Understanding Resistance and Flow in Vascular Circuits
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Questions and Answers

Which of the following is responsible for initiating the electrical impulses that cause the heart to beat?

  • Sinoatrial (SA) node (correct)
  • Atrioventricular (AV) node
  • Bundle of His
  • Purkinje fibers

    • Which part of the nervous system increases heart rate by releasing norepinephrine?

  • Central nervous system
  • Parasympathetic nervous system
  • Autonomic nervous system
  • Sympathetic nervous system (correct)

    • Which ions are responsible for initiating action potentials in the heart?

  • Sodium ions
  • Chloride ions
  • Potassium ions
  • Calcium ions (correct)

    • Which part of the heart conducts the electrical impulse rapidly through the ventricular septum?

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

    What causes the SA node action potential graph to shoot up?

    <p>Activation of Ca2+ channels</p> Signup and view all the answers

    Which nervous system releases acetylcholine to slow down the heart rate?

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

    What can cause tachycardia?

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

    Which of the following is a cause of bradycardia?

    <p>Excessive vagal stimulation</p> Signup and view all the answers

    What is paroxysmal atrial tachycardia characterized by?

    <p>A series of rapid heartbeats that suddenly start and then suddenly stop</p> Signup and view all the answers

    What is the cause of ventricular tachycardia (V-tach)?

    <p>Ischemic damage</p> Signup and view all the answers

    What is the effect of atrial fibrillation (AFib) on heart pumping efficiency?

    <p>Decreases efficiency by 20-30%</p> Signup and view all the answers

    Which of the following factors can increase right atrial pressure?

    <p>All of the above</p> Signup and view all the answers

    What are Korotkoff's sounds?

    <p>Sounds produced by the turbulent flow of blood through the compressed artery</p> Signup and view all the answers

    Which factor is defined by Poiseuille's law and directly proportional to the fourth power of the vessel radius?

    <p>Vessel length</p> Signup and view all the answers

    Which structure in the heart is responsible for generating and conducting electrical impulses throughout the heart?

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

    During which phase of the cardiac muscle action potential does rapid depolarization occur?

    <p>Phase 0</p> Signup and view all the answers

    What is the function of intercalated discs in the heart?

    <p>All of the above</p> Signup and view all the answers

    Which of the following is true about the refractory periods in the cardiac muscle action potential?

    <p>The relative refractory period lasts from the middle of phase 2 to the end of phase 3</p> Signup and view all the answers

    Which of the following is the primary pacemaker of the heart?

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

    What is the main function of the Atrioventricular (AV) node?

    <p>To serve as a gateway for the electrical impulses to pass from the atria to the ventricles</p> Signup and view all the answers

    What is the role of troponin in the contraction of cardiac muscle fibers?

    <p>To trigger a conformational change in the tropomyosin-troponin complex</p> Signup and view all the answers

    What is the function of the Purkinje fibers?

    <p>To spread the electrical impulses throughout the ventricles</p> Signup and view all the answers

    Which one of these is the correct relationship between resistance and flow in a circuit, according to Ohm's law?

    <p>Flow rate is equal to the pressure difference divided by the total resistance.</p> Signup and view all the answers

    Which one of these is the correct relationship between conductance and resistance?

    <p>Conductance is the reciprocal of resistance.</p> Signup and view all the answers

    Which one of these is the correct relationship between conductance and diameter?

    <p>Conductance increases in proportion to the fourth power of the diameter.</p> Signup and view all the answers

    What is the advantage of vascular compliance?

    <p>Allows the arterial tree to normally reduce pressure pulsations.</p> Signup and view all the answers

    Which of the following organs can influence the heart rate?

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

    What is the effect of the sympathetic nervous system on heart rate?

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

    Which of the following hormones can increase heart rate?

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

    What initiates the electrical impulses that cause the heart to beat?

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

    Which of the following is responsible for conducting the electrical impulse rapidly through the ventricular septum?

