Cardiovascular Physiology Overview
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Questions and Answers

What is the effect of acetylcholine on potassium permeability in SA node cells?

  • Has no effect on potassium permeability
  • Increases potassium permeability (correct)
  • Decreases sodium permeability
  • Decreases potassium permeability

    • What does the QRS complex in an ECG primarily represent?

  • Atrial depolarization
  • Ventricular repolarization
  • Ventricular depolarization (correct)
  • Atrioventricular conduction

    • Which statement about cardiac output is accurate?

  • Is larger when heart rate is minimal
  • At rest is approximately 10 l/min
  • Is the same for left and right ventricular outputs
  • At rest is about 5 l/min (correct)

    • During which phase is left ventricular pressure highest?

    <p>The ejection period</p> Signup and view all the answers

    What primarily influences blood flow in the cardiovascular system?

    <p>Vascular radius</p> Signup and view all the answers

    What is the primary role of the absolute refractory period in cardiomyocytes?

    <p>Prevents tetanic contractions</p> Signup and view all the answers

    Which condition would lead to a decrease in filtered fluid within capillaries?

    <p>Increased plasma colloid-osmotic pressure</p> Signup and view all the answers

    During which phase of the cardiac cycle do the semilunar valves open?

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

    Which of the following best describes angiotensin II's effect on the body?

    <p>Mediates vasoconstriction</p> Signup and view all the answers

    What is the driving force for blood flow as indicated by the pressure difference in the heart?

    <p>Pulse pressure</p> Signup and view all the answers

    Which of the following is an incorrect statement about venous return?

    <p>Decreases in standing position</p> Signup and view all the answers

    Where are the baroreceptors primarily located?

    <p>In the carotid sinuses</p> Signup and view all the answers

    When is atrial systole most important for ensuring adequate ventricular filling?

    <p>When ventricular compliance is reduced</p> Signup and view all the answers

    During which condition is the first heart sound most likely to include vibrations caused by the opening of the mitral valve?

    <p>At rest and during bradycardia</p> Signup and view all the answers

    In which situation is the mean electrical axis of the heart directed to the right?

    <p>During the last trimester of a pregnancy</p> Signup and view all the answers

    What factor does coronary blood flow depend on most significantly?

    <p>Local regulatory factors</p> Signup and view all the answers

    What is true about autoregulation of brain blood flow?

    <p>It ensures constant flow despite pressure changes.</p> Signup and view all the answers

    Where is the linear velocity of blood flow the slowest?

    <p>In the capillaries</p> Signup and view all the answers

    What role do venous valves play in venous blood flow?

    <p>They facilitate blood flow against gravity.</p> Signup and view all the answers

    How do kidneys contribute to long-term regulation of arterial pressure?

    <p>By independently regulating sodium excretion</p> Signup and view all the answers

    Which statement about arterial baroreceptors is true?

    <p>They are primarily mechanoreceptors.</p> Signup and view all the answers

    Which of the following describes elastic vessels?

    <p>They include aorta and large arteries.</p> Signup and view all the answers

    According to Poiseuille's law, laminar blood flow is influenced by which variable?

    <p>Length of the blood vessel</p> Signup and view all the answers

    What is true about pulse pressure?

    <p>It is highest in the aorta.</p> Signup and view all the answers

    Which capillaries are known for their high permeability?

    <p>Capillaries in endocrine glands</p> Signup and view all the answers

    Which statement accurately describes the conduction of excitation in the myocardium?

    <p>Conduction is facilitated by the excitatory-conductive system.</p> Signup and view all the answers

    Which excitatory structure generates an action potential with the longest plateau phase?

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

    Study Notes

    Cardiovascular Physiology Study Notes

    • Parasympathetic Stimulation:

      • Slows heart rate by increasing potassium permeability in SA node cells.
      • Decreases potassium permeability in AV node cells.
      • Does not affect sodium permeability in SA node cells.

    • ECG (Electrocardiogram) QRS Complex:

      • Represents ventricular depolarization.

    • Cardiac Output:

      • Approximately 5 liters per minute at rest.
      • Left ventricle output generally equals right ventricle output.
      • Varies with physical activity, not constant.
      • Highest when heart rate is maximal.

    • Left Ventricular Pressure Peak:

      • Highest during isovolumetric contraction.

    • Blood Flow Regulation:

      • Primarily influenced by vascular radius.
      • Affected by blood viscosity and plasma protein concentration, less so erythrocyte count.

    • Atrioventricular Valve Closure:

      • Occurs at the onset of isovolumetric contraction.

    • Stroke Volume:

      • Influenced by intrinsic regulatory mechanisms (Frank-Starling mechanism).
      • Varies with preload.
      • Not a fixed value.

    • Absolute Refractory Period (Cardiomyocytes):

      • Prevents tetanic contractions.
      • A time interval during which cardiomyocytes cannot be excited, even by strong stimuli.
      • Mostly due to potassium ion outflow.
      • Duration is only several milliseconds in the ventricular myocardium.

