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Questions and Answers
What is the primary role of the SA node in the cardiac conduction system?
What is the primary role of the SA node in the cardiac conduction system?
Which structure is responsible for transmitting impulses from the atria to the ventricles?
Which structure is responsible for transmitting impulses from the atria to the ventricles?
What is the primary function of the SA node in the heart?
What is the primary function of the SA node in the heart?
What is the function of the AV node in the cardiac conduction system?
What is the function of the AV node in the cardiac conduction system?
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Which pathway connects the SA node to the AV node?
Which pathway connects the SA node to the AV node?
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What role do Purkinje fibers play in the cardiac conduction system?
What role do Purkinje fibers play in the cardiac conduction system?
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Which of the following pathways is responsible for the fastest conduction of electrical impulses in the heart?
Which of the following pathways is responsible for the fastest conduction of electrical impulses in the heart?
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What structure divides into right and left bundle branches after signals leave the AV node?
What structure divides into right and left bundle branches after signals leave the AV node?
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When does contraction of the ventricles generally begin during the cardiac cycle?
When does contraction of the ventricles generally begin during the cardiac cycle?
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How does the autonomic nervous system affect heart rate?
How does the autonomic nervous system affect heart rate?
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What initiates the electrical impulse that causes contraction in cardiac muscle fibers?
What initiates the electrical impulse that causes contraction in cardiac muscle fibers?
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What role do specialized cardiac muscle cells play in the heart?
What role do specialized cardiac muscle cells play in the heart?
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Which part of the heart's conduction system is located near the opening of the coronary sinus?
Which part of the heart's conduction system is located near the opening of the coronary sinus?
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Which structure ensures that the heart chambers contract in a coordinated manner?
Which structure ensures that the heart chambers contract in a coordinated manner?
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Which fiber network provides the final signal to the ventricular myocardium for contraction?
Which fiber network provides the final signal to the ventricular myocardium for contraction?
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What is the resting rate of the SA node?
What is the resting rate of the SA node?
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What is the primary function of the sinoatrial (SA) node in the heart?
What is the primary function of the sinoatrial (SA) node in the heart?
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Which structure is primarily responsible for conducting electrical signals from the atria to the ventricles?
Which structure is primarily responsible for conducting electrical signals from the atria to the ventricles?
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In the cardiac conduction system, what is the role of the Bundle of His?
In the cardiac conduction system, what is the role of the Bundle of His?
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What role does cardiac innervation play in heart function?
What role does cardiac innervation play in heart function?
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How is myocardial perfusion affected during the cardiac cycle?
How is myocardial perfusion affected during the cardiac cycle?
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What percentage of oxygen is extracted by the heart muscle from each unit of blood at rest?
What percentage of oxygen is extracted by the heart muscle from each unit of blood at rest?
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Where does the electrical conduction pathway start within the heart?
Where does the electrical conduction pathway start within the heart?
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What is the primary role of the Purkinje fibers in the heart?
What is the primary role of the Purkinje fibers in the heart?
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What are the main coronary arteries supplying blood to the heart?
What are the main coronary arteries supplying blood to the heart?
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During which phase of the cardiac cycle does myocardial perfusion primarily occur?
During which phase of the cardiac cycle does myocardial perfusion primarily occur?
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What percentage of oxygen does the heart extract from the blood delivered to it at rest?
What percentage of oxygen does the heart extract from the blood delivered to it at rest?
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Which aspect of blood flow through the coronary vessels is true during systole?
Which aspect of blood flow through the coronary vessels is true during systole?
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What is the typical coronary blood flow at rest in relation to the overall cardiac output?
What is the typical coronary blood flow at rest in relation to the overall cardiac output?
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Which structure is responsible for the drainage of blood from the upper body into the heart?
Which structure is responsible for the drainage of blood from the upper body into the heart?
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What is the clinical significance of the foramen ovale in the adult heart?
What is the clinical significance of the foramen ovale in the adult heart?
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Which artery supplies the left ventricle and parts of the left atrium?
