PHYSIO HEMODYNAMICS
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Questions and Answers

What is the primary function of capillaries in systemic circulation?

  • To store blood for emergencies
  • To exchange diffusible substances between blood and tissues (correct)
  • To regulate blood pressure
  • To transport blood back to the heart

    • Which statement about veins in systemic circulation is true?

  • The number of veins increases as one approaches the heart
  • Veins of increasing size are formed from venules (correct)
  • Veins decrease in size but increase in number near the heart
  • Veins have thicker walls than arteries

    • What happens to blood after it passes through the capillaries?

  • It returns to the heart via small arteries
  • It flows into the aorta
  • It enters venules and then larger veins (correct)
  • It is pumped directly to the lungs

    • How does the structure of capillaries facilitate their function?

    <p>Their walls consist of only one cell thick layer</p> Signup and view all the answers

    In which aspect do veins differ from arteries in systemic circulation?

    <p>Veins are larger and have thinner walls compared to arteries</p> Signup and view all the answers

    What is the total blood flow in the total circulation of an adult person at rest?

    <p>5000 ml/min</p> Signup and view all the answers

    How does the blood flow through veins compare to the blood flow through capillaries?

    <p>Blood flow through veins is greater than through capillaries.</p> Signup and view all the answers

    What is the significance of the value '440' in relation to the heart?

    <p>Represents the end-diastolic volume.</p> Signup and view all the answers

    What is the combined blood flow through arteries in this context?

    <p>130 ml/min</p> Signup and view all the answers

    If a 70-kg woman has a total blood volume of '5000', what is the significance of the value '100' to the total blood volume?

    <p>It represents the percentage of blood volume in relation to body weight.</p> Signup and view all the answers

    What is the formula to approximate Mean Arterial Pressure (MAP)?

    <p>MAP = (1 systolic + 2 diastolic)/3</p> Signup and view all the answers

    If a patient's systolic blood pressure is 180 mmHg and diastolic blood pressure is 120 mmHg, what is their MAP?

    <p>140 mmHg</p> Signup and view all the answers

    How is Cardiac Output (CO) defined in relation to Heart Rate (HR) and Stroke Volume (SV)?

    <p>CO = HR x SV</p> Signup and view all the answers

    What happens to MAP if Systemic Vascular Resistance (SVR) increases?

    <p>MAP increases</p> Signup and view all the answers

    What is considered a normal range for Mean Arterial Pressure (MAP)?

    <p>70-100 mmHg</p> Signup and view all the answers

    What happens in a rigid artery during systole?

    <p>No blood is stored or saved in the walls.</p> Signup and view all the answers

    How does decreased arterial compliance affect workload on the heart?

    <p>It imposes a greater workload on the left ventricle.</p> Signup and view all the answers

    What is the relationship between stroke volume (SV) and flow to the capillaries during diastole in a rigid artery?

    <p>Flow to the capillaries ceases or decreases.</p> Signup and view all the answers

    What effect does aging have on arterial compliance?

    <p>Compliance decreases due to stiffness in arteries.</p> Signup and view all the answers

    What is the normal arterial compliance value?

    <p>2 ml/mmHg</p> Signup and view all the answers

    What is the primary reliance of pulse detection in oscillometric machines?

    <p>The amount of volume change in the arm with each pulse</p> Signup and view all the answers

    What makes it easier for the microprocessor in oscillometric machines to estimate blood pressure?

    <p>Regular pulses and smooth changing arm volume</p> Signup and view all the answers

    What can hinder precise calculations in oscillometric measurement?

    <p>Erratic pulse patterns and arm movements</p> Signup and view all the answers

    How is the average of systolic and diastolic blood pressure indicated in oscillometric measurement?

    <p>By maximum volume change in the artery</p> Signup and view all the answers

    Which component is essential for detecting pressure changes in a blood pressure cuff?

    <p>Solid-state transducers</p> Signup and view all the answers

    What will likely occur if the pulses detected are irregular?

    <p>Difficulty in making precise calculations</p> Signup and view all the answers

    What is the consequence of arm movements while measuring blood pressure oscillometrically?

    <p>Interference with pressure changes detection</p> Signup and view all the answers

    What factor can lead to a failure in oscillometric measurement?

    <p>Irregular pulse rates</p> Signup and view all the answers

    What happens to sympathetic outflow during expiration?

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

    How does the Bainbridge reflex primarily affect the heart rate?

    <p>It increases heart rate with high ventricular output.</p> Signup and view all the answers

    What receptors are activated during normal physiological conditions that influence sympathetic outflow?

