Endocrine System Quiz
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Questions and Answers

Which hormone is primarily responsible for regulating metabolism and is produced by the thyroid gland?

  • Prolactin
  • Calcitonin
  • Insulin
  • Thyroxine (correct)

    • What is the main target tissue for adrenocorticotropic hormone, and what is its primary function?

  • Digestive system; stimulates hunger
  • Muscle tissue; promotes growth
  • Heart; regulates heartbeat
  • Adrenal cortex; stimulates cortisol release (correct)

    • Which of the following hormones is NOT released during short-term stress?

  • Glucocorticoids (correct)
  • Norepinephrine
  • Epinephrine
  • Mineralocorticoids

    • Which hormone, produced by the pancreas, is primarily involved in lowering blood glucose levels?

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

    What can be a possible consequence of the endocrine organs failing to maintain homeostasis?

    <p>Severe fatigue and metabolic disorders</p> Signup and view all the answers

    What hormone is primarily responsible for stimulating growth hormone release from the anterior pituitary?

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

    How does GHIH affect growth hormone synthesis and release?

    <p>Inhibits GH synthesis and release</p> Signup and view all the answers

    Which of the following is a direct action of growth hormone?

    <p>Increased fat breakdown</p> Signup and view all the answers

    What effect do insulin-like growth factors (IGFs) have on the body?

    <p>Promotion of skeletal growth</p> Signup and view all the answers

    Which hormone is produced by the thyrotropic cells of the anterior pituitary?

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

    What triggers the release of thyroid-stimulating hormone (TSH)?

    <p>Thyrotropin-releasing hormone</p> Signup and view all the answers

    Which of the following statements about thyroid hormone regulation is true?

    <p>Thyroid hormones inhibit their own secretion by acting on the hypothalamus</p> Signup and view all the answers

    What forms DIT and MIT in the colloid?

    <p>Tyrosines that are oxidized</p> Signup and view all the answers

    What is the role of the Golgi apparatus in the process described?

    <p>To package and modify thyroglobulin</p> Signup and view all the answers

    What is the first step in the iodination process?

    <p>Iodide is actively transported in</p> Signup and view all the answers

    What is produced when iodinated tyrosines are linked together?

    <p>T3 and T4</p> Signup and view all the answers

    What process follows the endocytosis of thyroglobulin colloid?

    <p>It combines with a lysosome</p> Signup and view all the answers

    Which molecule is actively transported into the follicular cells?

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

    What process occurs after T4 is formed from linked iodinated tyrosines?

    <p>Lysosomal enzymes degrade thyroglobulin</p> Signup and view all the answers

    What occurs to iodide before it attaches to tyrosine?

    <p>It is oxidized to iodine</p> Signup and view all the answers

    Which statement about thyroglobulin is true?

    <p>It serves as a precursor for T3 and T4</p> Signup and view all the answers

    What stimulates the release of thyroid hormones from the thyroid gland?

    <p>Thyroid-stimulating hormone (TSH)</p> Signup and view all the answers

    Which hormone is primarily responsible for regulating the secretion of prolactin?

    <p>Prolactin-inhibiting hormone (PIH)</p> Signup and view all the answers

    What triggers the release of both follicle-stimulating hormone (FSH) and luteinizing hormone (LH)?

    <p>Gonadotropin-releasing hormone (GnRH)</p> Signup and view all the answers

    Which factor does NOT directly influence the regulation of Adrenocorticotropic Hormone (ACTH) release?

    <p>Follicle-stimulating hormone (FSH)</p> Signup and view all the answers

    What occurs in males due to hypersecretion of prolactin?

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

    Which hormone does NOT stimulate adrenal cortex to release corticosteroids?

    <p>Follicle-stimulating hormone (FSH)</p> Signup and view all the answers

    What physiological state primarily leads to a rise in prolactin levels?

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

    Which of the following is released in a daily rhythm triggered by the hypothalamus?

    <p>Adrenocorticotropic hormone (ACTH)</p> Signup and view all the answers

    Which statement is true regarding gonadotropins in prepubertal individuals?

    <p>FSH is absent from the blood.</p> Signup and view all the answers

    What is the correct order of events in the cyclic AMP signaling mechanism after a hormone binds to its receptor?

    <p>Hormone binds receptor, receptor activates G protein, G protein activates adenylate cyclase.</p> Signup and view all the answers

    What role does phosphodiesterase play in the cyclic AMP second-messenger system?

    <p>It degrades cAMP, halting the signaling cascade.</p> Signup and view all the answers

    Which of the following best describes the nature of lipid-soluble hormones in relation to their cellular action?