Which artery supplies the left ventricle and parts of the left atrium?
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What is the function of the ligamentum arteriosum in the adult heart?
What is the function of the ligamentum arteriosum in the adult heart?
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How do the cardiac plexuses relate to heart function?
How do the cardiac plexuses relate to heart function?
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Which artery is dominant in approximately 67% of the population?
Which artery is dominant in approximately 67% of the population?
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Which part of the heart does the Right Coronary Artery predominantly supply?
Which part of the heart does the Right Coronary Artery predominantly supply?
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Which area does the Left Coronary Artery supply?
Which area does the Left Coronary Artery supply?
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What condition is characterized by pressure or discomfort in the left substernal region of the chest?
What condition is characterized by pressure or discomfort in the left substernal region of the chest?
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In which percentage of people does the Right Coronary Artery supply the SA node?
In which percentage of people does the Right Coronary Artery supply the SA node?
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Angina pectoris can cause discomfort that radiates to which of the following areas?
Angina pectoris can cause discomfort that radiates to which of the following areas?
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What is a common symptom associated with transient myocardial ischemia?
What is a common symptom associated with transient myocardial ischemia?
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The Right Coronary Artery supplies which part of the inter-ventricular septum?
The Right Coronary Artery supplies which part of the inter-ventricular septum?
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Which artery is primarily associated with supplying the inferior wall of the left atrium?
Which artery is primarily associated with supplying the inferior wall of the left atrium?
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Which of the following structures does the Right Coronary Artery provide a significant supply to?
Which of the following structures does the Right Coronary Artery provide a significant supply to?
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Study Notes
Electrical Conduction System
- Specialized cardiac muscle cells transmit impulses throughout the heart
- This signals the chambers to contract in a specific order
Sinoatrial Node (SA Node)
- Located in the wall of the right atrium
- Sets the basic heart rate at 70-80 beats per minute
- It is the normal pacemaker of the heart
- The SA node's intrinsic rate is approximately 100 beats per minute
Impulse Transmission
- Impulse from the SA Node travels to the atria
- It also travels to the AV node via the internodal pathway
Atrioventricular Node (AV Node)
- Located in the interatrial septum, near the opening of the coronary sinus
AV Bundle (Bundle of His)
- Extends from the AV node into the interventricular septum
- Divides into right and left bundle branches, forming subendocardial branches (Purkinje fibers)
Ventricular Contraction
- Contraction begins at the apex of the heart
Coronary Circulation
- The right and left coronary arteries supply the heart with blood
- They arise from the ascending aorta, above the aortic valve
- These arteries supply the myocardium, papillary muscles, and conducting tissue
- The coronary sinus and cardiac veins are the primary routes for venous return
Cardiac Cycle
- The cardiac cycle represents a complete heartbeat from the start of one beat to the start of the next
- It consists of diastole (ventricular relaxation and filling) and systole (ventricular contraction and emptying)
Coronary Blood Flow During Systole and Diastole
- Systole:
- Left ventricle (LV) contraction compresses the sub-endocardial coronary vessels
- The epicardial coronary vessels remain open
- Diastole:
- LV relaxation allows blood flow through sub-endocardial coronary vessels to the capillaries
- Myocardial perfusion occurs during heart relaxation
Heart Muscle Properties
- The right ventricle (RV) generates less force than the left ventricle (LV)
- RV pressure is lower than diastolic blood pressure
Heart Muscle Oxygen Consumption
- At rest, the heart extracts 60-70% of oxygen from each unit of blood delivered
- Other tissues extract only 25% oxygen
- The heart muscle contains more mitochondria, indicating its high oxygen requirement
Heart Anatomy and Circulation
- The heart is supplied by the right and left coronary arteries, which arise from the ascending aorta just above the aortic valve.
- The heart receives about 5% of the total blood volume from the cardiac output.
- The heart pumps around 5 liters of blood per minute (adult).
- The coronary arteries supply the myocardium, papillary muscles, and conducting tissue.
- The coronary sinus and cardiac veins are responsible for venous drainage.
