________________
Preksha Dhyana:
especially influential in the period of rapid growth and development both in the womb and outside. On the other hand, sex hormones are inactive before puberty and again in old age. At puberty, the first signal is given by hypothalamus through gonadotropins from pituitary which stimulate the major producers of sex hormones-the testes and ovaries to grow and begin to secrete. The effect is dramatic In boys, hair grows on the face and elsewhere and the muscles strengthen. In girls, the breasts develop and menstruation begins. Both sexes become capable of reproduction. The endocrine rhythm is in-built.
110
For homeostasis, hormones are vital. Science cannot hope to mimic the fine control exercised by this powerful band of chemical messengers.
Interaction of Feeling and Behaviour
Having dealt with physical functions of the endocrine system, we shall now, briefly, discuss its action on the mental states and behavioural patterns of man.
The nervous system and the endocrine system are the two major control-systems of the body. The co-ordinating effects of the nervous system are transmitted nearly instantaneously by electro-chemical impulses; the endocrine glands secrete chemical regulators (hormones) which are carried through the body by the blood-stream. The action of the latter is more slowly established, but longer lasting than that of the former. While nerve-action is measured in milliseconds, some hormones need several days to get started and then last for weeks, months or even years. Nerveimpulses control the function only of muscles and glands, while hormones may act on all the cells of the body.
A serious study of the endocrines and their hormones commenced about the beginning of the century. It has now been known that besides the old method of chemical intercommunication between the two systems, another method by nerve-action also exists. Lately, it has been realised that nervous and endocrine systems, both functioning to integrate the organism, are not as divergent as was formerly supposed. Many endocrine glands act on the nervous system through their hormones; on the other hand, endo
Jain Education International
For Private & Personal Use Only
www.jainelibrary.org