    <p>They act on intracellular receptors and directly activate genes.</p> Signup and view all the answers

    What is the significance of the amplification effect seen in the cyclic AMP signaling cascade?

    <p>It allows a single hormone to elicit a much larger cellular response.</p> Signup and view all the answers

    What happens to proteins after they are phosphorylated by cAMP-activated protein kinases?

    <p>They can either be activated or inactivated depending on the function of the protein.</p> Signup and view all the answers

    What is the effect of prolactin-inhibiting hormone (PIH) on prolactin release?

    <p>It inhibits prolactin release</p> Signup and view all the answers

    Which factor does NOT influence the secretion of gonadotropins?

    <p>Circadian rhythms</p> Signup and view all the answers

    What physiological consequence can arise from hypersecretion of prolactin in females?

    <p>Inappropriate lactation</p> Signup and view all the answers

    What primarily triggers the release of adrenocorticotropic hormone (ACTH)?

    <p>Corticotropin-releasing hormone (CRH)</p> Signup and view all the answers

    Which function is NOT associated with adrenocorticotropic hormone (ACTH)?

    <p>Regulating gamete production</p> Signup and view all the answers

    Which hormone is associated with stimulating both egg and sperm production?

    <p>Follicle-stimulating hormone (FSH)</p> Signup and view all the answers

    Which of the following influences the release of corticosteroids from the adrenal cortex?

    <p>Adrenocorticotropic hormone (ACTH)</p> Signup and view all the answers

    During which physiological condition is the release of prolactin primarily heightened?

    <p>End of pregnancy</p> Signup and view all the answers

    What is the primary effect of luteinizing hormone (LH) in the body?

    <p>Increasing testosterone levels in males</p> Signup and view all the answers

    Which statement accurately reflects the activity of T3 and T4?

    <p>T4 is converted to T3 in peripheral tissues and is less active than T3.</p> Signup and view all the answers

    What physiological role does calcitonin play in calcium regulation?

    <p>At higher doses, it inhibits osteoclast activity and promotes calcium uptake into bone.</p> Signup and view all the answers

    What is the primary feedback mechanism regulating thyroid hormone release?

    <p>Negative feedback inhibition of TSH release by rising TH levels.</p> Signup and view all the answers

    Which condition is caused by hyposecretion of thyroid hormones in adults?

    <p>Myxedema, which can lead to serious metabolic issues.</p> Signup and view all the answers

    How does the hypothalamic thyrotropin-releasing hormone (TRH) influence thyroid hormone regulation during specific conditions?

    <p>It enhances TSH release, overcoming negative feedback during cold exposure.</p> Signup and view all the answers

    In the context of thyroid hormones, which of these statements correctly describes the relationship between T4 and T3?

    <p>T3 is derived from the conversion of T4 in peripheral tissues, making it more active.</p> Signup and view all the answers

    What is the primary cause of goiter formation in adults?

    <p>Hyposecretion of thyroid hormones caused by lack of iodine.</p> Signup and view all the answers

    Which of the following describes the primary role of thyroxine-binding globulins (TBGs) in relation to thyroid hormones?

    <p>They transport T3 and T4 in the bloodstream, facilitating their activity.</p> Signup and view all the answers

    Which structure is NOT a part of the pituitary gland?

    <p>Corpus callosum</p> Signup and view all the answers

    What role does the hypothalamus play in relation to the pituitary gland?

    <p>It synthesizes and releases hormones that regulate the pituitary.</p> Signup and view all the answers

    What is the function of hypophyseal portal veins?

    <p>To deliver hypothalamic hormones to the anterior pituitary.</p> Signup and view all the answers

    Which hormone does NOT directly influence the secretion process of the pituitary gland?

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

    What type of cells primarily make up the posterior lobe of the pituitary gland?

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

    Which part of the pituitary gland receives the hypothalamic hormones via the portal circulation?

    <p>Pars distalis</p> Signup and view all the answers

    Which hormone synthesis is controlled by hypothalamic neurons?

    <p>Prolactin Inhibiting Hormone (PIH)</p> Signup and view all the answers

    Which of the following terms refers to a chemical messenger produced by an endocrine gland that travels in the bloodstream to target cells?

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

    The nervous system communicates with body functions through electrical signals, while the endocrine system uses chemical signals.

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

    What are the two types of feedback mechanisms that control hormone release?

    <p>Negative feedback and positive feedback</p> Signup and view all the answers

    The ___ plays a crucial role in the release of hormones from the anterior and posterior pituitary glands.

