Cardiac Conduction System Quiz
144 Questions
1 Views

Cardiac Conduction System Quiz

Created by
@SpeedyFlerovium2749

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary role of the SA node in the cardiac conduction system?

  • To contract the ventricles
  • To regulate blood pressure
  • To initiate depolarization of the heart (correct)
  • To respond to external stimuli

    • Which phase of the cardiac muscle action potential is characterized by a plateau?

  • Phase 3
  • Phase 2 (correct)
  • Phase 1
  • Phase 0

    • How do the action potentials in cardiac pacemaker cells differ from those in skeletal muscle cells?

  • They are spontaneously generated without external stimuli. (correct)
  • They have a shorter duration.
  • They are entirely generated by nerve impulses.
  • They do not involve calcium ions.

    • Which component of the autonomic nervous system primarily influences cardiac function?

    <p>Sympathetic nervous system</p> Signup and view all the answers

    What is the primary purpose of the conduction system of the heart?

    <p>To ensure efficient pumping of blood</p> Signup and view all the answers

    What does the T wave in a normal ECG represent?

    <p>Ventricular repolarization</p> Signup and view all the answers

    Which ion movement is primarily responsible for depolarization in cardiac contractile cells?

    <p>Sodium influx</p> Signup and view all the answers

    What is automaticity in the context of cardiac function?

    <p>The intrinsic ability of heart cells to initiate action potentials</p> Signup and view all the answers

    What initiates atrial depolarization?

    <p>SA node</p> Signup and view all the answers

    What occurs at the AV node after complete atrial depolarization?

    <p>Impulse is delayed</p> Signup and view all the answers

    Which wave on an ECG represents atrial depolarization?

    <p>P wave</p> Signup and view all the answers

    Which sequence correctly represents the heart's electrical activity before ventricular contraction?

    <p>P wave, delay at AV node, QRS complex</p> Signup and view all the answers

    What is the function of the SA node in the cardiac cycle?

    <p>It is the pacemaker that regulates heart rhythm</p> Signup and view all the answers

    What initiates the action potential in cardiac pacemaker cells?

    <p>Ca2+ influx</p> Signup and view all the answers

    Which part of the heart is known as the pacemaker?

    <p>Sinoatrial node</p> Signup and view all the answers

    What happens in the heart during the delay caused by the Atrioventricular (AV) node?

    <p>Atrial contraction occurs before ventricular contraction</p> Signup and view all the answers

    What role does the AV bundle (bundle of His) play in the heart's conduction system?

    <p>It connects atria and ventricles electrically</p> Signup and view all the answers

    Which part of the conduction system carries impulses toward the apex of the heart?

    <p>Right and left bundle branches</p> Signup and view all the answers

    What occurs during repolarization of the action potential in cardiac pacemaker cells?

    <p>K+ efflux takes place</p> Signup and view all the answers

    What is the inherent rate of the Atrioventricular (AV) node in the absence of input from the SA node?

    <p>50 beats per minute</p> Signup and view all the answers

    How quickly do cardiac pacemaker cells pass impulses across the heart?

    <p>220 ms</p> Signup and view all the answers

    What allows for the ventricular contraction to follow immediately after the impulse reaches the inferior region of the heart?

    <p>Impulse spreading through the bundle branches</p> Signup and view all the answers

    Why do the atrial and ventricular myocytes not contract simultaneously?

    <p>The AV node delays the impulse transmission</p> Signup and view all the answers

    What is the primary function of the sympathetic innervation of the heart?

    <p>Increases heart rate and force of contraction</p> Signup and view all the answers

    Which center is associated with the parasympathetic control of the heart?

    <p>Cardioinhibitory center</p> Signup and view all the answers

    Which nerve is primarily involved in decreasing the heart rate?

    <p>Vagus nerve</p> Signup and view all the answers

    The medulla oblongata contains which centers for heart regulation?

