ABSTRACT
The biochemicals classified as hormones are exceedingly potent agents, capable of profoundly influencing cellular functions to establish the optimum internal environment for a particular set of environmental challenges or survival needs. By definition, these chemicals are produced within well-defined glands or organs, secreted into blood or other extracellular media, and transported at least some distance to exert their effects on unrelated tissues. Endocrine systems are typically regulated through stimulatory and negative feedback mechanisms, often involving separate endocrine glands in a cascading sequence of hormone release originating from central neurological structures. Other biochemical stimuli, such as rising blood glucose or changes in the ratio of sodium to potassium (Na:K) in plasma, are equally capable of eliciting endocrine responses from the structures that are responsible for maintaining those constituents within appropriate physiological limits.