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

    Match the following types of hormones with their primary characteristics:

    <p>Peptide hormones = Water-soluble and bind to cell membrane receptors Steroid hormones = Lipid-soluble and often bind to intracellular receptors Amino acid-derived hormones = Can be either water-soluble or lipid-soluble Eicosanoids = Derived from fatty acids and involved in local signaling</p> Signup and view all the answers

    Which hormone is primarily responsible for stimulating uterine contractions during childbirth?

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

    Glucocorticoids are a type of hormone released by the adrenal gland during long-term stress.

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

    What hormone produced by the pancreas is involved in raising blood glucose levels?

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

    The hormone predominantly responsible for regulating calcium levels in the blood is __________.

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

    Match the following hormones with their target tissues:

    <p>Insulin = Liver Testosterone = Skeletal Muscle Thyroxine = All Body Cells Epinephrine = Heart</p> Signup and view all the answers

    Which of the following functions is primarily associated with the hormone cortisol during stress?

    <p>Reduces inflammation</p> Signup and view all the answers

    Erythropoietin is produced by the kidneys and helps to lower red blood cell production.

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

    What is the first step in the cyclic AMP signaling mechanism?

    <p>Hormone binds to its receptor</p> Signup and view all the answers

    Lipid-soluble hormones cannot enter the cell.

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

    What enzyme is responsible for converting ATP to cAMP?

    <p>Adenylate cyclase</p> Signup and view all the answers

    CAMP acts as a ______ messenger in the signaling pathway.

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

    Match each component to its function in the cyclic AMP signaling process:

    <p>Hormone = First messenger that binds to the receptor G protein = Relays signals from the receptor to adenylate cyclase cAMP = Activates protein kinases Phosphodiesterase = Degrades cAMP to stop the cascade</p> Signup and view all the answers

    What is the role of protein kinases activated by cAMP?

    <p>To phosphorylate other proteins</p> Signup and view all the answers

    Phosphorylation always activates proteins.

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

    What effect does the degradation of cAMP by phosphodiesterase have on the signaling cascade?

    <p>It stops the cascade.</p> Signup and view all the answers

    What is the role of diacylglycerol (DAG) in the signaling mechanism?

    <p>Activates protein kinases</p> Signup and view all the answers

    Calcium ions serve as a second messenger in cell signaling.

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

    After the hormone binds to the receptor, the receptor activates a ______.

    <p>G protein</p> Signup and view all the answers

    What enzyme is activated by the hormone-activated G protein in the PIP2-calcium signaling mechanism?

    <p>Phospholipase C</p> Signup and view all the answers

    The activated ____ activates adenylate cyclase, which converts ATP to cAMP.

    <p>G protein (Gs)</p> Signup and view all the answers

    Match the following components with their functions in cellular signaling:

    <p>G protein = Activates adenylyl cyclase cAMP = Second messenger IP3 = Releases Ca2+ from storage Calmodulin = Binds calcium ions and activates enzymes</p> Signup and view all the answers

    Which molecule is split by phospholipase C to form second messengers?

    <p>PIP2</p> Signup and view all the answers

    Inactive G protein binds directly to adenylate cyclase.

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

    What triggers the activation of protein kinases in the signaling pathway?

    <p>DAG and Ca2+</p> Signup and view all the answers

    Activated adenylate cyclase converts ATP to ____.

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

    Study Notes

    Endocrine Physiology Overview

    • Endocrinology is the study of hormones and endocrine organs.
    • The endocrine system acts with the nervous system to coordinate and integrate body cell activities
    • Endocrine system responses are slower but longer lasting than nervous system responses.
    • Endocrine system influences metabolic activities
    • The endocrine system controls and integrates reproduction, growth, development and maintenance of electrolyte, water, and nutrient balance of blood; regulation of cellular metabolism and energy balance; and mobilization of body defenses.

    Chemical Messengers

    • Hormones are long-distance chemical signals that travel in blood or lymph.
    • Autocrines are chemicals that exert effects on the same cells that secrete them.
    • Paracrines are locally acting chemicals that affect cells other than the ones that secrete them.
    • Autocrines and paracrines are considered local chemical messengers and aren't part of the endocrine system.

    Mechanisms of Hormone Action

    • Hormones circulate systemically, but only cells with receptors for a specific hormone are affected.
    • Hormones alter target cell activity in several ways.
    • Some hormones alter plasma membrane permeability and/or membrane potential.
    • Other hormones stimulate the synthesis of enzymes or other proteins; activate or deactivate enzymes; or induce secretory activity.
    • Some hormones stimulate mitosis.