    <p>Cardioinhibitory and Cardioacceleratory centers</p> Signup and view all the answers

    What effect does the parasympathetic nervous system have on heart activity?

    <p>Decreases heart rate</p> Signup and view all the answers

    The sympathetic trunk ganglion's role in heart function is to?

    <p>Increase heart rate and force of contraction</p> Signup and view all the answers

    Which of the following is true regarding the cardioacceleratory center?

    <p>It affects the SA and AV nodes as well as myocardial tissue</p> Signup and view all the answers

    Which structure does NOT play a primary role in heart innervation?

    <p>Intercostal nerves</p> Signup and view all the answers

    What effect does the Cardioinhibitory center have on the SA and AV nodes?

    <p>Inhibits them via the vagus nerve</p> Signup and view all the answers

    Activation of which nervous system results in an increased heart rate?

    <p>Sympathetic nervous system</p> Signup and view all the answers

    What does the P wave in an electrocardiogram represent?

    <p>Atrial depolarization</p> Signup and view all the answers

    Which part of the ECG reflects the period between the beginning of atrial excitation and the beginning of ventricular excitation?

    <p>P-R interval</p> Signup and view all the answers

    What does the QRS complex signify in the electrocardiogram?

    <p>Ventricular depolarization and atrial repolarization</p> Signup and view all the answers

    Which electrical event is recorded as the T wave in an ECG?

    <p>Ventricular repolarization</p> Signup and view all the answers

    What is the primary purpose of an electrocardiograph?

    <p>To detect electrical currents generated by the heart</p> Signup and view all the answers

    What does the S-T segment reflect in the electrocardiogram?

    <p>Entire ventricular myocardium depolarized</p> Signup and view all the answers

    What leads to the electrocardiogram measuring voltage differences?

    <p>The placement of electrodes on the body</p> Signup and view all the answers

    Which interval measures the time from the start of ventricular depolarization to ventricular repolarization?

    <p>Q-T interval</p> Signup and view all the answers

    Which statement about the electrocardiogram is incorrect?

    <p>It is a tracing of a single action potential.</p> Signup and view all the answers

    What is typically the most common configuration used in electrocardiography?

    <p>12 lead ECG</p> Signup and view all the answers

    What does the P-R interval in an electrocardiogram primarily indicate?

    <p>The period between atrial depolarization and the onset of ventricular depolarization</p> Signup and view all the answers

    Which of the following accurately describes the Q-T interval on an ECG?

    <p>It represents the duration between the onset and completion of ventricular depolarization</p> Signup and view all the answers

    During which phase does the QRS complex occur on an ECG tracing?

    <p>Ventricular depolarization only</p> Signup and view all the answers

    Which segment of the ECG indicates the period of time when the ventricles are electrically silent?

    <p>S-T segment</p> Signup and view all the answers

    What does the T wave represent in the electrocardiogram's sequence of electrical activity?

    <p>Ventricular repolarization</p> Signup and view all the answers

    What is the significance of the plateau phase in the action potential of cardiac contractile cells?

    <p>It prolongs the action potential to prevent tetany.</p> Signup and view all the answers

    Which of the following correctly describes the role of the autonomic nervous system in cardiac function regulation?

    <p>The autonomic system has a dual role, with both sympathetic and parasympathetic divisions working to balance heart rate.</p> Signup and view all the answers

    What role do cardiac pacemaker cells play in the conduction system of the heart?

    <p>They initiate and regulate the electrical impulses that determine heart rate.</p> Signup and view all the answers

    How do cardiac contractile cells differ from skeletal muscle cells in terms of action potential generation?

    <p>Cardiac action potentials include a long plateau phase that is absent in skeletal muscle cells.</p> Signup and view all the answers

    Which sequence appropriately describes the conduction pathway of electrical impulses in the heart before ventricular contraction?

    <p>SA Node → AV Node → Bundle of His → Purkinje Fibers</p> Signup and view all the answers

    What does a normal ECG waveform indicate about the atrial and ventricular activity?

