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