Hormones and Pheromones: Key Concepts and Endocrine Glands

Introduction to the Endocrine System

  • The endocrine system is responsible for hormone production and their release into the bloodstream, affecting various bodily functions.

  • Lectures cover key structures and functions of various glands involved in hormone secretion.

Types of Hormones and Their Pathways

  • Hormones can be categorized based on their source and function.

  • Hormones travel through the bloodstream to target cells, influencing physiological processes.

Anterior and Posterior Pituitary Hormones

Posterior Pituitary

  • Originates from the hypothalamus; it stores and releases hormones produced by hypothalamic neurons.

Key Hormones:

  1. Oxytocin

    • Stimulates muscle contractions, e.g., uterine contractions during childbirth and milk ejection during breastfeeding.

    • Also involved in vasodilation and vasoconstriction in blood vessels.

  2. Antidiuretic Hormone (ADH)

    • Regulates the kidneys' permeability to control water reabsorption.

    • High secretion leads to high water reabsorption, while low secretion results in low reabsorption.

Other Endocrine Glands

1. Thyroid Gland

  • Secretes Thyroid Hormone (TH), composed of two hormones:

    • Thyroxine (T4)

    • Triiodothyronine (T3)

  • TH increases metabolic rate by stimulating enzymes for glucose oxidation, except in brain, spleen, and gonads.

2. Parathyroid Glands

  • Small glands (typically 4-8) located on the thyroid gland.

  • Secrete Parathyroid Hormone (PTH) to regulate calcium balance in the blood by increasing intestinal absorption and mobilizing calcium from bones.

3. Thymus Gland

  • Located over the heart; decreases in size with age.

  • Produces Thymopoietin and Thymosin to regulate immune system development by promoting T cell maturation.

4. Pineal Gland

  • Found at the brain's third ventricle.

  • Secretes Melatonin, which helps synchronize the circadian rhythm with environmental light-dark cycles.

5. Adrenal Gland

  • Comprised of two parts: cortex and medulla.

a. Adrenal Medulla

  • Produces hormones like epinephrine (adrenaline) and norepinephrine affecting the fight-or-flight response.

b. Adrenal Cortex

  • Produces corticosteroids affecting long-term stress, fat breakdown, glucose synthesis, and immune response suppression.

6. Pancreas

  • A mixed gland that produces digestive enzymes and hormones.

  • Islets of Langerhans contain:

    1. Alpha Cells - secrete glucagon to elevate blood glucose levels.

    2. Beta Cells - secrete insulin to lower blood glucose levels.

Diabetes Mellitus

  • A condition characterized by elevated blood glucose levels

  • Type I Diabetes: Auto-immune disorder leading to insulin non-production.

  • Type II Diabetes: Body's reduced response to insulin, often linked to obesity and lack of exercise.

7. Gonads

  • Ovaries (female) and Testes (male) produce sex hormones critical for reproduction.

Pheromones

  • Chemical signals secreted to influence the behavior or physiology of others of the same species.

Exam Information

  • Third lecture exam scheduled for Thursday, April 10th, covering material worth 40 points, consisting of multiple-choice, true/false, or fill-in-the-blank questions.