MCAT Behavioral Sciences Question 226: Answer and Explanation

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Question: 226

2. Bipolar disorder involves periods of mania and depression, and for some, episodes of hypomania. Hypomania, a state that is less severe than mania, is characterized by "feeling good/high" and increased well-being and productiveness. Which of the mechanisms is most likely involved with the hypomanic episodes experienced by individuals diagnosed with bipolar disorder?

  • A. Increased dopamine in the brain
  • B. Decreased stimulation of the enteric plexus
  • C. Increased activation of the posterior pituitary
  • D. Decreased serotonin in the central nervous system

Correct Answer: A

Explanation:

Dopamine is the primary neurotransmitter involved with the "reward centers" of the brain; since hypomania is characterized by "feeling good/high," it can reasonably be concluded that an increase of dopamine in the brain could produce this effect (choice A is correct). The enteric plexus or enteric nervous system is a portion of the autonomic nervous system that controls the gastrointestinal tract; decreased stimulation of the enteric nervous system would not produce any of the characteristics of hypomania described (choice B is wrong). The posterior pituitary is responsible for producing oxytocin, a hormone that controls lactation and uterine contractions, and vasopressin, a hormone that controls how much water the kidneys resorb; therefore, increased activation of the posterior pituitary would not produce any of the characteristics of hypomania described (choice C is wrong). Serotonin is a neurotransmitter with widespread effects in the brain; a decrease of serotonin in the brain has been shown to produce symptoms of depression, not hypomania (choice D is wrong).

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