Autorhythmic Cells Flashcards
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Autorhythmic Cells Flashcards

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Questions and Answers

What are autorhythmic cells?

  • Typically contractile
  • Not typically contractile (correct)
  • 99% of myocardial cells
  • 1% of myocardial cells (correct)

    • What is autorhythmicity?

    Capable of depolarizing and firing an action potential spontaneously without external influences.

    Which of these statements are true for contractile cells?

  • Typically initiate electrical signals
  • Have plateau in action potentials (correct)
  • 99% of myocardial cells (correct)
  • Not autorhythmic (correct)

    • What is pacemaker potential?

    <p>Slow drift towards threshold between action potentials caused by funny channels.</p> Signup and view all the answers

    What characterizes funny channels (IF)?

    <p>Opens at -60mV</p> Signup and view all the answers

    What is the function of T-type Ca2+ channels?

    <p>Opens briefly during the 2nd half of pacemaker potential to allow Ca2+ into the cell.</p> Signup and view all the answers

    What is the role of L-type Ca2+ channels?

    <p>Fast voltage-gated Ca2+ channels that open during the rising phase of action potential.</p> Signup and view all the answers

    What happens at the peak of the action potential?

    <p>Voltage-gated K+ channels open and K+ fluxes out of the cell.</p> Signup and view all the answers

    How are autorhythmic cells different from neurons?

    Signup and view all the answers

    Where is the sinoatrial (SA) node located?

    <p>Right atrial wall, near superior vena cava opening.</p> Signup and view all the answers

    Where is the atrioventricular (AV) node located?

    <p>Base of right atrium, near interatrial septum.</p> Signup and view all the answers

    What does the AV bundle do?

    <p>Transmits impulses from the AV node to the interventricular septum.</p> Signup and view all the answers

    What are Purkinje fibers?

    <p>Branches from AV bundles to ventricle muscles.</p> Signup and view all the answers

    What happens during the first conduction sequence?

    <p>AP initiated at SA node spreads between atria, causing contraction.</p> Signup and view all the answers

    What is the function of the ring of fibrous tissue?

    <p>Surrounds heart valves and electrically insulates atria from ventricles.</p> Signup and view all the answers

    What is AV nodal delay?

    <p>Delays depolarization spread to ensure atria finish contracting before ventricular contraction.</p> Signup and view all the answers

    What is the significance of conduction sequence 2?

    <p>It delays ventricular contraction allowing the ventricles to fill with blood.</p> Signup and view all the answers

    What occurs during conduction sequence 3?

    <p>AP travels from AV node to Purkinje fibers.</p> Signup and view all the answers

    What happens during conduction sequence 4?

    <p>AP spreads between ventricular cardiac muscles via gap junctions.</p> Signup and view all the answers

    What is fibrillation?

    <p>Random, uncoordinated excitation and contraction of cardiac cells.</p> Signup and view all the answers

    What does a defibrillator do?

    <p>Provides electrical shock to reset all autorhythmic cells.</p> Signup and view all the answers

    What is the interatrial pathway?

    <p>Rapid pathway that conducts depolarization from the SA node to the left atrium.</p> Signup and view all the answers

    What is an AV block?

    <p>Impaired conduction between the atria and ventricles.</p> Signup and view all the answers

    What does ventricular bradycardia imply?

    <p>Slowness of ventricular rate, usually due to atrioventricular block.</p> Signup and view all the answers

    What is Wolff-Parkinson-White Syndrome?

    <p>0.2% of population has an accessory pathway causing abnormal conduction.</p> Signup and view all the answers

    What occurs during AV reentrant tachycardia?

    <p>Electrical activity spreads from the ventricle back through an accessory pathway.</p> Signup and view all the answers

    What is required for efficient pumping of the heart?

    <p>Delay between atrial and ventricular depolarization, coordinated contraction of cells, simultaneous contraction of both atria and ventricles.</p> Signup and view all the answers

    Study Notes

    Autorhythmic Cells

    • Comprise 1% of myocardial cells, play a crucial role in initiating electrical signals.
    • Possess gap junctions but are not typically contractile; instead, they exhibit autorhythmicity and lack resting membrane potential (RMP).

