Haemodynamics Overview
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Questions and Answers

What is the primary focus of haemodynamics?

  • Study of blood circulation and properties of blood and vessels (correct)
  • Study of respiratory rate
  • Study of nutrient absorption
  • Study of heart rhythm

What percentage of total blood volume is found within the veins in systemic circulation?

  • 64% (correct)
  • 84%
  • 16%
  • 7%

Which mechanism of capillary exchange involves the movement of oxygen and carbon dioxide from areas of high concentration to low concentration?

  • Bulk flow
  • Diffusion (correct)
  • Filtration
  • Transcytosis

What role do arterioles play in the vascular system?

<p>Regulate blood flow and pressure (B)</p> Signup and view all the answers

What is the name of the mechanisms through which hormones like insulin are transported across capillaries?

<p>Transcytosis (D)</p> Signup and view all the answers

Which force primarily drives the movement of fluid from blood into interstitial fluid?

<p>Hydrostatic pressure (D)</p> Signup and view all the answers

What percentage of the total blood volume is represented by pulmonary circulation?

<p>16% (A)</p> Signup and view all the answers

What term describes the movement of fluid from blood capillaries into interstitial fluid?

<p>Filtration (A)</p> Signup and view all the answers

Which pressure is associated with forcing fluid inward through the capillary membrane?

<p>Capillary plasma colloid osmotic pressure (Πp) (A)</p> Signup and view all the answers

What physiological phenomenon is defined by a systolic blood pressure of 200/100 mmHg during resting conditions?

<p>Benign hypertension (A)</p> Signup and view all the answers

What is the normal range for diastolic blood pressure?

<p>80 mmHg (B)</p> Signup and view all the answers

In terms of blood pressure regulation, which factor is NOT directly mentioned as affecting blood pressure?

<p>Blood viscosity (D)</p> Signup and view all the answers

Which pressure directly opposes the capillary pressure in fluid exchange?

<p>Interstitial fluid pressure (Pif) (D)</p> Signup and view all the answers

Which of the following best represents what MAP stands for?

<p>Mean arterial pressure (D)</p> Signup and view all the answers

What is the characteristic of malignant hypertension?

<p>Systolic pressure of 250 mmHg (A)</p> Signup and view all the answers

What does an increase in total peripheral resistance (TPR) result from?

<p>Vasoconstriction (D)</p> Signup and view all the answers

What is the mean pressure combining arterial, capillary, and venous readings?

<p>6.5 mm Hg (D)</p> Signup and view all the answers

Which of the following factors is NOT involved in regulating blood pressure?

<p>Venoconstriction (A)</p> Signup and view all the answers

What type of regulation is primarily involved in short-term blood pressure control?

<p>Neurological regulation (D)</p> Signup and view all the answers

Which chemoreceptor responds primarily to low oxygen levels?

<p>Peripheral chemoreceptors (D)</p> Signup and view all the answers

During the auscultatory method of measuring blood pressure, what causes the sounds known as Korotkoff sounds?

<p>Blood jetting through a blocked artery (D)</p> Signup and view all the answers

What role do baroreceptors play in blood pressure regulation?

<p>Inhibit vasomotor center during high pressure (A)</p> Signup and view all the answers

What is the primary effect of inhalation on venous pressure?

<p>It decreases venous pressure (C)</p> Signup and view all the answers

Which of the following hormones is involved in long-term regulation of blood pressure?

<p>Aldosterone (B)</p> Signup and view all the answers

What determines blood flow according to Ohm's Law?

<p>Blood flow is determined by the difference in pressure divided by resistance. (B)</p> Signup and view all the answers

How does an increase in resistance affect blood flow?

<p>Blood flow decreases inversely. (D)</p> Signup and view all the answers

What arrangement of blood vessels allows each tissue to regulate its own blood flow?

<p>Parallel arrangement (A)</p> Signup and view all the answers

If blood vessels are arranged in series, how is total resistance calculated?

<p>Total resistance is equal to the sum of the resistances of each vessel. (D)</p> Signup and view all the answers

What happens to the pressure as blood flows through a series of vessels?

<p>Pressure decreases consistently. (C)</p> Signup and view all the answers

What is the effect of increased blood viscosity on blood flow?

<p>Decreases blood flow. (A)</p> Signup and view all the answers

In a parallel arrangement of blood vessels, how is total resistance calculated?

<p>Total resistance is equal to the reciprocal of the sum of the reciprocals of each resistance. (D)</p> Signup and view all the answers

What is the typical pressure difference between the aorta and the vena cava?