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

    What is the cause of an ectopic pacemaker?

    <p>A shift of pacemaker from the sinus node</p> Signup and view all the answers

    Which part of the nervous system releases acetylcholine to slow down the heart rate?

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

    What is the effect of sympathetic stimulation on the heart rate?

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

    Which of the following is the correct order of electrical signal transmission through the conduction system of the heart?

    <p>SA node -&gt; AV node -&gt; bundle of His -&gt; Purkinje fibers</p> Signup and view all the answers

    Which of the following is responsible for initiating each heartbeat and setting the heart rate?

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

    Which of the following is a characteristic of muscle cells in the heart?

    <p>Striated appearance</p> Signup and view all the answers

    Which of the following is a function of the atrioventricular (AV) node?

    <p>Acts as a gateway for electrical impulses to pass from the atria to the ventricles</p> Signup and view all the answers

    Which of the following is responsible for the rapid depolarization of the cardiac muscle cell membrane during Phase 0 of the action potential?

    <p>Voltage-gated Na+ channels</p> Signup and view all the answers

    Which of the following channels are responsible for the plateau phase in Phase 2 of the cardiac muscle action potential?

    <p>L-type Ca2+ channels</p> Signup and view all the answers

    Which of the following is true about the refractory periods in the cardiac muscle action potential?

    <p>The absolute refractory period is the period during which the cardiac muscle cell cannot be stimulated to depolarize again.</p> Signup and view all the answers

    Which of the following is true about the pressures and volumes during ventricular systole?

    <p>Ventricular pressure increases and volume decreases.</p> Signup and view all the answers

    According to the text, what is the relationship between the Reynolds number and the flow of blood in a vessel?

    <p>All of the above.</p> Signup and view all the answers

    What is the formula for the Reynolds number (Re) in terms of velocity (V), diameter (D), density (P) of blood, and viscosity (N)?

    <p>$Re = \frac{V \cdot D \cdot P}{N}$</p> Signup and view all the answers

    What is the relationship between conductance and resistance in a blood vessel?

    <p>Conductance is the reciprocal of resistance.</p> Signup and view all the answers

    What is the relationship between the diameter of a blood vessel and its ability to conduct blood flow?

    <p>Small changes in diameter cause significant changes in blood flow.</p> Signup and view all the answers

    Which of the following is true about ventricular tachycardia (V-tach) and ventricular fibrillation (V-fib)?

    <p>V-tach may lead to V-fib</p> Signup and view all the answers

    What is the effect of atrial fibrillation (AFib) on heart pumping efficiency?

    <p>Decreases heart pumping efficiency by 20-30%</p> Signup and view all the answers

    What are the physical characteristics of arteries, veins, and capillaries?

    <p>Arteries have strong vascular walls, capillaries have thin walls, and veins have thin and muscular walls</p> Signup and view all the answers

    What is the relationship between pressure, flow, and resistance in blood circulation?

    <p>Flow is determined by the pressure gradient and vascular resistance</p> Signup and view all the answers

    Which of the following factors can decrease right atrial pressure?

    <p>Decreased blood volume</p> Signup and view all the answers

    Which one of the following is responsible for regulating right atrial pressure?

    <p>The heart's ability to pump blood out of the right atrium and ventricle into the lungs</p> Signup and view all the answers

    Which one of the following is defined by Poiseuille's law and is directly proportional to the fourth power of the vessel radius?

    <p>The pressure gradient driving blood flow</p> Signup and view all the answers

    Which one of the following physical properties of blood vessels and blood determine hemodynamics?

    <p>All of the above</p> Signup and view all the answers

    Which one of the following is NOT a factor that can increase right atrial pressure?

    <p>Constriction of the arterioles</p> Signup and view all the answers

    Which one of the following is NOT a factor that can decrease right atrial pressure?

