Neuroanatomy of Posterior Pituitary
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Questions and Answers

What happens to the hormone ADH after it is secreted?

  • It separates almost immediately from neurophysin. (correct)
  • It binds permanently to neurophysin.
  • It remains bound to nerve terminals.
  • It undergoes a structural transformation.

    • What amino acid in the vasopressin structure replaces isoleucine found in oxytocin?

  • Leucine
  • Cysteine
  • Arginine
  • Phenylalanine (correct)

    • Which organ is NOT mentioned as a site of ADH and oxytocin synthesis?

  • Gonads
  • Thymus
  • Pancreas (correct)
  • Adrenal cortex

    • What effect does ADH have on the collecting ducts in the kidneys?

    <p>It enhances the reabsorption of water.</p> Signup and view all the answers

    What is the role of aquaporins in the action of ADH?

    <p>They provide channels for water to pass through cell membranes.</p> Signup and view all the answers

    How quickly does the insertion of aquaporins into cell membranes occur after ADH acts?

    <p>Within 5 to 10 minutes.</p> Signup and view all the answers

    What is the primary physiological effect of extremely minute quantities of ADH?

    <p>It reduces excretion of water by the kidneys.</p> Signup and view all the answers

    What happens to urine concentration in the absence of ADH?

    <p>Urine becomes extremely diluted.</p> Signup and view all the answers

    What condition may result from a lack of ADH secretion?

    <p>Diabetes insipidus</p> Signup and view all the answers

    Which hormone is mainly secreted by the paraventricular nucleus of the hypothalamus?

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

    What is the primary effect of oxytocin on the mammary glands?

    <p>Causes milk ejection</p> Signup and view all the answers

    How does oxytocin affect the uterus during pregnancy?

    <p>Facilitates fetal expulsion</p> Signup and view all the answers

    What physiological process is initiated when the cervix is stimulated during labor?

    <p>Discharge of oxytocin impulses</p> Signup and view all the answers

    Which of the following describes the role of ADH in the body?

    <p>Conserves water</p> Signup and view all the answers

    What happens to sodium levels in the blood when there is excessive ADH production?

    <p>They decrease</p> Signup and view all the answers

    What is the half-life of oxytocin in the bloodstream?

    <p>6 minutes</p> Signup and view all the answers

    What triggers the secretion of ADH in response to dehydration?

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

    Which receptors are primarily involved in regulating ADH secretion based on osmolarity changes?

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

    What primarily stimulates the secretion of antidiuretic hormone (ADH)?

    <p>Increased plasma osmolarity</p> Signup and view all the answers

    What physiological response occurs when a dilute solution is injected into the artery supplying the hypothalamus?

    <p>Cessation of ADH secretion</p> Signup and view all the answers

    Which cellular structure does the posterior pituitary gland primarily consist of?

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

    What is the primary site of synthesis for oxytocin?

    <p>Paraventricular nuclei</p> Signup and view all the answers

    How does low blood volume affect ADH secretion?

    <p>It stimulates ADH secretion</p> Signup and view all the answers

    What happens to the secretion of posterior pituitary hormones after cutting the pituitary stalk?

    <p>Secretion transitions to the hypothalamus</p> Signup and view all the answers

    What is one of the alternate names for ADH, reflecting its vasoconstrictor effects?

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

    How does oxytocin primarily exert its effects in the body?

    <p>Acting on smooth muscle cells</p> Signup and view all the answers

    What condition is characterized by a dramatic increase in the rate of ADH secretion?

    <p>Blood volume decrease by 15 to 25 percent</p> Signup and view all the answers

    What is the role of neurophysins in relation to posterior pituitary hormones?

    <p>They transport hormones to the nerve endings</p> Signup and view all the answers

    What role do stretch receptors in the atria play in ADH regulation?

    <p>They inhibit ADH secretion when excited.</p> Signup and view all the answers

    What happens to the ADH secretion when extracellular fluid becomes too dilute?

    <p>Cessation of ADH secretion occurs.</p> Signup and view all the answers

    Which of the following statements about anterior and posterior pituitary hormones is true?

    <p>ADH is synthesized in the supraoptic nuclei.</p> Signup and view all the answers

    What effect does vasopressin have on kidney function?

    <p>Increases water reabsorption</p> Signup and view all the answers

    What role does oxytocin play in the non-pregnant uterus during sexual intercourse?

    <p>Facilitates transport of sperm through uterine contractions</p> Signup and view all the answers

    Which action is NOT associated with oxytocin in males?

    <p>Stimulating aggressive behavior during mating</p> Signup and view all the answers

    Which statement accurately describes the synthesis of oxytocin?

    <p>Oxytocin is synthesized in the hypothalamus.</p> Signup and view all the answers

    What is the effect of vasopressin released from the posterior pituitary gland?

    <p>It increases permeability of kidney collecting ducts to water.</p> Signup and view all the answers

    Which of the following is an incorrect statement about oxytocin?

    <p>Oxytocin receptors are located in the nucleus of target cells.</p> Signup and view all the answers

    Study Notes

    Posterior Pituitary Hormones

    • The posterior pituitary (neurohypophysis) is primarily composed of glial-like cells called pituicytes.
    • Pituicytes support nerve fibers from the hypothalamus.
    • These nerve fibers originate from the supraoptic and paraventricular nuclei of the hypothalamus.
    • Hormones are transported along these fibers and stored in the posterior pituitary.

    Hypothalamic-Hypophyseal Relationship

    • Nerve fibers from the hypothalamus pass through the pituitary stalk (hypophysial stalk) to the posterior pituitary.
    • Nerve endings (bulbous knobs) contain secretory granules.
    • These granules release two hormones: ADH (vasopressin) and oxytocin.
    • ADH and oxytocin are synthesized in different hypothalamic nuclei (supraoptic and paraventricular nuclei, respectively).
    • Hormones are transported along the nerve fibers to the pituitary.

    Antidiuretic Hormone (ADH)

    • Also known as vasopressin.
    • ADH is a polypeptide with 9 amino acids.
    • It acts on the kidneys to increase water reabsorption, resulting in concentrated urine (antidiuresis).

    ADH Function Regulation

    • Increased extracellular fluid (ECF) osmolarity stimulates ADH secretion.
    • Dehydration stimulates ADH secretion.
    • Decreased ECF volume or blood pressure stimulates ADH secretion.
    • Osmoreceptors in the hypothalamus detect changes in ECF osmolarity and initiate ADH release.

    Oxytocin

    • A polypeptide with 9 amino acid.
    • Released from posterior pituitary.
    • Primarily involved in mammary glands and uterus functions

    Oxytocin in Mammary Glands

    • Stimulates milk ejection (let-down reflex)
    • Causes contraction of myoepithelial cells surrounding milk-producing alveoli.

    Oxytocin in Uterus

    • Has a role in uterine contractions during labor.
    • Increased sensitivity of receptors during pregnancy.
    • Contractions of the uterus for childbirth is also stimulated by oxytocin.
    • On non-pregnant uterus, it can facilitate transportation of sperm in female.

    Additional Notes

    • Small amounts of ADH can decrease water excretion by the kidneys.
    • Large amounts of ADH cause potent vasoconstriction.
    • ADH secretion is regulated by a feedback control system involving osmoreceptors in the hypothalamus.
    • The similarity of ADH and oxytocin suggests a common evolutionary origin.

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    Posterior Pituitary Hormones PDF

    Description

    This quiz explores the anatomy and function of the posterior pituitary, focusing on the role of pituicytes and hypothalamic connections. It also covers the synthesis and secretion of key hormones like ADH and oxytocin. Test your knowledge on this crucial aspect of neuroanatomy.

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