    Mechanisms of Hormone Action - Receptor Location

    • Water-soluble hormones (all amino-acid-based hormones, except thyroid hormone) act on plasma membrane receptors and use G protein second messengers.
    • Water-soluble hormones include Cyclic AMP, PIP2-Calcium
    • Lipid-soluble hormones (steroid and thyroid hormones) act on intracellular receptors, directly activating genes to enter cells.

    Plasma Membrane Receptors and Second-Messenger Systems

    • Hormone (first messenger) binds to the receptor.
    • Receptor activates a G protein.
    • G protein activates or inhibits an effector enzyme.
    • Effector enzyme generates a second messenger.
    • Second messenger activates protein kinases.
    • Protein kinases phosphorylate proteins.
    • Phosphorylated proteins cause the cell's response and amplification cascade.
    • Some second messenger systems use cyclic AMP (cAMP), or PIP2-calcium signal for different cell responses

    PIP2-calcium signaling mechanism

    • Hormone-activated G proteins activate phospholipase C.
    • Activated enzyme cleaves phospholipids, forming diacylglycerol (DAG) and inositol trisphosphate (IP3).
    • DAG activates protein kinases.
    • IP3 causes Ca2+ release from intracellular storage sites.
    • Calcium acts as a messenger, altering enzyme activity.

    Intracellular Receptors

    • Steroid hormones and thyroid hormones diffuse into target cells.
    • They bind to intracellular receptors within the target cells.
    • The receptor-hormone complex travels to the nucleus.
    • The hormone-receptor complex binds to specific DNA regions, promoting/inhibiting DNA transcription.
    • This process results in new proteins or changes affecting metabolic actions.

    Target Cell Activation

    • Target cell specificity depends on the blood level of hormone.
    • Relative number of receptors or in the target cell.
    • The affinity of receptor binding between receptor and hormone.
    • Hormones influence receptor numbers.
    • Up-regulation occurs in low hormone levels which increase receptor numbers.
    • Down-regulation occurs in high hormone levels which reduces receptor numbers,

    Control of Hormone Release

    • Endocrine gland stimuli include hormonal, neural, and humoral stimuli.

    Hormones in the Blood

    • Hormones circulate freely or bound to plasma proteins.
    • Steroid and thyroid hormones travel bound.
    • Others circulate freely.
    • Hormone concentration reflects the rates of hormone release.
    • Hormone half-life is the time needed for the hormone's blood level to reduce by half.

    Interaction of Hormones at Target Cells

    • Multiple hormones may act on the same target cell.
    • Permissiveness is when one hormone is needed for the action of another hormone.
    • Synergism is when the actions of multiple hormones enhance each other.
    • Antagonism occurs when multiple hormones oppose each other's actions.

    Comparison of Lipid- and Water-Soluble Hormones

    • Lipid-soluble hormones are usually steroids or thyroid hormones.
    • Lipid-soluble hormones have longer half-lives in blood.
    • Lipid-soluble hormones act on intracellular receptors.
    • Water-soluble hormones are most amino acid based hormones.
    • Water-soluble hormones have shorter half-lives in blood.
    • Water-soluble hormones act on membrane receptors.

    Hypothalamus & Pituitary

    • The hypothalamus and pituitary glands are essential for regulating many body functions.
    • The hypothalamus controls pituitary hormone release through neural or hormonal pathways.
    • The anterior pituitary is controlled by hormonal pathways of releasing and inhibiting hormones from the hypothalamus.
    • The posterior pituitary releases hormones synthesized in the hypothalamus via neural pathways.

    Posterior Pituitary and Hypothalamic Hormones

    • Oxytocin is associated with uterine contractions and milk ejection.
    • ADH (vasopressin) regulates water balance.
    • ADH deficiency/excess can cause many health problems.

    Anterior Pituitary Hormones

    • The main anterior pituitary hormones include growth hormone (GH), thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin (PRL).
    • Most are proteins.
    • TSH and ACTH, FSH and LH are tropic hormones.

    Growth Hormone (GH)

    • GH has metabolic and growth effects on the body
    • Direct actions affect metabolism, including increase blood fatty acids, decrease glucose uptake, and glycogen breakdown to release glucose into the blood.
    • Indirect actions involve growth via growth hormone like factors promoting growth of cartilage, bone and skeletal muscle.
    • Imbalances include gigantism in children and acromegaly in adults.

    Thyroid-stimulating Hormone (Thyrotropin)

    • Produced by thyrotropic cells of the anterior pituitary.
    • Stimulates normal development and secretory activity of the thyroid.

