The Cardiac Cycle
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Questions and Answers

What is the primary function of atrial systole in the cardiac cycle?

  • To close the atrioventricular valves
  • To open the pulmonic and aortic valves
  • To preload the ventricles with additional blood (correct)
  • To increase the pressure in the ventricles

    • During which phase of the cardiac cycle do the pulmonic and aortic valves open?

  • Systole (correct)
  • Atrial systole
  • Ventricular contraction
  • Diastole

    • What is the main purpose of understanding the cardiac cycle?

  • To analyze the cardiac output of the heart
  • To evaluate heart sounds and read electrocardiographs (correct)
  • To understand the structure of the heart
  • To study the function of the atrioventricular valves

    • What percentage of additional blood does atrial systole provide to the ventricles?

    <p>20 to 25 percent</p> Signup and view all the answers

    During which phase of the cardiac cycle do the ventricles fill with blood?

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

    What is the sequence of contractions in the cardiac cycle?

    <p>Atria contract first, followed by ventricles</p> Signup and view all the answers

    What is the primary function of the natriuretic peptides?

    <p>To counteract the effects of the sympathetic nervous system and the renin–angiotensin–aldosterone system</p> Signup and view all the answers

    Which of the following electrolytes is NOT involved in myocardial depolarization?

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

    What is the effect of hypercalcemia on myocardial contractility?

    <p>Increased contractility</p> Signup and view all the answers

    What is the role of intercalated disks in cardiac muscle fibers?

    <p>To conduct electrical impulses quickly from one muscle fiber to the next</p> Signup and view all the answers

    What is the effect of BNP on blood pressure?

    <p>Decrease blood pressure</p> Signup and view all the answers

    What is the difference between the contraction of atrial and ventricular syncytia?

    <p>Atrial syncytium contracts from superior to inferior, whereas ventricular syncytium contracts from inferior to superior</p> Signup and view all the answers

    What is the effect of hypokalemia on cardiac function?

    <p>Increased irritability</p> Signup and view all the answers

    What is the function of the sympathetic nervous system in response to left ventricular dysfunction?

    <p>To increase heart rate and cardiac contractile force</p> Signup and view all the answers

    What is the difference between ANP and BNP?

    <p>ANP is secreted by the atria, whereas BNP is secreted by the ventricles</p> Signup and view all the answers

    What is the effect of Nesiritide (Natrecor) on cardiac function?

    <p>It decreases cardiac output and blood pressure</p> Signup and view all the answers

    What percentage of the blood it contains at the end of systole does the normal ventricle eject?

    <p>50 to 70 percent</p> Signup and view all the answers

    What is the term for the pressure in the filled ventricle at the end of diastole?

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

    According to Starling's law of the heart, what happens when the myocardial muscle is stretched?

    <p>It contracts with greater force</p> Signup and view all the answers

    What is the term for the volume of blood that the heart pumps in 1 minute?

    <p>Cardiac output</p> Signup and view all the answers

    What is the average heart rate in beats per minute?

    <p>60 to 100</p> Signup and view all the answers

    What is the result of an increase in peripheral vascular resistance on stroke volume?

    <p>It decreases</p> Signup and view all the answers

    What is the sympathetic nervous system's role in regulating the heart?

    <p>It speeds up the heart rate</p> Signup and view all the answers

    What is the term for the amount of blood ejected from the ventricle during each contraction?

    <p>Stroke volume</p> Signup and view all the answers

    What is the result of a decrease in stroke volume on blood pressure?

    <p>It remains the same</p> Signup and view all the answers

    What is the average cardiac output in liters per minute?

    <p>5 L/min</p> Signup and view all the answers

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

    <p>To slow the impulse and allow the ventricles time to fill</p> Signup and view all the answers

    What is the term for the ability of conductive system cells to depolarize without an outside impulse?

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

    Which component of the cardiac conduction system has the slowest intrinsic rate of self-excitation?

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

    What is the purpose of the internodal atrial pathways in the cardiac conduction system?

    <p>To transmit the impulse to the atrial muscle mass</p> Signup and view all the answers

    Which of the following is NOT a property of conductive system cells?

    <p>Pacemaker potential</p> Signup and view all the answers

    What is the name of the bundle that divides into the right and left bundle branches in the ventricles?

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

    What is the primary function of the fibrous structure that separates the atria from the ventricles?

    <p>To physically separate the atria from the ventricles</p> Signup and view all the answers

    What is the characteristic of cardiac muscle function that ensures complete depolarization of the atria or ventricles?

    <p>The 'all-or-none' principle of depolarization</p> Signup and view all the answers

    What is the approximate millivolt difference between the inside and outside of a myocardial cell in its resting state?

    <p>-70mV</p> Signup and view all the answers

    What is the purpose of the sodium-potassium pump in a myocardial cell?

    <p>To regulate the ionic difference across the cell membrane</p> Signup and view all the answers

    What is the effect of the influx of sodium ions into a myocardial cell during depolarization?

    <p>The inside of the cell becomes more positively charged</p> Signup and view all the answers

    What is the function of the cardiac conduction system in terms of ventricular depolarization?

    <p>To stimulate the ventricles to depolarize from inferior to superior</p> Signup and view all the answers

    What is the reason why the ventricles would be ineffective if the depolarization impulse originated in the atria and spread passively to the ventricles?

    <p>The ventricles would contract from superior to inferior</p> Signup and view all the answers

    What is the role of the intercalated disks in the cardiac muscle?

    <p>To transmit depolarization throughout the entire syncytium</p> Signup and view all the answers

    What is the effect of the calcium ions influx through the calcium channels during depolarization?

    <p>The positive charge inside the cell is increased</p> Signup and view all the answers

    What is the duration of the sodium influx through the sodium channels during depolarization?

    <p>A fraction of a second</p> Signup and view all the answers

    What is the primary function of alpha receptors in the sympathetic nervous system?

    <p>Regulate vasoconstriction in peripheral blood vessels</p> Signup and view all the answers

    What is the effect of norepinephrine on the heart rate?

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

    What is the primary function of the vagus nerve in terms of heart control?

    <p>Decrease heart rate and slow atrioventricular conduction</p> Signup and view all the answers

    What is the term for the autonomic control of heart rate?

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

    What is the effect of a negative chronotropic agent on the heart?

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

    What is the primary difference between a native heart and a transplanted heart in terms of nervous system connections?

    <p>A transplanted heart has less nervous system connections</p> Signup and view all the answers

    What is the effect of a transplanted heart on the patient's ability to feel chest pain?

    <p>Decreases the patient's ability to feel chest pain</p> Signup and view all the answers

    What is the primary function of beta1 receptors in the sympathetic nervous system?

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

    What is the primary function of the cardiac plexus?

    <p>Innervate the atria and ventricles</p> Signup and view all the answers

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

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

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