Note that a particular gland can produce particular hormones and act as a target tissue for 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. The distance to target tissue differs substantially for the two systems, that is, across the synaptic cleft for neurotransmitters vs. the entire circulatory system for hormones. Neurohormones are produced like neurotransmitters and released into circulation.