Cardio-Vascular System Quiz
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Questions and Answers

What is the earliest manifestation of hyperkalaemia on an ECG?

  • QRS widening
  • PR prolongation
  • P wave flattening
  • Increase in T wave amplitude (correct)

    • Which abnormality occurs in the ECG due to hypokalaemia?

  • Tall, tented T waves
  • Flattened T waves and ST depression (correct)
  • Widened QRS complex
  • Prolonged PR interval

    • Which leads are included in the unipolar limb leads for ECG recording?

  • Lead AVR, AVL, AVF (correct)
  • Lead II, V1, V4
  • Lead V1, V2, V3
  • Lead I, Lead II, Lead III

    • In bipolar limb leads, which leads record voltage between the left arm and the left leg?

    <p>Lead III</p> Signup and view all the answers

    What effect does hyperkalaemia have on the T wave in an ECG?

    <p>The T wave is pulled upwards</p> Signup and view all the answers

    What primarily initiates the contraction of cardiac muscle?

    <p>Increased Ca2+ concentration in the sarcoplasm</p> Signup and view all the answers

    What is a key difference between the T-tubules in cardiac muscle compared to skeletal muscle?

    <p>They have a larger diameter.</p> Signup and view all the answers

    What does the electrocardiogram (ECG) primarily record?

    <p>The electrical activity leading to contraction</p> Signup and view all the answers

    What occurs during the repolarization phase of the cardiac muscle action potential?

    <p>Ca2+ is actively transported back into the SR</p> Signup and view all the answers

    Which wave of the ECG corresponds to atrial depolarization?

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

    In cases of hyperkalaemia, how is the serum potassium level characterized?

    <p>Greater than 5.2 mmol/L</p> Signup and view all the answers

    What phase of the cardiac cycle does the S-T segment of the ECG represent?

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

    What role does the Na+-Ca2+ exchanger play in cardiac muscle function?

    <p>It extrudes Ca2+ through the plasma membrane</p> Signup and view all the answers

    What is the primary function of the sinoatrial node (SA node)?

    <p>To act as the heart's pacemaker</p> Signup and view all the answers

    What structures are involved in conducting action potentials in the heart?

    <p>SA node, AV node, bundle of His, and Purkinje fibers</p> Signup and view all the answers

    Which ion is primarily responsible for the depolarization phase of action potentials in nodal fibers?

    <p>Na+ ions</p> Signup and view all the answers

    What is the threshold potential for action potentials to be generated in sinus nodal fibers?

    <p>-40 millivolts</p> Signup and view all the answers

    What separates the electrical activity of the atria from that of the ventricles?

    <p>The fibrous skeleton</p> Signup and view all the answers

    Which of the following accurately describes the role of the AV node?

    <p>It ensures the atria contract before the ventricles.</p> Signup and view all the answers

    Which fibers are responsible for stimulating ventricular contraction?

    <p>Purkinje fibers</p> Signup and view all the answers

    What is a potential consequence of atrial fibrillation?

    <p>Increased risk of thrombi</p> Signup and view all the answers

    What characteristic is associated with the cardiac muscle cells' automaticity?

    <p>Self-excitation and intrinsic rhythm generation</p> Signup and view all the answers

    What happens in ventricular fibrillation that makes it life-threatening?

    <p>The ventricles are unable to pump blood</p> Signup and view all the answers

    What characterizes third degree AV node block?

    <p>No electrical impulses reach the ventricles</p> Signup and view all the answers

    Which of the following describes a consequence of atrial flutter leading to atrial fibrillation?

    <p>Ineffective contraction of atrial muscles</p> Signup and view all the answers

    What can occur as ventricular fibrillation progresses?

    <p>Sudden death may occur transitioning to asystole</p> Signup and view all the answers

    What sound is produced when the AV valves close in the heart cycle?

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

    Which condition is characterized by a heart rate below 60 bpm?

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

    What is the consequence of ventricular tachycardia?

    <p>Potential for sudden death</p> Signup and view all the answers

    When does the 'Dub' sound occur in the cardiac cycle?

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

    Which arrhythmia occurs when pacemakers in the ventricles contract out of sync with the atria?

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

    What distinguishes flutter from fibrillation in terms of cardiac contractions?