    <p>P wave represents atrial depolarization, while QRS complex signifies ventricular depolarization.</p> Signup and view all the answers

    What is the primary function of the AV node in the cardiac conduction system?

    <p>To delay the transmission of electrical impulses to allow for atrial contraction before ventricular contraction.</p> Signup and view all the answers

    What effect does the sympathetic nervous system typically have on cardiac muscle cells?

    <p>It increases heart rate and the velocity of impulse conduction.</p> Signup and view all the answers

    What occurs in the heart shortly after depolarization from the pacemaker potential reaches threshold?

    <p>Atrial contraction begins</p> Signup and view all the answers

    During which sequence does the cardiac impulse pass through the conduction system?

    <p>Sinoatrial node → Atrioventricular node → Atrioventricular bundle</p> Signup and view all the answers

    What is responsible for the delay of approximately 0.1 seconds at the Atrioventricular (AV) node?

    <p>Reduced number of gap junctions</p> Signup and view all the answers

    What is the inherent pacemaker rate of the Sinoatrial (SA) node under normal conditions?

    <p>75 beats per minute</p> Signup and view all the answers

    What is the effect of the long absolute refractory period in cardiac muscle?

    <p>It prevents tetanic contractions.</p> Signup and view all the answers

    What initiates ventricular contraction following depolarization in the heart?

    <p>Subendocardial conducting network stimulation</p> Signup and view all the answers

    What causes the repolarization phase in cardiac muscle contraction?

    <p>Inactivation of Ca2+ channels and opening of K+ channels</p> Signup and view all the answers

    Which structure serves as the only electrical connection between the atria and ventricles?

    <p>Atrioventricular bundle</p> Signup and view all the answers

    What effect does the inactivation of Ca2+ channels and opening of K+ channels have during cardiac action potential?

    <p>Repolarization of the membrane</p> Signup and view all the answers

    How does cardiac muscle contraction differ from skeletal muscle contraction in terms of cell connectivity?

    <p>All cardiomyocytes contract as a unit.</p> Signup and view all the answers

    Which ion is responsible for the plateau phase of depolarization in cardiac muscle?

    <p>Ca2+ influx</p> Signup and view all the answers

    Which of the following structures depolarizes at a slower intrinsic rate when the SA node input is absent?

    <p>Atrioventricular (AV) node</p> Signup and view all the answers

    What role does Ca2+ play in cardiac muscle contraction?

    <p>It binds to troponin to enable filament sliding.</p> Signup and view all the answers

    Which node is characterized as the primary pacemaker of the heart, generating impulses most rapidly?

    <p>Sinoatrial node</p> Signup and view all the answers

    What role do the right and left bundle branches play in the heart's conduction system?

    <p>Carrying impulses toward the apex of the heart</p> Signup and view all the answers

    What is the significance of the automaticity of cardiac muscle cells?

    <p>They can initiate contractions independently.</p> Signup and view all the answers

    Which feature is unique to the cardiac muscle contraction mechanism?

    <p>T tubule involvement for Ca2+ release.</p> Signup and view all the answers

    What primarily prevents tetanic contractions in the heart?

    <p>Long refractory period</p> Signup and view all the answers

    During which phase does the cardiac muscle measure the longest duration of action potential?

    <p>Plateau phase</p> Signup and view all the answers

    What is a key difference in the action potentials of cardiac and skeletal muscle cells?

    <p>Cardiac cells have an absolute refractory period lasting longer.</p> Signup and view all the answers

    What does the P-R interval in an electrocardiogram signify?

    <p>Time from the beginning of atrial excitation to the beginning of ventricular excitation</p> Signup and view all the answers

    Which component of the electrocardiogram indicates ventricular repolarization?

    <p>T wave</p> Signup and view all the answers

    What does the QRS complex not represent in an electrocardiogram?

    <p>Atrial depolarization</p> Signup and view all the answers

    What impact does the S-T segment have on understanding the ECG?