<p>20 mm Hg (D)</p> Signup and view all the answers

What happens to blood flow in anemia as viscosity decreases?

<p>Blood flow increases. (B)</p> Signup and view all the answers

How does vessel length affect resistance in the circulatory system?

<p>Longer vessels increase resistance. (A)</p> Signup and view all the answers

What is the relationship between blood vessel diameter and resistance?

<p>Resistance decreases as diameter increases. (A)</p> Signup and view all the answers

What is the velocity of blood flow through the aorta under resting conditions?

<p>33 cm/sec (A)</p> Signup and view all the answers

Which factor is NOT one of the main determinants of blood flow velocity?

<p>Blood vessel length (A)</p> Signup and view all the answers

What role does vascular distensibility play in blood circulation?

<p>Enables vessels to accommodate changes in pressure. (B)</p> Signup and view all the answers

According to Poiseuille’s law, the flow rate (F) is influenced by which of the following parameters?

<p>Length of vessel and vessel radius (D)</p> Signup and view all the answers

Which of the following statements about atherosclerosis is correct?

<p>It decreases the diameter of blood vessels. (C)</p> Signup and view all the answers

What factor primarily describes the ability of blood vessels to stretch and store blood under pressure?

<p>Compliance (D)</p> Signup and view all the answers

Which blood vessel type has a higher compliance compared to its corresponding artery?

<p>Veins (B)</p> Signup and view all the answers

During blood loss, which mechanism helps to maintain arterial pressure?

<p>Sympathetic nerve stimulation to veins (A)</p> Signup and view all the answers

What is the primary source of blood reservoir in the circulatory system?

<p>Veins (B)</p> Signup and view all the answers

Which substance is NOT typically involved in the hormonal regulation of blood flow?

<p>Insulin (D)</p> Signup and view all the answers

What role does vasopressin play during severe hemorrhage?

<p>Increases arterial pressure (B)</p> Signup and view all the answers

How does the compliance of veins compare to that of arteries?

<p>Twenty-four times greater (B)</p> Signup and view all the answers

Which of the following factors is NOT involved in regulating blood flow to tissues?

<p>Blood cell production (A)</p> Signup and view all the answers

Flashcards

Haemodynamics

The study of physical laws governing blood circulation, encompassing the properties of blood and blood vessels.

Systemic Circulation

The circulatory network supplying blood to all body tissues except the lungs. Consists of arteries, veins, arterioles, and capillaries.

Pulmonary Circulation

The circulatory network that transports blood between the heart and lungs for oxygenation.

Arteries

Large elastic blood vessels that carry oxygenated blood away from the heart.

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Arterioles

Small blood vessels that regulate blood flow and pressure by adjusting their diameter.

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Capillaries

Microscopic blood vessels where exchange of nutrients and waste products occurs between blood and tissues.

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Venules

Small veins that collect blood from capillaries and lead into larger veins.

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Veins

Large blood vessels that carry deoxygenated blood back to the heart. Equipped with valves to prevent backflow.

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Capillary Pressure (Pc)

The force that pushes fluid out of the capillary, primarily due to blood pressure.

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Interstitial Fluid Pressure (Pif)

The force that pulls fluid into the capillary, influenced by the pressure surrounding the capillary.

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Capillary Plasma Colloid Osmotic Pressure (Πp)

Draws water into the capillary due to the high concentration of proteins within the blood.

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Interstitial Fluid Colloid Osmotic Pressure (Πif)

Pulls water out of the capillary due to the presence of proteins in the interstitial fluid.

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Net Filtration Pressure

The pressure that pushes fluid out of the capillary.

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Blood Pressure (BP)

The force exerted by blood against the walls of blood vessels, measured in mmHg.

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Systolic Blood Pressure

The highest pressure measured during a heartbeat, when the heart contracts.

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Diastolic Blood Pressure

The lowest pressure measured during a heartbeat, when the heart relaxes.

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Mean blood pressure

The average pressure measured in the arteries, capillaries, and veins.

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End-diastolic volume (EDV)

The volume of blood filling the ventricle at the end of diastole (relaxation).

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Contractility

The force exerted by the heart muscle during contraction.

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Afterload

The resistance the heart has to overcome to eject blood into the aorta.

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Total peripheral resistance (TPR)

The resistance to blood flow offered by all the blood vessels in the body.

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Baroreceptor reflex

A physiological response triggered by changes in arterial pressure, involving baroreceptors located in the carotid sinus and aortic arch.

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Central chemoreceptors

Chemoreceptors located near the fourth ventricle in the brainstem, sensitive to changes in pCO2, pH, and pO2.