    <p>Fast and coordinated vs. slow and uncoordinated</p> Signup and view all the answers

    What can cause abnormal tachycardia at rest?

    <p>Medication or ectopic pacemakers</p> Signup and view all the answers

    What is the normal heart rate range for tachycardia at rest?

    <p>Above 100 bpm</p> Signup and view all the answers

    What uniquely characterizes the sinoatrial node (SA node) within the heart's conduction system?

    <p>It is the primary pacemaker with the highest self-excitation rate.</p> Signup and view all the answers

    What physiological mechanism initiates the action potential in the sinus nodal fibers?

    <p>Leakage of Na+ ions leading to threshold depolarization.</p> Signup and view all the answers

    Which structure serves as the primary conduit for the electrical signal from the atria to the ventricles?

    <p>Bundle of His</p> Signup and view all the answers

    What is the primary role of the intercalated discs in cardiac muscle cells?

    <p>To enable electrical impulses to spread between cells rapidly.</p> Signup and view all the answers

    At which point does the conduction system of the heart separate the electrical stimulation of the atria from that of the ventricles?

    <p>At the fibrous skeleton surrounding the heart.</p> Signup and view all the answers

    Which ions predominantly contribute to the sudden depolarization and action potential in nodal fibers?

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

    What is the primary risk associated with ventricular tachycardia?

    <p>It can result in ventricular fibrillation and sudden death.</p> Signup and view all the answers

    Which statement accurately describes flutter in the context of cardiac arrhythmias?

    <p>Flutter includes extremely fast but coordinated contractions between 200−300 bpm.</p> Signup and view all the answers

    When does the 'Dub' sound occur in the cardiac cycle?

    <p>At the beginning of the T wave.</p> Signup and view all the answers

    What distinguishes fibrillation from flutter in terms of heart contractions?

    <p>Fibrillation has disorganized contractions while flutter maintains some coordination.</p> Signup and view all the answers

    Which condition is characterized by a heart rate exceeding 100 bpm?

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

    What role do ectopic pacemakers play in abnormal tachycardia?

    <p>They generate abnormal electrical signals that may lead to tachycardia.</p> Signup and view all the answers

    What effect does sympathetic activity have on the heart rate?

    <p>It increases the rate of SA node discharge.</p> Signup and view all the answers

    What characterizes the resting membrane potential of cardiac muscle cells?

    <p>It ranges between -85 to -90 millivolts.</p> Signup and view all the answers

    Which type of receptors are primarily involved in sympathetic modulation of cardiac function?

    <p>Beta receptors.</p> Signup and view all the answers

    What is the maximum overshoot potential in ventricular membrane potential?

    <p>$+20$ millivolts.</p> Signup and view all the answers

    What ion is mainly responsible for the depolarization of the sinoatrial node?

    <p>Sodium ions (Na+).</p> Signup and view all the answers

    How does parasympathetic activity affect cardiac function?

    <p>It secretes acetylcholine to slow heart rate.</p> Signup and view all the answers

    What distinguishes the plateau phase of cardiac muscle action potentials from those of skeletal muscle?

    <p>Cardiac muscle has a significantly longer plateau phase.</p> Signup and view all the answers

    What causes the difference in potential between SA fibers and ventricular fibers?

    <p>The intrinsic leakiness to sodium ions in sinus fibers.</p> Signup and view all the answers

    What primarily contributes to the prolonged action potential in cardiac muscle compared to skeletal muscle?

    <p>Opening of slow calcium-sodium channels</p> Signup and view all the answers

    Which statement accurately describes the role of calcium during the excitation-contraction coupling process?

    <p>Calcium binds to troponin to stimulate contraction</p> Signup and view all the answers

    During the action potential, what primarily happens to potassium permeability in cardiac muscle?

    <p>Decreased significantly</p> Signup and view all the answers

    What initiates the opening of calcium release channels from the sarcoplasmic reticulum during muscle contraction?

    <p>Ca2+ diffusion into the cells</p> Signup and view all the answers

    What is the effect of calcium that enters the muscle during the action potential?

    <p>It is involved in stimulating muscle contraction</p> Signup and view all the answers

    How does the opening of potassium channels contribute to the cardiac action potential?

    <p>It facilitates repolarization of the membrane</p> Signup and view all the answers

    Which type of calcium channel opens more slowly but remains open for a longer duration during the cardiac muscle action potential?

