The endocrine system
The endocrine system is a collection of ductless glands which are positioned through the whole body. The endocrine glands pass their secretions of hormones directly into the blood stream so that they are always adjacent to blood vessels. Hormones are chemicals in the body produced and secreted in the body that regulate the function of a particular tissue or organ (Bing dictionary). These chemical messengers transfer information from one set of cells to another. Despite many chemicals being transmitted and circulated around the body via the bloodstream, each one only acts on the cells that are genetically programmed to receive and respond to its message. Hormone levels can be influenced by many factors including stress, infection and changes in the balance of fluids within the body. A gland is a group of cells that produce and secrete chemicals (http://kidshealth.org/parent/general/body_basics/endocrine.html). A gland will select and eliminate waste materials from the blood, then process it and secrete the end product for use at another location in the body. Endocrine glands release more than 20 major hormones straight into the bloodstream and from here they can be transported to the cells in other parts of the body. There are many major glands that make up the endocrine system and these include the: hypothalamus, pituitary, thyroid, parathyroid, adrenals, pineal body and the reproductive glands (testes for males and ovaries for females). The pancreas is also involved in secreting hormones which are involved with the maintaining of blood sugar levels within the body. The pancreas is also associated with the digestive system as it produced hydrolytic enzymes which aid with digestion. Neuro-endocrine system
The nervous and endocrine systems control all the biological processes within the body and they can almost control one another. The nervous system can stimulate or inhibit the release of certain hormones while the endocrine system can promote of inhibit nerve impulses.
The hypothalamus is found in the lower part of the brain and is a collection of particular cells. It has key links with the nervous system and the endocrine system and has an important role in secreting hormones. The nerve cells in the hypothalamus control the pituitary gland by producing certain chemicals that can stimulate or supress hormone secretions from the pituitary gland. The pituitary gland is moderately small and is located at the base of the brain beneath the hypothalamus. It is considered the most important part of the endocrine system as it produced hormones that control other endocrine glands within the body. The hypothalamus can convey information sensed by the brain to the pituitary gland to make any changes that could be influenced by factors like emotions and seasonal changes.
The pituitary Gland
The pituitary gland is divided into 2 sections:
This regulates the activity of the thyroid, adrenals, and reproductive glands. It also produces growth hormone which stimulates the growth of bone and other body tissues. It also produces prolactin which stimulates mammary gland growth and activates milk production in females. Thyrotropin is another hormone produced and this stimulates the thyroid gland to produce thyroid hormones. Corticotrophin is produced which causes the adrenal glands to produce certain hormones. Follicle-stimulating hormone (FSH) is also produced and affects ovaries in females and stimulates the development of oocytes. It also affects the testes of males and stimulates the production of sperm. Luteinizing hormone (LH) affects the ovaries in females and stimulates ovulation, the formation of the corpus luteum and results in secretion of oestrogen and progesterone. It affects the testes of males and stimulates the production of testosterone. The pituitary gland also secretes endorphins. These are chemicals that act on the nervous system...
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