Heroin

Heroin and the brain 2

The human body contains receptors to which opiates can bind. But the body also produces substances of its own called endorphins, which also bind to these receptors.

One function of endorphins is to combat pain. The big difference between them and the opiates is that the body produces the endorphins itself, and quickly breaks them down after they are released. That means there is little risk of addiction.

In terms of evolution, endorphins are important for survival. If you need to flee after sustaining an injury, endorphins can ease the pain.

When heroin is taken, it converted into morphine in the body. The effects of heroin derive from the fact that morphine mimics endorphins, the natural neurotransmitters.

Both endorphins and morphine indirectly stimulate the brains reward centre, and that makes you feel pleasant.

Morphine also inhibits the release of substance P. Substance P plays a role in the transmission of pain signals.

The neurons that regulate breathing also contain opioid receptors. Morphine can bind to them too.