Cardiovascular
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Cardiovascular

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Questions and Answers

What is the primary role of chemoreceptors in cardiovascular regulation?

  • Regulate the release of hormones
  • Detect changes in heart rate
  • Monitor chemical changes in blood (correct)
  • Monitor blood pressure changes

    • Which of the following substances decreases cardiac activity?

  • Thyroid hormones
  • Hypoxia (correct)
  • Calcium
  • Adrenaline

    • How do adrenaline and noradrenaline affect heart function?

  • They exclusively influence blood chemistry
  • They enhance efficiency and increase heart rate (correct)
  • They stabilize blood pressure without affecting heart rate
  • They lower heart rate and reduce contractility

    • What type of receptor is primarily responsible for detecting changes in blood pressure?

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

    What effect do moderate increases in calcium ions have on heart rate?

    <p>They speed up the heart rate</p> Signup and view all the answers

    What role do positive inotropic agents play in heart function?

    <p>They enhance the contractility of ventricular muscle fibers.</p> Signup and view all the answers

    Which neurotransmitter is primarily associated with sympathetic stimulation of the heart?

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

    How does the autonomic nervous system regulate heart rate?

    <p>It processes nerve impulses to give sympathetic and parasympathetic responses.</p> Signup and view all the answers

    What is the effect of glucagon on the heart?

    <p>It increases contractility and supports cardiac metabolism.</p> Signup and view all the answers

    What is the impact of increased extracellular K+ concentration on cardiac muscle?

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

    What is the function of receptors activated by adrenergic hormones like adrenaline?

    <p>They enhance the force of cardiac muscle contraction and metabolism.</p> Signup and view all the answers

    What effect does anoxia have on cardiac function?

    <p>It serves as a negative inotropic agent, decreasing contractility.</p> Signup and view all the answers

    Which drug is known for its positive inotropic effects by blocking calcium flux out of sarcoplasm?

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

    What effect does noradrenaline have on cardiac output?

    <p>Increases heart rate and contraction force</p> Signup and view all the answers

    Which hormone is primarily responsible for causes vasodilation?

    <p>Atrial natriuretic peptide</p> Signup and view all the answers

    Which factor does NOT influence resistance to blood flow?

    <p>Emotional stress</p> Signup and view all the answers

    What is the primary effect of aldosterone on blood pressure?

    <p>Increases blood volume</p> Signup and view all the answers

    Which of the following hormones does NOT lead to vasoconstriction?

    <p>Parathyroid hormone</p> Signup and view all the answers

    How does increased blood viscosity affect blood flow?

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

    What role does angiotensin II play in blood pressure regulation?

    <p>Increases systemic vascular resistance</p> Signup and view all the answers

    What is hydrostatic pressure in the context of blood flow?

    <p>Pressure exerted in all directions by a fluid at rest</p> Signup and view all the answers

    Which of these hormones primarily causes an increase in heart rate?

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

    What effect does atrial natriuretic peptide have on blood pressure?

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

    Study Notes

    Regulation of Heart Rate

    • Increased input to cardiovascular center: Happens upon movement, this is a significant stimulus for rapid heart rate increase at the start of physical activity.
    • Chemoreceptors: Monitor chemical changes in the blood.
    • Baroreceptors: Monitor blood pressure in major arteries and veins.
      • Located in the aortic arch and carotid arteries.
      • Detect blood pressure changes, influencing blood pressure and heart rate.
    • Chemical Regulation:
      • Depression of cardiac activity:
        • Hypoxia (low oxygen levels).
        • Acidosis (low pH).
        • Alkalosis (high pH).
      • Major effects on the heart:
        • Hormones:
          • Adrenaline (E) and noradrenaline (NE): (both from adrenal medulla) enhance heart efficiency.
          • E and NE increase heart rate (HR) and contractility.
          • Thyroid hormones also enhance HR and contractility.
        • Ions:
          • Relative concentrations of K+, Na+, and Ca2+ have a major impact on cardiac function.
          • Excess K+ and Na+ have negative effects.
          • Moderate increases in Ca2+ speed HR.
    • Nervous System Control of the Heart
      • Higher Brain Centers:
        • Sensory receptors
        • Cerebral Cortex
        • Limbic System
        • Hypothalamus
      • Proprioceptors: Monitor limb and muscle position.
      • Chemoreceptors: Monitor blood chemistry.
      • Baroreceptors: Monitor blood pressure.

