Opioid Receptor

An opioid receptor is a protein which mediates responses to a number of neurotransmitters, hormones, and drugs (such as opioids) which are involved in sensory perception. Opioid receptors are situated in cellular membranes and are spread throughout the nervous system and digestive tract.

For instance, when a person is injected with morphine, the opioid molecules create a signal and bind with the opioid receptors in the brain, spinal cord, peripheral nerves, and the gastrointestinal tract. As a result, the person does not perceive pain and experiences lethargy.