MCAT Behavioral Sciences Question 194: Answer and Explanation

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Question: 194

6. Alcohol withdrawal syndrome occurs when an individual with a dependence on alcohol suddenly limits or stops alcohol consumption. Symptoms of withdrawal can be very dangerous, including seizures, uncontrollable shaking of the extremities, and other nervous system issues. What is the most plausible mechanism of action for these physical symptoms?

  • A. Chronic alcohol consumption causes down-regulation of GABA receptors, leading to a reduction in CNS inhibition, and excito-neurotoxicity.
  • B. Long-term alcohol abuse stimulates the autonomic nervous system, causing tremors.
  • C. Cessation of alcohol consumption leads to a reduction in dopamine production in the nucleus accumbens.
  • D. Alcohol is a hallucinogenic, and withdrawal acts by relaxing, disinhibiting, and amplifying sensory information.

Correct Answer: A

Explanation:

Alcohol is a depressant (choice D is wrong) and inhibits neural activity. GABA receptors in the central nervous system respond to GABA, an inhibitory neurotransmitter. Alcohol acts on GABA receptors, inhibiting neuronal signaling. Chronic alcohol consumption causes a down-regulation of GABA receptors; therefore, once the artificial depressant (alcohol) is removed from the system, the CNS no longer has an inhibitory influence, and excito-neurotoxicity occurs, which can result in seizures and tremors (choice A is correct). Alcohol is a depressant and does not stimulate the autonomic nervous system (choice B is wrong). While alcohol consumption does promote dopamine release in the nucleus accumbens (which stimulates the reward pathway in the brain and helps to explain why alcohol is addictive), and cessation of alcohol consumption would surely lead to a decrease in dopamine, this does not explain the physical symptoms of withdrawal described in the question stem (choice D is wrong).

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