1 / 54

Introduction to Hormones and their Effects on Endocrine Organs

This lecture provides an overview of hormones, their general biochemistry, and their effects on various endocrine organs such as the anterior and posterior pituitary, adrenal cortex, and adrenal medulla. It also discusses the regulation of hormones and receptor activity, as well as the interactions between different hormones.

hsuggs
Download Presentation

Introduction to Hormones and their Effects on Endocrine Organs

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 11 Hormones

  2. Lecture map • Hormones: • - general biochemistry • endocrine organs and effects • - anterior pituitary • - hypothalamus • - posterior pituitary • - adrenal cortex • - adrenal medulla

  3. Lecture map • Next: • endocrine organs and effects • - thyroid • - parathyroid • - pancreas • - pineal • - thymus • - placenta, gonads • - adipose, skin, kidneys, heart, GI tract • autocrine system • - endocrine signal transduction

  4. HORMONES

  5. Hormones • Endocrine: into blood • Exocrine: ducts • Autocrine: same organ, same tissue • Paracrine: same organ, different tissue

  6. Endocrine hormones • Endocrine hormones are in blood, so they reach all cells of the body. • Each hormone only affects SOME cell types and tissues. • - the cell has to express the particular receptor to “hear” the hormone signal.

  7. Endocrine hormones Secretion hormone receptor Target cell

  8. Hormone types • Polar: • Most hormones. • Bind to receptor protein on pm. • Lipophilic (nonpolar): • Cross pm, act inside target cells. • Steroid hormones and thyroid hormones. • Can take orally, as pills.

  9. Hormone types • Hormones: • Often amino acid derivatives or peptides. • Steroid hormones are made from cholesterol.

  10. Receptors • Hormone receptors on target cells: • Very specific • Often high affinity (bond strongly) • Integral mb proteins.

  11. Effect of hormones • Effect of hormone depends on… • blood levels • number of receptors on target cells • affinity of receptors for hormones

  12. Effect of hormones • Blood levels depend on: • - gene expression • half-life of hormone • - for lipophilic hormones: how much is bound to protein carriers

  13. Regulation • Endocrine hormones: secreted into blood, then removed by target organs and liver, converted to inactive form, and excreted. • Half-life: • Is general term for time required for the [molecule] to be reduced to half of reference level. • This lecture: blood [hormone]. • Way to quantify permanence of hormone. • Minutes to hours, even days.

  14. Regulation of receptor • Upregulation: • High or constant hormone levels can lead to more receptor proteins on target cells (usually through gene expression) and a greater response by the target cell.

  15. Regulation of receptor • Downregulation (desensitization): • Prolonged, continuous exposure to high [hormone] can lead to diminished response (to same amount of hormone). • One way: decrease in number of receptors on target cells. • Through endocytosis, lysosomes, protein degradation. • Pulsatile secretion of hormone (in spurts, over time) may prevent downregulation of receptor.

  16. Regulation of hormone • Hormone regulation: • Active form= a certain configuration. • Often inactive in blood.

  17. Regulation of hormone • Prohormone/prehormone: precursor molecule, usually inactive and can be modified (often cut) to become active. • Preprohormone: precursor to prohormone!

  18. Hormone effects • Physiological range: [hormone] which produces normal responses. • [pharmacological] are usually higher, can have different effects from physiological range.

  19. Side effects of drugs • Pharmacological drugs have side effects because: • Hormones, neurotransmitters, etc., regulate many targets, in many parts of the body. • High doses may cause binding to other receptors (less specificity).

  20. Hormonal Interactions • Synergistic: enhance each other’s action. • “two is better than one plus one!” • Permissive: permits action of another hormone. • Antagonistic: act in opposition; important for homeostasis!

  21. PITUITARY GLAND

  22. Pituitary Gland • In diencephalon. • Anterior lobe. • Posterior lobe.

  23. Anterior pituitary • Anterior pituitary • Derived from epithelial tissue. • Controls growth of many other endocrine glands (“master gland”) • - each known as an axis • Trophic effects: • High blood [hormone] causes target organ to hypertrophy. • Low blood [hormone] causes target organ to atrophy.