- Blood flow through the coronary vessels is interrupted during ventricular systole (contraction) while epicardial coronary vessels remain open.
- Myocardial perfusion occurs during ventricular diastole (relaxation).
- The heart extracts a high percentage of oxygen from the blood (60-70%) compared to other tissues (25%), due to the presence of many mitochondria in heart muscle.
- The right coronary artery is dominant in 67% of individuals and supplies the right atrium, interatrial septum, inferior wall of the left atrium, SA node (60%) and AV node (80%), right ventricle, and 1/3 of the interventricular septum.
- The left coronary artery supplies the posterior wall of the left atrium, the remaining parts of the left ventricle, and the anterior 2/3 of the interventricular septum.
- The right coronary artery typically originates from the ascending aorta near the right aortic sinus, while the left coronary artery arises from the left aortic sinus.
- The most common sites of coronary artery occlusion are the left anterior descending artery, and the left anterior descending artery at its bifurcation.
- Angina pectoris, a symptom of myocardial ischemia, can be described as precordial discomfort or pressure resulting from transient myocardial ischemia.
- Angina pectoris often radiates to the left arm, left shoulder, neck, jaw, and teeth. This is described as referred pain attributed to visceral afferents from the heart travelling with somatic afferents to the spinal cord with convergence in the dorsal horn.
Pericardium
- Pericarditis refers to inflammation of the pericardium.
- Cardiac constriction can happen due to the buildup of fluid in the pericardial sac, leading to restricted heart function.
- Pericardial tamponade necessitates pericardiocentesis, which can be performed by inserting a needle into the pericardial sac from the cardiac notch of the left lung.
Heart Chambers and Structures
- The right atrium forms part of the right border of the heart and contains the atrioventricular groove, tricuspid valve, chordae tendineae, papillary muscles, interventricular septum, trabeculae carneae, trabecula septomarginalis (moderator band), pulmonary valve, and pulmonary trunk.
- The left atrium forms the posterior part of the heart and contains the left auricle, interatrial septum, and 4 pulmonary veins.
- The right ventricle forms the anterior part of the heart and contains the right auricle, chordae tendineae, papillary muscles, interventricular septum, trabeculae carneae, and trabecula septomarginalis (moderator band).
- The left ventricle forms the base of the heart and contains the bicuspid (mitral) valve, chordae tendineae, papillary muscles, trabeculae carneae, interventricular septum, aortic valve, aorta, and ligamentum arteriosum.
Conduction System
- The SA node, located in the superior portion of the right atrium, acts as the main pacemaker and initiates the cardiac impulse, which travels to the atria, causing them to contract.
- The AV node, located in the interatrial septum, allows the impulse to reach the ventricles.
- The bundle of His, located in the interventricular septum, transmits the impulse to the right and left bundles branches.
- Purkinje fibers, located in the ventricular walls, transmit the impulse to the ventricular myocardium, causing ventricular contraction.
Cardiac Innervation: Cardiac Plexus
- The cardiac plexus is a complex network of sympathetic and parasympathetic nerve fibers located below the aortic arch, above the pulmonary trunk, and anterior to the tracheal bifurcation.
- Cardiac plexus branches traveling with the right pulmonary artery reach the atria.
- Branches of the cardiac plexus are joined with the coronary arteries.
- The cardiac plexus contributes to regulating heart rate and contractility.
- Parasympathetic innervation (via the vagus nerve) decreases heart rate, while sympathetic innervation (mainly from the upper thoracic nerves) increases heart rate.
- Visceral afferent fibers carry sensory information from the heart and are involved in referred pain.
- These fibers travel with sympathetic fibers and enter the spinal cord through the T1 white rami communicantes.
- T1 dermatome is responsible for the medial cord of the brachial plexus.
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Description
Explore the specialized electrical conduction system of the heart in this quiz. Learn about key components like the Sinoatrial Node (SA Node), Atrioventricular Node (AV Node), and the impulse transmission process. Test your knowledge on how these elements work together to regulate heart rhythm.