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

    What is the response of low-pressure stretch receptors in the atria and pulmonary arteries during an increase in blood volume?

    <p>They inhibit blood pressure changes.</p> Signup and view all the answers

    What effect does the change in intrathoracic pressure have during expiration?

    <p>It increases venous return.</p> Signup and view all the answers

    What is the impact of high blood pressure on baroreceptor activation?

    <p>It leads to decreased heart rate.</p> Signup and view all the answers

    What type of outflow increases during inspiration due to receptor activation?

    <p>Sympathetic outflow.</p> Signup and view all the answers

    What physiological phenomenon is associated with high ventricular output?

    <p>Increased atrial pressure.</p> Signup and view all the answers

    Which mechanism is primarily responsible for maintaining blood pressure during periods of stress?

    <p>Extrinsic mechanisms</p> Signup and view all the answers

    The primary role of venous valves is to allow blood to flow freely in both directions.

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

    What do venous compliance and central venous pressure have in common in relation to venous return?

    <p>They both influence the efficiency of blood returning to the heart.</p> Signup and view all the answers

    The heart and ________ work together to maintain systemic blood pressure.

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

    Match the following blood pressure measurement terms with their definitions:

    <p>Systolic Pressure = Pressure during heart contraction Diastolic Pressure = Pressure during heart relaxation Mean Arterial Pressure = Average blood pressure in a cycle Pulse Pressure = Difference between systolic and diastolic pressure</p> Signup and view all the answers

    What is the relationship between venous return and cardiac output?

    <p>Higher venous return leads to higher cardiac output.</p> Signup and view all the answers

    Arterioles are considered primary exchange vessels in the circulatory system.

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

    What is the primary role of elastic arteries?

    <p>Conducting blood under high pressure</p> Signup and view all the answers

    Veins have walls thicker than those of arteries.

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

    Name two examples of elastic arteries.

    <p>Aorta, Pulmonary artery</p> Signup and view all the answers

    The diameter of capillaries ranges from _______ to _______ μm.

    <p>5, 10</p> Signup and view all the answers

    Match the following arteries with their characteristics:

    <p>Aorta = Largest elastic artery Pulmonary artery = Carries blood to the lungs Brachiocephalic artery = Branches into subclavian and carotid Common iliac artery = Supplies blood to the lower limbs</p> Signup and view all the answers

    What function do smooth muscles in arteries provide?

    <p>Allowing for vasoconstriction and vasodilation</p> Signup and view all the answers

    Elastic arteries contain a high amount of smooth muscle compared to muscular arteries.

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

    What do veins primarily rely on to facilitate blood flow back to the heart?

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

    Muscular arteries are also known as _______ arteries.

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

    What type of flow is characterized by fluid moving in layers with different velocities, where the highest velocity is at the center of the tube?

    <p>Laminar flow</p> Signup and view all the answers

    The Reynolds number for laminar flow is greater than 3000.

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

    What happens to the lateral pressure when the velocity and dynamic pressures are increased in a narrowed area?

    <p>Lateral pressure decreases.</p> Signup and view all the answers

    In anemic patients, the viscosity of blood is __________ due to low hematocrit.

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

    Match the terms related to flow types with their Reynolds number thresholds:

    <p>Laminar flow = Less than 2000 Turbulent flow = Greater than 4000 Unsteady flow = Between 2000 and 4000</p> Signup and view all the answers

    Which statement is true regarding the relationship between dynamic pressure and velocity?

    <p>Increasing dynamic pressure increases velocity.</p> Signup and view all the answers

    Unsteady flow cannot be converted to laminar or turbulent flow.

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

    What compensatory mechanism occurs in the heart of patients with anemia due to low viscosity?

    <p>Increased cardiac output.</p> Signup and view all the answers

    Total pressure in a fluid system is the sum of __________ and lateral pressure.

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

    What is the Reynolds number threshold indicating turbulent flow?

    <p>Greater than 4000</p> Signup and view all the answers

    What is the formula for calculating Pulse Pressure?

    <p>Pulse Pressure = Systolic BP - Diastolic BP</p> Signup and view all the answers

    A rigid aortic wall can distend during systole.

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

    What are the main determinants of Pulse Pressure?

    <p>Stroke Volume and Arterial Compliance</p> Signup and view all the answers

    Pulse Pressure is directly proportional to _____ and inversely proportional to _____.

