Endocrine System Quiz - Adrenal Hormones
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Questions and Answers

Which of the following best describes the effect of norepinephrine on blood vessels in most organs?

  • Vasoconstriction via β2-receptors
  • Vasodilation via β2-receptors
  • Vasoconstriction via α1-receptors (correct)
  • Vasodilation via α1-receptors

    • What is the primary mechanism by which dopamine, when injected, causes vasodilation in the kidneys?

  • By releasing epinephrine in the cortex
  • By inhibition of heart β1-adrenergic receptors
  • By direct action on a dopaminergic receptor (correct)
  • By stimulating renal Na, K, ATPase activity

    • Which of the following best represents the effect of catecholamines on insulin and glucagon secretion?

  • Inhibit both hormones via β-adrenergic mechanisms.
  • Increase both hormones via α-adrenergic mechanisms.
  • Increase secretion via β-adrenergic and inhibit via α-adrenergic mechanisms. (correct)
  • Inhibit secretion via β-adrenergic and increase via α-adrenergic mechanisms.

    • During sleep, what generally happens to adrenal medullary secretion?

    <p>Secretion of both epinephrine and norepinephrine is reduced.</p> Signup and view all the answers

    Which of the following is a primary physiological effect of dopamine on the heart?

    <p>Positive inotropic effect via β1-adrenergic receptors.</p> Signup and view all the answers

    What is the precursor molecule for all hormones of the adrenal cortex?

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

    Among the secreted steroids, which of the following is considered the most potent mineralocorticoid?

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

    Epinephrine dilates blood vessels in skeletal muscle and the liver through which mechanism?

    <p>Via β2-receptors</p> Signup and view all the answers

    What is the primary fate of cortisone produced in the liver?

    <p>It is rapidly reduced and conjugated to tetrahydrocortisone glucuronides.</p> Signup and view all the answers

    Compared to cortisol, how does the secretion amount of aldosterone differ?

    <p>Aldosterone's secretion is very small compared to cortisol's.</p> Signup and view all the answers

    Which of the following is the major adrenal androgen?

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

    In adult males, what is the primary effect of excess secretion of adrenal androgens?

    <p>It mainly accentuates existing masculinization.</p> Signup and view all the answers

    What is the primary molecule from which all steroids are synthesized?

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

    What role does peripheral tissue play in the context of androstenedione?

    <p>It converts androstenedione into both testosterone and estrogens.</p> Signup and view all the answers

    What is the role of cholesterol ester hydrolase in steroid biosynthesis?

    <p>It catalyzes the formation of free cholesterol from lipid droplets.</p> Signup and view all the answers

    Which mechanism do glucocorticoids use when affecting target cells?

    <p>By acting as transcription factors through steroid-receptor complexes.</p> Signup and view all the answers

    Where does the conversion of cholesterol to pregnenolone occur?

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

    Which of the following is an effect of glucocorticoids on glucose metabolism?

    <p>Increased hepatic glycogenesis and gluconeogenesis</p> Signup and view all the answers

    Which of the following describes the relationship between ACTH and pregnenolone?

    <p>ACTH stimulates an increase in the formation of pregnenolone and its derivatives.</p> Signup and view all the answers

    What is the approximate proportion of the urinary 17-ketosteroids in men derived from the adrenal glands or formed from cortisol in the liver?

    <p>About two-thirds</p> Signup and view all the answers

    Which protein primarily binds cortisol in the bloodstream?

    <p>Transcortin (CBG)</p> Signup and view all the answers

    Which of the following factors would decrease CBG levels?

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

    Why is protein binding significant for cortisol?

    <p>It lengthens the half-life of cortisol in the circulation.</p> Signup and view all the answers

    What is the main site for glucocorticoid metabolism in the body?

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

    Why do glucocorticoids increase plasma glucose levels despite having an anti-insulin effect?

    <p>They prevent the uptake of glucose by peripheral tissues, ensuring a greater availability for brain and heart.</p> Signup and view all the answers

    The negative feedback response of glucocorticoids on ACTH secretion works by:

    <p>Inhibiting ACTH secretion directly at the pituitary.</p> Signup and view all the answers

    What is a key neurological effect seen in adrenal insufficiency that is reversed by glucocorticoids?

    <p>Appearance of electroencephalographic waves slower than the normal β rhythm.</p> Signup and view all the answers

    Water intoxication in adrenal insufficiency occurs primarily because of:

    <p>An inability to excrete a water load, leading to fluid accumulation.</p> Signup and view all the answers

    What is the primary long-term effect of increased ACTH levels that is considered detrimental?

    <p>Development of Cushing syndrome abnormalities.</p> Signup and view all the answers

    How does stress influence ACTH secretion?

    <p>Most, but not all, forms of stress activate processes that increase ACTH production.</p> Signup and view all the answers

    What is the role of glucocorticoids concerning vascular reactivity to catecholamines during stress?

    <p>They help maintain vascular reactivity to catecholamines.</p> Signup and view all the answers

    In a patient with adrenal insufficiency, what is a critical risk of administering glucose without prior glucocorticoid treatment?

    <p>High fever followed by circulatory collapse and potential death.</p> Signup and view all the answers

    Which of the following is a cellular change in the blood caused by glucocorticoids?

    <p>Increased number of circulating red blood cells.</p> Signup and view all the answers

    Which of the following is a consequence of excess protein catabolism in Cushing syndrome?

    <p>Poorly developed muscles and thin skin</p> Signup and view all the answers

    In Cushing syndrome, where does fat typically accumulate disproportionately in the body?

    <p>The abdominal wall, face, and upper back</p> Signup and view all the answers

    What contributes to the 'moon-faced' appearance observed in patients with Cushing syndrome?

    <p>Salt and water retention and facial obesity</p> Signup and view all the answers

    How do glucocorticoids suppress the inflammatory response to tissue injury?

    <p>Through inhibiting the inflammatory response</p> Signup and view all the answers

    What role does ACTH play in the regulation of glucocorticoid secretion?

    <p>It provokes increased glucocorticoid secretion and increases the adrenal's sensitivity to further ACTH.</p> Signup and view all the answers

    The anti-inflammatory and anti-allergic effects of glucocorticoids require what condition?

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

    What is the approximate half-life of ACTH in human circulation?

    <p>10 minutes</p> Signup and view all the answers

    What is the primary pattern of ACTH secretion throughout the day?

    <p>Regular bursts with peak frequency in the early morning.</p> Signup and view all the answers

    How does the presence of free glucocorticoids impact ACTH secretion?

    <p>They inhibit ACTH secretion in a proportionality to their circulating levels.</p> Signup and view all the answers

    What is the main effect of mineralocorticoids, such as aldosterone, on the body?

    <p>Increase in sodium reabsorption and expansion of ECF volume.</p> Signup and view all the answers

    How does aldosterone facilitate sodium reabsorption at a cellular level?

    <p>Through an initial rapid increase in ENaCs activity and then a slower increase in synthesis of ENaCs.</p> Signup and view all the answers

    Which of the following correctly describes how aldosterone affects potassium and hydrogen in the renal tubules?

    <p>Exchanges K+ and H+ for Na+, causing K+ to be secreted and increasing urine acidity.</p> Signup and view all the answers

    Which of these is a primary stimulus for aldosterone secretion?

    <p>Renin from the kidney via angiotensin II.</p> Signup and view all the answers

    In the context of adrenal function, what happens to ACTH secretion rate in patients with chronic adrenal insufficiency?

    <p>The secretion rate is increased markedly.</p> Signup and view all the answers

    What is the immediate effect of ACTH on the adrenal cortex when first administered?

    <p>It stimulates the output of aldosterone, glucocorticoids and sex hormones.</p> Signup and view all the answers

    Study Notes

    Adrenal Medulla & Adrenal Cortex

    • Two endocrine organs in the adrenal gland, one surrounding the other
    • Adrenal medulla secretes catecholamines: epinephrine, norepinephrine, and dopamine
    • Adrenal cortex secretes steroid hormones:
      • Glucocorticoids - affect carbohydrate and protein metabolism
      • Mineralocorticoids - maintain Na+ balance and extracellular fluid (ECF) volume
      • Androgens (e.g., testosterone) - secondary site of androgen synthesis, affects reproductive function

    Adrenal Medulla

    • Makes up 28% of adrenal gland mass
    • Two cell types:
      • Epinephrine-secreting type (90% in humans)
      • Norepinephrine-secreting type (10% in humans)

    Adrenal Cortex

    • Divided into three zones:
      • Zona glomerulosa - outermost layer, secretes aldosterone
      • Zona fasciculata - middle layer, secretes corticosterone, cortisol
      • Zona reticularis - innermost layer, secretes corticosterone, cortisol, and androgens

    Catecholamines

    • Norepinephrine, epinephrine, and small amounts of dopamine
    • Synthesized by the adrenal medulla
    • Norepinephrine from hydroxylation and decarboxylation of tyrosine
    • Epinephrine from methylation of norepinephrine
    • In plasma, mostly conjugated to sulfate (inactive)

    Effects of Epinephrine & Norepinephrine

    • Glycogenolysis in liver and skeletal muscle
    • Mobilization of free fatty acids (FFA)
    • Increased plasma lactate
    • Stimulation of metabolic rate

    Effects of Dopamine

    • Unknown physiologic function in circulation
    • Renal vasodilation
    • Vasonconstriction
    • Positive inotropic effect on heart (β1-adrenergic receptors)
    • Natriuresis (possible by inhibiting renal Na,K-ATPase)

    Adrenocortical Hormones (Structure)

    • Derivatives of cholesterol
    • Contain a cyclopentanoperhydrophenanthrene nucleus

    Secreted Steroids

    • Numerous steroids isolated, but only a few in physiologically significant amounts:
      • Aldosterone (mineralocorticoid)
      • Cortisol and corticosterone (glucocorticoids)
      • Dehydroepiandrosterone (DHEA) and androstenedione (androgens)
    • Deoxycorticosterone – mineralocorticoid, about 3% mineralocorticoid activity of aldosterone

    Steroid Biosynthesis

    • Cholesterol is the precursor
    • Some synthesized from acetate, but most from LDL in circulation
    • Cholesterol ester hydrolase forms free cholesterol inside lipid droplets
    • Cholesterol transported into mitochondria, converted to pregnenolone
    • Pregnenolone converted to other steroids like progesterone, etc, in smooth endoplasmic reticulum

    Regulation of Adrenal Medullary Secretion

    • Primarily through the nervous system
    • Secretion is low in basal states, reduced during sleep
    • Increased secretion during emergency situations ("emergency function of the sympathoadrenal system")

    Regulation of Adrenal Medulla & Cortex

    • ACTH (from the anterior pituitary) acutely controls adrenal androgen secretion
    • ACTH only slightly affects aldosterone levels
    • Plasma K+ levels also influence aldosterone secretion
    • Other factors affecting aldosterone secretion include glomerular filtration rate, ANP, osmotic diuresis, and tubular reabsorption of Na+

    Glucocorticoids (Effects)

    • Affect intermediary metabolism: increased protein catabolism, hepatic glycogenesis, gluconeogenesis, glucose-6-phosphatase activity, increased plasma glucose
    • Anti-insulin action in peripheral tissues, exacerbates diabetes
    • Extra glucose to vital organs in diabetics, increases plasma lipids and ketone bodies
    • Inhibit ACTH production (negative feedback)
    • Affect nervous system (mild changes, slow EEG waves)
    • Affect water metabolism (inability to excrete a water load; could cause water intoxication)
    • Affect blood cells & lymphatic organs - decrease eosinophils, decrease basophils, increase neutrophils, platelets, and red blood cells
    • Affects response to stress

    Mineralocorticoids (Effects)

    • Increased reabsorption of Na+ from urine, sweat, saliva, colon contents
    • Increased ECF volume
    • Na+ exchanged for K+ and H+ in renal tubules (resulting in K+ diuresis & increased urine acidity)

    Mechanism of Action - Mineralocorticoids (Aldosterone)

    • Cytoplasmic receptor
    • Receptor-hormone complex moves to nucleus, alters mRNA transcription
    • Increases epithelial sodium channels
    • Increases enzyme synthesis in slower effects

    Circadian Rhythm of Glucocorticoids

    • ACTH secretion in irregular bursts during the day, peaks in early morning
    • Cortisol production peaks in early morning, is low in late evening

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    Description

    Test your knowledge on the endocrine system, focusing specifically on adrenal hormones and their physiological effects. This quiz covers topics such as norepinephrine, dopamine, catecholamines, and adrenal androgens. Get ready to explore the fascinating world of hormones and their roles in the body.

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