Endocrine System Overview

Endocrine System Overview

• Works with the nervous system to control and regulate the body's functions
• Influences metabolic activities by transporting hormones via blood
• Key functions include reproduction, growth/development, homeostasis maintenance, metabolism/energy regulation, and defense mobilization

Endocrine Glands

• Lack ducts; release hormones directly into surrounding tissue
• Examples: pituitary, thyroid, parathyroid, adrenal, pineal glands
• Hypothalamus: 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

Hormone Types and Actions

• Amino acid-based hormones: Peptide/protein based, water-soluble
• Steroids: Derived from cholesterol, lipid-soluble
• Eicosanoids: Classified as paracrines; influence nearby cells
• Hormones affect target cells with specific receptors
• Hormonal actions include changing plasma membrane permeability, protein/enzyme synthesis, activating/deactivating enzymes, inducing secretion, and stimulating mitosis

Hormone Regulation

• Humoral stimuli: Response to blood levels of ions/nutrients
• Neural stimuli: Nerve fibers stimulate hormone release
• Hormonal stimuli: Hormones trigger the release of other hormones
• The nervous system can override endocrine controls, like during stress

Pituitary Gland

• Posterior Pituitary (Neurohypophysis):
  • Oxytocin: Uterine contractions, milk ejection
  • ADH (Antidiuretic Hormone): Water retention by kidneys; increases blood volume
  • ADH imbalances:
    • Hyposecretion: Diabetes insipidus
    • Hypersecretion: Syndrome of Inappropriate Antidiuretic Hormone (SIADH)
• Anterior Pituitary (Adenohypophysis):
  • 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, regulates growth/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 sodium and potassium balance
  • Glucocorticoids (e.g., Cortisol): Increases blood glucose, stress response
    • Hypersecretion: Cushing's syndrome
    • Hyposecretion: Addison's disease
  • Gonadocorticoids: Weak androgens that convert to testosterone or estrogen
    • Hypersecretion: Adrenogenital syndrome (masculinization)
• Adrenal Medulla: Produces catecholamines (epinephrine & norepinephrine), short-term stress response (fight or flight)

Pineal Gland

• Secretes melatonin, regulating 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 and Organs

• 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 Considerations

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

Explore the fundamental aspects of the endocrine system and its interplay with the nervous system. This quiz covers key functions, types of hormones, and the role of various endocrine glands. Understand how hormones influence bodily functions and maintain homeostasis.