    <p>Increased blood flow from the peripheral veins into the right atrium</p> Signup and view all the answers

    Study Notes

    Heart Electrical Activity and Regulation

    • The sinoatrial (SA) node serves as the primary pacemaker, initiating electrical impulses for heartbeats.
    • The sympathetic nervous system increases heart rate by releasing norepinephrine.
    • Calcium (Ca²⁺) and sodium (Na⁺) ions primarily initiate action potentials in cardiac cells.
    • The Purkinje fibers conduct electrical impulses rapidly through the ventricular septum.
    • The steep rise in the SA node action potential graph is caused by the influx of sodium ions during depolarization.
    • The parasympathetic nervous system releases acetylcholine to decrease heart rate.

    Arrhythmias and Heart Rate Variations

    • Tachycardia can be caused by factors such as stress, fever, or electrolyte imbalances.
    • Bradycardia may result from hypothyroidism, certain medications, or high fitness levels.
    • Paroxysmal atrial tachycardia is characterized by episodes of rapid heartbeats that start and stop suddenly.
    • Ventricular tachycardia (V-tach) often results from scar tissue or abnormal pathways in the heart.

    Cardiac Function and Blood Flow

    • Atrial fibrillation (AFib) significantly reduces heart pump efficiency, leading to increased risk of stroke or heart failure.
    • Elevated right atrial pressure can result from heart failure, fluid overload, or certain lung conditions.
    • Korotkoff's sounds are the sounds heard through a stethoscope during blood pressure measurement.

    Hemodynamics and Vascular Physiology

    • According to Poiseuille’s law, resistance to flow is directly proportional to the fourth power of the vessel radius.
    • The heart generates and conducts electrical impulses through the conduction system, including the SA node, AV node, and Purkinje fibers.
    • Rapid depolarization in the cardiac muscle action potential occurs during Phase 0.
    • Intercalated discs allow for synchronized contraction and facilitate the spread of action potentials between cardiac muscle cells.
    • Refractory periods in cardiac muscle prevent excessive stimulation and arrhythmias.

    Cardiac Physiology and Muscle Function

    • The AV node primarily functions to slow down electrical impulses, coordinating timing between atrial contraction and ventricular filling.
    • Troponin plays a crucial role in muscle contraction by regulating calcium interactions with actin and myosin.
    • Purkinje fibers ensure rapid conduction of the action potential throughout the ventricles.

    Conductance Relationships

    • Ohm's law defines the relationship between resistance and flow as Flow = Pressure/Resistance.
    • Conductance is inversely related to resistance, meaning as conductance increases, resistance decreases.
    • Higher diameter of blood vessels results in increased conductance, promoting enhanced blood flow.
    • Vascular compliance allows vessels to accommodate varying volumes of blood without significant changes in pressure.

    Control of Heart Rate and Influencing Factors

    • Organs like the adrenal glands, thyroid, and kidneys can influence heart rate through hormones and fluid balance.
    • The sympathetic nervous system accelerates heart rate, while hormones like epinephrine also contribute to increasing it.
    • Ectopic pacemakers arise from abnormal pacemaker activity outside the SA node, potentially leading to arrhythmias.
    • Ventricular systole is characterized by increased pressure and decreased volume in the ventricles, essential during blood ejection.

    Important Relationships in Circulation

    • The Reynolds number (Re) indicates flow characteristics in a vessel, calculated as Re = (Density × Velocity × Diameter) / Viscosity.
    • Relation of pressure, flow, and resistance drives blood circulation, impacting cardiovascular health.
    • Factors influencing right atrial pressure include blood volume, venous return, and intrathoracic pressure changes.

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    Related Documents

    Physiology II Exam 2 PDF

    Description

    Test your knowledge on the total resistance to blood flow in series and parallel vascular circuits in this quiz. Explore the relationship between Reynolds' number and flow characteristics, and understand how velocity, diameter, density, and viscosity affect blood flow.

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