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Questions and Answers
Which component of blood pressure is directly associated with the contraction of the heart?
What is primarily responsible for the pressure wave felt as a pulse in the arterial system?
Which of the following statements about Korotkoff sounds is correct?
Which of the following factors can contribute to abnormal findings in pulse palpation?
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During which phase of the cardiac cycle is the left ventricle primarily responsible for pumping oxygenated blood into the systemic circulation?
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What condition is characterized by insufficient oxygen supply to the heart leading to chest pain?
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Which structure in the heart is primarily responsible for setting the basic rhythm of heartbeats?
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What occurs in the heart during a myocardial infarction?
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Which phase of the cardiac cycle allows unoxygenated blood to flow back to the heart?
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In the intrinsic conduction system, what is the function of the Bundle of His?
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Which heart sound is typically associated with the closure of the AV valves?
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What is a common consequence of a total blockage in blood flow to the heart?
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Which component of the heart's conduction system can take over if the Sinoatrial Node fails?
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What is the primary factor influencing the stroke volume according to Starling's law of the heart?
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Which heart sound is characterized by a long and loud sound due to the closure of the atrioventricular valves?
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During which phase of the cardiac cycle do the atria and ventricles contract and then relax?
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What does a healthy heart typically pump out in terms of percentage of blood present in its ventricles?
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Which of the following best describes the second heart sound (S2)?
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Which of the following best defines tachycardia?
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Which heart valve closure contributes to the S1 heart sound?
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What is indicated by a 'thrill' during a cardiac examination?
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Study Notes
Cardiac Cycle and Sounds
- Repolarization is the reverse of depolarization; the last cells to depolarize are the first to repolarize.
- Depolarization is associated with contraction, systole, and the sound "lub".
- Repolarization is associated with relaxation, diastole, and the sound "dub".
- The cardiac cycle is one complete heartbeat, including contraction and relaxation of the atria and ventricles.
- The average heartbeat is 75 beats per minute, with a range of 60 to 100.
- A slow heartbeat (less than 60 beats per minute) is bradycardia.
- A fast heartbeat (more than 100 beats per minute) is tachycardia.
Heart Sounds
- The first heart sound (S1, Lub) is caused by the closure of the atrioventricular valves (tricuspid and mitral valves).
- The second heart sound (S2, Dup) is caused by the closure of the semilunar valves (pulmonic and aortic valves).
- S1 is longer and louder than S2.
- The diaphragm of the stethoscope is best for listening to higher-pitched sounds, like breath sounds and normal heart sounds.
- The bell of the stethoscope is best for listening to lower-pitched sounds, like murmurs.
Cardiac Valves and Locations
- The pulmonary valve is best heard in the 2nd intercostal space (ICS) just left of the sternum.
- The aortic valve is best heard in the 2nd ICS just right of the sternum.
- The tricuspid valve is best heard in the 5th ICS, left of the sternum.
- The mitral valve is best heard at the point of maximum impulse, the apical pulse, in the 5th ICS, left midclavicular line.
Cardiac Output
- A healthy heart pumps out about 60% of the blood present in its ventricles with each beat.
- Stroke volume, the amount of blood pumped by each ventricle per beat, is a crucial factor in cardiac output.
- The normal stroke volume is 70 ml/beat, with a range of 50 to 100 ml/beat.
Starling’s Law of the Heart
- The amount of stretch of the cardiac muscle cells just before contraction directly affects stroke volume.
- Venous return, the amount of blood returning to the heart, is a key factor in stretching (preload) the heart muscle.
Pulse
- The pulse is a pressure wave that travels through the arterial system due to each contraction of the left ventricle.
- This pressure wave results from the alternating expansion and recoil of arteries.
- Normal pulse findings include a rate of 60 to 100 beats/minute, a strong, not weak, and bounding pulse, a regular rhythm, symmetry of right and left pulses, and warm to touch.
Blood Pressure
- Blood pressure is the force exerted by blood against the inner walls of the arteries.
- Blood pressure keeps blood circulating continuously, even between heartbeats.
- Normal blood pressure is 120/80 mmHg (systolic/diastolic).
- Systolic pressure is the pressure measured during ventricular contraction.
- Diastolic pressure is the pressure measured during ventricular relaxation.
Korotkoff Sounds
- The first soft tapping sounds heard when taking blood pressure indicate the systolic pressure.
- As the pressure is reduced, the sounds become louder.
- The disappearance of Korotkoff sounds signals the diastolic pressure.
Blood Flow in and Out of the Heart
- The cardiac arteries transport oxygenated blood from the aorta to the heart muscle.
- The cardiac veins carry deoxygenated blood from the heart muscle back to the vena cava, completing the circulatory cycle.
Arterial Blood Flow Problems
- Angina pectoris is insufficient oxygen supply to the heart, resulting in crushing chest pain. It may be caused by a narrowing of a blood vessel, restricting blood flow.
- Myocardial infarction is a heart attack, caused by a complete blockage in the blood flow to the heart muscle, often due to a clot. This leads to oxygen deprivation and cell death.
What Makes the Heart Beat?
- The nervous system (sympathetic and parasympathetic) regulates heart rate. These nerves act as "gas pedals" and "brakes", increasing or decreasing heart rate as needed.
- The intrinsic conduction system or the nodal system is a system of specialized cells within the heart muscle responsible for initiating and conducting electrical impulses.
Intrinsic Conduction System
- The intrinsic conduction system sets the basic rhythm for the heart.
- Electrical impulses travel from the atria to the ventricles in a specific sequence.
- This system enables the heart to beat autonomously.
Sinoatrial (SA) Node
- The SA node is located at the junction of the superior vena cava and right atrium.
- It is the pacemaker of the heart, generating electrical impulses at a rate of 60 to 100 times per minute.
- The SA node is regulated by the sympathetic and parasympathetic nervous systems.
Atrioventricular (AV) Node
- The AV node is located in the lower aspect of the atrial septum.
- It receives electrical impulses from the SA node.
Bundle of His
- The Bundle of His is a specialized pathway that fuses with the AV node to form a secondary pacemaker site.
- If the SA node fails, the Bundle of His can initiate and sustain a heart rate of 40 to 60 beats per minute.
Purkinje Fibers
- Purkinje fibers are a network of conducting strands that spread beneath the ventricular endocardium.
- They rapidly transmit the wave of depolarization through the ventricles.
- Ventricular activation begins in the septum and moves from apex upward.
- Depolarization within the ventricular walls proceeds from endocardium to epicardium.
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Description
Explore the intricate details of the cardiac cycle, including depolarization, repolarization, and the sounds associated with each phase. Learn about normal heart rates, bradycardia, tachycardia, and how to listen to heart sounds using a stethoscope. Test your understanding of these crucial concepts in cardiovascular physiology.
