A 70-year-old female with major depressive disorder presents with a 15-pound unintentional weight loss over the past 3 months, poor appetite, and severe insomnia. She has a history of falls and the PMHNP wants to avoid SSRIs due to their association with hyponatremia in the elderly. The PMHNP selects mirtazapine 15 mg at bedtime. Which of the following best describes mirtazapine's receptor profile and why it is a reasonable choice for this patient?