    Adrenocorticotropic Hormone (ACTH)

    • Produced by corticotropic cells of the anterior pituitary.
    • Stimulates adrenal cortex to release corticosteroids.
    • Daily rhythm triggered by hypothalamic CRH.

    Gonadotropins

    • Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) stimulate gamete production.
    • FSH stimulates gamete products.
    • LH promotes production of gonadal hormones.
    • Regulation of release triggered by gonadotropin-releasing hormone (GnRH).
    • Release is suppressed by gonadal hormones.

    Prolactin (PRL)

    • PRL is produced by prolactin cells of the anterior pituitary.
    • Stimulates milk production.
    • Role in males not well understood.
    • Release regulated by prolactin-inhibiting hormone and suckling reflexes.
    • Hypersecretion leads to inappropriate lactation.

    Thyroid Gland

    • The thyroid gland produces thyroid hormones (T4 and T3).
    • T4 and T3 have major metabolic and developmental effects regulating virtually every cell in the body.
    • They increase metabolic rate and heat production, influencing skeletal growth, nervous system development, reproduction, and blood pressure.
    • Control of release is through negative feedback regulation.
    • Homeostatic imbalances can cause myxedema in adults and cretinism in infants.

    Calcitonin

    • Calcitonin is produced by parafollicular cells.
    • It is the antagonist of parathyroid hormone.
    • It has lower than normal doses.
    • It regulates calcium levels.

    Parathyroid Glands

    • Parathyroid glands regulate calcium levels via actions through the body.
    • PTH is the main hormone produced in the parathyroid.
    • PTH increases calcium levels through the bone, kidneys and intestines.
    • Imbalances in PTH can cause bones to soften, deform, kidney stones or tetany

    Adrenal Glands

    • Adrenal glands consist of cortex and medulla regions.
    • Corticosteroid hormones (mineralocorticoids, glucocorticoids, and gonadocorticoids) are secreted in the cortex.
    • The adrenal medulla releases epinephrine and norepinephrine, leading to short-term stress response.
    • Imbalances can lead to several health issues.

    Mineralocorticoids

    • Mineralocorticoids like Aldosterone regulate electrolytes like sodium and potassium, vitally important for fluid balance, blood volume and pressure.
    • Aldosterone increases sodium reabsorption and water retention in the kidneys.
    • It also promotes the excretion of potassium.
    • Its release is triggered by decreasing blood volume, blood pressure, and rising potassium levels.
    • Imbalances may result in serious health problems.

    Glucocorticoids

    • Glucocorticoids like Cortisol are important in regulating blood glucose and pressure.
    • They help maintain constant blood glucose levels in the body during stress, while promoting glucose production and utilization.
    • Cortisol enhances metabolism in many tissues and affects immune function.
    • Homeostatic imbalances can lead to Cushing's syndrome or Addison's disease.

    Gonadocorticoids

    • Gonadocorticoids are weak androgens (male hormones).
    • They convert to androgens and estrogens.
    • They play a role in the onset of puberty, appearance of secondary sex characteristics, sex drive in women (estrogen in postmenopausal women).

    Adrenal Medulla

    • Adrenal medulla releases epinephrine, norepinephrine and are part of the body's stress response affecting metabolic activity, dilation of the bronchi, heart and skeletal muscle blood flow.
    • Imbalance results in several physiological conditions.

    Pancreas

    • Pancreas produces hormones regulating blood glucose levels.
    • Glucagon increases blood sugar levels.
    • Insulin lowers blood sugar levels, increasing glucose uptake.
    • Imbalances in these hormones lead to many conditions including hypo and hyperglycemia.
    • Imbalances may lead to diabetes.

    Factors Influencing Insulin Release

    • Blood glucose, amino acids and fatty acids are primary factors that trigger insulin release.
    • Parasympathetic neurons and hormones like glucagon lead to insulin release.

    Homeostatic Imbalances of Insulin

    • Diabetes mellitus is a common result from insulin imbalances and has several types.

    Diabetes Mellitus: Signs

    • Polyuria, polydipsia and polyphagia collectively form the three cardinal signs of diabetes mellitus (DM) indicating issues with blood glucose regulation.

    Gonads

    • Gonads are reproductive organs producing steroid sex hormones that influence reproductive organs.

    Ovaries and Placenta

    • Ovaries produce estrogen and progesterone.
    • These hormones are essential for reproductive development.
    • The placenta also produces estrogen, progesterone and human chorionic gonadtropin (hCG) to support pregnancy.

    Testes

    • Testes produce testosterone, which is essential for male reproductive function.
    • It triggers male reproductive organ maturation and secondary sexual characteristics.

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