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Questions and Answers
What causes the brief rise in aortic pressure during the cardiac cycle?
What causes the brief rise in aortic pressure during the cardiac cycle?
Which part of the nervous system stimulates the heart rate?
Which part of the nervous system stimulates the heart rate?
What do heart sounds 'lub-dub' indicate?
What do heart sounds 'lub-dub' indicate?
How is cardiac output (CO) calculated?
How is cardiac output (CO) calculated?
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What does cardiac reserve indicate?
What does cardiac reserve indicate?
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What initiates the heartbeat by generating impulses at a rate of about 75 times per minute?
What initiates the heartbeat by generating impulses at a rate of about 75 times per minute?
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Which component of the electrocardiogram (EKG) corresponds to the depolarization of the ventricles?
Which component of the electrocardiogram (EKG) corresponds to the depolarization of the ventricles?
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During which phase of the cardiac cycle do the ventricles relax and the semilunar valves close due to backflow of blood?
During which phase of the cardiac cycle do the ventricles relax and the semilunar valves close due to backflow of blood?
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What occurs during atrial systole in the cardiac cycle?
What occurs during atrial systole in the cardiac cycle?
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Which part of the cardiac conduction system delays the impulse transmission to allow time for atrial contraction?
Which part of the cardiac conduction system delays the impulse transmission to allow time for atrial contraction?
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What is the correct order of cardiac cycle phases starting from relaxation to contraction of the heart?
What is the correct order of cardiac cycle phases starting from relaxation to contraction of the heart?
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Which structure carries the impulse from the AV bundle toward the apex of the heart?
Which structure carries the impulse from the AV bundle toward the apex of the heart?
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What is the effect of rising ventricular pressure during ventricular systole?
What is the effect of rising ventricular pressure during ventricular systole?
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Study Notes
Heart Physiology: Sequence of Excitation
- The sinoatrial (SA) node generates impulses 75 times per minute
- The atrioventricular (AV) node delays the impulse approximately 0.1 second
- The impulse travels from the atria to the ventricles through the atrioventricular bundle (bundle of His)
- This bundle splits into two pathways within the interventricular septum (bundle branches)
- Bundle branches carry the impulse towards the apex of the heart
- Purkinje fibers transport the impulse to the heart apex and ventricular walls
Electrocardiography
- An electrocardiogram (ECG or EKG) records electrical activity
- The P wave reflects depolarization of the SA node
- The QRS complex corresponds to ventricular depolarization
- The T wave signifies ventricular repolarization
- Atrial repolarization is obscured by the larger QRS complex
Cardiac Cycle
- The cardiac cycle encompasses all events associated with blood flow through the heart
- Systole refers to the contraction of heart muscle
- Diastole refers to the relaxation of heart muscle
Phases of the Cardiac Cycle
-
Ventricular Filling: Occurs during mid-to-late diastole
- Blood pressure in the heart is low as blood enters the atria and flows into the ventricles
- AV valves are open, followed by atrial systole
-
Ventricular Systole:
- Atria relax
- Increased ventricular pressure leads to the closing of AV valves
- Isovolumetric contraction phase: Ventricles contract, but no blood ejection occurs
- Ventricular ejection phase: Semilunar valves open, allowing blood to flow out of the ventricles
-
Isovolumetric relaxation: Early diastole
- Ventricles relax
- Blood flow back into the aorta and pulmonary trunk closes the semilunar valves
- Dicrotic notch: A brief rise in aortic pressure caused by blood rebounding off the closed semilunar valves
Extrinsic Innervation of the Heart
- The heart is stimulated by the sympathetic cardioacceleratory center
- The heart is inhibited by the parasympathetic cardioinhibitory center
Heart Sounds
- Heart sounds (lub-dup) are produced by the closing of heart valves
Cardiac Output (CO) and Reserve
- CO is the amount of blood pumped by each ventricle per minute
- CO is calculated as the product of heart rate (HR) and stroke volume (SV)
- HR represents heart beats per minute
- SV refers to the amount of blood pumped out by a ventricle with each beat
- Cardiac reserve is the difference between resting and maximal CO
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Description
Test your understanding of heart physiology, including the sequence of excitation in cardiac tissues and the basics of electrocardiography. This quiz covers key concepts like the sinoatrial node's function, the cardiac cycle, and the interpretation of ECG waves. Perfect for students of cardiovascular biology and medicine.