    Contractility

    • The forcefulness of contraction of individual ventricular muscle fibers.
    • The strength of contraction for any given preload.
    • Regulated by:
      • Positive inotropic agents: Increase contractility.
      • Negative inotropic agents: Decrease contractility.

    Afterload

    • The pressure that must be exceeded before blood ejection from ventricles can begin.
    • It’s the pressure needed to force open semilunar valves.
    • When increased (e.g., elevated blood pressure, atherosclerosis), stroke volume decreases, and more blood remains in the ventricles at the end of systole.

    Positive Inotropic Agents (Regulation of Stroke Volume)

    • Often promote Ca2+ influx during cardiac action potentials, strengthening muscle fiber contraction force.
    • Types:
      • Sympathetic stimulation:
        • Noradrenaline (NE) released from postganglionic fibers binds receptors on cardiac muscle cell membrane.
        • Adrenaline (E) and NE released from adrenal medulla bind receptors on cardiac muscle cell membrane.
      • Stimulation of cardiac muscle metabolism.
      • Hormones:
        • Adrenaline (E) and noradrenaline (NE).
        • Glucagon.
        • Thyroid hormones.
      • Increased extracellular Ca2+ concentration.
      • Drugs:
        • Isoproterenol, dopamine, and dobutamine: (via α- and β-receptor-mediated effects).
        • Digitalis: (via blocking Ca2+ flux out of sarcoplasm).

    Negative Inotropic Agents (Regulation of Stroke Volume)

    • Types:
      • Sympathetic inhibition:
        • Acetylcholine (ACh) released from the vagus nerve binds receptors and hyperpolarizes the cardiac muscle cell membrane.
        • Decreased heart rate (via effects on SA and AV nodes).
        • Reduced force of contraction.
      • Anoxia (oxygen deficiency).
      • Acidosis (low pH).
      • Increased extracellular K+ concentration.
      • Drugs:
        • Propanolol, artenolol, and barbiturates: (via α- and β-receptor-mediated effects).
        • Anaesthetics (e.g., halothane): via reduced intracellular Ca2+.

    Regulation of Heart Rate: Autonomic Innervation

    • Cardiovascular center:
      • Processes nerve impulses (input) to deliver specific responses (output) via sympathetic and parasympathetic nerves.
    • Proprioceptors: Monitor limb and muscle position.

    Hormonal Regulation of Blood Pressure

    • Factor influencing blood pressure | Hormone | Effect on blood pressure
      • Increased heart rate and force of contraction | Noradrenaline | Increase
      • Vasoconstriction | Angiotensin II | Increase
      • Vasoconstriction | Antidiuretic hormone | Increase
      • Vasoconstriction | Noradrenaline | Increase
      • Vasoconstriction | Adrenaline | Increase
      • Vasoconstriction | Calcitriol (active form of vitamin D) | Increase
      • Vasodilation | Atrial natriuretic peptide | Decrease
      • Vasodilation | Adrenaline | Decrease
      • Vasodilation | Parathyroid hormone | Decrease
      • Blood volume increase | Aldosterone | Increase
      • Blood volume increase | Antidiuretic hormone | Increase
      • Blood Volume decrease | Atrial natriuretic peptide | Decrease

    Other Key Points

    • Blood flow depends on the heart to maintain a pressure head.
    • Hydrostatic pressure: Force exerted in all directions when a fluid is not moving.
    • Resistance to blood flow depends on:
      • Total blood vessel length
      • Blood viscosity
      • Turbulence
      • Average blood vessel radius
    • Increased | Increased | Increased | Increased total blood vessel radius (vasoconstriction)
      • Heart rate | Stroke volume (preload) | Blood viscosity | Increased vessel length
      • Increased cardiac output | Increased systemic vascular resistance | Increased mean arterial pressure (MABP)

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    Related Documents

    YAW BBL Cardiovascular System Lecture 4 PDF

    Description

    This quiz covers the key aspects of heart rate regulation, including the roles of chemoreceptors, baroreceptors, and the impact of hormones and ions. Understanding how these factors influence cardiac activity is essential for grasping physiological responses during physical activity. Test your knowledge on how the cardiovascular system adapts to various stimuli.

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