BLOCK 4: MPP: (4.2) Vascular Physiology II: Special Circulations
56 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What primarily regulates blood flow in resting skeletal muscle?

  • Increased metabolic activity
  • External compression by surrounding tissues
  • Sympathetic nervous system activity (correct)
  • Increased heart rate

    • What happens to capillary perfusion during muscle activity?

  • More capillaries are perfused (correct)
  • Blood flow decreases
  • All capillaries are constricted
  • There is no change in perfusion

    • What is the primary effect of metabolic byproducts on blood flow regulation during exercise?

  • Decrease blood viscosity
  • Cause vasodilation of arterioles (correct)
  • Narrow blood vessels
  • Increase sympathetic nervous system activity

    • What is reactive hyperemia?

    <p>Temporary increase in blood flow after an occlusion</p> Signup and view all the answers

    How do isotonic exercises affect blood flow in skeletal muscles?

    <p>Create a phasic flow pattern</p> Signup and view all the answers

    What happens to blood flow in skeletal muscles during rest due to sympathetic activation?

    <p>Blood flow decreases</p> Signup and view all the answers

    What is the role of capillaries in skeletal muscle circulation?

    <p>Facilitate diffusion of O2 to muscle fibers</p> Signup and view all the answers

    What physiological change occurs during active hyperemia?

    <p>Increase in blood flow associated with metabolic activity</p> Signup and view all the answers

    Which of the following statements is true regarding terminal arterioles in skeletal muscle?

    <p>They play a critical role in delivering blood to capillaries.</p> Signup and view all the answers

    What characterizes isometric contractions in terms of blood flow?

    <p>Diminished blood flow for short periods</p> Signup and view all the answers

    What is the primary function of the tight junctions in cerebral capillary endothelial cells?

    <p>Prevent bulk flow and diffusion of substances</p> Signup and view all the answers

    Which of the following factors allows for the autoregulation of cerebral blood flow?

    <p>Constant cerebral blood flow despite arterial pressure changes</p> Signup and view all the answers

    What type of substances can readily diffuse across the capillary wall of the blood-brain barrier?

    <p>Lipid-soluble molecules like O2 and CO2</p> Signup and view all the answers

    Which condition is primarily associated with ischemic strokes?

    <p>Blockage of blood flow to the brain</p> Signup and view all the answers

    How do cerebral resistance vessels respond to increased levels of Pco2?

    <p>By dilating to enhance blood flow</p> Signup and view all the answers

    What role do transporters in the blood-brain barrier serve?

    <p>Transporting glucose and amino acids into the brain</p> Signup and view all the answers

    What is a significant outcome of hypertension in relation to stroke risk?

    <p>Increased likelihood of capillary leakage</p> Signup and view all the answers

    What impact does decreased Pco2 have on the cerebral blood vessels?

    <p>Causes vasoconstriction reducing blood flow</p> Signup and view all the answers

    How does the chemical barrier of the blood-brain barrier operate?

    <p>With enzymes degrading hormones and neurotransmitters</p> Signup and view all the answers

    Which area is categorized as a sensory circumventricular organ (CVO)?

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

    What is the primary action of endothelial-derived hyperpolarizing factor (EDHF)?

    <p>Promotes vasodilation by opening K+ channels</p> Signup and view all the answers

    Which type of prostaglandins are known to function as potent vasodilators?

    <p>PGI2</p> Signup and view all the answers

    What physiological response occurs during sudden loss of blood volume?

    <p>Fluid is pulled into blood vessels from interstitium</p> Signup and view all the answers

    How do endothelins contribute to vascular function?

    <p>They act as potent vasoconstrictors and increase intracellular Ca++</p> Signup and view all the answers

    What mechanism causes edema during heart failure?

    <p>Increased hydrostatic pressure in the venous system</p> Signup and view all the answers

    Which of the following agents can induce vasoconstriction via increased calcium levels?

    <p>Angiotensin II (Ang-II)</p> Signup and view all the answers

    How does calcium concentration affect blood vessel diameter?

    <p>Low calcium levels cause vasodilation</p> Signup and view all the answers

    What role do prostaglandins play in endothelial function?

    <p>Act as both vasodilators and vasoconstrictors</p> Signup and view all the answers

    What is the consequence of decreased Pc in the venous system during blood loss?

    <p>Fluid is pulled into the blood vessels from the interstitium</p> Signup and view all the answers

    Which description accurately reflects the blood-brain barrier's function?

    <p>Allows selective transport of ions and nutrients</p> Signup and view all the answers

    What physiological change occurs in cerebral blood flow when carbon dioxide levels increase?

    <p>Cerebral blood flow undergoes immediate vasodilation.</p> Signup and view all the answers

    During which state does the brain show higher blood flow to the frontal areas?

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

    How does the brain adapt its blood flow during specific experiences such as reading or writing?

    <p>Blood flow is redistributed to active brain regions.</p> Signup and view all the answers

    What is a characteristic of cerebral blood flow in a patient experiencing a permanent coma?

