أسئلة المحاضرة الـ 17 فسيولوجي (قبل التعديل)
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Questions and Answers

What is the overall blood flow in circulation at rest?

  • 10000 ml/minute
  • 3000 ml/minute
  • 7000 ml/minute
  • 5000 ml/minute (correct)

    • How is blood flow related to effective perfusion pressure (ΔP)?

  • Directly proportional (correct)
  • Constant regardless of ΔP
  • Unrelated
  • Inversely proportional

    • What effect does an increase in the resistance of blood vessels have on blood flow?

  • Decreases blood flow (correct)
  • Maintains blood flow
  • Increases blood flow
  • Eliminates blood flow

    • Which of the following factors is directly proportional to the resistance in blood flow?

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

    Which factor does NOT determine the resistance faced by blood flow?

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

    If the radius of a blood vessel decreases, what will happen to the resistance and blood flow?

    <p>Resistance increases and blood flow decreases</p> Signup and view all the answers

    What is the formula used to determine blood flow in relation to effective perfusion pressure and resistance?

    <p>Flow (Q) = ΔP / R</p> Signup and view all the answers

    Which factor is inversely proportional to resistance in blood flow?

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

    What is the primary characteristic of laminar blood flow?

    <p>It consists of thin layers of blood with varying velocities.</p> Signup and view all the answers

    Which of the following methods for measuring blood flow is considered direct?

    <p>Electromagnetic flow meter</p> Signup and view all the answers

    Under which condition does turbulent blood flow most likely occur?

    <p>When vessel diameter decreases.</p> Signup and view all the answers

    How does resistance change when the radius of a blood vessel is reduced to half its original size?

    <p>Resistance increases to 16 times its previous value.</p> Signup and view all the answers

    Which of the following factors is NOT associated with an increase in blood viscosity?

    <p>Low plasma protein concentration.</p> Signup and view all the answers

    Fick's principle states that blood flow to an organ is calculated by which of the following?

    <p>The quantity of substance taken by the organ divided by the difference in arteriovenous concentration.</p> Signup and view all the answers

    What is a defining feature of turbulent flow as compared to laminar flow?

    <p>It produces audible sounds or murmurs.</p> Signup and view all the answers

    What is the primary site of resistance to blood flow in the vascular system?

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

    Which flow meter method relies on sound waves to determine blood flow?

    <p>Ultrasonic flow meter</p> Signup and view all the answers

    In the Poiseuille equation, what is the relationship between viscosity and resistance?

    <p>Resistance is directly proportional to viscosity.</p> Signup and view all the answers

    What is the Reynolds number threshold that signifies laminar flow?

    <p>Less than 2000</p> Signup and view all the answers

    What effect does polycythemia have on blood viscosity and resistance?

    <p>Increases blood viscosity and resistance.</p> Signup and view all the answers

    In which scenario is the blood flow most likely to be turbulent?

    <p>Increased blood velocity and decreased viscosity.</p> Signup and view all the answers

    Which statement about the effect of vessel length on blood resistance is true?

    <p>Resistance increases with longer vessels.</p> Signup and view all the answers

    Which system primarily controls the diameter of arterioles?

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

    According to the Poiseuille equation, what factor has the most significant impact on resistance to blood flow?

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

    What happens to blood flow if the radius of a blood vessel is decreased by 75%?

    <p>It decreases to 1/256 of its original value</p> Signup and view all the answers

    Which of the following factors has the least impact on blood viscosity?

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

    What happens to blood flow when the perfusion pressure (ΔP) increases significantly?

    <p>Blood flow increases due to a direct proportionality to ΔP.</p> Signup and view all the answers

    How does increased plasma protein concentration affect blood resistance?

    <p>It increases resistance</p> Signup and view all the answers

    Which characteristic of blood flow is directly influenced by the viscosity of blood?

    <p>Rate of laminar flow.</p> Signup and view all the answers

    How does the length of a blood vessel affect resistance?

    <p>Longer vessels increase resistance proportionally.</p> Signup and view all the answers

    What role does the sympathetic nervous system play in arteriolar function?

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

    Which statement accurately reflects the relationship between viscosity and blood flow?

    <p>Increasing viscosity decreases blood flow</p> Signup and view all the answers

    Which of the following best describes the relationship between blood viscosity and flow?

    <p>Increased viscosity decreases blood flow.</p> Signup and view all the answers

    Which factor directly contributes to the resistance encountered in blood flow according to the Poiseuille equation?

