MCAT Behavioral Sciences Question 209: Answer and Explanation

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Question: 209

7. Parkinson's disease involves:

I. overstimulation of dopamine-producing neurons in the peripheral nervous system.

II. cell death in the basal ganglia and substantia nigra.

III. neurofibrillary tangles and neuritic plaques in the brain.

  • A. I only
  • B. II only
  • C. I and II
  • D. II and III

Correct Answer: B

Explanation:

Item I is false: Parkinson's disease is the result of the death of dopamine-producing neurons in the brain; furthermore, while there are some dopamine-producing neurons in the peripheral nervous system, the primary neurotransmitter responsible for muscle movement is acetylcholine, not dopamine (choices A and C can be eliminated). Note that both remaining answer choices include Item II so it must be true: Parkinson's is primarily caused by cellular death of neurons in the basal ganglia and substantia nigra of the brain; these neurons are dopamine-producing and inhibitory, connecting with the motor cortices in the brain and help to smooth out movement and inhibit excessive movement. Death of neurons in these areas results in the characteristic shaking, rigidity, and slowness of movement initiation. Item III is false: neurofibrillary tangles and neuritic plaques in the brain are characteristic of Alzheimer's disease, not Parkinson's disease (choice D can be eliminated and choice B is correct).

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