    <p>It indicates the time the entire ventricular myocardium is depolarized</p> Signup and view all the answers

    Which description best captures the fundamental characteristic of an electrocardiogram?

    <p>A graphical representation of all action potentials at a specific moment</p> Signup and view all the answers

    What is the role of electrodes in the electrocardiograph system?

    <p>To measure voltage differences across the body</p> Signup and view all the answers

    Which interval measures the time from the start of ventricular depolarization to the start of ventricular repolarization?

    <p>Q-T interval</p> Signup and view all the answers

    In a standard 12 lead ECG, which wave is primarily associated with the depolarization of the SA node?

    <p>P wave</p> Signup and view all the answers

    What does a typical electrocardiogram NOT reflect?

    <p>A singular action potential event</p> Signup and view all the answers

    What best characterizes the action potentials detected by an electrocardiograph?

    <p>A combination of nodal and contractile cells' activities</p> Signup and view all the answers

    What does the completion of ventricular depolarization signify in an ECG tracing?

    <p>The completion of the QRS complex</p> Signup and view all the answers

    Atrial repolarization occurs simultaneously with ventricular depolarization.

    <p>True</p> Signup and view all the answers

    What wave on an ECG represents ventricular repolarization?

    <p>T wave</p> Signup and view all the answers

    What substance do ischemic cardiac cells primarily produce due to anaerobic respiration?

    <p>Lactic acid</p> Signup and view all the answers

    Cardiac muscle cells have a high ability for anaerobic respiration.

    <p>False</p> Signup and view all the answers

    The beginning of ventricular depolarization causes the ________ complex in an ECG reading.

    <p>QRS</p> Signup and view all the answers

    Match the following phases of cardiac electrical activity with their corresponding ECG features:

    <p>Ventricular depolarization = QRS complex Atrial depolarization = P wave Ventricular repolarization = T wave Atrial repolarization = Not directly displayed</p> Signup and view all the answers

    What term describes the cells in the heart that initiate pacemaker potential?

    <p>Autorhythmic cells</p> Signup and view all the answers

    The __________ is known as the primary pacemaker of the heart.

    <p>SA node</p> Signup and view all the answers

    Match the following cardiac terms with their definitions:

    <p>Arrhythmias = Irregular heart rhythms Fibrillation = Rapid, uncoordinated contractions Ischemia = Reduced blood supply to tissue Defibrillation = Restoration of normal rhythm</p> Signup and view all the answers

    What effect does high H+ concentration have on cardiac function?

    <p>Disrupts gap junctions</p> Signup and view all the answers

    Only the SA node can generate pacemaker potentials in the heart.

    <p>False</p> Signup and view all the answers

    Identify one common homeostatic imbalance related to the intrinsic conduction system.

    <p>Arrhythmias</p> Signup and view all the answers

    Which phase of the cardiac muscle action potential is primarily characterized by potassium ion efflux?

    <p>Repolarization</p> Signup and view all the answers

    The autonomic nervous system solely stimulates cardiac pacemaker cells.

    <p>False</p> Signup and view all the answers

    What is the role of the AV node in the conduction system of the heart?

    <p>The AV node delays the electrical impulse from the atria before transmitting it to the ventricles, allowing for proper timing of contraction.</p> Signup and view all the answers

    The primary function of the __________ system in the heart is to regulate heart rate and force of contraction.

    <p>autonomic nervous</p> Signup and view all the answers

    Match the following ion movements with their corresponding actions during the cardiac action potential:

    <p>Sodium (Na+) = Depolarization Potassium (K+) = Repolarization Calcium (Ca2+) = Plateau Phase Chloride (Cl-) = Resting Phase</p> Signup and view all the answers

    Which component of the cardiac conduction system is known as the heart's pacemaker?

    <p>SA Node</p> Signup and view all the answers

    The T wave on an ECG represents ventricular depolarization.

    <p>False</p> Signup and view all the answers

    What does the QRS complex on an ECG signify?

