The nervous system alone is not sufficient to reach every cell. To coordinate our internal activities, we need a system which influences every cell in the body.
For this our body secrets many chemicals. We call them hormones.
These Hormones reach every cell unlike of nerve fibers.
Hormones reach target organs and cells and exert its effect by acting as a chemical messenger.
For example,
When the blood sugar level is high, the pancreas secretes insulin to lower the sugar level.
When there is a dangerous situation or emergency condition, Adrenal glands secrete adrenaline. It increases blood flow to the brain and respiration rate to combat the case.
Younghood requires a high growth rate. The pituitary releases growth hormone which increases our height.
