Overview
This lecture covers the endocrine system, its major glands, the hormones they release, and their impact on bodily functions, with examples of hormone-related disorders.
Introduction to Hormones and the Endocrine System
- Hormones are chemical messengers critical for many body processes.
- The endocrine system is made of glands and cells that secrete hormones directly into the bloodstream (ductless).
Major Endocrine Glands and Their Hormones
- Brain glands: hypothalamus, pineal gland, pituitary gland.
- Neck glands: thyroid and parathyroid glands.
- Upper chest gland: thymus.
- Glands above kidneys: adrenal glands.
- Near the stomach: pancreas.
- Reproductive glands (gonads): ovaries and testes.
Endocrine vs. Exocrine Glands
- Endocrine glands release hormones into surrounding tissue/blood without ducts.
- Exocrine glands use ducts to release substances onto surfaces or into body cavities (e.g., sweat, milk).
- Some organs, like the pancreas, have both endocrine and exocrine functions.
Hormone Types and Functions
- Hormones can be derived from amino acids, polypeptides, or lipids (like steroids).
- Hormone structure affects function and determines which receptors and target cells they bind to.
Gland-by-Gland Hormone Summary
- Hypothalamus-pituitary complex regulates most of the endocrine system.
- Posterior pituitary releases oxytocin (uterine contractions) and ADH (water absorption by kidneys).
- Anterior pituitary produces GH (growth), PRL (milk), TSH (thyroid stimulation), FSH & LH (gonad function), and ACTH (adrenal cortex stimulation).
- Pineal gland secretes melatonin (regulates sleep-wake cycle).
- Thyroid gland produces T4 and T3 (regulate metabolism) and calcitonin (lowers blood calcium).
- Parathyroid gland produces PTH (raises blood calcium).
- Thymus produces thymosin (promotes T cell development for immunity).
- Adrenal medulla releases epinephrine/norepinephrine (fight-or-flight).
- Adrenal cortex produces cortisol (stress), aldosterone (regulates sodium/potassium).
- Pancreas releases insulin (lowers blood glucose) and glucagon (raises blood glucose).
- Ovaries produce estrogen (female sex traits, uterine lining), progesterone (maintains uterine lining).
- Testes produce androgens like testosterone (male sex traits, sperm).
Hormone Signaling and Examples of Dysfunction
- Hormones act as chemical signals, triggering actions in target cells.
- Endocrine signaling can be slow or fast and cover short or long distances.
- Hormonal disorders like hypothyroidism illustrate the system's importance; symptoms include fatigue and slow heart rate due to low thyroid hormone.
Key Terms & Definitions
- Hormone — chemical messenger that affects target cells.
- Endocrine gland — ductless gland releasing hormones into the blood.
- Exocrine gland — gland releasing substances through ducts to surfaces/cavities.
- Hypothalamus — brain region controlling the pituitary and many hormones.
- Pituitary gland — "master gland" regulating other endocrine glands.
- TSH — hormone stimulating thyroid activity.
- Insulin — hormone lowering blood glucose.
- Cortisol — stress hormone from adrenal cortex.
Action Items / Next Steps
- Review further reading suggestions for additional examples of endocrine disorders.
- Study diagrams of endocrine glands and their hormone targets.