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

    Which factor would most likely lead to decreased blood flow in the circulatory system?

    <p>Increase in blood vessel length.</p> Signup and view all the answers

    Which of the following accurately reflects the relationship between resistance and blood flow?

    <p>Increased resistance results in decreased blood flow.</p> Signup and view all the answers

    What is the impact of hemoconcentration on resistance and blood flow?

    <p>Decreases flow and increases resistance</p> Signup and view all the answers

    What is a primary determinant of effective perfusion pressure (ΔP) in the vascular system?

    <p>The difference in arterial and venous pressure.</p> Signup and view all the answers

    Which of the following accurately describes the effect of blood vessel length on blood flow?

    <p>Longer vessels lead to increased resistance and decreased blood flow</p> Signup and view all the answers

    Which of the following statements regarding blood flow and vessel radius is true?

    <p>Increased radius generally allows for greater blood flow.</p> Signup and view all the answers

    Which method of measuring blood flow does NOT involve direct measurement?

    <p>Venous occlusion plethysmography</p> Signup and view all the answers

    Under what condition is turbulent blood flow most likely to occur?

    <p>When there is a sharp decrease in vessel diameter.</p> Signup and view all the answers

    What is the Reynolds number threshold that typically indicates turbulent flow?

    <p>Greater than 3000</p> Signup and view all the answers

    Fick's principle describes blood flow in relation to which of the following?

    <p>The concentration difference of a substance in the blood.</p> Signup and view all the answers

    What happens to the velocity of blood flow in laminar flow as you move towards the vessel's center?

    <p>Velocity increases to a maximum.</p> Signup and view all the answers

    Which condition is associated with a Reynolds number less than 2000?

    <p>Blood with increased viscosity.</p> Signup and view all the answers

    How does venous occlusion plethysmography measure blood flow?

    <p>By observing changes in blood volume in a limb.</p> Signup and view all the answers

    Which characteristic distinguishes true isoenzymes from multiple forms produced by post-translational modifications?

    <p>They are produced by more than one gene.</p> Signup and view all the answers

    What is the composition of lactate dehydrogenase (LDH)?

    <p>A tetramer formed of four distinct protein subunits.</p> Signup and view all the answers

    Which of the following statements is TRUE regarding creatine kinase (CK)?

    <p>It is a dimer made up of two subunits.</p> Signup and view all the answers

    What distinguishes lactate dehydrogenase from other enzymes in terms of its structure?

    <p>It exists as a tetramer of different subunits.</p> Signup and view all the answers

    In terms of electrophoretic mobility, how do true isoenzymes differ from multiple forms of the same enzyme?

    <p>Multiple forms show varied mobility due to post-translational modifications.</p> Signup and view all the answers

    Which type of plasma enzymes are present in higher concentrations compared to tissues?

    <p>Functional plasma enzymes</p> Signup and view all the answers

    What is the primary characteristic of non-functional plasma enzymes?

    <p>Present in very low concentrations</p> Signup and view all the answers

    Which of the following enzymes is primarily associated with liver diseases?

    <p>Serum glutamic pyruvic transaminase</p> Signup and view all the answers

    What can cause an increase in enzyme concentration in plasma?

    <p>Reduction of liver function</p> Signup and view all the answers

    Which plasma enzyme is primarily responsible for indicating heart diseases?

    <p>Creatine kinase</p> Signup and view all the answers

    What is one of the assumed reasons for the release of enzymes into the blood?

    <p>Cellular destruction</p> Signup and view all the answers

    Which condition is NOT associated with an elevation in the concentration of lactate dehydrogenase?

    <p>Muscle hypertrophy</p> Signup and view all the answers

    Which of the following statements best describes functional plasma enzymes?

    <p>They have known functions in the body.</p> Signup and view all the answers

    Which isoenzyme is primarily associated with increases in myocardial infarction?

    <p>Lactate dehydrogenase (LDH)</p> Signup and view all the answers

    In which condition would you expect to see an increase in creatine kinase (CK) levels?

    <p>Brain tumors</p> Signup and view all the answers

    What is the clinical significance of isoenzymes?

    <p>They help differentiate between various organ diseases.</p> Signup and view all the answers

    Which isoenzyme is primarily linked to an increase in blood diseases?

    <p>Lactate dehydrogenase (LDH)</p> Signup and view all the answers

    Which enzyme is associated with skeletal muscle diseases?

