Drugs and their effects - Heroin

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Drugs and their effects.

Agonist:- a drug that mimics the effects of a neurotransmitter and increases pre- synaptic activity, for example, by stimulating post- synaptic receptors.

Antagonist:- A drug that limits the effect of a neurotransmitter and reduces post- synpatic activity, for example, by blocking post- synaptic receptors or preventing recycling or release of neurotransmitters.

Classifying drugs.

Drugs can be classified into different types of drugs based on their effects on the neurones:

  • Stimulants - increase the frequency of neural impulses.

  • Depressants - decrease the frequency of neural impulses.


They can also be classified based on the effect they have on the individual:

  • Sedatives- Produce sedation, makes the user calm and sleepy.

  • Hallucinogens- produces hallucinations in the user and can cause the user to experience perceptions without a stimulus.

They can also be classified due to their chemicals:

Opiates- similar in structure to those derived from the opium poppy.


Heroin is an opiate drug, It is a chemically altered version of morphine. Although it is used medically as it is a powerful analgesic, it is the most commonly abused drug.

How is it taken?

Heroin may be administered in different ways. It may be taken orally, inhaling vapours when burned or injected. Heroin is more commonly injected.

Why is Heroin so effective?

The chemical alteration that converts morphine into heroin makes it three times as powerful. This is partly because heroin is more soluble in lipids and as a result, passes into the brain more quickly.

This means that the speed and intensity of its effect is greater than morphie if it is smoked or injected.

Pert &Snyder (1973) identified the receptors to which opiate drugs attach. These receptors exist to receive input from endogenous opioids called endorphins.

The key role of endorphins are to reduce the experience of pain and toprovide reinforcement.

Mode of Action: Heroin.

Heroin acts by stimulating opioid receptors and mimics the effects of endorphins making it an agonist. The attachment of either an endorphin or heroin molecule to a receptor…


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