    <p>The QRS complex signifies ventricular depolarization.</p> Signup and view all the answers

    Automaticity refers to the heart's ability to create an action potential without __________ stimulation.

    <p>external</p> Signup and view all the answers

    What is the primary function of the plateau phase in cardiac contractile cells?

    <p>To prolong the contraction time</p> Signup and view all the answers

    Which part of the nervous system is responsible for increasing heart rate and force of contraction?

    <p>Sympathetic nervous system</p> Signup and view all the answers

    The cardioacceleratory center is associated with parasympathetic control of the heart.

    <p>False</p> Signup and view all the answers

    What effect does the vagus nerve have on heart rate?

    <p>Decreases heart rate</p> Signup and view all the answers

    The __________ center inhibits the SA and AV nodes.

    <p>cardioinhibitory</p> Signup and view all the answers

    Match each center with its function regarding heart innervation:

    <p>Cardioacceleratory center = Increases heart rate Cardioinhibitory center = Decreases heart rate Vagus nerve = Parasympathetic innervation Sympathetic trunk = Sympathetic innervation</p> Signup and view all the answers

    Which of the following statements about the sympathetic trunk ganglion is true?

    <p>It increases heart rate and force of contraction.</p> Signup and view all the answers

    The medulla oblongata contains centers that only have a sympathetic effect on the heart.

    <p>False</p> Signup and view all the answers

    Which nervous system activation leads to a decrease in heart rate?

    <p>Parasympathetic nervous system</p> Signup and view all the answers

    The __________ nerves are primarily involved in sympathetic innervation of the heart.

    <p>sympathetic cardiac</p> Signup and view all the answers

    What is the primary function of the cardioacceleratory center?

    <p>To increase heart rate and force of contraction</p> Signup and view all the answers

    What is the inherent rate of the sinoatrial (SA) node in a healthy heart?

    <p>100 beats per minute</p> Signup and view all the answers

    The Atrioventricular (AV) node allows the atria to contract before the ventricles.

    <p>True</p> Signup and view all the answers

    What is the role of the subendocardial conducting network?

    <p>To distribute electrical impulses to the ventricular walls.</p> Signup and view all the answers

    The sinoatrial node is located in the ________ atrial wall.

    <p>right</p> Signup and view all the answers

    Match the cardiac conduction system components with their functions:

    <p>Sinoatrial node = Pacemaker of the heart Atrioventricular node = Delays impulses AV bundle = Electrical connection between atria and ventricles Bundle branches = Carry impulses toward apex of heart</p> Signup and view all the answers

    Which phase of cardiac action potential is marked by calcium influx?

    <p>Depolarization</p> Signup and view all the answers

    The AV bundle has a higher rate of impulse generation than the SA node.

    <p>False</p> Signup and view all the answers

    What is the total time taken for cardiac pacemaker cells to pass impulses across the heart?

    <p>Approximately 220 milliseconds.</p> Signup and view all the answers

    During repolarization, K+ channels ________, allowing potassium to leave the cell.

    <p>open</p> Signup and view all the answers

    Why do the atrial and ventricular myocytes not contract simultaneously?

    <p>The AV node delays the impulse.</p> Signup and view all the answers

    Cardiac muscle can easily rely on anaerobic respiration due to its high mitochondria count.

    <p>False</p> Signup and view all the answers

    Ischemic cells lead to increased ATP production and proper heart function.

    <p>False</p> Signup and view all the answers

    The SA node, AV node, and Purkinje fibers are all considered pacemakers in the heart.

    <p>False</p> Signup and view all the answers

    Fibrillation refers to slow, regular contractions of the heart muscle.

    <p>False</p> Signup and view all the answers

    Cardiac muscle can utilize lactic acid produced by skeletal muscles as a fuel source.

    <p>True</p> Signup and view all the answers

    The SA node has an inherent rate of approximately 60 to 100 beats per minute in the absence of external influences.

