Introduction (ii)

The endocrine system regulates function by secreting chemical messengers or hormones into the bloodstream. This transports them to target cells. These may be close to the secreting gland, as with the hypothalamus and pituitary gland, or some distance away, as with the pituitary gland and the sex organs. Compared to the nervous system, hormonal regulation is less precise and slow.

Additional Information

Hormones
Hormones are chemical mediators which co-ordinate cellular metabolism and contribute to homeostasis. The term 'hormone' was first used by E. H. Starling in 1905 to describe the gastrointestinal hormone secretin, a peptide hormone secreted by the duodenum.