A 68-year-old man with a history of Parkinson disease is hospitalized for pneumonia and sepsis. The patient is treated with intravenous (IV) fluids and antibiotics. He is also started on an infusion of IV dopamine for hemodynamic support. Although the manifestations of Parkinson disease are attributed to dopaminergic neuron degeneration in the substantia nigra, IV dopamine does not improve this patient's Parkinson symptoms. Which of the following cell structures accounts for this lack of responsiveness?

Question

A 68-year-old man with a history of Parkinson disease is hospitalized for pneumonia and sepsis.  The patient is treated with intravenous (IV) fluids and antibiotics.  He is also started on an infusion of IV dopamine for hemodynamic support.  Although the manifestations of Parkinson disease are attributed to dopaminergic neuron degeneration in the substantia nigra, IV dopamine does not improve this patient's Parkinson symptoms.  Which of the following cell structures accounts for this lack of responsiveness?

Quizplus · Accepted Answer

Eductional Objective: The blood-brain barrier is formed by tight junctions between nonfenestrated capillary endothelial cells that prevent the paracellular passage of fluid and solutes.  This barrier only permits the passage of substances from the blood to the brain via transcellular movement across the endothelial plasma membrane, which is limited by diffusion or carrier-mediated transport.

A 68-Year-Old Man with a History of Parkinson Disease Is