Question

define hormone.write any four characteristics of hormones in humans.

Answer 1

Hormones are the chemical substances which coordinate the activities of living organisms and also their growth.Four characteristics of hormones in humans are:

1) Hormones are secreated in small amountsby endocrine glands

2) The hormones are poured directly into blood and carried throughout the body

3) The hormones have their effect at the sight different from the sight at which they are made.

4) The hormones act only on target organs

Answer 2

 Hormones are organic chemical substances released by a cell, or organ or a gland or any body part of plants and animals that functions in the regulation of physiological activities and to maintain homeostasis.

characteristics are
 Hormones are secreted by endocrine cells. 
Hormones are chemical messengers.
The are chemical signals that circulate in the body fluids. 
The hormones regulate the behavior of the target cells. 
Hormones, unlike enzymes do not catalyze any reaction. 
They are secreted only when needed, they are not stored prior to requirement. 
Hormones may be proteinaceous or non-proteinaceous in nature (amino-acids or steroids). 
The secretion of hormones is regulated by the nervous system through the feed back effect. 
Hormones usually cause long term effects like change in behavior, growth, etc.
The hormones function is to stimulate or inhibit the target organs.