Question

alejandra has started to use heroin. how will this most likely affect her body systems? (1 point) it will fill the lungs with toxic material. it will release serotonin and dopamine to the brain. it will block the transmission of pain signals to her brain. it will speed up the central nervous system.

Explanation:

Heroin is an opioid. Opioids bind to opioid - receptors in the brain and nervous system, primarily blocking the transmission of pain signals. While it can also have other effects like causing the release of some neurotransmitters, the main and most direct effect related to its action mechanism is pain - signal blocking. It is a depressant, so it doesn't speed up the central nervous system; and it doesn't primarily fill the lungs with toxic material. The release of serotonin and dopamine is a secondary consequence related to its rewarding effects, but the pain - blocking is more fundamental to its action on the body.

Answer:

It will block the transmission of pain signals to her brain.