Endocrine System
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The Hypothalamus
1.3 Hypothalamus is a small area at the base of the brain. It plays a key role in regulating the body’s general level of activity. In addition to other functions, it controls the pituitary gland, the so-called “master gland” of the body’s endocrine system. Certain parts of the hypothalamus regulate body temperature, breathing, sleep, hunger, thirst, urination and emotions. Other parts produce hormones which control the secretion of individual pituitary hormones. The pituitary hormones, in turn, affect many of the body’s endocrine glands. These glands secrete hormones that influence growth, sexual development, and the rate at which the body changes food into energy and living tissue. The hypothalamus produces other hormones which are stored in and released by the pituitary gland. One of these hormones reduces the amount of water lost from the body in urine.
The Central Nervous System
1.4 Hormones act as chemical messengers and regulate many body functions. Each hormone carries a particular message to specific cells of the body. The central nervous system regulates the secretion of these hormones.
1.5 In fact the Central Nervous System and the Endocrine System are so closely linked that they are sometimes called the Neuroendocrine System. Coordinating centres in the hypothalamus regulate the activities of these two systems. The hypothalamus is sometimes called the “master switch” of the endocrine system because most endocrine glands, including the pituitary “master gland”, are either directly or indirectly under its control. The hypothalamus constantly monitors the internal state of the body and sends out messages that keep body functions stable. Sometimes, the messages are in the form of nerve impulses; at other times, they are hormonal. Nerve impulses produce rapid changes, while the release of hormones causes slower but long-lasting effects.
The Pituitary Gland
1.6 The pea-sized important pituitary gland lies at the base of the brain near the centre of the skull and is connected to the hypothalamus by a slender stalk. Hormones produced by the hypothalamus move through the pituitary gland. In response to these hormones, the pituitary gland produces at least six hormones of its own which regulate growth and direct the reproductive organs, the adrenal glands and the thyroid gland. In women, pituitary hormones stimulate uterine contractions during childbirth and release of breast milk during nursing.
