Problem: A 60-year-old woman presents with unusual movements like chewing, puffing of cheeks, smacking of her lips, and twisting her body from side to side. Her medical history includes schizophrenia treated with fluphenazine for the last 15 years. Her physical examination demonstrates a protruding tongue, perioral movements, dystonic postures of the neck, and wriggling of her arms and legs. Which of the following is the underlying pathophysiology of her signs and symptoms? A. Dopamine receptor upregulation B. Dopamine receptor downregulation C. Serotonin receptor upregulation D. Serotonin receptor downregulation