    <p>True</p> Signup and view all the answers

    Cardiac pacemaker cells can only generate action potentials when influenced by external neural stimuli.

    <p>False</p> Signup and view all the answers

    The plateau phase of the cardiac action potential is primarily due to the influx of potassium ions.

    <p>False</p> Signup and view all the answers

    The autonomic nervous system does not influence the conduction speed of impulses through the heart's conduction system.

    <p>False</p> Signup and view all the answers

    Ventricular myocytes contract simultaneously with atrial myocytes during the cardiac cycle.

    <p>False</p> Signup and view all the answers

    Pacemaker cells have stable resting membrane potentials due to the opening of slow Na+ channels.

    <p>False</p> Signup and view all the answers

    Calcium channels opening leads to a huge influx and the rising phase of the action potential in pacemaker cells.

    <p>True</p> Signup and view all the answers

    Repolarization in pacemaker cells occurs because of the closure of K+ channels and the opening of Na+ channels.

    <p>False</p> Signup and view all the answers

    The intrinsic cardiac conduction system is composed entirely of contractile cardiac muscle cells.

    <p>False</p> Signup and view all the answers

    During the repolarization phase of action potential, K+ channels open allowing for the efflux of K+ ions.

    <p>True</p> Signup and view all the answers

    Study Notes

    Cardiac Conduction System

    • SA node is the natural pacemaker of the heart, initiating the electrical impulse that triggers each heartbeat.

    Cardiac Muscle Action Potential

    • Plateau phase is characterized by prolonged calcium influx into the cell, maintaining a prolonged depolarized state.

    Cardiac Pacemaker Cells

    • Pacemaker cells exhibit spontaneous depolarization due to "funny" current and calcium influx, resulting in a constant rhythm.
    • Skeletal muscle cells require external stimulation to trigger action potentials.

    Autonomic Nervous System

    • Parasympathetic nervous system primarily slows down heart rate through vagus nerve.
    • Sympathetic nervous system increases heart rate and contractility through norepinephrine.

    Heart's Conduction System

    • The heart's conduction system ensures coordinated contraction of the heart chambers.
    • It facilitates electrical transmission throughout the heart, ensuring efficient blood pumping.

    ECG Interpretation

    • T wave represents ventricular repolarization.

    Depolarization in Cardiac Contractile Cells

    • Sodium influx is primarily responsible for depolarization in cardiac contractile cells.

    Automaticity

    • Automaticity is the intrinsic ability of specialized cardiac cells to spontaneously generate action potentials, driving the heart's rhythm.

    Atrial Depolarization

    • SA node initiates atrial depolarization, triggering the contraction of the atria.

    AV Node

    • AV node delays the transmission of the electrical impulse, allowing for complete atrial depolarization and ventricular filling.

    ECG: Atrial Depolarization

    • P wave represents atrial depolarization.

    Heart's Electrical Activity

    • SA node initiates the electrical impulse (P wave) → atrial depolarization → AV node delays transmission → ventricular depolarization (QRS complex) → ventricular contraction.

    SA Node in Cardiac Cycle

    • SA node sets the heart's rhythm by initiating the electrical impulse that leads to atrial contraction and ventricular filling.

    Cardiovascular Physiology

    • The cardiovascular system is responsible for transporting oxygen, nutrients, and hormones throughout the body; it also removes waste products.

    • The cardiac muscle action potential has five phases:

      • Phase 0: Rapid depolarization due to sodium influx
      • Phase 1: Initial repolarization due to potassium efflux
      • Phase 2: Plateau phase due to calcium influx
      • Phase 3: Rapid repolarization due to potassium efflux
      • Phase 4: Resting membrane potential

    • Pacemaker cells:

      • Their action potentials are initiated by a slow, gradual depolarization called the pacemaker potential
      • They exhibit automaticity
      • Depolarization is driven by sodium influx through funny channels (If channels) and calcium influx through T-type calcium channels

    • Contractile cells:

      • Depolarization is initiated by a rapid influx of sodium ions
      • The plateau phase is caused by sustained calcium influx
      • Repolarization occurs due to potassium efflux

    • Skeletal muscle cells:

      • They depend on nervous system stimulation for depolarization
      • They do not exhibit automaticity

    • The plateau phase of the action potential in cardiac contractile cells is crucial for ensuring a long-lasting contraction, allowing sufficient time for blood ejection from the heart.

