Note that a particular gland can produce hormones which target other endocrine tissue which, in turn, secretes other hormones. In some ways, hormones differ from neurotransmitters , in other ways they resemble them. In some case the same chemical serves as both a hormone and a neurotransmitter, but at different sites in the body. Receptors on target tissues, may be at the level of the cell membrane or intracellular . Peptide hormones are large molecules, making penetration of the membrane difficult, so they usually have membrane receptors, while steroids are fat soluble and can penetrate inside the cell to act on the cell nucleus.
Steroids activate or inhibit specific genes which then alter the production of particular proteins.
Hormones may have organisational and activating effects . The endocrine system has slow onset, widespread and often long term effects on behaviour and physical growth. This contrasts with the rapid, specific response of the neural system. Feedback is an important process for regulating the secretion and release of hormones.