Endorphins are endogenous opioid neuropeptides and peptide hormones in humans and other animals. They are produced by the central nervous system and the pituitary gland. The term "endorphins" implies a pharmacological activity (analogous to the activity of the corticosteroid category of biochemicals) as opposed to a specific chemical formulation. It consists of two parts: endo- and -orphin; these are short forms of the words endogenous and morphine, intended to mean "a morphine-like substance originating from within the body".The class of endorphins includes three compounds-α-endorphin (alpha endorphins), β-endorphin (beta endorphins), and γ-endorphin (gamma endorphins)-which preferentially bind to μ-opioid receptors.The principal function of endorphins is to inhibit the communication of pain signals; they may also produce a feeling of euphoria very similar to that produced by other opioids.
Endorphins are naturally produced in response to pain. This phenomenon happens in both the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). In the PNS, endorphins, primarily β-endorphin, are released from the pituitary gland and bind to μ-receptors. The binding of these two components inhibits the pain signal of the periphery nerves by blocking the neurotransmitter substance P. The mechanism in the CNS is similar but works by blocking a different neurotransmitter. When the endorphin binds to the μ-receptor, it inhibits the release of the neurotransmitter gamma-aminobutyric acid (GABA) which, in turn, increases the production and release of dopamine, the neurotransmitter associated with pleasure.
Their production can also be triggered by various human activities. Vigorous aerobic exercise can stimulate the release of β-endorphin which contributes to a phenomenon known as a "runner's high."
Laughter may also stimulate endorphin production; a 2011 study showed that attendees at a comedy club showed increased resistance to pain.Endorphins are also released during various activities including eating food, sex, orgasm, listening to music and eating chocolate. Research has also demonstrated meditation by trained individuals to trigger endorphin release. 
