Kidney Regulation of Water and Salt
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Kidney Regulation of Water and Salt

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Questions and Answers

What is the primary factor that regulates the glomerular filtration rate (GFR)?

  • Renal blood flow and blood volume (correct)
  • Blood pressure in the glomerulus
  • Oncotic pressure in Bowman’s capsule
  • Pressure in the peritubular capillaries

    • Which mechanism allows each nephron to regulate its own GFR?

  • Tubuloglomerular feedback (correct)
  • Pressure in the renal artery
  • Hormonal regulation by aldosterone
  • Sympathetic nervous system stimulation

    • How does hypovolemia primarily affect GFR?

  • Has no effect on GFR
  • Increases GFR due to high blood pressure
  • Increases GFR by vasodilating renal arterioles
  • Decreases GFR due to reduced renal blood flow (correct)

    • What role do macula densa cells play in renal function?

    <p>They sense sodium levels in the distal tubule</p> Signup and view all the answers

    In the event of persistent hypertension, what is a likely renal response?

    <p>Increased fluid excretion</p> Signup and view all the answers

    Which of the following changes in afferent and efferent arterioles would lead to decreased GFR?

    <p>Afferent constriction and efferent dilation</p> Signup and view all the answers

    What effect does renal sympathetic nervous system (SNS) stimulation have in severe acute disturbances in arterial blood pressure?

    <p>Decreases GFR to protect the kidneys</p> Signup and view all the answers

    Which factor most directly affects the oncotic pressure in the glomerulus?

    <p>Plasma protein concentration</p> Signup and view all the answers

    What is the primary effect of ANP and BNP on sodium absorption?

    <p>They decrease sodium absorption to promote diuresis.</p> Signup and view all the answers

    Which of the following hormones promotes increased sodium reabsorption?

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

    How do osmotic diuretics primarily function?

    <p>They increase the osmolality of filtrate, retaining water.</p> Signup and view all the answers

    What occurs when there is an increase in extracellular fluid K+ concentration?

    <p>Acidosis may occur due to H+ ions moving into cells.</p> Signup and view all the answers

    Which diuretic is known to block sodium reabsorption in the distal convoluted tubule?

    <p>Thiazide diuretics</p> Signup and view all the answers

    What is the relationship between Na reabsorption and K secretion?

    <p>Increased Na reabsorption leads to increased K secretion.</p> Signup and view all the answers

    Which factor can lead to an increase in K+ secretion?

    <p>High levels of ANP</p> Signup and view all the answers

    What physiological change promotes the release of urodilatin?

    <p>Increase in circulating volume detected by renal cells.</p> Signup and view all the answers

    What role does adenosine play in the function of afferent and efferent arterioles?

    <p>It causes contraction of afferent arterioles and relaxation of efferent arterioles.</p> Signup and view all the answers

    How does the macula densa respond to high sodium levels?

    <p>It inhibits renin secretion by affecting the JGA through adenosine.</p> Signup and view all the answers

    What effect does low sodium have on nitric oxide and prostaglandins?

    <p>It increases both nitric oxide and prostaglandin synthesis.</p> Signup and view all the answers

    Which receptor type is associated with the inhibition of cAMP formation in response to adenosine?

    <p>Adenosine type I receptors.</p> Signup and view all the answers

    What is the primary function of the renin-angiotensin-aldosterone system (RAAS)?

    <p>To regulate sodium and blood volume.</p> Signup and view all the answers

    How does sympathetic nerve stimulation affect renin secretion from the JGA cells?

    <p>It enhances renin secretion by stimulating beta receptors.</p> Signup and view all the answers

    What initiates the secretion of renin from the juxtaglomerular cells?

    <p>Decreased blood pressure and low sodium levels trigger renin release.</p> Signup and view all the answers

    What happens when the macula densa works very hard and ATP leaks out of the cell?

    <p>It stimulates purine receptors, inhibiting renin release.</p> Signup and view all the answers

    What is the primary mechanism through which increased intracellular calcium leads to contraction in smooth muscle?

    <p>Phosphorylation of myosin light chain by MLCK</p> Signup and view all the answers

    Which substance is regarded as the most potent vasoconstrictor?

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

    Which factor contributes to vasodilation by increasing cGMP levels?

    <p>Nitric oxide (NO)</p> Signup and view all the answers

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

    <p>To exchange materials between blood and cells</p> Signup and view all the answers

    What physiological response occurs during the latch state of smooth muscle?

    <p>Maintained force with decreasing myosin phosphorylation</p> Signup and view all the answers

    How does myogenic control contribute to the regulation of blood flow?

    <p>By constricting vessels in response to increased pressure</p> Signup and view all the answers

    How is Mean Arterial Pressure (MAP) calculated?

    <p>Pd + (Ps - Pd) / 3</p> Signup and view all the answers

    Which of the following relates to metabolic control of blood flow?

    <p>Build-up of lactic acid</p> Signup and view all the answers

    Which factor does NOT directly impact vascular resistance?

