While the nervous system uses neurotransmitters as its chemical signals,
the endocrine system uses hormones. The pancreas, kidneys, heart,
adrenal glands, gonads, thyroid, parathyroid, thymus, and even fat are
all sources of hormones. The endocrine system works in large part by
acting on neurons in the brain, which controls the pituitary gland. The
pituitary gland secretes factors into the blood that act on the
endocrine glands to either increase or decrease hormone production. This
is referred to as a feedback loop, and it involves communication from
the brain to the pituitary to an endocrine gland and back to the brain.
This system is very important for the activation and control of basic
behavioral activities, such as sex; emotion; responses to stress; and
eating, drinking, and the regulation of body functions, including
growth, reproduction, energy use, and metabolism. The way the brain
responds to hormones indicates that the brain is very malleable and
capable of responding to environmental signals. http://www.brainfacts.org/brain-basics/cell-communication/articles/2012/hormones-communication-between-the-brain-and-the-body/
