The Endocrine System

Endocrine System The Endocrine System consists of an organization of glands, each that secrete different kinds of hormones into the bloodstream that serves the purpose to maintain homeostasis. A hormone is a chemical signal that circulates through body fluids and affects distant target cells. These chemical signals allow animals to manage the activities of cells through the body. – In charge for maintaining trillions of cells

Discovery In the early 1900s, research of animal hormones began after the discovery of secretin. Researchers added a small amount of HCl to the small intestine to emulate the arrival of acidic material from the stomach. It was confirmed that the pancreas secreted compounds that neutralized the acid in the small intestine.

Structure Hormones are characterized into three different major classes. – Polypeptides – chains of amino acids linked by peptide bonds – Amino Acid Derivatives – molecules that are made by an original amino acids. (Tyrosine  epinephrine) – Steroids – family of lipids differentiated by a four- ring structure

Endocrine System: glands Organs that secrete a hormone into the bloodstream are considered endocrine glands. The types major glands that have endocrine functions are: – Hypothalamus- Kidneys – Pituitary gland- Adrenal glands – Thyroid gland- Pancreas – Parathyroid glands- Testes – Pineal gland - Ovaries

Hypothalamus Part of the brain that maintains homeostasis Hormones found in the Hypothalamus: – Oxycotin Induces labor and milk production in females – Dopamine – Antidiuretic hormone (ADH) Promotes reabsorption of H2O by kidneys – Corticotropin-releasing hormone (CRH)

Pituitary Gland Found at the protrusion off the bottom of the hypothalamus. Hormones found in the hypothalamus – Growth hormone – Thyroid-stimulation hormone (TSH) – Adrenocorticotropic hormone (ACTH) – Follicle-stimulating hormone (FSH) – Luteinizing hormone – Prolactin – Melanocytes stimuli

Thyroid The thyroid gland is found in the neck. Tridothyonine (T3) Throxine (T4) Calcitonin

Parathyroid glands Located on the rear surface of the thyroid gland about the size of a grain of rice. Produces the parathyroid hormone: – Control the amount of calcium in the blood and within the bones

Adrenal Gland Endocrine glands that sit right above the kidneys. Hormones involved: – Epinephrine (many effects related to short term stress response) – Cortisol (many effects related to short term and long term stress responses) – Aldosterone (increases reabsorption of Sodium ions by kidneys)

Kidneys They are essential in the urinary system and also serve homeostatic functions such as the regulation of acid-base levels. Also regulating salt-water balance. Hormones: – Erythropoietin (EPO) Increases synthesis of red blood cells.

Pancreas The pancreas produced several important hormones, including insulin and glucagon. It is also a digestive organ that secretes pancreatic juice, which contains digestive enzymes to assist the absorption of nutrients. Hormones: – Somatostatin – Insulin (decreases blood glucose) – Glucagon (increases blood glucose)

Ovaries Estradiol – regulates development and maintenance of secondary sex characteristics in females – Secondary sex characteristic: features that distinguish two sexes of a species

Testes Testosterone: regulates development and maintenance of secondary sex characteristics in males