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The endocrine system is primarily composed of glands that
produce chemical messengers called hormones. Glands of the
endocrine system include the pituitary gland, the thyroid gland,
the parathyroid glands, the thymus, and the adrenal glands. Other
glands are also included within the endocrine system since they
contain endocrine tissue that secretes hormones such as the
pancreas, ovaries and testes.
The endocrine and nervous systems work very closely together. The
brain continuously sends instructions to the endocrine system, and
in return receives feedback from the endocrine glands. Because of
this intimate relationship, the nervous and endocrine systems are
referred to as the neuroendocrine system.
The hypothalamus is known as the master switchboard because it’s
the part of the brain that controls the endocrine system. The
pituitary gland, which hangs by a thin stalk from the hypothalamus,
is called the master gland of the body because it regulates the
activity of the endocrine glands.
The hypothalamus detects the rising level of the target organ’s
hormones then sends either hormonal or electrical messages to the
pituitary gland. In response, the pituitary gland releases
hormones, which travel through the bloodstream to a target
endocrine gland, instructing it to stop producing its
hormones.
The endocrine system constantly adjusts hormone levels so that the
body can function normally. This process is called homeostasis.
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