Endocrine System Overview

Endocrine System Overview

• Works with the nervous system to control and regulate bodily functions.
• Influences metabolic activities via hormones, transported through the bloodstream.
• Key functions include reproduction, growth and development, homeostasis maintenance (electrolyte, water, and nutrient balance), metabolism and energy regulation, and mobilization of body defenses.

Endocrine Glands

• Endocrine glands lack ducts, releasing hormones directly into surrounding tissues.
• Examples include: pituitary, thyroid, parathyroid, adrenal, and pineal glands.
• Hypothalamus is a neuroendocrine organ, with both neural and hormonal functions.
• Other organs with endocrine tissues include pancreas, gonads, placenta, adipose cells, thymus, stomach, kidneys, and heart.

Hormones

• Types of hormones:
  • Amino acid-based hormones (peptides and proteins): water-soluble.
  • Steroid hormones: lipid-soluble, synthesized from cholesterol.
  • Eicosanoids: paracrines (acting locally).
• Hormones act on specific target cells possessing receptors.
• Actions on Target Cells:
  • Alter plasma membrane permeability.
  • Stimulate protein/enzyme synthesis.
  • Activate/deactivate enzymes.
  • Induce secretory activity.
  • Stimulate mitosis.

Hormone Regulation and Secretion

• Stimuli for Hormone Release:
  • Humoral: Response to blood levels of ions/nutrients.
  • Neural: Nerve fibers stimulate hormone release.
  • Hormonal: Hormones stimulate the release of other hormones.
• Nervous system can override normal endocrine controls (e.g., stress).

Key Hormones and Their Functions

Pituitary Gland

• Posterior Pituitary:
  • Oxytocin: Uterine contractions, milk ejection.
  • ADH (Antidiuretic Hormone): Water retention, increases blood volume.
  • ADH Imbalances:
    • Hyposecretion: Diabetes insipidus.
    • Hypersecretion: Syndrome of Inappropriate ADH secretion (SIADH).
• Anterior Pituitary:
  • GH (Growth Hormone): Stimulates growth via IGFs.
    • Hypersecretion: Gigantism (children), acromegaly (adults).
    • Hyposecretion: Pituitary dwarfism.
  • TSH (Thyroid-Stimulating Hormone): Stimulates thyroid hormone release.
  • ACTH (Adrenocorticotropic Hormone): Stimulates cortisol release.
  • FSH & LH: Regulate gonadal hormone production.
  • PRL (Prolactin): Stimulates milk production.

Thyroid and Parathyroid Glands

• Thyroid Hormone (TH):
  • Increases basal metabolic rate and heat production.
  • Regulates tissue growth and development.
  • Imbalances:
    • Hyposecretion: Myxedema (adults), goiter (iodine deficiency).
    • Hypersecretion: Graves’ disease (autoimmune).
• Parathyroid Hormone (PTH): Maintains calcium homeostasis.
  • Imbalances:
    • Hyperparathyroidism: Weak bones, kidney stones.
    • Hypoparathyroidism: Tetany, respiratory paralysis.

Adrenal Glands

• Adrenal Cortex:
  • Mineralocorticoids (e.g., Aldosterone): Regulates Na+ and K+ balance.
  • Glucocorticoids (e.g., Cortisol): Increases blood glucose, stress response.
    • Hypersecretion: Cushing’s syndrome.
    • Hyposecretion: Addison’s disease.
  • Gonadocorticoids: Weak androgens; converted to testosterone or estrogens.
    • Hypersecretion: Adrenogenital syndrome (masculinization).
• Adrenal Medulla: Produces catecholamines (epinephrine and norepinephrine). Short-term stress response (fight-or-flight).

Pineal Gland

• Secretes Melatonin: Regulates sleep-wake cycles.

Pancreas

• Glucagon: Raises blood glucose levels.
• Insulin: Lowers blood glucose levels.
• Diabetes Mellitus:
  • Type 1: Hyposecretion of insulin.
  • Type 2: Insulin resistance.

Other Hormones

• Gonads: Produce sex hormones (estrogen, progesterone, testosterone).
• Placenta: Temporary endocrine organ during pregnancy.
• Other Organs:
  • Heart: ANP (reduces blood pressure).
  • Kidneys: Erythropoietin (RBC production), Renin (blood pressure regulation).

Clinical Insights

• Hormone imbalances significantly affect metabolism, growth, and homeostasis.
• Environmental pollutants can disrupt hormone function.

Explore the functions and components of the endocrine system in this quiz. Learn about key endocrine glands, hormone types, and how they influence various bodily processes. Test your knowledge on how the endocrine system works alongside the nervous system to maintain homeostasis.