The Endocrine System

Another system in the human body that serves as a regulatory and information signaling system much like the nervous system is known as the endocrine system. While the nervous system controls and regulates faster human processes such as movement, heartbeat, and breathing, the endocrine system controls and regulates slower body processes such as reproduction, metabolism, growth, development, and aging. Whereas the nervous system utilizes nerves to conduct and transfer information, the endocrine system utilizes blood vessels as channels for information transfer. The human endocrine system is comprised of several ductless glands which produce and release signaling molecules known as hormones into the circulatory system. Hormones travel to distant organs, tissues, and cells through blood vessels to regulate the functions of their target. How these hormones indentify and influence their specific targets is a miracle. Blood levels of hormones can be influenced by infection, disease, lifestyle, stresses of daily living, body fluid balance, electrolytes and minerals in the blood, as well as our thoughts, emotions, and moods. The major glands that constitute the endocrine system are the hypothalamus, pituitary, pineal, thyroid, parathyroid, pancreas, adrenals, testes, and ovaries. Pituitary The pituitary gland, also called the "master gland” of the endocrine system, controls most of the functions of other endocrine glands. It is about the size of a pea, and located in the base of the brain, just behind the bridge of the nose. Attached to the hypothalamus by nerve fibers, the pituitary establishes an important link between the nervous system and the endocrine system. The pituitary gland has two distinct parts, the anterior and the posterior lobes, each of which releases different hormones which affect bone growth and regulate activity in other glands. This master gland releases many hormones which affect growth, sexual development, metabolism and the system of reproduction. The anterior lobe produces thyroid stimulating hormone (TSH), growth hormone, adrenocorticotropic hormone (ACTH), luteinizing hormone (LH), follicle stimulating hormone (FSH), and prolactin (PRL). Thyroid stimulating hormone stimulates the thyroid gland to produce and secrete thyroid hormone which controls and regulates the basal metabolic rate and plays an important role in growth and maturation. Almost every organ in the body is affected by thyroid hormone. Growth hormone regulates the growth and metabolism of the human system, and the adrenocorticotropic hormone triggers the production and release the hormone cortisol, by the adrenals. Cortisol regulates carbohydrate, fat, and protein metabolism as well as blood pressure. The adrenal glands which sit above the kidneys produce hormones which are also responsible for the body's fight or flight response mechanisms. Luteinizing hormone and follicle stimulating hormone stimulate the ovaries and testes to synthesize and release sex hormones including estrogen and testosterone. These hormones are in charge of sperm and egg maturation and release, while prolactin stimulates the production of milk during breast feeding. The posterior lobe of the pituitary gland produces antidiuretic hormone (ADH) and oxytocin. Antidiuretic hormone, also referred to as vasopressin, increases absorption of water into the blood by the kidneys and therefore decreases urine production. Oxytocin stimulates contractions of the uterus during childbirth and the ejection of milk during breast-feeding.