    <p>Stroke Volume, Arterial Compliance</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Stroke Volume = The amount of blood pumped by the heart with each beat Arterial Compliance = The ability of a blood vessel to expand and contract Systolic Blood Pressure = The pressure in arteries during heart contraction Diastolic Blood Pressure = The pressure in arteries during heart relaxation</p> Signup and view all the answers

    Which of the following factors does NOT affect blood flow according to Poiseuille's law?

    <p>Blood temperature</p> Signup and view all the answers

    Blood flow is inversely proportional to the viscosity of the fluid.

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

    What is the consequence of blood having apparent viscosity in the circulatory system?

    <p>It does not follow Poiseuille's law accurately.</p> Signup and view all the answers

    The formula for resistance in Poiseuille's law is given by R = __________.

    <p>ΔP / Q</p> Signup and view all the answers

    Match the following parameters with their corresponding roles in Poiseuille's law:

    <p>η = Viscosity of the fluid l = Length of the tube r = Radius of the tube ΔP = Pressure difference</p> Signup and view all the answers

    According to Poiseuille's law, how does the flow rate (Q) change if the radius is doubled?

    <p>It increases by a factor of 4</p> Signup and view all the answers

    The flow of blood in the circulatory system is fully laminar and non-pulsatile.

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

    In Poiseuille's law, which parameter is identified as the principal determinant of resistance to blood flow?

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

    The change in pressure over flow is described in physics as __________.

    <p>Ohm's Law</p> Signup and view all the answers

    What assumption must hold true for Poiseuille's law to be accurate?

    <p>Fluid must be Newtonian</p> Signup and view all the answers

    Study Notes

    Circulatory System

    • The circulatory system transports nutrients and hormones to tissues, removes waste products, and maintains internal homeostasis. Its components include arteries, arterioles, capillaries, venules, and veins.

    Hemodynamics

    • Blood flow is the volume of blood passing a given point in a certain time. A normal rate is 5000ml/min.

    • Velocity describes the distance a particle of fluid travels in a certain time.

      • Fluid velocity is directly proportional to the flow and inversely to the cross-sectional area.

    • Blood pressure is the force exerted by the blood against the walls of the arteries. It has systolic (maximal) and diastolic (minimal) levels. The difference between systolic and diastolic pressures is the pulse pressure.

    • Mean arterial pressure is the average pressure during a cardiac cycle. It's often calculated using a formula including the systolic and diastolic values.

    Blood Pressure

    • Blood pressure measurement is crucial for examining the cardiovascular system.
    • Several factors affect blood pressure:
      • Fluid volume
      • Cardiac output (heart rate x stroke volume)
      • Total peripheral resistance
      • Arterial compliance

    Venous Return

    • Venous return is the rate at which blood returns to the heart.
    • Factors affecting venous return include:
      • Skeletal muscle pump
      • Respiratory pump
      • Venous valves
      • Gravity
      • Vena cava compression
      • Venous compliance

    Regulation of Arterial Blood Pressure

    • Short-term control (seconds-minutes):
      • Autonomic nervous system (ANS) reflexes (baroreceptors, chemoreceptors, central nervous system (CNS) ischemic response)
    • Intermediate-term control (minutes-hours):
      • Renin-angiotensin-aldosterone system (RAAS)
      • Stress-relaxation of vasculature
      • Capillary fluid shift.
    • Long-term control (days-weeks):
      • Renal blood volume pressure control.

    Arteries

    • Arteries are categorized as elastic arteries (large diameter, high compliance) and muscular arteries (medium-sized, low compliance). These differences relate to blood pressure and flow.

    • Arterioles are the primary resistance vessels in the circulatory system.

    Veins

    • Veins act as capacitance vessels, holding a large volume of blood. Factors modulating venous return include sympathetic activation, venous valves, gravity, respiratory function and muscle movement.
    • Venous valves prevent backflow of blood.

    Blood Pressure Measurement

    • Proper blood pressure measurement techniques, including palpation and auscultation, minimise errors during measurement.
    • Several factors can cause inaccurate BP readings: cuff size, patient positioning, and other factors.

    Exercise and Blood Pressure

    • When exercising, sympathetic activity causes an increase in heart rate (HR) and stroke volume (SV).
    • There's an initial increase in blood pressure because of the increase in cardiac output.

    Respiratory Sinus Arrhythmia

    • Respiratory sinus arrhythmia is a phenomenon where heart rate increases during inhalation and decreases during exhalation. This is due to vagal tone fluctuations.

    The Cardiovascular System

    • The cardiovascular system comprises the heart, blood vessels, and blood, and plays a fundamental role in delivering oxygen and nutrients throughout the body.

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