    <p>Blood flow becomes unresponsive and does not redistribute.</p> Signup and view all the answers

    What is the relationship between carbon dioxide levels in the arterial blood and cerebral blood flow?

    <p>There is a linear relationship where modest increases in carbon dioxide cause corresponding increases in blood flow.</p> Signup and view all the answers

    What happens to cerebral blood flow during a stroke?

    <p>Cerebral blood flow can become compromised and ineffectual.</p> Signup and view all the answers

    What factors could lead to changes in blood flow dynamics during muscle activity?

    <p>Muscle contraction types and the activity's intensity.</p> Signup and view all the answers

    How is metabolic control of blood flow primarily achieved?

    <p>Via changes in metabolic byproducts that signal for vasodilation.</p> Signup and view all the answers

    What role does the sympathetic nervous system have regarding blood flow during rest?

    <p>It maintains a minimal signaling level for vascular tone.</p> Signup and view all the answers

    Which statement differentiates isotonic and isometric exercises in terms of blood flow?

    <p>Isometric exercises reduce blood flow due to muscle contraction.</p> Signup and view all the answers

    What is the driving factor behind active hyperemia in skeletal muscles?

    <p>Accumulation of metabolic byproducts.</p> Signup and view all the answers

    During exercise, how do the arterioles respond in relation to metabolic control of blood flow?

    <p>They dilate due to rising metabolic waste and oxygen demands.</p> Signup and view all the answers

    What is the relationship between capillary perfusion and muscle activity?

    <p>More capillaries become perfused during increased muscle activity.</p> Signup and view all the answers

    What mechanism primarily controls blood flow in skeletal muscles during rest?

    <p>Minimal sympathetic nervous system activity maintaining vascular tone.</p> Signup and view all the answers

    Which physiological response is associated with reactive hyperemia?

    <p>Immediate restoration of blood flow following a brief ischemic period.</p> Signup and view all the answers

    What happens to capillary perfusion levels during periods of muscle rest?

    <p>A significant reduction in capillary perfusion occurs.</p> Signup and view all the answers

    Which factor primarily triggers an increase in sympathetic nervous system activity regarding blood flow?

    <p>Decreased arterial pressure.</p> Signup and view all the answers

    How does metabolic control influence local blood flow during active muscle contractions?

    <p>It prompts vasodilation to meet acute metabolic needs.</p> Signup and view all the answers

    What is the primary role of the sympathetic nervous system when arterial pressure is low?

    <p>Maintain rest by limiting blood flow changes</p> Signup and view all the answers

    Which type of exercise is specifically associated with active hyperemia?

    <p>Jogging or swimming</p> Signup and view all the answers

    What is the difference between active hyperemia and reactive hyperemia?

    <p>Active hyperemia is associated with rhythmic exercise; reactive is due to a previous lack of blood flow.</p> Signup and view all the answers

    How does skeletal muscle blood flow change immediately after exercise stops?

    <p>There is a prolonged increase followed by a tapering of blood flow.</p> Signup and view all the answers

    What best characterizes the blood flow dynamics during isotonic exercises?

    <p>Regular fluctuations in blood flow corresponding to muscle contractions.</p> Signup and view all the answers

    Which statement best describes the role of local metabolites during exercise?

    <p>They promote vasodilation to improve blood flow despite sympathetic activation.</p> Signup and view all the answers

    What type of exercise is primarily linked to reactive hyperemia?

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

    Which physiological phenomenon is likely to occur immediately after prolonged isotonic exercise?

    <p>A tapering off of blood flow, but higher than at rest.</p> Signup and view all the answers

    Study Notes

    Lecture #26: Vascular Phys II & Special Circulations

    • Lecture delivered by Julia M. Hum, Ph.D.
    • Monday/Wednesday/Friday schedule: 2:00 PM - 2:50 PM
    • Office hours: Monday/Wednesday/Friday, 11:00 AM - 12:00 PM
    • Email: [email protected]
    • Website: marian.edu/medicalschool

    Endothelial Control of Blood Flow: Prostaglandins

    • Endothelium produces prostaglandins.
    • Prostaglandins are a family of molecules that can act as vasodilators or vasoconstrictors.
    • The effect depends on the specific prostaglandin type and receptor.

    Endothelial Control of Blood Flow: EDHF

    • "Endothelium-Derived Hyperpolarizing Factor" is a vasodilator.
    • Opens K+ channels in vascular smooth muscle cells (VSMCs).
    • Leads to hyperpolarization, limiting Ca²⁺ permeability, decreasing intracellular Ca²⁺ levels.

    Endothelial Control of Blood Flow: Endothelins

    • A potent vasoconstrictor.
    • Synthesized and released by endothelial cells in response to various factors (e.g., Ang-II, trauma, hypoxia).
    • Binds to ETA receptors on VSMCs, triggering intracellular Ca²⁺ release via IP₃ pathway.