    • Cardiac vs. Skeletal Muscle Contraction:

      • Similarities: Both rely on calcium-mediated actin-myosin cross-bridge formation
      • Differences: Cardiac muscle exhibits a longer duration of contraction, a longer refractory period, and is influenced by the autonomic nervous system

    Cardiac Conduction System

    • The cardiac conduction system is responsible for the coordinated and efficient flow of electrical impulses throughout the heart, ensuring a synchronized contraction of the chambers.

    • It ensures atrial contraction precedes ventricular contraction, leading to efficient blood flow from the atria to the ventricles.

    • Components:

      • Sinoatrial (SA) node: The "pacemaker" of the heart located in the right atrial wall
        • It spontaneously generates impulses at a rate of approximately 75 beats per minute (sinus rhythm)
        • Has an inherent rate of 100 beats per minute but is regulated by autonomic nerves
      • Atrioventricular (AV) node: Located in the inferior interatrial septum
        • Delays impulses by about 0.1 second, allowing the atria to contract before the ventricles
        • This delay is due to the smaller diameter and fewer gap junctions of its fibers
        • Has an inherent rate of 50 beats per minute in the absence of SA node input
      • Atrioventricular (AV) bundle (Bundle of His): Located in the superior interventricular septum
        • The only electrical connection between the atria and ventricles
      • Right and left bundle branches: Pathway in the interventricular septum
        • Carry impulses towards the apex of the heart.
      • Subendocardial conducting network (Purkinje fibers):
        • Extends from the apex to the ventricular walls
        • Depolarizes at 30 beats per minute in the absence of AV node input

    The EKG

    • Electrocardiography records the electrical activity of the heart, which is represented as a composite of all action potentials generated by the nodal and contractile cells at a given time.

    • The EKG is a graphic recording of these electrical events.

    • Key waveforms:

      • P wave: Reflects atrial depolarization initiated by the SA node
      • QRS complex: Represents ventricular depolarization and the repolarization of the atria (which is obscured by the larger ventricular event)
      • T wave: Shows ventricular repolarization
      • PR interval: Represents the time from the start of atrial excitation to the beginning of ventricular excitation
      • ST Segment: Indicates the time when the entire ventricular myocardium is depolarized
      • QT interval: Represents the overall duration of ventricular depolarization and repolarization

    Autonomic Nervous System

    • Sympathetic Nervous System:
      • Increases heart rate and contractility
      • This is achieved through the release of norepinephrine, which binds to beta-adrenergic receptors in the heart.
    • Parasympathetic Nervous System:
      • Decreases heart rate
      • This occurs through the release of acetylcholine which binds to muscarinic receptors in the heart.

    Pacemaker Potential

    • The SA node, atrial muscle, AV node, and ventricular muscle all have different action potential shapes
    • The SA node exhibits pacemaker potential, which is a slow, gradual depolarization leading to an action potential
    • This is due to the opening of slow Na+ channels and the closing of K+ channels

    Energy Requirements for Cardiac Muscle

    • Cardiac muscle has many mitochondria and relies heavily on aerobic respiration
    • It has a limited ability to perform anaerobic respiration
    • Can readily switch fuel sources for respiration
    • Can even utilize lactic acid from skeletal muscles

    Homeostatic Imbalance

    • Ischemic cells lead to anaerobic respiration
    • This produces lactic acid
    • High H+ concentration increases Ca2+ concentration leading to mitochondrial damage and decreased ATP production
    • Consequently, the gap junctions between cells close resulting in fatal arrhythmias