    <p>L-type calcium-sodium channels</p> Signup and view all the answers

    What occurs after the cessation of calcium and sodium influx into the cardiac muscle?

    <p>An increase in potassium membrane permeability</p> Signup and view all the answers

    What is the physiological consequence of the decreased permeability of potassium during the action potential?

    <p>Prolonged action potential duration</p> Signup and view all the answers

    What is a key difference between fast sodium channels in skeletal muscle compared to those in cardiac muscle?

    <p>There is a prolonged opening in cardiac muscle channels</p> Signup and view all the answers

    Study Notes

    Introduction to the Cardiovascular System

    • Cardiac muscle cells interconnect via intercalated discs (gap junctions).
    • Myocardium refers to the contracting area from one stimulation event.
    • Electrical isolation of atria and ventricles is due to the fibrous skeleton.

    Automatic Rhythmicity and Pacemaker Function

    • The sinoatrial (SA) node is the primary pacemaker, located in the right atrium.
    • It has the highest rate of self-excitation and intrinsic discharge.
    • Atrioventricular (AV) node and Purkinje fibers serve as secondary or ectopic pacemakers.

    Electrical Conduction Pathway

    • Action potentials propagate through intercalated discs from the SA node to the AV node, facilitating atrial contraction.
    • AV node is positioned at the base of the right atrium and connects to the bundle of His for ventricular stimulation.
    • The bundle of His splits into right and left bundle branches and eventually into Purkinje fibers, which initiate ventricular contraction.

    Cardiac Muscle Contraction

    • Sodium ions (Na+) leak into sinus nodal fibers, raising membrane potential to a threshold of -40 millivolts.
    • Opening of Ca2+ and Na+ channels triggers the action potential.
    • Ca2+ diffuses into myofibrils, leading to contraction through actin-myosin filament sliding.

    Repolarization Process

    • Ca2+ levels decrease in the cytoplasm through transport back to the sarcoplasmic reticulum (SR) and Na+-Ca2+ exchanger.
    • Myocardium transitions to a relaxed state after repolarization.

    Differences: Cardiac vs. Skeletal Muscle

    • Cardiac muscle relies on substantial Ca2+ influx from T-tubules for contraction.
    • Cardiac muscle's sarcoplasmic reticulum is less developed than in skeletal muscle, but T-tubules are significantly larger.

    Electrocardiogram (ECG or EKG)

    • ECG measures the heart’s electrical activity via ion movement, not direct action potentials.
    • It represents electrical events leading to heart contraction and relaxation through depolarization waves.

    ECG Waves and Intervals

    • P wave corresponds to atrial depolarization.
    • P-Q interval indicates atrial systole.
    • QRS wave represents ventricular depolarization.
    • S-T segment indicates plateau phase during ventricular systole.
    • T wave signifies ventricular repolarization.

    Implications of Electrolyte Abnormalities on ECG

    • Hyperkalaemia (serum potassium > 5.2 mmol/L) results in notable ECG changes; T wave amplitude increases, P waves flatten, and QRS widens.
    • Hypokalaemia yields T wave flattening or inversion, ST depression, and prominent U waves.

    ECG Leads

    • Bipolar limb leads measure voltage between electrodes on wrists and legs.
    • Unipolar leads involve a single electrode on the body connected to ECG machinery.
    • Includes multiple limb leads (AVR, AVL, AVF) and six chest leads.

    Heart Sounds and ECG Relationship

    • "Lub" sound coincides with the QRS wave when AV valves close.
    • "Dub" sound occurs at the beginning of the T wave when semilunar valves close.

    Heart Arrhythmias Detected by ECG

    • Bradycardia: heart rate below 60 bpm; possible normal in active individuals.
    • Tachycardia: heart rate exceeding 100 bpm; can be caused by drugs or ectopic pacemakers.
    • Ventricular tachycardia: dangerous condition leading to ineffective pumping and potential sudden death.

    Flutter and Fibrillation

    • Flutter involves rapid yet coordinated contractions (200-300 bpm).
    • Fibrillation signifies uncoordinated contractions between atria and ventricles.

    Specific Types of Fibrillation

    • Atrial fibrillation reduces cardiac output by 15% and increases thrombi risk.
    • Ventricular fibrillation leads to mortality without intervention by CPR or defibrillation.

    AV Node Block

    • Changes in P-R interval indicate AV node damage.
    • First-degree block shows prolonged impulse conduction (>0.2 sec).
    • Second-degree block prevents every electrical wave from reaching ventricles.
    • Third-degree block results in no stimulation to the ventricles, necessitating a slower pacemaker from Purkinje fibers (20-40 bpm).

    Introduction to Cardiac Electrical Activity

    • Cardiac muscle cells interconnected by intercalated discs allow for rapid impulse propagation.
    • Myocardium refers to the area of the heart contracting from a single stimulation event.
    • Atria and ventricles are electrically insulated by the fibrous skeleton.

    Automatic Rhythmicity of the Heart

    • Sinoatrial (SA) node is the primary pacemaker with the highest discharge rate.
    • Automaticity refers to the heart's inherent ability to beat without external stimulation.
    • Atrioventricular (AV) node and Purkinje fibers can act as secondary pacemakers with a slower discharge rate.

    Conducting Tissues of the Heart

    • Action potentials propagate through intercalated discs, from the SA node to the AV node, initiating atrial contraction.
    • AV node is located at the right atrium's base; it conducts impulses to the ventricles via the bundle of His.
    • Bundle of His branches into right and left bundle branches, which convert to Purkinje fibers for ventricular contraction.

    Self-Excitation of Nodal Fibers

    • Sodium ions leak into SA nodal fibers, raising membrane potential to a threshold of -40 mV, opening Ca²⁺ and Na⁺ channels.
    • Inherent leakiness to Na⁺ in SA node contributes to its self-excitation.

    Mechanism of SA Node Rhythmicity

    • Sympathetic activity involves epinephrine and norepinephrine, increasing heart rate and contractility.
    • Parasympathetic activity releases acetylcholine, opening K⁺ channels, slowing heart rate.
    • Membrane potential of SA node fibers is between -55 mV to -60 mV.

    Action Potentials in Cardiac Muscle

    • Resting membrane potential for cardiac muscle is around -85 mV to -90 mV.
    • Ventricular membrane potential can rise to +20 mV during depolarization.
    • Action potential plateau phase in cardiac muscle is significantly longer than in skeletal muscle.

    Prolonged Action Potential

    • In cardiac muscle, fast Na⁺ and slow Ca²⁺ channels open, creating a longer depolarization phase.
    • Calcium influx sustains muscle contractility, while delayed K⁺ permeability contributes to repolarization.

    Excitation-Contraction Coupling

    • Calcium-initiated calcium release occurs; action potentials open voltage-gated Ca²⁺ channels.
    • Ca²⁺ stimulates contractile mechanisms via binding to troponin.

    Electrocardiogram (ECG) and Heart Sounds

    • "Lub" sound occurs after the QRS wave as AV valves close.
    • "Dub" sound occurs at the start of the T wave as semilunar valves close.

    Heart Arrhythmias

    • Bradycardia indicates a heart rate below 60 bpm; tachycardia indicates a rate above 100 bpm, potentially abnormal at rest.
    • Ventricular tachycardia involves ventricles contracting independently of the atria, posing a significant danger.

    Flutter and Fibrillation

    • Atrial flutter consists of fast but coordinated contractions (200-300 bpm).
    • Fibrillation indicates uncoordinated contractions between atria and ventricles.

    Types of Atrial Fibrillation

    • Can result from atrial flutter, resulting in ineffective atrial contractions while maintaining a 15% reduction in cardiac output.
    • Associated with increased risks of stroke and heart failure.

    Types of Ventricular Fibrillation

    • It leads to the ventricles failing to pump blood, requiring immediate CPR or defibrillation.
    • Caused by continuous cycling of electrical waves with a risk of sudden death from progressing tachycardia to fibrillation.

    AV Node Block

    • Damage to the AV node reflects changes in the P-R interval on an ECG.
    • First-degree block shows prolonged impulse conduction; second-degree block results in missed impulses; third-degree block results in complete failure of conduction requiring a slow pacemaker substitute.

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    Description

    Test your knowledge on the cardio-vascular system with a focus on the electrical activity of the heart and the electrocardiogram. This quiz will cover essential concepts and terminology related to cardiac muscle cells and their interconnections. Perfect for students in medical or health-related fields!

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