    Fluid Movement in Capillary Beds

    • Sudden blood loss reduces venous pressure.
    • Fluid shifts from interstitium into blood vessels to compensate.
    • Heart failure: Fluid builds up in the venous system.
    • Fluid is then pushed into the interstitium leading to edema.

    What's Next?

    • Dr. Skinner's lectures, focusing on anticoagulants and antiplatelets begin Monday and Wednesday.
    • Students are encouraged to review Dr. Skinner's case studies if missed.

    L26: Learning Objectives

    • Blood-brain barrier function.
    • Comparison of sensory and secretory circumventricular organs (CVOs).
    • Autoregulation of cerebral blood flow in relation to CO₂.
    • Significance of regional patterns in cranial blood flow.
    • Mechanism of stroke related to blood clots
    • Description of skeletal vasculature.
    • Contrasting local vs. central control over skeletal muscle circulation.
    • Differentiating isometric vs. isotonic muscle exercise and its effects on hyperemia.

    Circulation Needs

    • Anatomical considerations of blood flow pathways.
    • Regulation of blood flow to organs.
    • Local metabolic control over blood flow.
    • Neural control of blood flow.
    • Capacity to respond to blood pressure.
    • Autoregulation capability of circulatory system.

    "Special" Circulations

    • List of specific circulations (cerebral, hepatic, skeletal muscle, coronary, splanchnic, and renal).

    Cerebral Circulation

    • Brain accounts for 2% of body weight but needs 15% of cardiac output.
    • High metabolic rate driving demand.
    • Limited metabolic reserves hence heavily dependent on cerebral circulation.

    Blood Brain Barrier

    • Characteristic feature of brain vasculature.
    • Prevents solutes in capillaries from entering brain extracellular fluid.
    • Unique chemical barriers exist, with enzymes to degrade hormones and NTs.
    • Protects brain from abrupt changes in blood composition.
    • Can become damaged in specific brain regions.
    • Composed of capillaries featuring tight junctions between cells to limit the passage of large molecules.

    Blood Brain Barrier - CVOs

    • CVOs (Circumventricular organs): allow direct access between cerebrospinal fluid and blood.
    • Categorized as sensory and secretory CVOs for sensing certain blood factors.
    • Sensory CVOs (hypothalamus, brainstem) are responsive to various substances and regulate hormones.
    • Secretory CVOs (hypothalamus, posterior pituitary, pineal gland) release and regulate hormones.

    Cerebral Blood Flow Autoregulation

    • Maintains stable blood flow to the brain despite fluctuations in mean arterial pressure (60-150mmHg).
    • Wider autoregulatory range than in other vascular beds.

    Cerebral Blood is Sensitive to Pco2

    • Cerebral vessels dilate in response to metabolic change, especially CO2 levels.
    • High CO2 promotes vasodilation, increasing blood flow.
    • Low CO2 causes vasoconstriction decreasing blood flow.

    Regional Changes in Cranial Blood Flow

    • Blood flow patterns shift based on cognitive/physical activity.
    • Flow can remain steady during focused mental activities.
    • Changes in blood flow can happen in case of injury or disease.

    Clinical Connection: Stroke

    • Stroke is a leading cause of serious disability.
    • Causes of stroke include cardiovascular disease, thrombotic events, or embolic events leading to poor brain circulation.
    • Ischemic stroke is the most common type, accounting for 87% of all strokes.
    • Prevention strategies include measures to lessen clots, lower blood pressure, and lower cholesterol.
    • Medical interventions, Lifestyle modifications,

    Skeletal Muscle Circulation

    • Muscle tissue is richly supplied with capillaries for efficient oxygen and nutrient exchange to facilitate metabolic demands.
    • Skeletal vasculature is supplied by arteries that branch and form arterioles.
    • Arterioles in turn create capillary networks, optimizing oxygen/nutrient exchange and waste removal.

    Skeletal Muscle Circulation - Regulation: Local vs Central

    • Local control:
    • Resting muscle: limited capillary perfusion due to vasoconstriction in terminal arterioles.
    • Active muscle: increased metabolite concentrations trigger vasodilation, increasing capillary perfusion for heightened metabolic activity.
    • Central control:
      • Sympathetic nervous system (SNS) maintains minimal blood flow at rest.
    • During activity, the local control factors take over, increasing blood flow.

    Skeletal Muscle - Extravascular Compression

    • Contractions compress blood vessels.
    • Isometric exercises inhibit blood flow (short term).
    • Active hyperemia (increased blood flow after exercise) occurs as blood vessel constriction relaxes.
    • Reactive hyperemia (temporary increase in blood volume) occurs after an occlusion.

    Studying That Suits You

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

    Quiz Team

    Related Documents

    Fall 2024 Lecture Notes - Vascular Physiology
    Pre-Recorded Lecture - Friday Time Slot PDF

    Description

    Explore the intricacies of endothelial control of blood flow and the roles of various molecules like prostaglandins, EDHF, and endothelins. This quiz will test your understanding of how these factors influence vascular activity and blood flow regulation. Perfect for students interested in advanced vascular physiology.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser