Endocrine Glands

Chapter 18: Endocrine Glands

Levels of Organization

  • Atomic Level: Smallest particle of an element with chemical characteristics.

  • Subatomic Level: Composed of neutrons, protons, electrons.

  • Elemental Level: Simplest type of matter with unique chemical properties.

  • Chemical/Molecular Level: Combination of two or more atoms forming a structure.

  • Cellular Level: Molecules form organelles that constitute a cell.

  • Tissue Level: Specialized cells and extracellular matrix arranged to form tissues.

  • Organ Level: Different tissues combine to create organs.

  • System Level: Organs work together in systems to perform complex functions.

  • Organism Level: Organ systems combine to formulate a complete organism.

Major Endocrine Glands and Tissues

  • Functions of the Endocrine System:

    1. Pineal Gland

    2. Hypothalamus

    3. Pituitary Gland

    4. Thyroid Gland

    5. Parathyroid Glands

    6. Thymus

    7. Adrenal Glands

    8. Pancreas

    9. Ovaries (females)

    10. Testes (males)

Overview of the Endocrine System

  • Definition: Glands and cells that secrete hormones into the bloodstream.

  • Functions Include:

    1. Regulation of metabolism

    2. Control of food intake and digestion

    3. Modulation of tissue development

    4. Ion balance regulation

    5. Maintenance of water balance

    6. Heart rate and blood pressure regulation

    7. Control of blood glucose levels and other nutrients

    8. Control of reproductive functions

    9. Regulation of uterine contractions and milk release

    10. Immune system regulation.

Study Tips for the Endocrine System

  • Five Essential Questions:

    1. What are the stimuli?

    2. What is the gland and hormone involved?

    3. How is regulation achieved?

    4. What are the target tissues and their effects?

    5. What are the consequences of high or low gland function?

Hypothalamus and Pituitary Gland

  • Junction of Nervous and Endocrine Systems:

    • Pituitary Gland (Hypophysis):

    • Secretes nine hormones regulating body functions and secretions of other endocrine glands.

    • Hypothalamus:

    • Regulates anterior pituitary hormone secretion.

    • Posterior pituitary is an extension of the hypothalamus.

Structure of the Pituitary Gland

  • Posterior Pituitary (Neurohypophysis):

    • Extension of the hypothalamus; secretes neurohormones.

  • Anterior Pituitary (Adenohypophysis):

    • Secretes various hormones, many of which are tropic hormones stimulating other glands.

Hormones of the Hypothalamus

  • Key Hormones Include:

    1. GHRH (Growth Hormone-Releasing Hormone): Stimulates GH secretion.

    2. GHIH (Somatostatin): Inhibits GH secretion.

    3. TRH (Thyrotropin-Releasing Hormone): Stimulates TSH secretion.

    4. CRH (Corticotropin-Releasing Hormone): Stimulates ACTH secretion.

    5. GnRH (Gonadotropin-Releasing Hormone): Stimulates LH and FSH secretion.

    6. Dopamine: Inhibits prolactin secretion.

Anterior Pituitary Hormones

  • GOAT FLAP: Mnemonic for remembering anterior pituitary hormones:

    • Growth Hormone (GH)

    • Oxytocin

    • Anti-Diuretic Hormone (ADH)

    • Thyroid Stimulating Hormone (TSH)

    • Follicle Stimulating Hormone (FSH)

    • Luteinizing Hormone (LH)

    • Adrenocorticotropic Hormone (ACTH)

    • Prolactin

Thyroid Gland Functions

  • Anatomy and Hormones:

    • Composed of follicles storing hormone precursors i.e., T3 and T4.

    • Regulates metabolic rate and protein synthesis.

    • Calcitonin: Produced by parafollicular cells; lowers blood calcium levels.

Parathyroid Glands

  • Function: Secretes PTH which increases blood calcium and phosphate levels.

    • Stimulates osteoclast activity and enhances calcium reabsorption in kidneys.

Adrenal Glands

  • Structure: Comprises the adrenal medulla and cortex;

    • Medulla: Secretes epinephrine and norepinephrine (fight-or-flight response).

    • Cortex: Produces important hormones like cortisol, aldosterone, and androgens.

Pancreas Functions

  • Exocrine Role: Secretes digestive enzymes.

  • Endocrine Role: Produces insulin (lowers blood glucose) and glucagon (raises blood glucose).

Hormonal Regulation of Nutrient Utilization

  • After meals: Increased insulin secretion; reduced glucagon, cortisol, GH, and epinephrine.

  • During exercise: Epinephrine and glucagon elevate blood glucose.

Hormones of the Reproductive System

  • From Testes: Testosterone and inhibin.

  • From Ovaries: Estrogen and progesterone, as well as inhibin and relaxin.

Effects of Aging on the Endocrine System

  • Gradual decrease in secretory activity of some glands with age, resulting in lower GH, melatonin, and thyroid hormones.