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Endocrine System. Biology 2122. Introduction. (1) What are hormones? (2) What are the functions of hormones? (3) What are the types of hormones? Amino Acids Steroids Eicosanoids. How do Hormones Work?. (1) Action on Target Cells Membrane permeability Synthesis of proteins or enzymes

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Endocrine system

Endocrine System

Biology 2122


Introduction
Introduction

(1) What are hormones?

(2) What are the functions of hormones?

(3) What are the types of hormones?

  • Amino Acids

  • Steroids

  • Eicosanoids


How do hormones work
How do Hormones Work?

(1) Action on Target Cells

  • Membrane permeability

  • Synthesis of proteins or enzymes

    • Or inhibits

  • Induces secretory activity

  • Stimulates mitosis

    (2) Target-Specific

  • Target cell receptor sites

  • “Turns on cell”

  • “Dynamic”


How do hormones work1
How do Hormones Work?

(3) Half-Life

(4) Interaction – Target Cells

  • Permissive

  • Synergistic

  • Antagonistic

    (5) Control of Release

  • Negative feedback

  • Endocrine Gland Stimuli

    • Humoral stimuli

    • Neural stimuli

    • Hormonal stimuli


Plasma membrane receptors
Plasma Membrane Receptors

(1) Second Messenger System

  • All amino acid hormones (except thyroid)


Plasma membrane receptors1
Plasma Membrane Receptors

(2) Intracellular – Direct Gene Activation

  • Lipid soluble; steroid

  • Binds to intracellular receptors

  • Binds to DNA

  • Activates a gene


Anterior pituitary hormones hgh
Anterior Pituitary Hormones-HGH

(1). Somatotroph cells produce GH

(2). Secretion

  • GHRH – stimulates release (GHIH) inhibits

  • Produced in the hypothalamus

    (3). Effects

  • Anabolic – protein synthesis

  • Targets bones and muscles

  • Stimulates epiphyseal plates during development

    (4). Disorders

  • Gigantism and Acromegaly


Thyroid stimulating hormone
Thyroid-Stimulating Hormone

  • (1). Also referred to as thyrotropin.

    • Produced by thyrotroph cells

  • (2). Secretion

    • TRH or thyrotropin releasing hormone stimulates the release of TSH

    • Negative feedback – rising levels of thyroid hormones

      • ANIMATION

  • (3). Effects

    • Moderates normal thyroid gland activity.


Adrenocorticotropic hormones
Adrenocorticotropic Hormones

  • (1). ACTH – adrenocorticotropic hormone secreted

    • corticotroph cells

  • (2). Stimulation-Secretion

    • CRH – corticotropin-releasing hormone – hypothalamus

      • Levels peak in the morning

    • Negative feedback

  • (3). Effects

    • Stimulates the Adrenal gland (cortex) to release Glucocorticoids

      • Cortisol (stress hormone)


Gonadotropins
Gonadotropins

  • (1). FSH and LH – gonadotrophic cells

  • (2). Stimulus-Secretion

    • Puberty

    • GnRH – prompts the anterior pituitary to release hormones

    • ANIMATION

  • (3). Effects

    • (a). LH

      • FSH -maturation of follicle

      • Ovulation

      • Stimulates interstitial cells - testosterone in males

    • (b). FSH – stimulates gamete production; follicle development.


Prolactin
Prolactin

(1). PRL or prolactin is a protein hormone.

  • Produced by the lactrotroph cells

    (2). Stimulus – Secretion

  • PRH and PRH

  • PRH plays dominant role – dopamine prevents secretion

    (3). Effects

  • Stimulate milk production in the breasts



Posterior pituitary gland hormones
Posterior Pituitary Gland Hormones

(1). Production- hypothalamic neurons

(2). ADH or Antidiuretic Hormone

  • Reabsorption of water– collecting tubules

  • Release stimulated by – increasing osmolarity

    • Diabetes insipidus

      (3). Oxytocin

  • Stimulated release by positive feedback – contractions during birth

  • Milk ejection

  • Synthetic – induce contractions


Thyroid gland
Thyroid Gland

(1). Produces TH or thyroid hormones

  • T4 or thyroxin; T3 or triiodonthyronine

    (2). Stimulus – Secretion

  • Hypothalamus (TRH) - Pituitary (TSH) -- TH

  • Stress - cold, pregnancy – cause hypothalamus to produce TRH.

  • Rising TH levels – negative feedback to hypothalamus-pituitary axis.

    (3). Effects

  • Increases BMR

  • body heat production (stimulates enzymes to increase glucose oxidation)



Thyroid imbalances
Thyroid Imbalances

  • (1). Myxedema – hypothyroid

  • (2). Goiter

  • (3). Cretinism

    • Infant hypothyroidism

  • (4). Grave’s Disease

    • Hyperthyroid


Calcitonin
Calcitonin

(1). Polypeptide hormone

  • Parafollicular cells of the thyroid

  • Lowers calcium blood levels

  • Reabsorption back into the bones

    (2). Stimulus for release

  • 20% above normal levels for calcium blood levels

  • Lower than normal – inhibitory effect

    (3). More important in childhood

  • Due to developing bones and keeps calcium levels in check


Parathyroid hormones
Parathyroid Hormones

(1). Cells in the parathyroid gland

  • Oxyphil and chief cells (secretes ) PTH

    (2). Stimulus and Secretion

  • Hypocalcemia ----- PTH


Adrenal hormones
Adrenal Hormones

(1). Adrenal gland has two distinct regions

  • (a). Cortex - outer region

  • (b). Medulla - inner region

    (2). Hormones produced

  • corticosteroids

    • 12 total

      (3). Steroid Hormones

  • Not stored in cells – rate of release depends on productivity

    (4). Cortical regions

  • (a). Zonaglomerulosa– mineralocorticoids

  • (b). Zonafasciculata– glucocorticoids

  • (c). Zonareticualaris– adrenal sex hormones called gonadocorticoids.


Mineralocorticoids
Mineralocorticoids

(1). Produced in the zona glomerulosa of the cortex

  • Mostly aldosterone

  • Balances ions and water

    (2). Stimulus and Secretion

  • Renin-angiotensin mechanism

  • Elevated K+ levels

    (3). Disorders

  • Aldosteronism

  • Addison’s disease


Glucocorticoids
Glucocorticoids

(1). Produced in the zonafasciculata

  • Metabolic hormones

    (2). Cortisol is the main hormone

  • Gluconeogenesis; lipolysis; protein metabolism

    (3). Stimulation and secretion

  • ACTH from the anterior pituitary (low levels of hormones)

    (4). Disorders

  • Cushing’s syndrome

  • Addison’s disease


Gonadocorticoids
Gonadocorticoids

(1). Androgens produced in the zonareticularis

  • Converted to testosterone and estrogen

    (2). Stimulus and secretion

  • ACTH released from anterior pituitary

    (3). Effects

  • Males

  • Female libido; pubic and axillary hair in females; estrogen after menopause


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