Circulatory System and Blood Flow
72 Questions
4 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary requirement for the circulatory system to function properly?

  • The vessels must be completely rigid to maintain blood pressure.
  • The flow of blood returning to the heart must equal the flow of blood pumped by the left ventricle into the aorta. (correct)
  • The heart must pump blood at a fixed rate.
  • The total volume of blood must be constant at all times.

    • What are the two circulations in series in the cardiovascular system?

  • Systemic and muscular circulations
  • Pulmonary and systemic circulations (correct)
  • Pulmonary and nervous circulations
  • Cardiac and peripheral circulations

    • What is the primary function of the pulmonary circulation?

  • To regulate blood pressure
  • To remove carbon dioxide from the body
  • To deliver oxygenated blood to the body
  • To carry deoxygenated blood away from the heart to the lungs and return oxygenated blood back to the heart (correct)

    • What are the factors that determine the exact amount of flow around the circulatory circuit?

    <p>The number and strength of heart contractions, the total volume of blood, and the characteristics of the vessels</p> Signup and view all the answers

    What is the term for the part of the cardiovascular system that carries oxygenated blood away from the heart to the body and returns deoxygenated blood back to the heart?

    <p>Systemic circulation</p> Signup and view all the answers

    What is the primary function of the ventricles in the circulatory system?

    <p>To pump blood into the arteries</p> Signup and view all the answers

    Where does the exchange of oxygen and carbon dioxide occur in the circulatory system?

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

    What is the function of the collecting system in the circulatory system?

    <p>To collect deoxygenated blood from the body</p> Signup and view all the answers

    Which of the following is NOT part of the distribution system?

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

    What is the term for the part of the circulatory system that includes venules, veins, and atria?

    <p>Collecting System</p> Signup and view all the answers

    What is a characteristic feature of the walls of arteries?

    <p>Extensive development of elastic tissue, smooth muscle, and connective tissue</p> Signup and view all the answers

    What type of blood flow occurs in arteries?

    <p>High-pressure flow</p> Signup and view all the answers

    What type of volume do arteries carry?

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

    What is the primary function of arteries?

    <p>To deliver oxygen and nutrients to organs</p> Signup and view all the answers

    Which artery is the largest in the systemic circulation?

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

    What is the primary function of elastic arteries?

    <p>To hold large volumes of blood</p> Signup and view all the answers

    What is the significance of compliance in the circulatory system?

    <p>It describes the volume of blood a vessel can hold at a given pressure</p> Signup and view all the answers

    What is the primary feature of muscular arteries?

    <p>More smooth muscle</p> Signup and view all the answers

    What is the formula to calculate compliance?

    <p>C = V/P</p> Signup and view all the answers

    What is the primary difference between elastic and muscular arteries?

    <p>Amount of elastin and smooth muscle</p> Signup and view all the answers

    Which of the following is a characteristic of arterioles?

    <p>They are extensively innervated by sympathetic adrenergic nerve fibers.</p> Signup and view all the answers

    What is the primary function of arterioles?

    <p>To regulate blood flow in each tissue according to its needs.</p> Signup and view all the answers

    Where is the highest resistance to blood flow encountered?

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

    What is the purpose of vasoconstriction and vasodilation in arterioles?

    <p>To control blood flow in each tissue according to its needs</p> Signup and view all the answers

    Which receptor subtype is predominantly expressed in the arterioles of most visceral organs and couples to Gq?

    <p>Alpha 1</p> Signup and view all the answers

    What is the primary endogenous agonist that binds to alpha 1 and alpha 2 receptors in arterioles?

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

    What is the effect of alpha 1 receptor activation on smooth muscle in arterioles?

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

    In which location are alpha 2 receptors also present, in addition to arterioles?

    <p>Nerve terminals</p> Signup and view all the answers

    What is the primary function of alpha 1 receptor-mediated vasoconstriction in arterioles?

    <p>To increase peripheral resistance</p> Signup and view all the answers

    What type of receptor does beta 2 adrenergic receptors couple to?

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

    What is the primary endogenous agonist that binds to beta 2 adrenergic receptors?

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

    Where are beta 2 adrenergic receptors primarily expressed?

    <p>Arterioles of the coronaries, skeletal muscle, and liver</p> Signup and view all the answers

    What is the effect of beta 2 adrenergic receptor activation on smooth muscle?

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

    What is the significance of beta 2 adrenergic receptors in the body?

    <p>They help regulate fight or flight responses</p> Signup and view all the answers

    What type of receptor do M3 receptors on coronaries couple to?

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

    What is the primary endogenous agonist that binds to M3 receptors?

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

    What is the effect of M3 receptor activation on vascular smooth muscle?

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

    Where are M3 receptors typically found?

    <p>Vascular smooth muscle</p> Signup and view all the answers

    What is the downstream effect of M3 receptor activation on eNOS?

    <p>Activation of eNOS</p> Signup and view all the answers

    What is unique about arterioles in the vasculature?

    <p>They are the site of highest resistance and can be changed by sympathetic activity.</p> Signup and view all the answers

    What can change the resistance in arterioles?

    <p>Sympathetic activity, circulating catecholamines, and other vasoactive substances.</p> Signup and view all the answers

    Where is the highest resistance to blood flow encountered?

    <p>In the arterioles.</p> Signup and view all the answers

    What type of substances can change the resistance in arterioles?

    <p>Circulating catecholamines and vasoactive substances.</p> Signup and view all the answers

    What is the significance of arterioles in the vasculature?

    <p>They are the site of highest resistance and can be changed by sympathetic activity.</p> Signup and view all the answers

    What is the primary function of capillaries in the circulatory system?

    <p>To exchange fluid, nutrients, electrolytes, hormones, and other substances between the blood and the interstitial fluid</p> Signup and view all the answers

    How do lipid-soluble substances cross the capillary wall?

    <p>By dissolving in and diffusing across the endothelial membrane</p> Signup and view all the answers

    What type of capillaries have large pores in their walls?

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

    Why are not all capillaries always perfused with blood?

    <p>Because it depends on metabolic needs</p> Signup and view all the answers

    What is the structure that surrounds the endothelial cells in capillaries?

    <p>Basal lamina</p> Signup and view all the answers

    What is the main function of venules in the circulatory system?

    <p>To collect blood from capillaries and transport it back to the heart</p> Signup and view all the answers

    What is a characteristic of veins in the circulatory system?

    <p>They are thin-walled structures with low blood pressure</p> Signup and view all the answers

    What type of volume do veins carry?

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

    What is the characteristic of veins compared to arteries?

    <p>They hold larger volumes of blood at lower pressures</p> Signup and view all the answers

    What determines the volume of blood a vessel can hold?

    <p>The compliance of the vessel</p> Signup and view all the answers

    Why do arteries hold lower volumes of blood?

    <p>Because they have lower compliance</p> Signup and view all the answers

    What is the significance of compliance in the circulatory system?

    <p>It determines the volume of blood a vessel can hold</p> Signup and view all the answers

    What is the relationship between compliance and distensibility?

    <p>Compliance is directly related to distensibility</p> Signup and view all the answers

    What happens when the veins constrict?

    <p>Blood is shifted from the veins to the arteries</p> Signup and view all the answers

    What type of nerve fibers innervate the smooth muscle in the walls of veins?

    <p>Sympathetic nerve fibers</p> Signup and view all the answers

    What is the effect of alpha-1 adrenergic activation on the veins?

    <p>Decreasing the capacitance and unstressed volume</p> Signup and view all the answers

    What is the result of changes in compliance of the veins?

    <p>Redistribution of blood between the veins and arteries</p> Signup and view all the answers

    What is the significance of compliance in the veins?

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

    What is the rate of displacement of blood per unit of time?

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

    Which blood vessels have larger cross-sectional areas?

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

    What is the significance of the large cross-sectional area of veins?

    <p>Increased blood storage capacity</p> Signup and view all the answers

    What is the formula to calculate the cross-sectional area of a blood vessel?

    <p>πr^2</p> Signup and view all the answers

    What is the result of a larger cross-sectional area in blood vessels?

    <p>Decreased resistance to blood flow</p> Signup and view all the answers

    What happens to the total cross-sectional area of blood vessels as systemic arteries branch to form small arteries, arterioles, and capillaries?

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

    What is the relationship between the velocity of blood flow and the total cross-sectional area of blood vessels?

    <p>Velocity varies inversely with cross-sectional area</p> Signup and view all the answers

    What happens to the velocity of blood flow when it enters venules and veins?

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

    Why does the velocity of blood flow decrease in small arteries, arterioles, and capillaries?

    <p>Due to the increase in total cross-sectional area</p> Signup and view all the answers

    What is the primary reason for the change in velocity of blood flow in different parts of the circulatory system?

