Endocrine Glands and Hormone Classes (3A) - Bio & Biochem

1. What is the defining property of peptide hormones regarding membrane permeability and receptor location?

   Water-soluble; bind cell-surface receptors. Their hydrophilic nature prevents membrane crossing, so they activate G-protein-coupled receptors to initiate intracellular signaling.

2. Which anterior pituitary hormone stimulates milk production in the mammary glands?

   Prolactin. It acts on mammary alveolar cells to promote lactogenesis, essential for postpartum milk synthesis and secretion.

3. Which adrenal cortex layer secretes androgens such as DHEA?

   Zona reticularis. This innermost layer generates weak androgens that serve as precursors for sex hormone synthesis in peripheral tissues.

4. Which endocrine gland secretes melatonin to regulate circadian rhythms?

   Pineal gland. It produces melatonin in response to darkness, influencing sleep-wake cycles and seasonal biological rhythms.

5. Which adrenal cortex layer secretes cortisol?

   Zona fasciculata. This middle layer synthesizes glucocorticoids like cortisol in response to ACTH for stress adaptation and immune modulation.

6. Which thyroid gland cell type secretes calcitonin?

   Parafollicular (C) cells. These cells lower serum calcium by inhibiting osteoclast activity and promoting renal calcium excretion.

7. Which adrenal cortex layer secretes aldosterone?

   Zona glomerulosa. This outermost layer produces mineralocorticoids under renin-angiotensin system control to regulate electrolyte balance.

8. What is the key anatomical link that connects the hypothalamus to the posterior pituitary?

   Infundibulum (pituitary stalk). This structure facilitates the transport of hormones from hypothalamic neurons to the posterior pituitary for storage and release.

9. Which anterior pituitary hormone directly stimulates the thyroid gland to secrete $T_3$ and $T_4$?

   TSH (thyroid-stimulating hormone). It binds to thyroid receptors, promoting the synthesis and release of thyroid hormones that regulate metabolism and development.

10. Which anterior pituitary hormone stimulates the adrenal cortex to secrete cortisol?

    ACTH (adrenocorticotropic hormone). It targets the adrenal cortex to induce glucocorticoid production, which modulates stress responses and metabolism.

11. Which hormone increases serum calcium by increasing bone resorption and renal calcium reabsorption?

    Parathyroid hormone (PTH). It elevates blood calcium levels by stimulating osteoclasts and enhancing renal and intestinal calcium absorption.

12. What is the primary physiologic effect of ADH on the kidney?

    Increases water reabsorption in collecting ducts. It promotes aquaporin insertion in renal collecting ducts, enhancing water permeability and reducing urine volume to maintain blood osmolarity.

13. Which endocrine gland is the master regulator that secretes tropic hormones to control other glands?

    Anterior pituitary. It acts as the central controller by releasing tropic hormones that stimulate and regulate hormone production in target endocrine glands.

14. Which hypothalamic hormone inhibits prolactin release from the anterior pituitary?

    Dopamine (prolactin-inhibiting factor). It tonically suppresses prolactin secretion via the hypothalamic-pituitary portal system, preventing inappropriate lactation.

15. Which anterior pituitary hormone stimulates linear bone growth and increases IGF-1 production?

    Growth hormone (GH). It promotes tissue growth by direct anabolic effects and indirectly via liver-derived IGF-1, crucial for development and metabolism.

16. Which hormone increases blood glucose primarily by stimulating glycogenolysis and gluconeogenesis?

    Glucagon. It acts on liver enzymes to break down glycogen and synthesize glucose, maintaining blood sugar levels during fasting.

17. Which anterior pituitary hormone triggers ovulation and stimulates Leydig cells to produce testosterone?

    LH (luteinizing hormone). It surges to induce egg release in females and stimulates androgen production in male Leydig cells for reproductive function.

18. Which hormone class typically uses second messengers such as cAMP to amplify the signal?

    Peptide (and catecholamine) hormones. They activate membrane receptors linked to signaling cascades that amplify responses via molecules like cAMP for rapid cellular effects.

19. Which two hormones are synthesized in the hypothalamus and released from the posterior pituitary?

    ADH (vasopressin) and oxytocin. These hormones are produced in hypothalamic nuclei and transported via axons to the posterior pituitary for secretion into the bloodstream.

20. What is the primary reproductive physiologic effect of oxytocin?

    Stimulates uterine contractions and milk ejection. It binds to receptors in uterine smooth muscle and mammary myoepithelial cells, facilitating labor and milk letdown during breastfeeding.

21. Which adrenal region secretes epinephrine and norepinephrine?

    Adrenal medulla. This chromaffin cell-rich region responds to sympathetic stimulation by releasing catecholamines for fight-or-flight responses.

22. Which anterior pituitary hormone stimulates ovarian follicle development and Sertoli cell function?

    FSH (follicle-stimulating hormone). It promotes gametogenesis by stimulating follicle maturation in ovaries and spermatogenesis support in testicular Sertoli cells.

23. What is the defining property of steroid hormones regarding transport and receptor location?

    Lipid-soluble; intracellular receptors; carrier-bound. Derived from cholesterol, they diffuse through membranes to bind nuclear receptors, altering gene expression, and require plasma carriers for transport.

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