    Autorhythmicity

    • Refers to the ability to spontaneously depolarize and generate action potentials without external stimuli.

    Contractile Cells

    • Make up 99% of myocardial cells, rely on the conduction system for stimulation.
    • Also contain gap junctions; however, they are not autorhythmic and have action potentials featuring a plateau phase.

    Pacemaker Potential

    • Characterized by a slow drift towards threshold between action potentials, facilitated by funny channels.

    Funny Channels (IF)

    • Unique slow voltage-gated sodium channels that open only at negative membrane voltages (-60mV).
    • Allow sodium influx, initiating the pacemaker potential, but close when T-type calcium channels open.

    T-type Calcium Channels

    • These voltage-gated calcium channels briefly open during the latter half of the pacemaker potential, allowing calcium to enter and reach threshold for action potential generation.

    L-type Calcium Channels

    • Fast voltage-gated calcium channels that open during the rising phase of the action potential, enabling calcium influx, crucial for action potential propagation.

    Voltage-gated Potassium Channels

    • Open at the peak of action potential, allowing potassium to flow out of the cell, aiding in repolarization.

    Sinoatrial (SA) Node

    • Located on the right atrial wall near the superior vena cava, acts as the primary pacemaker by spontaneously depolarizing to initiate heartbeats.

    Atrioventricular (AV) Node

    • Positioned at the base of the right atrium near the interatrial septum, serves as a vital relay station for electrical impulses.

    AV Bundle & Branches

    • Conducts electrical signals from the AV node to the interventricular septum, forming right and left branches for further signal propagation.

    Purkinje Fibers

    • Extend from the AV bundle to ventricular muscles; larger diameter allows for rapid action potential propagation and coordinated contraction of ventricles.

    Conduction Sequence (Initial Phase)

    • Action potential begins at the SA node, spreading through gap junctions to the atrial walls and causing synchronous contraction of atria.

    Ring of Fibrous Tissue

    • Surrounds heart valves and electrically isolates the atria from ventricular conduction, ensuring orderly contraction.

    AV Nodal Delay

    • Occurs due to small diameter fibers and reduced gap junctions within the AV node, allowing complete atrial contraction before ventricular contraction begins.

    Conduction Sequence (Second Phase)

    • Insulation by the fibrous ring allows action potential to move through the AV node, creating a brief pause that lets blood fill the ventricles.

    Conduction Sequence (Continuation)

    • Action potential travels from the AV node through AV bundle, branching into Purkinje fibers, ensuring timely and effective ventricular contraction.

    Fibrillation

    • Characterized by random, uncoordinated excitation of cardiac cells; ventricular fibrillation is especially dangerous as it prevents blood circulation.

    Defibrillator

    • Delivers an electrical shock to reset all autorhythmic cells, with the SA node resuming control of the heartbeat sequence.

    Interatrial Pathway

    • A rapid conduction pathway that transmits depolarization signals from the SA node to the left atrium efficiently.

    AV Block

    • Refers to impaired conduction between atria and ventricles, allowing ventricles to maintain a lower heart rate independently if SA node activity is absent.

    Ventricular Bradycardia

    • Slowed ventricular rate, typically indicative of an atrioventricular block condition.

    Wolff-Parkinson-White Syndrome

    • Affects 0.2% of the population with an accessory pathway between atria and ventricles, causing abnormal conduction patterns like AV reentrant tachycardia.

    AV Reentrant Tachycardia

    • Occurs when electrical activity re-enters the atria from the ventricles via an accessory pathway, potentially resulting in a rapid heart rate increase.

    Efficient Cardiac Pumping

    • Requires a delay between atrial and ventricular depolarization, coordinated contraction of contractile cells in each chamber, and synchronicity in contraction between both atria and ventricles.

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    Test your knowledge on autorhythmic cells and their functions within the heart. These flashcards cover essential definitions and characteristics crucial for understanding cardiac physiology. Perfect for anyone studying biomedical sciences or physiology.

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