Chapter 17 The Endocrine System

Page 3: Overview of the Endocrine System

• Definition: Comprised of ductless glands synthesizing and secreting hormones.

• Hormones: Released into the bloodstream and transported to target cells with specific receptors.

• Transport Mechanism:

  • Hormones are released into interstitial fluid > enter blood > diffuse into interstitial fluid > bind to target cell receptors.

Page 4: Comparison of Control Systems

• Endocrine and Nervous Systems:

  • Both systems release ligands as chemical messengers that bind to receptors on target cells.

  • Differences:

    • Endocrine system transmits hormones through blood, targets all cells with appropriate receptors, has widespread effects, longer reaction times, and more prolonged effects (minutes to weeks).

Page 5: Nervous and Endocrine System Communication Methods

• Figure illustrating the communication methods between these two systems.

Page 6: General Functions of the Endocrine System

1. Development, Growth, and Metabolism Regulation: Hormones regulate cell division, differentiation, anabolism, and catabolism.

2. Homeostasis: Maintain blood composition, volume, and regulate solute concentrations (e.g., glucose, ions).

3. Digestive Control: Hormones influence digestive tract movement and secretion.

4. Reproductive Control: Affect reproductive system development, function, and sexual behavior expression.

Page 7: Major Endocrine Glands Location

• Endocrine Glands: Composed of epithelial tissue releasing hormones, some also serve non-endocrine functions.

• Glands exclusively endocrine: Pituitary, pineal, thyroid, parathyroid, adrenal.

• Endocrine cells also present in other tissues (e.g., hypothalamus, heart, pancreas).

Page 8: Major Endocrine Glands, Organs, and Tissues

• Figure detailing locations of major endocrine glands and associated cells.

Page 9: Types of Endocrine Stimulation

• Figure depicting various modes of endocrine stimulation.

Page 10: Circulating Hormones

• Steroids: Lipid-soluble; synthesized from cholesterol.

  • Include gonadal steroids (e.g., estrogen) and adrenal cortex steroids (e.g., cortisol).

  • Calcitriol: Sometimes classified as a steroid, more accurately a sterol.

Page 11: Biogenic Amines (Monoamines)

• Definition: Modified amino acids.

  • Include catecholamines, thyroid hormone, melatonin.

  • Water-soluble (except for thyroid hormone, which is lipid soluble).

Page 12: Local Hormones

• Definition: Do not circulate in blood; bind to the releasing cells (autocrine) or neighboring cells (paracrine).

• Eicosanoids: Derived from fatty acids; includes prostaglandins that induce pain and inflammation.

• Drugs (e.g., Aspirin): Block prostaglandin formation.

Page 13: Hormone Interactions on Target Cells

• Types of Hormonal Interactions:

  • Synergistic: One hormone enhances another's effects (e.g., estrogen and progesterone).

  • Permissive: One hormone depends on another's presence (e.g., oxytocin and prolactin).

  • Antagonistic: One hormone counteracts the effects of another (e.g., glucagon and insulin).

Page 14: Hormone Interactions

• Figure illustrating interactions between different hormones.

Page 15: Hypothalamus and Pituitary Gland Connection

1. Control: Hypothalamus governs the pituitary, influencing other endocrine organs.

2. Pituitary Gland: Pea-sized structure located beneath the hypothalamus, comprised of anterior and posterior sections.

Page 16: Posterior Pituitary Gland

• Structure: Smaller neural part of the pituitary.

• Function: Stores hormones released by hypothalamic neurons (i.e., ADH and oxytocin).

Page 17: Hypothalamus and Posterior Pituitary Interaction

• Posterior pituitary releases ADH and oxytocin produced by hypothalamic neurosecretory cells.

  • ADH: Decreases urine production, stimulates thirst, and constricts blood vessels.

  • Oxytocin: Causes uterine contractions and milk ejection.

Page 18: Hypothalamus and Anterior Pituitary Interaction

• Regulation: Hypothalamus stimulates anterior pituitary via hormonal signals.

Page 19: Anterior Pituitary Hormones

• Hypothalamic Hormones:

  • Releasing: TRH, PRH, GnRH, CRH, GHRH (increase pituitary hormones).

  • Inhibitory: PIH, GIH (decrease pituitary hormone secretion).

Page 20: Anterior Pituitary Hormones

• Figure illustrating the hormones produced by the anterior pituitary.

Page 21: Anterior Pituitary Hormones Function

• Hormones:

  • TSH: Stimulated by TRH, promotes thyroid hormone release.

  • PRL: Milk production; regulated by PRH and PIH.

  • ACTH: Release of corticosteroids from the adrenal cortex, stimulated by CRH.

Page 22: Anterior Pituitary Gonadotropins & GH

• Gonadotropins (FSH and LH): Regulate reproductive functions and hormone secretion.

• Growth Hormone (GH): Stimulates liver to secrete IGFs, promotes cell growth and division.

Page 23: Hypothalamo-Hypophyseal Tract

• Figure showing the hypothalamo-hypophyseal tract.

Page 24: Clinical View: Hypophysectomy

• Definition: Removal of the pituitary gland (due to tumors), affecting hormone levels which need to be monitored and replaced.

Page 25: Regulation and Effects of Growth Hormone

1. Control: Regulated by hypothalamic hormones (GHRH and GHIH).

2. Factors Influencing Release: Age, time of day, nutrient levels, stress, exercise.

Page 26: Effects of Growth Hormone

• Functions similar to GH but with a longer half-life.

• Stimulates protein synthesis, cell division, nutrient release, and affects glucose metabolism (glycogenolysis, gluconeogenesis, and lipolysis).

Page 27: Regulation and Action of Growth Hormone

• Figure depicting the regulation of growth hormone action.

Page 28: Disorders of Growth Hormone Secretion

• Growth Hormone Deficiency (Pituitary Dwarfism): Results from low production leading to short stature.

• Pituitary Gigantism: Excess GH leading to excessive growth.

Page 29: Clinical View: Acromegaly

• Acromegaly: Excessive GH in adults leading to enlarged bones and increased glucose production.

Page 30: Anatomy of the Thyroid Gland

• Location: Inferior to the thyroid cartilage of the larynx, anterior to trachea.

• Structure: Composed of follicles with surrounding epithelial cells, rich in blood vessels, producing thyroid hormones and calcitonin.

Page 31: Thyroid Gland Anterior View

• Figure showcasing the anterior view of the thyroid gland.

Page 32: Thyroid Hormone Synthesis

• Figure illustrating the synthesis, storage, and release of thyroid hormones.

Page 33: Regulation of Thyroid Hormone Release

• Axis: Hypothalamic-pituitary-thyroid axis regulates TH levels.

• TRH from hypothalamus stimulates TSH from anterior pituitary leading to T3 and T4 release.

Page 34: Effects of Thyroid Hormone

• Role: Increases metabolic rate, protein synthesis; T3 is more active than T4.

• Calorigenic Effect: Generates heat, stimulates glucose uptake, increases respiration rate, and heart function.

Page 35: Regulation and Action of Thyroid Hormone

• Figure depicting the regulation and action of thyroid hormone.

Page 36: Continued Effects of Thyroid Hormone

• Influences ATP production, regulates blood glucose, and has significant effects on bodily functions.

Page 37: Disorders of Thyroid Hormone Secretion 1

• Hyperthyroidism: Caused by excessive TH with symptoms of weight loss and increased activity.

• Hypothyroidism: Result from decreased TH, leading to lethargy and weight gain.

Page 38: Disorders of Thyroid Hormone Secretion 2

• Goiter: Enlargement due to iodine deficiency, historically common in the U.S.

Page 39: Calcitonin: Regulation and Effects

• Source: From parafollicular cells.

• Function: Decreases blood calcium by inhibiting osteoclasts and promoting calcium excretion in urine.

Page 40: Adrenal Glands Anatomy 1

• Location: On superior surface of each kidney.

• Regions: Medulla (releases epinephrine/norepinephrine) and cortex (synthesizes over 25 corticosteroids).

Page 41: Adrenal Gland Location

• Figure showing the location of adrenal glands.

Page 42: Adrenal Glands Anatomy 2

• Cortex Hormones: Mineralocorticoids (e.g., aldosterone), glucocorticoids (e.g., cortisol), and gonadocorticoids (sex hormones).

Page 43: Cortisol Regulation and Effects 1

• Regulation: Stress and sleep stages stimulate CRH > ACTH > cortisol release.

• Feedback Loop: Cortisol inhibits CRH and ACTH release.

Page 44: Regulation and Action of Cortisol Hormone

• Figure illustrating the regulation and effects of cortisol hormone.

Page 45: Cortisol: Effects and Side Effects

• Therapeutic Use: Corticosterone for inflammation; high doses can lead to infections and tissue repair issues.

Page 46: Disorders in Adrenal Cortex Hormone Secretion 1

• Cushing Syndrome: Results from excessive glucocorticoids leading to various health concerns.

• Addison Disease: Adrenal insufficiency causing weight loss and fatigue.

Page 47: Disorders in Adrenal Cortex Hormone Secretion 2

• Adrenogenital Syndrome: Hormone overproduction causes masculinization in newborns.

Page 48: Stress Response Stages

• Stages:

  1. Alarm Reaction: Sympathetic activation.

  2. Resistance Stage: Cortisol secretion for energy demands.

  3. Exhaustion Stage: Protein breakdown and weakening due to prolonged stress.

Page 49: Anatomy of the Pancreas

• Location: Posterior to stomach, with both endocrine and exocrine functions.

• Islets of Langerhans: Contain alpha (glucagon), beta (insulin), delta (somatostatin), and F cells (pancreatic polypeptide).

Page 50: Pancreas Image

• Figure of the pancreas location.

Page 51: Pancreatic Hormones 1

• Function: Maintain blood glucose.

• Insulin: Secreted by beta cells post food intake to lower blood sugar levels.

Page 52: Regulation and Action of Insulin

• Figure illustrating the mechanism of insulin action.

Page 53: Conditions Resulting in Abnormal Glucose Levels 1

• Diabetes Mellitus: Leading to abnormal glucose levels, causing serious complications.

  • Type 1: Insulin deficiency; autoimmune component.

Page 54: Conditions Resulting in Abnormal Glucose Levels 2

• Type 2 Diabetes: Related to insulin effectiveness; linked to obesity.

• Gestational Diabetes: Occurs in some pregnant women; can cause fetal risk.

Page 55: Conditions Resulting in Abnormal Glucose Levels 3

• Hypoglycemia: Low blood sugar; various causes and symptoms treatable with glucagon.

Page 56: Regulation and Action of Glucagon

• Glucagon raises low blood sugar; stimulates glycogenolysis and lipolysis while inhibiting glycogenesis.

Page 57: Regulation and Action of Glucagon Figure

• Figure illustrating glucagon regulation and action.

Page 58: Pineal Gland

• Location: In the epithalamus; secretes melatonin for sleep regulation and mood.

Page 59: Parathyroid Glands

• Structure: Small glands on the posterior thyroid.

• Function: Chief cells secrete parathyroid hormone (PTH) for calcium regulation.

Page 60: Structures with Endocrine Function 1

• Thymus: Matures T-lymphocytes during childhood.

• Heart: Releases ANP to lower blood pressure.

• Kidney: Secretes erythropoietin for red blood cell production.

Page 61: Structures with Endocrine Function 2

• Liver: Secretes growth factors and angiotensinogen.

• Stomach: Secretes gastrin for digestion.

Page 62: Structures with Endocrine Function 3

• Small Intestine: Secretes secretin and CCK for digestion and bile release.

• Skin: Converts cholesterol to vitamin D, crucial for calcium regulation.

Page 63: Structures with Endocrine Function 4

• Adipose Tissue: Secretes leptin for appetite control; low levels may affect menstrual cycles and reproductive health.

Page 64: Aging and the Endocrine System

• Effects of Aging: Decreased secretory activity leads to reduced efficiency and lower hormone levels, impacting bodily functions.