Endocrine glands present in the body produce chemical substances called .

Electrical impulses are an excellent means of quick transfer of information in animals but there are limitations to the use of electrical impulses. State the other means of communication used by most multicellular organisms between the cells.

A and B are the two systems of control and coordination in the human body. The messages in system A are transmitted in the form of chemical substances C which travels comparatively slowly through the bloodstream. The substances C are made in tissues D present in the head and trunk of the human body. The messages in system B are transmitted very quickly in the form of electrical impulses through fibres E. The effect of messages transmitted by system B usually lasts for a much shorter time as compared to those transmitted by system A.

Name the system A. What does system A consist of?

Name the control - voluntary (V), involuntary (I) and endocrine (E) in the following (Key or Checklist Items):

The gland X which is located just below the brain in the human head secretes a chemical substance Y which controls the development of bones and muscles in the body of a person. Secretion of too little of substance Y as well as the secretion of too much of substance Y by the gland X leads to abnormal development of the body of a person.

Name the system of glands in the human body of which gland X (pituitary gland) is a part.