OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What effect do hallucinogens, like LSD and magic mushrooms, have on nerve impulses?

1. They increase blood flow to the brain

2. They change the type of chemicals released across the synapse

3. They block pain signals in the brain

4. They stabilize electrical activity within neurons

The correct answer is: They change the type of chemicals released across the synapse

Hallucinogens such as LSD and magic mushrooms primarily affect the brain by altering the neurotransmitter systems. This leads to a change in the type and amount of chemicals that are released into the synapse, which is the gap between nerve cells. These substances mimic or interfere with natural neurotransmitters, altering perceptions, mood, and cognition. Specifically, hallucinogens often affect serotonin receptors in the brain, leading to altered sensory perceptions and an overall change in the way your brain processes information. This change in chemical signaling can cause the profound alterations in thought and perception that are characteristic of hallucinogen use. While other options may refer to different physiological processes, they do not accurately describe the primary action of hallucinogens on nerve impulses and synaptic transmission. For example, increasing blood flow to the brain (mentioned in another option) is not a direct effect of hallucinogens on nerve impulses.