Chemical co-ordination

The two major systems of the human body that coordinate, regulate
and integrate almost all physiological functions are the nervous system and
the endocrine system. The information transmitted by the nervous system in
the form of electric impulses is conducted rapidly in the neurons. The signals
from the endocrine glands or ductless glands are communicated by means of
chemical substances called hormones. The hormones are secreted into and
carried by the blood stream from their point of origin to the target organs or
tissues. In the target tissues, the hormone action is manifested.

A hormone may be defined as a chemical substance synthesized by
the cells of endocrine glands and carried by blood to the site of action where
it exerts its physiological effects. Hormones are considered as chemical
messengers.

Functions of Endocrine glands

Endocrine glands play an important role in maintaining the constancy
of internal environment (milieu interior) and hormones integrate and
regulate various physiological functions. They regulate the general
metabolism viz., the metabolism of carbohydrates, proteins, fats, minerals
and water. The endocrine glands also control the reproductive functions of
animals. The adrenal hormones prepare the body to meet emergency and
stressful situations. The hormones are also responsible for intercellular
communication.

Each endocrine gland may secrete excess quantities of its own
hormone. However, once the normal physiological response is over, this
information is fed back to the endocrine gland. As a result, its secretion
decreases or inhibited. Conversely, if the secretion of the hormone is
subnormal and the physiological effects or responses are reduced, the
information is taken to the gland and it secretes the hormone at an increased
rate. Thus, homeostatic equilibrium is restored.

Chemical co-ordination

Functions of Endocrine glands

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