  24. Anterior pituitary • Growth hormone (GH) -> many tissues, grow! • Thyroid-stimulating hormone (TSH) -> thyroid secretes T3, T4 • ACTH -> adrenal cortex to secrete glucocorticoids • Prolactin -> milk • Gonadotrophic hormones: • FSH -> ovarian follicles, sperm cells • LH -> ovulation; testosterone

  25. Anterior Pituitary

  26. Hypothalamus • Hypothalamus regulates the anterior pituitary! • Physically linked, blood portal system. • Hypothalamic hormones often called “(something) releasing hormones”

  27. Hypothalamus

  28. Hypothalamus • Hypothalamic hormones -> Anterior pituitary hormones • GHRH increases GH • Somatostatin inhibits GH • TRH increases TSH • CRH increases ACTH • PIH inhibits prolactin • GnRH increases FSH and LH

  29. Regulation of Anterior Pituitary • Mostly through negative feedback inhibition from target organs to hypothalamus or directly to anterior pituitary. • Ex: TSH -> T4 ---l TSH

  30. Regulation of Anterior Pituitary • So, once a certain amount of hormones are made, they shut off the system producing them!

  31. Antagonistic effectors • GHRH -> GH l- Somatostatin • Somatostatin -l GH • TRH -> TSH -> T4 • T4 -l TSH, TRH • CRH -> ACTH -> Glucocorticoids • Glucocorticoids -l CRH • PRH -> Prolactin • PIH -l Prolactin

  32. Antagonistic effectors • GnRH -> FSH, LH • Gonadal hormones -l FSH, LH • Estogen can inhibit, or stimulate, depending on levels! • Some levels even stimulate synthesis of FSH, LH, but prevent release. (p. 932) • Testosterone -l GnRH, FSH, LH

  33. Hormones • Estrogens are a family of several hormones. (Testosterone is one hormone.) • Male brains have an enzyme that turns testosterone into estrogens! • (note: PIH is dopamine!)

  34. Hormones • GH: • “fountain of youth?!?” • secreted mostly in adolescence • too much: gigantism, acromegaly • too little: pituitary dwarfism • stimulates uptake of amino acids into cells

  35. Hormones • Note: • stress -> CRH -> ACTH -> glucocorticoids

  36. Posterior pituitary • Posterior pituitary • Formed by downgrowth of the brain during fetal development. • Under direct neural control. • Nerve fibers extend through the infundibulum.

  37. Posterior pituitary Stores and releases 2 hormones that are produced in the hypothalamus: - Antidiuretic hormone (ADH) - Oxytocin Posterior pituitary

  38. Antidiuretic hormone (ADH): - aka vasopressin - promotes the retention of H20 by the kidneys Posterior pituitary

  39. Oxytocin: - stimulates contractions of the uterus during parturition. stimulates contractions of the mammary gland alveoli for milk-ejection reflex. bonding with baby?! orgasm? Posterior pituitary

  40. Posterior Pituitary

  41. ADRENAL GLANDS

  42. Adrenal Glands • Paired organs that cap the kidneys. • Each: outer cortex and inner medulla.

  43. Adrenal cortex • Adrenal cortex: • - stimulated by ACTH. • - secretes corticosteroids • - different regions secrete different hormones. • - all made from cholesterol.

  44. Adrenal Cortex • Corticosteroids include: • - mineralocorticoids: • - glucocorticoids • - gonadocorticoids

  45. Adrenal Cortex • Mineralocorticoids: • - aldosterone • - targets kidneys • - affects Na+ and K+ balance • - stimulates transcription of Na+/K+ ATPase pump! • - more aldosterone -> more Na+, water in body • - stress -> CRH -> ACTH -> aldosterone -> retain • fluid -> high blood pressure!

  46. Adrenal Cortex • Glucocorticoids (gc) • - cortisol (aka hydrocortisone) • - metabolism, more glucose in blood • - stress -> large increase in gc • - pharmacologically: suppress inflammation, asthma, • rheumatoid arthitis

  47. Adrenal Cortex • Gonadocorticoids: • - aka sex steroids • - include DHEA (precursor for estrogen, testosterone) • - not well understood • http://www.quackwatch.org/01QuackeryRelatedTopics/dhea.html

  48. Adrenal Cortex

  49. Adrenal Medulla • Adrenal medulla: • Derived from embryonic neural crest ectoderm (same tissue that produces the sympathetic ganglia). • Controlled by preganglionic sympathetic innervation • (is like a postganglionic neuron!) • Secretes adrenaline (aka epenephrine) • (also secretes norepenephrine)

  50. Sympathetic response • Adrenaline: • part of sympathetic response to a threat! • “fight or flight” • Also, fear, sex • Also: tend and befriend • Triggered by physical and emotional/psychological stress: body responds similarly to “bear in woods” or to stressful words.

More Related