Lecture Notes - Chapter 56 Homework – Review Questions #1, 4-8 I. Chemical Messengers in Endocrine Control The endocrine system is so named due to the fact that its components consist mainly of ductless glands (endocrine glands). The chemicals secreted by these endocrine glands are called hormones, and they are delivered to the cells they act upon via the bloodstream. There are several categories of hormones, but the two major types are peptide hormones and steroid hormones. Peptide hormones Steroid hormones – All remaining hormones are amino acid derivatives. II. The Mechanisms of Hormone Action A. Hormones that Enter Cells - a hormone must be lipid-soluble to diffuse through the plasma membrane of a cell. B. Hormones that Do Not Enter Cells – III. The Major Endocrine Glands and Their Hormones A. Posterior Pituitary Gland - derived embryologically from neural tissue. Hormones secreted include: 1) Antidiuretic hormone (ADH) – Disorder – 2) Oxytocin – Both of these hormones are stored in the axon terminals of nerves whose cell bodies are in the hypothalamus, where they are produced. When stimulated, the hormones are released from the axon terminals into the blood. B. Anterior Pituitary Gland - derived embryologically from an epithelial pouch which detaches from the oral cavity - Rathke’s pouch. Tropic hormones secreted include: 1) Growth hormone (GH) – Disorders: 2) Adrenocorticotrophic hormone (ACTH) – 3) Thyroid-stimulating hormone (TSH) – 4) Luteinizing hormone – 5) Follicle stimulating hormone – 6) Prolactin – 7) Melanocyte-stimulating hormone - C. The Thyroid Gland - located anterior to the trachea just below the larynx - is bilobed. Hormones include: 1) Thyroxine – Disorders: 2) Calcitonin – D. Parathyroid glands - 4 small glands on the posterior surface of the thyroid gland (2 on each side). One hormone: 1) Parathyroid hormone (PTH) – Disorders: E. The Adrenal Glands: Two Glands in One Adrenal Medulla: Emergency Warning Siren - involved in ANS - releases epinephrine and norepinephrine. Cause an increase of blood glucose, heartbeat, blood flow. Adrenal Cortex: Homeostasis of Glucose 1) Cortisol – 2) Aldosterone – F. The Pancreas: Regulating Energy Balance - contains small clusters of cells called islets of Langerhans, which secrete two key hormones related to blood glucose levels: 1) Insulin – Disorders: 2) Glucagon - peptide hormone - from alpha cells - promotes breakdown of glycogen and fat to increase blood glucose levels when too low.