    Homeostatic Imbalances (Continued)

    • Defects in the intrinsic conduction system of the heart can lead to various conditions, including arrhythmias, uncoordinated atrial and ventricular contractions, and fibrillation
    • Fibrillation is a rapid, irregular contraction that is inefficient for pumping blood, leading to circulatory cessation and brain death
    • Defibrillation can be used to treat fibrillation

    Cardiac Muscle: Similarities and Differences

    • Cardiac muscle shares similarities with skeletal muscle in that it is striated and contains sarcomeres
    • However, cardiac muscle is involuntary while skeletal muscle is voluntary
    • Cardiac muscle also has a longer refractory period and is more resistant to fatigue compared to skeletal muscle

    Intrinsic Conduction System

    • The heart has its own intrinsic conduction system, also known as the pacemaker system
    • It is a network of non-contractile cells that initiate and distribute impulses, ensuring coordinated depolarization and contraction of the heart
    • These pacemaker cells have an unstable resting membrane potential and are referred to as autorhythmic cells

    Pacemaker Cells

    • Pacemaker cells have an unstable resting membrane potential due to the opening of slow Na+ channels
    • This continuous depolarization eventually reaches the threshold leading to the opening of Ca2+ channels
    • Ca2+ influx creates the rising phase of the action potential
    • Repolarization occurs with the inactivation of Ca2+ channels and the opening of voltage-gated K+ channels

    Extrinsic Innervation of the Heart

    • The heartbeat can be modified by the autonomic nervous system via cardiac centers in the medulla oblongata
    • The sympathetic nervous system increases heart rate and force, while the parasympathetic nervous system decreases heart rate
    • The cardioacceleratory center (sympathetic) affects the SA and AV nodes, heart muscle, and coronary arteries
    • The cardioinhibitory center (parasympathetic) inhibits the SA and AV nodes via the vagus nerves

    Electrocardiography

    • The electrocardiograph (ECG or EKG) measures electrical currents generated by the heart
    • It provides a graphic recording of this electrical activity
    • The ECG represents a composite of all action potentials at a given time, not a single action potential
    • Electrodes are placed on different parts of the body to measure voltage differences
    • A 12-lead ECG is the most common type

    Key Components of an ECG

    • P wave: Depolarization of SA node and atria
    • QRS complex: Ventricular depolarization and atrial repolarization
    • T wave: Ventricular repolarization
    • P-R interval: Beginning of atrial excitation to the beginning of ventricular excitation
    • S-T segment: Entire ventricular myocardium is depolarized
    • Q-T interval: Beginning of ventricular depolarization through ventricular repolarization

    ECG Summary

    • The electrocardiogram (ECG or EKG) is a composite representation of all action potentials across the nodal and contractile cells at a particular moment
    • It displays three prominent waves:
      • P wave: Depolarization of the SA node and the subsequent conduction to the atria
      • QRS complex: Ventricular depolarization coinciding with atrial repolarization
      • T wave: Ventricular repolarization

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Cardiac Electrical Physiology PDF

    Description

    Test your knowledge on the cardiac conduction system, including the roles of the SA node, pacemaker cells, and the influence of the autonomic nervous system. Explore how electrical impulses are generated and maintained for coordinated heart contractions.

    More Like This

    Cardiac Conduction System
    10 questions

    Cardiac Conduction System

    GenuineGenre avatar
    GenuineGenre
    Autonomic Effects on Heart Rate and Conduction Velocity
    46 questions

    Autonomic Effects on Heart Rate and Conduction Velocity

    FlexibleHilbert2844 avatar
    FlexibleHilbert2844
    Cardiac Conduction System Overview
    40 questions

    Cardiac Conduction System Overview

    CleanestCamellia avatar
    CleanestCamellia
    Cardiac Conduction System Quiz
    5 questions

    Cardiac Conduction System Quiz

    BoomingConnemara1312 avatar
    BoomingConnemara1312
    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser