The Endocrine System General Characteristics Hormone Action Control of Hormonal Secretions Stress and Health Introduction • Endocrine system – includes cells, tissues and organs collectively called endocrine glands. • Secrete hormones – substances that diffuse from the interstitial fluid into the blood stream and eventually act on cells. – Paracrine hormones = only affect neighboring cells. – Autocrine hormones = affect only the secreting cell itself. General Characteristics • Both the endocrine and nervous systems communicate with cells using chemical signals. • Hormones are to the endocrine system as neurotransmitters are to the nervous system. • Endocrine glands and their hormones help regulate metabolic processes. • They control – Rates of certain chemical reactions – Aid in transport of substances across membranes – Help regulate water and electrolyte balances. – Play vital roles in reproduction, development, and growth. Glands we will look at: • • • • • Pituitary Thyroid Parathyroid Adrenal Pancreas Hormones • Amines – norepinephrine, epinephrine • Peptides – oxytocin, antidiuretic hormone, • Proteins – growth hormone, parathyroid hormone, prolactin • Glycoproteins – FSH, LH, TSH • *Steroids – Estrogen, testosterone, aldosterone, cortisol Steroid Hormones events that occur when they enter a target cell 1. Diffuses through the cell membrane 2. Combines with a specific protein molecule 3. Resulting bound protein binds with a particular region of the DNA of the nucleus and activates transcription of specific genes into messenger RNA molecules 4. mRNA molecules enter the cytoplasm 5. mRNA molecules associate with ribosomes to direct the synthesis of specific proteins. Analogy • Lobbyists in Washington, D.C.(Mr. Pierson story time) Glands Pituitary Thyroid Parathyroid Adrenal Pancreas Pituitary Gland • Located at the base of the brain. • About 1 cm in diameter • Consists of an anterior lobe and a posterior lobe. • ***THE BRAIN CONTROLS MOST OF THE PITUITARY GLAND’S ACTIVITIES.*** Anterior Pituitary Hormones • Growth hormone(GH)- stimulates cell growth in size and frequency. • Prolactin(PRL)- stimulates a woman’s milk production after the birth of an infant. • Thyroid-stimulating hormone(TSH)- controls thyroid gland secretion. • Adrenocorticotropic hormone(ACTH)- controls the manufacture and secretion of certain hormones from the outer layer of the adrenal gland. • Follicle-stimulating hormone(FSH) and Lutenizing hormone (LH)- also called gonadotropins because they exert their actions on the gonads (reproductive organs.) Posterior Pituitary Hormones • Antidiuretic hormone (ADH)- diuretics are chemicals that increase urine production, so antidiuretics decrease urine production. • Oxytosin (OT)- deals mostly with uterine wall contractions for childbirth, but also functions as an antidiuretic. Thyroid Gland • Vascular structure that consists of 2 large lobes connected by a broad isthmus. • Located below the larynx and anterior to the trachea. Thyroid Hormones • Thyroxine (T4) • Triiodothyronine (T3) **These have primarily the same function, except Triiodothyronine is 5 x’s more potent. They help regulate the metabolism of carbohydrates, lipids, and proteins. • They are the major factors determining how many calories the body must consume at rest in order to maintain life. = Basal Metabolic Rate (BMR) Parathyroid Glands • Located on the posterior surface of the thyroid gland. • 4 lobes: superior and inferior located on each of the 2 lobes of the thyroid. Parathyroid hormone • Parathyroid hormone (PTH) – increases blood calcium concentration and decreases blood phosphate ion concentration. • Affects the bones, kidneys and intestines. Adrenal Glands • Closely associated with the kidneys. • A gland sits atop each kidney like a cap. • Consists of 2 parts: – Adrenal medulla = central portion – Adrenal cortex = outer part Adrenal Medulla Hormones • Epinephrine – makes up 80% of adrenal medullary secretion. • Norepinephrine **The effects of epinephrine and norepinephrine include increased heart rate, force of cardiac muscle contraction, increased breathing rate, elevated blood pressure, increased blood glucose, and decreased digestive activity. Hormones of the Adrenal Cortex • Aldosterone – helps regulate the concentration of mineral electrolytes. – Helps maintain blood volume and blood pressure. • Cortisol – affects glucose metabolism. Also influences protein and fat metabolism. • Adrenal sex hormone = androgens and estrogens. – Supplement the supply of sex hormones from the gondads and stimulate early development of the reproductive organs. Pancreas • Flattened, elongated organ posterior to the stomach. • Consists of 2 major types of secretory tissue = endocrine and exocrine • Endocrine = Islets of Langerhans • Has a dual function: – Secretes digestive enzymes – Releases hormones Hormones of the Islets of Langerhans • Glucagon – stimulates the liver to break down glycogen into glucose. • Insulin – stimulates the liver to form glycogen from glucose.