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Peripheral chemoreceptors

Chemoreceptors located in the carotid and aortic bodies, detecting changes in pO2, pCO2, and pH.

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Velocity of blood flow

The rate of blood flow through a specific region. It is determined by cardiac output, cross-sectional area of the blood vessel, and viscosity of blood flow.

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Cardiac output (CO)

The volume of blood pumped by the heart per minute. A higher cardiac output will increase the velocity of blood flow.

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Cross-sectional area (TCA)

The area of the cross-section of a blood vessel. A larger cross-sectional area means slower blood flow, and vice versa.

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Viscosity of blood

The resistance to flow caused by friction between blood cells and vessel walls. Higher viscosity means slower blood flow due to thicker blood.

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Conductance of a vessel

A measure of how easily blood flows through a vessel. It depends on vessel radius, length, and blood viscosity.

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Vascular Distensibility

The ability of a vessel to expand and contract in response to changes in blood pressure. This helps ensure smooth blood flow and adjust blood pressure.

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Distensible nature of arteries

The stretching and expansion of blood vessels under increased pressure, reducing resistance to blood flow.

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Veins: Most distensible vessels

Veins are the most distensible blood vessels, allowing them to accommodate changes in blood volume and pressure.

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Vascular Resistance

The resistance to blood flow in blood vessels, impacting how easily blood travels through the circulatory system.

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Series Flow

A system where blood vessels are arranged in a line, one after the other, like a chain. Each vessel experiences the same blood flow but pressure drops with each vessel.

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Parallel Flow

A system where blood vessels branch out, offering multiple pathways for blood flow like a network. Each part of the network can independently adjust its blood flow.

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Pressure Difference (ΔP)

The force that propels blood through the circulatory system. It is the difference in pressure between two points in the blood vessel.

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Viscosity

The measure of resistance to flow within a fluid. In blood, it depends on factors like the thickness of the blood and the size of the blood vessel.

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Blood Viscosity Increase

The tendency of blood to clot or thicken, increasing the viscosity of blood and making it flow less easily.

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Polycythemia

A condition where the volume of red blood cells in the blood is higher than normal, making blood thicker and increasing the resistance to flow.

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Ohm's Law (in Hemodynamics)

The relationship between blood flow, pressure difference, and resistance in the circulatory system. It states that blood flow is directly proportional to pressure difference and inversely proportional to resistance.

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Vascular Compliance

The ability of a blood vessel to expand and store blood. It's the opposite of stiffness.

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Vein Compliance vs Artery Compliance

Veins are more compliant than arteries, meaning they can store more blood for a given pressure change. Think of a balloon vs a water bottle.

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Venous System as Blood Reservoir

The venous system acts as a reserve for blood, holding about 60% of the total blood volume.

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Venous Constriction During Blood Loss

When blood loss occurs, the body uses mechanisms to constrict veins, forcing stored blood into circulation to maintain blood pressure.

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Other Blood Reservoirs

The spleen, liver, large abdominal veins, and skin veins all contribute to blood volume regulation.

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Functions of Blood Flow to Tissues

The primary functions of blood flow to tissues involve supplying oxygen and nutrients, removing waste products, and maintaining proper ion concentrations.

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Hormonal Vasoconstrictors

Hormones that cause blood vessels to narrow, increasing blood pressure.

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Examples of Vasoconstrictors

Norepinephrine, epinephrine, angiotensin II, and vasopressin are examples of hormones that constrict blood vessels.

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Study Notes

Circulatory System

  • The circulatory system is responsible for blood circulation, encompassing both blood and blood vessels.
  • Haemodynamics studies the physical laws governing blood circulation and blood vessel characteristics.

Systemic Circulation

  • Systemic circulation (peripheral circulation) supplies blood to all body tissues except the lungs.
  • This comprises approximately 84% of the circulatory system.
  • Blood flow distribution to various tissues is: 64% in veins, 13% in arteries, 7% in systemic arterioles and capillaries.

Pulmonary Circulation

  • Pulmonary circulation is dedicated to supplying the lungs, comprising about 16% of the circulatory system.
  • This involves:
    • 9% in pulmonary blood vessels
    • 7% in the heart

Vascular System

  • Arteries: Large, elastic arteries carry blood from the heart to muscular arteries that branch to organs. Arterioles deliver blood to capillaries.
  • Arterioles: These regulate blood flow to capillaries through precapillary sphincters and metarterioles.
  • Capillaries: Tiny vessels where nutrient and waste exchange between blood and interstitial fluid occurs.
  • Venules: These are small veins formed by the convergence of capillaries; they transport blood back to the heart.
  • Veins: Large, compliant vessels with low resistance; they carry blood back to the heart with valves to prevent backflow.
  • Vasa vasorum: These are small blood vessels that supply blood to the walls of larger blood vessels.