    <p>Change in total cross-sectional area</p> Signup and view all the answers

    Study Notes

    The Circulatory System

    • The circulatory system is a closed circuit, meaning that the flow of blood returning to the heart must equal the flow of blood pumped by the left ventricle into the aorta.

    Factors Affecting Blood Flow

    • The exact amount of flow around the circuit depends on three key factors: • The number and strength of heart contractions • The total volume of blood • The characteristics of the vessels

    The Cardiovascular System

    • The cardiovascular system has two circulations in series:

    Pulmonary Circulation

    • Carries deoxygenated blood away from the heart to the lungs
    • Returns oxygenated blood back to the heart

    Systemic Circulation (Peripheral or Greater)

    • Carries oxygenated blood away from the heart to the body
    • Returns deoxygenated blood back to the heart

    Circulatory System Divisions

    • Each circulation (systemic and pulmonary) has 3 major divisions.

    Distribution System

    • Composed of ventricles, arteries, and arterioles.

    Perfusion/Exchange System

    • Composed of capillaries where exchange of oxygen and nutrients with cells occurs.

    Collecting System

    • Composed of venules, veins, and atria.
    • Responsible for collecting and returning blood to the heart.

    Characteristics of Arteries

    • Aorta is the largest artery of the systemic circulation, receiving blood directly from the heart
    • Arteries have strong vascular walls to withstand the high velocity of blood flow
    • The walls of arteries are composed of extensive elastic tissue, smooth muscle, and connective tissue
    • Arteries transport blood under high pressure to the tissues

    Function of Arteries

    • Deliver oxygen and other nutrients to the organs
    • Carry the stressed volume of blood

    Artery Types

    • There are two main types of arteries: Elastic Arteries and Muscular Arteries
    • Elastic Arteries are high-compliance arteries, meaning they can hold large volumes of blood
    • They contain more elastin, which increases their distensibility
    • Examples of Elastic Arteries include the Aorta and Carotid Artery

    Characteristics of Elastic Arteries

    • Have more elastin, allowing for increased distensibility
    • Capable of holding large volumes of blood
    • Can stretch to accommodate increased blood pressure

    Characteristics of Muscular Arteries

    • Contain more smooth muscle, enabling vasoconstriction and dilation
    • Are high-resistance arteries, distributing blood according to tissue needs
    • Examples of Muscular Arteries include the Femoral and Mesenteric Arteries

    Compliance and Capacitance

    • Compliance (C) is the volume of blood a vessel can hold at a given pressure, measured in mL/mm Hg
    • C = V/P, where V is the volume in mL and P is the pressure in mm Hg
    • Compliance describes the ability of a vessel to expand and accommodate changes in blood pressure

    Vascular Resistance

    • Vascular Resistance is the opposition to blood flow in the circulatory system
    • Must be overcome to create blood flow and maintain blood pressure

    Arterioles

    • Are the last smallest branches of the arterial system
    • Act as control conduits that regulate blood flow into capillaries
    • Characterized by strong muscular walls that enable vasoconstriction and vasodilation
    • Heavily innervated by sympathetic adrenergic nerve fibers
    • Allow alteration of blood flow in each tissue in response to its specific needs
    • Site of the highest resistance to blood flow

    Receptor Distribution and Function

    • Alpha 1 and 2 receptors are found in the arterioles of most visceral organs.
    • Alpha 1 receptors are predominant in these organs and couple to Gq protein.
    • Alpha 2 receptors, on the other hand, couple to Gi protein.

    Receptor Location and Feedback Mechanism

    • Alpha 2 receptors are also present in nerve terminals, where they inhibit norepinephrine (NE) release through a feedback mechanism.

    Norepinephrine and Vasoconstriction

    • Norepinephrine is the primary endogenous agonist for these receptors.
    • It is released from postganglionic neurons and acts on vascular smooth muscle.
    • Activation of these receptors leads to smooth muscle contraction, resulting in vasoconstriction.

