Cellular function is regulated and governed by hormones produced in the endocrine glands and conveyed to the appropriate site by the circulatory system.
The hormones are catalysts only – they do not add to the cells or alter their genetically determined purpose but are necessary to instigate and control specific cellular mechanisms which are implemented by enzymes.
Although the hormones and enzymes are among the latest physiologic catalysts to be discovered, they probably were one of the first means of regulation to evolve- a primitive system of controls which later surrendered part of its independence to the nervous system in the interests of faster and more specific action, particularly in emergencies.
Thus the endocrine system, as one of the major physiologic regulators, is now recognized as partly autonomous and partly associated with the neurologic coordinating system.
This is how hormone function can be influenced by psychological and emotional forces and can in turn initiate profound changes in both psychologic and physiologic aspects of nervous function.As one studies the increasing evidence of neuroendocrine interrelationships, it appears more and more certain that the nervous and endocrine systems are the prime regulators.
Viewed in this light, neuroendocrine mechanisms can be seen to operate as both cause and effect of physiologic events.”
From HOAG, COLE, BRADFORD
Edition MC GRAW-HILL