(i) Hormones, a chemical messenger is transported by blood, they reach target organs, i.e., organs for which they are intended.
(ii) Hormones may stimulate or inhibit specific biological processes in target organs to modify their activities. Thus they regulate organs and tissues.
(iii) The activity of these messenger molecules, i.e., hormones secreted in the blood by endocrine glands is under the direct control of the nervous system.