    Beta 2 Adrenergic Receptors

    • Expressed in arterioles of coronaries, skeletal muscle, and liver
    • G protein-coupled receptor that couples to Gs, a stimulatory G protein
    • Activates the cAMP pathway

    Agonist and Release

    • Epinephrine is the primary endogenous agonist for beta 2 adrenergic receptors
    • Released from the adrenal gland

    Physiological Effects

    • Found in vascular smooth muscle
    • Cause vasodilation in areas that will need increased blood flow in "fight or flight" situations

    Parasympathetic Innervation and Vasodilation

    • Parasympathetic innervation is minimal or absent in most blood vessels of the body

    M3 Receptors and Vasodilation

    • M3 receptors are present on coronary vessels and respond to vagal tone
    • M3 receptors are G protein-coupled receptors that couple to Gq
    • Activation of M3 receptors stimulates phospholipase C, leading to the production of DAG and IP3
    • DAG and IP3 trigger calcium release, which activates eNOS
    • Activated eNOS produces nitric oxide (NO), a potent vasodilator
    • Acetylcholine is the primary endogenous agonist that activates M3 receptors
    • Acetylcholine is released from postganglionic neurons and acts on vascular smooth muscle
    • Vasodilation occurs through the activation of the cAMP pathway, leading to smooth muscle relaxation

    Arterioles Function

    • Arterioles are the site of highest resistance in the vasculature
    • They are the site where resistance can be changed by: • Sympathetic activity • Circulating catecholamines • Other vasoactive substances

    Capillaries

    • Exchange various substances, including fluids, nutrients, electrolytes, hormones, and others, between blood and interstitial fluid
    • Thin-walled structures with a single layer of endothelial cells surrounded by a basal lamina
    • Lipid-soluble substances cross the capillary wall by dissolving in and diffusing across the endothelial membrane
    • Water-soluble substances, such as ions, cross the capillary wall through:
      • Water-filled clefts (spaces) between endothelial cells
      • Large pores in the walls of some capillaries (e.g., fenestrated capillaries)

    Blood Perfusion in Capillaries

    • Not all capillaries are always perfused with blood
    • Blood perfusion in capillaries depends on metabolic needs

    Venules

    • Collect blood from capillaries and merge into larger veins
    • Thin-walled structures composed of endothelial layer, elastic tissue, smooth muscle, and connective tissue

    Veins

    • Function as conduits to transport blood from venules back to the heart
    • Characterized by low pressure and thin walls
    • Carry unstressed volume, meaning they can expand or contract to meet changing blood volume needs
    • Serve as a major controllable reservoir for extra blood depending on the body's requirements

    Vascular Compliance

    • Compliance of veins is higher than that of arteries
    • Compliance is directly related to distensibility
    • Higher compliance vessels can hold more volume at a given pressure
    • Veins can hold larger volumes of blood at lower pressures
    • Arteries have lower compliance compared to veins
    • Arteries hold lower volumes of blood, but at higher pressures

    Compliance of Veins

    • Changes in compliance of the veins lead to redistribution of blood between the veins and arteries
    • Constriction of the veins results in a decrease in the volume they can hold
    • This causes blood to shift from the veins to the arteries

    Regulation of Vein Constriction

    • Smooth muscle in the walls of veins is innervated by sympathetic nerve fibers
    • Alpha-1 adrenergic activation leads to constriction of the veins
    • Constriction of the veins reduces capacitance and unstressed volume

    Blood Flow and Vessel Characteristics

    • The velocity of blood flow is defined as the rate of displacement of blood per unit of time.
    • Blood vessels vary in terms of diameter and cross-sectional area.
    • Veins have much larger cross-sectional areas compared to arteries.
    • The large cross-sectional area of veins explains their high blood storage capacity.
    • The cross-sectional area of a blood vessel is equal to the area of a circle.

    Blood Flow Velocity and Cross-Sectional Area

    • As systemic arteries branch to form smaller vessels (arterioles and capillaries), the total cross-sectional area of these vessels increases.
    • This increase in cross-sectional area leads to a decrease in the forward velocity of blood flow.
    • The reverse happens when blood is collected into venules and veins: the total cross-sectional area decreases, and the velocity of blood flow increases again.
    • There is an inverse relationship between the velocity of blood flow and the total cross-sectional area of blood vessels.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Description

    This quiz covers the basics of the circulatory system, including the flow of blood, heart contractions, and the characteristics of blood vessels.

    More Like This

    Cardiovascular System Overview Quiz
    10 questions

    Cardiovascular System Overview Quiz

    ComfortingCerium avatar
    ComfortingCerium
    Human Heart Function and Blood Circulation
    37 questions

    Human Heart Function and Blood Circulation

    GracefulThallium avatar
    GracefulThallium
    Cardiovascular System Overview Quiz
    30 questions

    Cardiovascular System Overview Quiz

    FabulousCornet7664 avatar
    FabulousCornet7664
    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser