Introduction to Endocrinology
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Questions and Answers

What is the primary function of the endocrine system?

  • Storage of nutrients
  • Coordination of muscle movement
  • Maintenance of homeostasis (correct)
  • Regulation of immune responses

    • Which hormone synthesis process begins with the transcription of a gene in the nucleus?

  • Steroid hormone synthesis
  • Eicosanoid hormone synthesis
  • Mineral hormone synthesis
  • Proteins and polypeptides synthesis (correct)

    • Which of the following is NOT a classic endocrine gland?

  • Thyroid gland
  • Liver (correct)
  • Pituitary gland
  • Adrenal cortex

    • What type of hormone is insulin classified as?

    <p>Protein and polypeptide hormone (B)</p> Signup and view all the answers

    What triggers the release of hormones stored in vesicles?

    <p>External signals such as cAMP or calcium (A)</p> Signup and view all the answers

    What happens to the receptor when leptin binds to it?

    <p>It causes the activation of janus kinase 2 (JAK2). (C)</p> Signup and view all the answers

    Which domain of the steroid hormone receptor is responsible for binding to DNA?

    <p>The C domain. (D)</p> Signup and view all the answers

    How does the steroid hormone-receptor complex regulate gene transcription?

    <p>By binding to steroid-responsive elements (SREs). (C)</p> Signup and view all the answers

    What occurs after the hormone-receptor complex enters the nucleus?

    <p>It dimerizes and binds to specific DNA sequences. (C)</p> Signup and view all the answers

    What role does the phosphorylation of JAK2 play in the signaling mechanism of leptin?

    <p>It activates various enzyme systems for rapid effects. (A)</p> Signup and view all the answers

    Which of the following hormones is derived from cholesterol?

    <p>Cortisol (C)</p> Signup and view all the answers

    What is the typical onset and duration of action for epinephrine?

    <p>Onset within seconds with full action shortly after (C)</p> Signup and view all the answers

    Which statement accurately describes negative feedback in the endocrine system?

    <p>It prevents overactivity by inhibiting further hormone secretion (A)</p> Signup and view all the answers

    What type of feedback is exemplified by the surge of luteinizing hormone (LH) before ovulation?

    <p>Positive feedback (B)</p> Signup and view all the answers

    What characterizes amine hormones like thyroxine and epinephrine?

    <p>They include adrenal medullary hormones. (A)</p> Signup and view all the answers

    In the context of hormonal feedback, what is long-loop feedback?

    <p>When the hormone travels back to the hypothalamic-pituitary axis (A)</p> Signup and view all the answers

    Which hormone is primarily associated with short-loop feedback?

    <p>LH from the anterior pituitary (A)</p> Signup and view all the answers

    Which of the following statements best describes cyclical variations in hormone release?

    <p>They can be influenced by seasonal changes, aging, and diurnal cycles. (C)</p> Signup and view all the answers

    What effect does LH have on estrogen secretion?

    <p>It causes more secretion of estrogen. (A)</p> Signup and view all the answers

    What happens during down-regulation of receptors?

    <p>The number or affinity of receptors decreases. (D)</p> Signup and view all the answers

    Which hormone is known to up-regulate its own receptor in the ovary?

    <p>Estrogen (B)</p> Signup and view all the answers

    What initiates the cellular action after a hormone binds to its receptor?

    <p>Formation of a hormone-receptor complex. (B)</p> Signup and view all the answers

    Which second messenger is produced by the activation of adenylyl cyclase?

    <p>Cyclic adenosine monophosphate (cAMP) (D)</p> Signup and view all the answers

    What is the role of inositol triphosphate (IP3) in hormone action?

    <p>It mobilizes calcium from internal stores. (A)</p> Signup and view all the answers

    Which hormones utilize the phospholipase C signaling pathway?

    <p>Angiotensin II and catecholamines (D)</p> Signup and view all the answers

    What mechanism initiates calcium entry into cells?

    <p>Changes in membrane potential or hormonal interaction. (C)</p> Signup and view all the answers

    What initiates multiple effects inside the cell when calmodulin has 3 binding sites filled?

    <p>Interaction with target proteins (B)</p> Signup and view all the answers

    Which enzyme is responsible for generating cGMP from GTP?

    <p>Guanylyl cyclase (A)</p> Signup and view all the answers

    Which of the following hormones acts through the guanylyl cyclase mechanism?

    <p>Atrial natriuretic peptide (ANP) (D)</p> Signup and view all the answers

    How do receptor tyrosine kinases become activated?

    <p>Upon binding to their corresponding ligand (D)</p> Signup and view all the answers

    Which type of receptor tyrosine kinase is a monomer in its active form?

    <p>Epidermal growth factor receptor (D)</p> Signup and view all the answers

    What characterizes tyrosine kinase–associated receptors?

    <p>They have an extracellular binding domain that binds hormones. (A)</p> Signup and view all the answers

    What role does cGMP play in cellular signaling?

    <p>It serves as a second messenger that activates kinases. (B)</p> Signup and view all the answers

    Which of the following is an example of an enzyme-linked hormone receptor?

    <p>Insulin receptor (C)</p> Signup and view all the answers

    Flashcards

    Endocrine System

    A system that regulates homeostasis through hormone secretion.

    Classic Endocrine Glands

    Glands like the hypothalamus, pituitary, thyroid, that secrete hormones.

    Hormone Synthesis - Protein

    Proteins are made as preprohormones, processed into hormones.

    Hormone Release Trigger

    Release triggered by cAMP, calcium, or other chemicals.

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    Steroid Hormones

    Hormones derived from cholesterol, involved in metabolism and immune response.

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    LH Function

    LH induces secretion of estrogen from ovaries.

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    Dose-Response Relationship

    Response magnitude is related to hormone concentration.

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    Regulation of Receptors

    Hormones influence tissue responsiveness by altering receptor quantity and sensitivity.

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    Down-Regulation

    Decreased receptor number or affinity for a hormone, reducing sensitivity.

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    Up-Regulation

    Increased receptor number or affinity for a hormone, enhancing sensitivity.

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    Hormone-Receptor Complex

    Formed when a hormone binds to its membrane receptor, initiating action.

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    Second Messengers

    Molecules like cAMP or IP3 that amplify hormone signals inside cells.

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    Calcium-Calmodulin Mechanism

    Calcium entry into cells affects various responses via calmodulin activation.

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    Calmodulin

    A protein that binds calcium ions and has 4 binding sites.

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    Calcium binding effects

    When 3 binding sites of calmodulin are filled, it triggers multiple intracellular effects.

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    Catalytic receptors

    Cell surface receptors with enzymatic activity on the intracellular side.

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    Guanylyl cyclase

    An enzyme that converts GTP to cGMP, activated by certain hormones.

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    cGMP

    A second messenger activated by guanylyl cyclase to phosphorylate proteins.

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    Tyrosine kinases

    Enzymes that phosphorylate tyrosine residues on proteins, crucial for signaling.

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    Receptor tyrosine kinases

    A type of tyrosine kinase with intrinsic activity and hormone binding.

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    Enzyme-linked receptors

    Hormone receptors with external binding and internal catalytic sites.

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    Leptin Receptor Mechanism

    Leptin binds to a receptor, activating JAK2 and phosphorylating STAT proteins, leading to gene expression.

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    Homodimer

    A structure formed by two identical receptor parts, as seen in the leptin receptor.

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    JAK2 Activation

    The process where leptin binding causes JAK2 to phosphorylate other proteins, mediating leptin's rapid effects.

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    Steroid Hormone Action

    Steroid hormones diffuse through membranes, bind receptors, and alter gene transcription over hours.

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    Transcription Factor

    A hormone-receptor complex that regulates gene transcription by binding to specific DNA sequences.

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    Hormone types

    Cortisol, aldosterone, estrogen, progesterone, testosterone are derived from cholesterol and are lipid soluble.

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    Amine Hormones

    Derived from tyrosine, including thyroxine, epinephrine, and norepinephrine.

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    Thyroid storage

    Thyroid hormones are stored in thyroglobulin.

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    Epinephrine action

    Epinephrine acts within seconds and reaches full effect shortly after secretion.

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    Negative feedback

    Inhibitory mechanism where hormone action prevents further secretion of that hormone.

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    Feedback loop types

    Long-loop feedback involves hormones acting throughout the hypothalamic-pituitary axis; short-loop is restricted to the hypothalamus.

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    Positive feedback

    Rare self-reinforcing mechanism where hormone action causes more secretion, e.g., LH surge before ovulation.

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    Hormone secretion variation

    Hormones have characteristic patterns influenced by cycles such as seasonal changes and sleep.

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    Study Notes

    Endocrinology Introduction

    • Endocrinology is a study of hormones and their effects, working with the nervous system to maintain homeostasis.
    • This involves growth, development, reproduction, blood pressure regulation.
    • It also controls ion and substance concentrations, and influences behavior.
    • Endocrine glands secrete hormones, impacting target tissues

    The Endocrine System

    • The endocrine system, alongside the nervous system, governs homeostasis.
    • Responsibilities include growth, development, reproduction, blood pressure control, ion concentration, and influencing behavior.
    • Endocrine physiology entails hormone secretion and their downstream actions.
    • Key endocrine glands include the hypothalamus, anterior and posterior pituitary, thyroid, parathyroid, adrenal cortex, adrenal medulla, gonads, placenta, and pancreas.
    • The kidney also acts as an endocrine gland with endocrine cells dispersed throughout the gastrointestinal tract.

    Endocrine Glands and Hormones

    • The hypothalamus secretes hormones that control the pituitary gland activities.
    • The anterior pituitary secretes many hormones like TSH, LH, FSH, ACTH, MSH, growth hormone, and prolactin.
    • The posterior pituitary releases hormones like oxytocin and ADH (antidiuretic hormone).
    • The thyroid gland produces T3 and T4 hormones, while calcitonin is produced as well.
    • The parathyroid regulates calcium levels with the hormone PTH.
    • The adrenal cortex makes cortisol, aldosterone, and adrenal androgens (like DHEA and androstenedione).
    • The adrenal medulla generates norepinephrine and epinephrine.
    • The testes produce testosterone.
    • The ovaries produce estradiol and progesterone.
    • The placenta creates hormones like HCG, hPL, estriol, and progesterone, for pregnancies.
    • The pancreas secretes insulin and glucagon to regulate blood sugar levels.
    • The kidney plays roles in producing 1,25-dihydroxycholecalciferol, and renin

    Hormone Synthesis

    • Hormones are classified into proteins/polypeptides, steroids, and amino acid derivatives.
    • Protein/polypeptide hormones are initially produced as preprohormones, then proceed through prohormone stages.
    • They are synthesized in the rough endoplasmic reticulum, and packaged in secretory vesicles.
    • Release occurs through exocytosis, triggered by various stimuli (e.g., cAMP, calcium).

    Hormone Mechanisms

    • Hormone actions begin with binding to a membrane receptor, forming a hormone-receptor complex.
    • This initiates various pathways, including G protein, adenylyl cyclase, phospholipase C, or directly coupling to catalytic receptors.
    • Second messengers (cAMP, IP3) amplify and orchestrate physiologic effects.
    • Hormones can trigger changes in membrane potential, Ca2+ entry, or enzyme activation, leading to multiple actions.

    Hormone Regulation

    • Negative feedback mechanisms in hormone systems prevent overactivity.
    • The hypothalamus plays a role in regulating the pituitary hormones.
    • Positive feedback loops, though less common, can cause hormone surges, like the pre-ovulation LH surge spurred by estrogen.

    Receptor Regulation and Mechanisms

    • Hormones manage receptor sensitivity by either upregulating or downregulating receptor numbers or affinity.
    • Downregulation decreases receptors to avoid excessive hormone effects.
    • Upregulation increases receptors to enhance effects.

    Steroid and Thyroid Hormones

    • Steroid hormones (e.g., cortisol, estrogen, testosterone) and thyroid hormones act by entering the cell.
    • They bind to intracellular receptors, forming hormone-receptor complexes.
    • The complexes, bound to DNA, create transcription factors, regulating gene expression and protein synthesis.

    Other

    • Specific hormones have individual onset and duration of effects ranging from seconds to months
    • These mechanisms regulate cell functions like metabolism, growth, and reproduction.

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    Related Documents

    Endocrinology Introduction PDF

    Description

    Explore the fundamentals of endocrinology, focusing on hormones and their critical roles in maintaining homeostasis. This quiz covers the functions of the endocrine system, the major glands involved, and the physiological effects of hormone secretion. Test your understanding of how hormones influence growth, reproduction, and behavior.

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