    <p>Heart rate</p> Signup and view all the answers

    Which of the following substances is NOT a vasodilator?

    <p>Angiotensin II</p> Signup and view all the answers

    What is the role of myosin light chain kinase (MLCK) in smooth muscle contraction?

    <p>To phosphorylate myosin and enable contraction</p> Signup and view all the answers

    What triggers the release of calcium from intracellular stores in smooth muscle cells during vasoconstriction?

    <p>Activation of phospholipase C by norepinephrine</p> Signup and view all the answers

    What effect does the activation of phosphatases have on muscle contraction?

    <p>Facilitating muscle relaxation</p> Signup and view all the answers

    What is a characteristic feature of smooth muscle compared to skeletal muscle?

    <p>Regulation by MLCK instead of calcium ions directly</p> Signup and view all the answers

    How does an increase in vessel length affect blood flow?

    <p>Decreases flow due to increased friction</p> Signup and view all the answers

    What is the effect of bradykinin on vascular smooth muscle?

    <p>Increases cAMP and cGMP leading to relaxation</p> Signup and view all the answers

    Study Notes

    Kidney Regulation of Water and Salt

    • Aldosterone increases the number of Na/K pumps to enhance water absorption.
    • Factors influencing GFR include:
      • Kf (permeability),
      • Pg (blood pressure),
      • Pb (Bowman's capsule pressure),
      • Oncotic pressures (Pi g and Pi b).
    • Renal perfusion is crucial for GFR; volume or salt in ECF affects kidney’s excretion decisions.

    Factors Affecting GFR

    • Major GFR regulators:
      • Blood volume and renal blood flow (RBF).
      • Increased renal BF/blood volume raises GFR and fluid excretion.
    • Sympathetic nervous system, macula densa, and myogenic responses regulate changes.
    • GFR decreases significantly during hypotension, while hypertension results in excessive fluid loss.
    • Autoregulation maintains GFR and RBF between mean arterial pressures (MAP) of 80-170 mmHg.

    Tubuloglomerular Feedback

    • Each nephron can self-regulate GFR, controlled by juxtaglomerular apparatus (JGA).
    • Macula densa senses Na levels and influences JGA cells and afferent arteriole response.
    • Low GFR prompts renin production from JGA cells, increasing ANG II to maintain GFR.

    Macula Densa Function

    • High sodium levels lead to afferent arteriole constriction through adenosine signaling.
    • JGA cells secrete renin in response to low sodium detection, catalyzing RAAS activation.
    • Sympathetic stimulation and hormonal actions (e.g., prostaglandins) modify renin levels.

    Sodium and Blood Pressure Regulation

    • Elevated sodium intake typically raises blood pressure; only about 1% of filtered sodium is excreted.
    • Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) counteract RAAS, promoting fluid excretion and vasodilation.
    • Urodilatin, uroguanylin, and guanylin reduce sodium reabsorption in response to increased plasma volume or dietary salt intake.

    Diuretic Agents

    • Diuretics alter urinary filtrate osmolality, increasing urine volume.
    • Osmotic, loop, and thiazide diuretics function by inhibiting sodium reabsorption and promoting water retention.

    Potassium Distribution

    • Potassium is primarily secreted in the cortical collecting duct; aldosterone enhances this process.
    • Factors shifting potassium include acidosis, insulin, and catecholamines.
    • Na/K pump plays a pivotal role in potassium homeostasis.

    Vessel Control of Blood Pressure

    • Mean arterial pressure (MAP) estimates are calculated considering diastolic and systolic pressures.
    • Vascular resistance depends on vessel length, diameter, and blood viscosity.

    Smooth Muscle Contraction in Vessels

    • Smooth muscles contract through a sliding filament mechanism, regulated by MLCK and calcium interactions.
    • Norepinephrine binding to alpha-1 receptors triggers vasoconstriction by increasing intracellular calcium via Gq protein activation.

    Myogenic and Metabolic Control

    • Myogenic responses involve vessel constriction during increased internal pressure.
    • Metabolic control occurs via local factors like CO2, H+, and metabolic waste, influencing vasodilation.

    Vasodilators and Mechanisms

    • Significant vasodilators include bradykinin, histamine, and nitric oxide (NO).
    • NO production triggers vasodilation through cGMP pathways, affecting smooth muscle relaxation.

    Summary of Regulatory Mechanisms

    • RAAS and aldosterone increase sodium reabsorption, whereas ANP, BNP, urodilatin, uroguanylin, and guanylin function antagonistically.
    • Smooth muscle's latch state allows sustained contraction with reduced myosin light chain phosphorylation over time.

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    Description

    Explore the intricate mechanisms of kidney regulation of water and salt, focusing on elements such as the Na/K pump and the factors influencing glomerular filtration rate (GFR). Understand how various pressures and perfusion impact kidney function. This quiz will challenge your knowledge of renal physiology and homeostasis.

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