    • Capillary Fluid Filtration:

      • Decreases with decreased capillary hydrostatic pressure and increased plasma colloid osmotic pressure.
      • Increased capillary permeability raises the filtration.

    • Cardiac Cycle:

      • Ejection period begins with semilunar valve opening.
      • Atrial cycle is shorter than ventricular cycle.
      • Ventricular pressure changes during isovolumetric contraction.
      • Ventricular filling occurs when atrioventricular valves are open.

    • Atrial Pressure Difference:

      • Pulse pressure.

    • Angiotensin II:

      • A vasoconstrictor acting on vascular smooth muscle (ATI receptors).

    • Vasodilators:

      • Prostacyclin and nitric oxide are vasodilators.
      • Serotonin is not a vasodilator.
      • Bradykinin is a vasodilator.

    • Vasopressin:

      • A potent vasoconstrictor, not a hypotensive agent.
      • Affected by hypovolemia.

    • Venous Return:

      • Influenced by skeletal muscle activity (contractions hinder), and breathing (inspiration increases).
      • Not increased by standing position (initially, but adjustment occurs).

    • Baroreceptors:

      • Stretch receptors located in major arteries (major blood vessels).
      • Activated by changes in blood pressure.

    • Mitral Valve Opening:

      • Occurs at the end of isovolumetric relaxation.

    • Atrial Systole Importance:

      • Greatest importance for ventricular filling at rest and during bradycardia (slow heart rate).

    • First Heart Sound:

      • Begins slightly before the Q wave of the ECG.
      • Primarily due to atrioventricular valve closure.

    • Electrical Axis of Heart:

      • Varies depending on conditions (expiration, pregnancy, hypertrophy).

    • Coronary Blood Flow:

      • Primarily regulated by local factors.
      • Reduced by hypoxia, not significantly by sympathetic stimulation.
      • Minimal during diastole.

    • Autoregulation (Brain Blood Flow):

      • Maintains constant blood flow despite blood pressure changes within a vital range (60-160 mmHg).
      • Blood flow does not depend on volume limitations.

    • Blood Velocity (Smallest):

      • Blood velocity is smallest in capillaries due to their large total cross-sectional area.

    • Venous Blood Flow:

      • Influenced by respiration and skeletal muscle contraction.
      • Venous valves help maintain flow direction.
      • More influential during expiration, less influenced by skeletal muscle contraction.

    • Kidney's Role in Blood Pressure Regulation:

      • Regulates blood volume through urine production in response to various factors.
      • Maintains circulating blood volume.

    • Venous Return to Heart:

      • Affected by gravity and skeletal muscle activity.
      • Valves aid in one-way flow.

    • Sympathetic Nervous System Activity:

      • Typically produces vasoconstriction in many vessels.
      • Affects coronary vessel dilation.
      • Primary regulator of brain circulation.

    • Arterial Baroreceptors:

      • Respond to blood pressure changes, not directly to the limbic system.
      • Essential in short-term pressure regulation; mechanoreceptors.

    • Vascular Resistance:

      • Laminar blood flow resistance influenced by vessel diameter, length, and blood viscosity; the Reynolds number.
      • Number of blood cells doesn't directly factor in laminar resistance.

    • Elastic Vessels:

      • Aorta and large arteries; act as pressure reservoirs during cardiac systole.

    • Poiseuille's Law (Laminar Blood Flow):

      • Blood flow is directly proportional to the fourth power of the vessel radius, not the second power.

    • Pulse Pressure:

      • Highest in the aorta, influenced by stroke volume.
      • Decreases with greater aortic compliance.

    • Capillary Permeability:

      • High permeability is seen in capillaries in endocrine glands, and also in the skin.

    • Pulmonary Arterioles:

      • Exhibit lower resistance than systemic arterioles.
      • Dilate in hypoxia.

    • Capacitance Vessels:

      • Veins, due to their high compliance, are capacitance vessels.

    • Cardiac Excitation Conduction:

      • Conducted by the excitatory-conductive system.

    • Action Potential Plateau:

      • AV node cells have the longest action potential plateau.

    • Mean Electrical Axis:

      • The mean direction of atrial and ventricular depolarization, which varies based on bodily conditions.

    • Parasympathetic Inotropic Effect:

      • Reduces heart contractility by affecting N-cholinergic receptors, decreasing cAMP production, reducing adenylyl cyclase activation.

    • PQ Interval:

      • Represents excitation conduction time from the SA node to the ventricles.
      • Lengthens with parasympathetic stimulation; not fixed (but usually, under 0.2 seconds).

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    Description

    This quiz covers key concepts in cardiovascular physiology, including blood flow regulation, cardiac output, and the electrocardiogram. It explores the effects of parasympathetic stimulation and the mechanics of heart contractions. Perfect for students studying physiology or preparing for exams.

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