiological change is NOT likely to increase cardiac output (C.O.)?
What physiological change is NOT likely to increase cardiac output (C.O.)?
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What effect does hyperthyroidism have on the heart rate?
What effect does hyperthyroidism have on the heart rate?
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Which of the following factors will lead to an increase in cardiac output (C.O.P)?
Which of the following factors will lead to an increase in cardiac output (C.O.P)?
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What effect does an increase in arterial blood pressure (ABP) have on cardiac output?
What effect does an increase in arterial blood pressure (ABP) have on cardiac output?
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Which statement accurately describes the role of the muscle pump in relation to venous return?
Which statement accurately describes the role of the muscle pump in relation to venous return?
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How does an increase in body temperature affect heart rate and cardiac output?
How does an increase in body temperature affect heart rate and cardiac output?
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According to Starling's law, what is the relationship between the length of ventricular muscle fibers and force of contraction?
According to Starling's law, what is the relationship between the length of ventricular muscle fibers and force of contraction?
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Which of the following scenarios can lead to decreased venous return?
Which of the following scenarios can lead to decreased venous return?
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What is the resting heart rate of an adult typically classified as?
What is the resting heart rate of an adult typically classified as?
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How does extreme cardiac output change in relation to changes in heart rate?
How does extreme cardiac output change in relation to changes in heart rate?
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What is the primary function of the SA node in the heart's electrical activity?
What is the primary function of the SA node in the heart's electrical activity?
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During which phase of the cardiac cycle does the end diastolic volume occur?
During which phase of the cardiac cycle does the end diastolic volume occur?
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What does stroke volume represent?
What does stroke volume represent?
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Which equation correctly calculates cardiac output?
Which equation correctly calculates cardiac output?
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What factor does NOT directly affect cardiac output?
What factor does NOT directly affect cardiac output?
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Which of the following best describes end systolic volume?
Which of the following best describes end systolic volume?
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What is the normal stroke volume value provided in the content?
What is the normal stroke volume value provided in the content?
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Which statement regarding atrial repolarization is true?
Which statement regarding atrial repolarization is true?
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What is the duration of one cardiac cycle at a heart rate of 70 beats per minute?
What is the duration of one cardiac cycle at a heart rate of 70 beats per minute?
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During which phase of the cardiac cycle are the A-V valves (mitral and tricuspid) closed?
During which phase of the cardiac cycle are the A-V valves (mitral and tricuspid) closed?
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What occurs during ventricular systole?
What occurs during ventricular systole?
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What is the sound associated with the closure of the aortic and pulmonary valves during ventricular diastole?
What is the sound associated with the closure of the aortic and pulmonary valves during ventricular diastole?
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Which phase represents the filling of the ventricles?
Which phase represents the filling of the ventricles?
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Which of the following statements about the cardiac cycle is correct?
Which of the following statements about the cardiac cycle is correct?
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What is the sound produced during the closure of the A-V valves?
What is the sound produced during the closure of the A-V valves?
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Which of the following correctly describes the relationship between systole and diastole?
Which of the following correctly describes the relationship between systole and diastole?
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Study Notes
Cardiovascular System - Cardiac Cycle
- The cardiac cycle encompasses events from the start of one heartbeat to the next.
- A normal heart rate of 70 beats per minute results in a 0.8-second cardiac cycle.
- During the cycle, heart chamber muscles either contract (systole) or relax (diastole).
- Systole is the contraction phase, pushing blood out of the chamber.
- Diastole is the relaxation phase, allowing the chamber to fill with blood.
Events of the Cardiac Cycle
- Atrial systole (0.1 sec): Atria contract, pushing blood into the ventricles.
- Ventricular systole (0.3 sec): Ventricles contract, pushing blood out of the heart into the arteries. Associated with closure of AV valves (lub sound) and opening of semilunar valves.
- Complete diastole (0.4 sec): Both atria and ventricles relax, preparing to receive blood.
- Ventricular diastole (0.5 sec): Ventricles relax, allowing them to fill with blood. Associated with closure of semilunar valves (dup sound) and opening of AV valves.
- Atrial diastole (0.7 sec): Atria relax, allowing them to fill with blood.
Heart Sounds
- First heart sound (Lub): Loud sound, due to closure of the AV valves (mitral and tricuspid) during ventricular systole.
- Second heart sound (Dup): Softer sound, due to closure of the semilunar valves (aortic and pulmonary) during ventricular diastole.
Electrical Changes in the Heart (ECG)
- Electrical events in the heart are recorded as an ECG.
- P wave: Atrial depolarization.
- QRS complex: Ventricular depolarization.
- T wave: Ventricular repolarization.
- Atrial repolarization occurs during ventricular depolarization and is masked by the larger QRS complex.
Volume Changes During the Cardiac Cycle
- End-diastolic volume (EDV): The volume of blood in the ventricle at the end of diastole (approximately 110-140 ml).
- End-systolic volume (ESV): The volume of blood in the ventricle at the end of systole (approximately 40-70 ml).
Stroke Volume
- Stroke volume is the volume of blood ejected by each ventricle per beat.
- Normal stroke volume is 70 ml.
- Stroke volume calculates as the difference between end-diastolic volume and end-systolic volume.
Cardiac Output (COP)
- Cardiac output is the volume of blood ejected by each ventricle per minute.
- Normal cardiac output is 5 Liters per minute.
- Cardiac output is calculated as stroke volume multiplied by heart rate.
Factors Affecting Cardiac Output (COP)
- Venous return: The amount of blood returning to the heart. Increasing venous return increases COP.
- Force of contraction: The strength of ventricular contraction. Increased force increases COP.
- Heart rate: The speed of heartbeats. Increasing heart rate increases COP to a certain limit (when it starts to reduce ventricular filling).
- Arterial blood pressure (ABP): Increased blood pressure decreases COP.
Physiological Variations in COP
- Exercise, pregnancy, emotions, and food intake can increase COP.
Pathological Variations in COP
- Increased COP: Anemia, fever, hyperthyroidism, and adrenaline increase COP to compensate for issues.
- Decreased COP: Hemorrhage, aortic stenosis, ischemic heart disease, and heart failure can decrease COP.
Control of Heart Rate
- Resting adult heart rate is approximately 70 beats/min.
- Heart rate is controlled by the autonomic nervous system.
- Sympathetic nervous system: Increases heart rate.
- Parasympathetic nervous system: Decreases heart rate.
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Description
Explore the stages of the cardiac cycle, including atrial and ventricular systole and diastole. Understand how the heart's chambers contract and relax to maintain blood flow. This quiz covers the events and timing associated with a normal heart rate.