Microcirculation of Capillary Exchange

  • Substances move between blood and interstitial fluid via three mechanisms:
    • Diffusion: Movement of O2, CO2, nutrients, and wastes across the capillary membrane down their respective concentration gradients.
    • Transcytosis: Transport of large molecules like hormones and antibodies across the capillary wall via vesicles.
    • Bulk flow: Movement of fluid and solutes between blood and interstitial fluid via filtration (blood to interstitial fluid) and reabsorption (interstitial fluid to blood) mechanisms.

Capillary Exchange in Kidneys and other Organs

  • Four forces influence fluid movements across capillary walls:
    • Capillary pressure (Pc) – pushes fluid outward.
    • Interstitial fluid pressure (Pif) – pushes fluid inward.
    • Capillary plasma colloid osmotic pressure (Ï€p) – pulls fluid inward.
    • Interstitial fluid colloid osmotic pressure (Ï€if) – pulls fluid outward.

Blood Pressure

  • Blood pressure is the force exerted by blood against the vessel walls.
  • Normal blood pressure is 120/80 mmHg.
  • Blood pressure is the product of cardiac output and vascular resistance.

Hypertension and Hypotension

  • Hypertension:
    • Elevated systemic blood pressure.
    • Types include primary (essential), benign and malignant.
  • Hypotension:
    • Lowered systemic blood pressure.

Pulse Pressure

  • The difference between systolic and diastolic pressures.
  • The two primary factors influencing pulse pressure include stroke volume and compliance of the arterial tree.

Blood Flow

  • The amount of blood that flows through a particular tissue per unit time.
  • Two types of blood flow are laminar and non-pulsatile (steady).
  • The third type is turbulent flow.

Factors Determining Blood Flow

  • Pressure gradient: Driving force for blood flow.
  • Resistance to blood flow: Opposing force to blood flow.
  • Blood vessel diameter: Crucial for resistance to blood flow.
  • Velocity and viscosity of blood: Blood velocity and viscosity influence blood flow.

Blood Flow and Resistance

  • Resistance to blood flow plays a pivotal role in influencing local blood pressure and affects blood flow as well. There are several factors which contribute to resistance including blood viscosity, total blood vessel length and blood vessel diameter.

Vascular Resistance

  • Resistance occurs in series, or parallel, circuits. When blood vessels are arranged in series, the resistance collectively is the sum of individual resistances. In parallel arrangements, resistance is lower than that in series arrangements.

Vascular Control by lons

  • Vasoconstrictors: Calcium ions increase vasoconstriction.
  • Vasodilators: Potassium and magnesium ions, hydrogen ions, and anions like acetate and citrate cause vasodilation. Carbon dioxide also causes vasodilation.

Hormonal Vasoconstrictors and Vasodilators

  • Hormonal vasoconstrictors (e.g., Norepinephrine, Angiotensin II, and Vasopressin, Endothelin): These hormones promote vasoconstriction in various situations.
  • Hormonal vasodilators (e.g., bradykinin, histamine): These promote vasodilation and regulate blood flow to specific tissues.

Factors regulating blood flow to tissues

  • Delivery of oxygen, nutrients (e.g. glucose, amino acids, and fatty acids), and removal of waste products (e.g CO2, H+ ions) and other ions. This includes the transport of hormones to the tissues, as well.

Vascular Distensibility and Compliance

  • Vascular distensibility refers to a vessel's ability to stretch.
  • Vascular compliance pertains to the ability of the circulatory system to accommodate blood volume changes.
  • Veins have significantly higher distensibility and compliance than arteries.

Venous System as a Blood Reservoir

  • The venous system holds a substantial proportion of circulating blood (ç´„60%).
  • When blood loss occurs, the venous system acts as a reservoir, constricting to deliver blood to peripheral tissues as needed. Some organs that serve as reservoirs include the spleen, liver and venous plexus around the skin.

Neurological Regulation of Blood Pressure

  • Cardiovascular center: Plays a crucial role in regulating heart rate and blood vessel tone; it is activated by impulses from higher brain centers, baroreceptors, and chemoreceptors. There are distinct cardio inhibitory and cardio acceleratory centers.

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Description

This quiz explores key concepts in haemodynamics, focusing on the principles of blood flow, pressure, and the mechanisms of capillary exchange. Test your knowledge on topics such as blood volume distribution, the role of arterioles, and blood pressure regulation.

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