The Endocrine System
Characteristics of Hormones Chemical nature Made of either proteins or steroids Protein hormones cannot be delivered orally
Mechanism of hormone action Cells that respond to specific hormones have receptor sites (target tissue) Works like lock and key model Receptors either on the surface (protein) or interior (steroid) of cell
Control of hormone action Negative feedback mechanisms Tropic hormones Nervous stimulation
Endocrine Glands
Pituitary Gland Also called the hypophysis Consists of two regions: Adenohypophysis neurohypophysis
Hormones of the Adenohypophysis Growth hormone (GH) Thyroid-Stimulating Hormone (TSH) Adenocorticotropic Hormone (ACTH) Gonadotropic Hormone (LH, ICSH, & FSH) Prolactin (PRL)
Hormones of the Neurohypophysis Antidiuretic Hormone (ADH) Oxytocin
Thyroid Gland Thyroxine Triiodothyronine Calcitonin
Parathyroid Gland Parathyroid Hormone (PTH)
Pancreas Both endocrine and exocrine Islets of Langerhans – alpha and beta cells Glucagon Insulin
Adrenal Glands Located on top of kidneys Composed of a cortex and medulla Hormones of the cortex: Mineralcorticoids (aldosterone) Glucocorticoids (cortisol) Gonadocorticoids (androgens and estrogens) Hormones of the medulla: Epinephrine Norepinephrine
Gonads - Male Testes Produce group of hormones called androgens Testosterone
Gonads - Female Ovaries Estrogens Progesterone
Pineal Gland Melatonin
Other Endocrine Glands Thymus Gastric mucosa Small intestine mucosa Atria of heart Placenta