    <p>Creatine kinase (CK)</p> Signup and view all the answers

    What role do isoenzymes play in the diagnosis of diseases?

    <p>They reflect the functional status of a particular organ.</p> Signup and view all the answers

    Which isoenzyme should be monitored in cases of viral hepatitis?

    <p>Lactate dehydrogenase (LDH)</p> Signup and view all the answers

    Which conditions can lead to an increase in lactate dehydrogenase (LDH)?

    <p>Pulmonary embolism and cardiac arrest</p> Signup and view all the answers

    Study Notes

    Blood Flow

    • Blood flow is the quantity of blood passing a given point in the circulatory system per unit time, typically measured in milliliters or liters per minute.
    • The overall blood flow at rest is 5000 ml/minute, which equals cardiac output.
    • Blood flow (Q) is equal to perfusion pressure (P) divided by resistance (R).
    • Blood flow is expressed in milliliters or liters per minute.

    Factors Affecting Blood Flow Rate

    • Two major factors influencing blood flow are effective perfusion pressure (ΔP) and resistance of blood vessels.
    • Effective perfusion pressure is the difference in pressure between the arterial and venous ends of a blood vessel.
    • Blood flow is directly proportional to the perfusion pressure; as perfusion pressure increases, blood flow increases.
    • Blood flow is inversely proportional to resistance. Increased resistance decreases blood flow.

    Resistance of Blood Vessels

    • Resistance is the difficulty the blood encounters during its flow through the vessels.
    • Resistance is inversely related to vessel radius raised to the fourth power (1/r4). A smaller radius means greater resistance.
    • Resistance is directly proportional to blood viscosity and vessel length.

    Factors Determining Resistance

    • Vessel radius: Resistance is inversely proportional to the fourth power of the vessel radius. A smaller radius significantly increases resistance.
    • Blood viscosity: Resistance is directly proportional to blood viscosity. Higher viscosity means greater resistance.
    • Vessel length: Resistance is directly proportional to vessel length. Longer vessels offer more resistance.

    Poiseuille's Equation

    • The equation that describes the relationship between flow, pressure, vessel radius, viscosity, and length is Poiseuille's equation:

      Q = (πr<sup>4</sup>ΔP) / (8ηL)

      where:

    • Q = flow

    • r = radius of the blood vessel

    • ΔP = pressure difference

    • η = viscosity of blood

    • L = length of the blood vessel

    Vessel Radius

    • Resistance is inversely proportional to the fourth power of the vessel radius.
    • If the radius is reduced to half its original value, blood flow decreases to 1/16 of its previous value.
    • Arteriolar diameter is controlled by the sympathetic nervous system, various drugs, and hormones.

    Blood Viscosity

    • Blood viscosity is the ability of a substance to resist changes in shape.
    • Blood viscosity is directly proportional to resistance and inversely proportional to blood flow.
    • Factors affecting blood viscosity include hematocrit (the volume percentage of red blood cells in blood) and plasma proteins. Higher hematocrit and higher plasma proteins result in increased viscosity.
    • Increased hematocrit increases blood viscosity and reduces flow.

    Length of Blood Vessel

    • Resistance is directly proportional to the length of the blood vessel.
    • The length of blood vessels is generally fixed in the body, so changes in length do not significantly affect flow.

    Methods for Measuring Blood Flow

    • Direct methods: Electromagnetic flow meters, ultrasonic flow meters, venous occlusion plethysmography.
    • Indirect methods: Fick's principle can be used to estimate blood flow to an organ. Flow (F) = Q / (A-V).

    Laminar vs. Turbulent Blood Flow

    • Laminar flow is smooth and streamline flow.
    • Turbulent flow is irregular and crosswise, generating eddy currents.
    • Laminar flow occurs at relatively low velocities, while turbulent flow occurs at higher velocities or under conditions that increase resistance.
    • Reynolds number (< 2000) predicts laminar flow, while a number > 3000 predicts turbulent flow.
    • Turbulent flow is characterized by the production of murmurs (sounds).

    Reynolds Number

    • The Reynolds number (Re) is a dimensionless number that predicts the probability of turbulence.
    • The higher the Reynolds number, the greater the probability of turbulence.
    •   A Reynolds number < 2000 indicates laminar flow; > 3000, turbulent flow.
    • Factors like increased velocity, reduced viscosity (e.g., anemia), and changes in vessel diameter can cause turbulence.

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