Biological Systems MCAT Practice Exam

What specialized cells are responsible for producing and circulating cerebrospinal fluid?

1. Afferent neurons

2. Ependymal cells

3. Interneurons

4. Microglia

The correct answer is: Ependymal cells

Ependymal cells are specialized glial cells that line the ventricles of the brain and the central canal of the spinal cord. Their primary role is to produce and circulate cerebrospinal fluid (CSF). These cells have cilia on their surfaces that help move the CSF through the brain's ventricular system, ensuring its continuous flow and distribution within the central nervous system. The production of CSF is vital for cushioning the brain, providing buoyancy, and serving as a medium for nutrient and waste exchange. Ependymal cells play an essential role in maintaining the homeostasis of the brain's environment, contributing to functions such as protection against mechanical injury and providing metabolic support to neurons. In contrast, afferent neurons are sensory neurons responsible for carrying signals to the central nervous system, while interneurons serve as connectors between other neurons, facilitating communication within the brain and spinal cord. Microglia act as the immune cells of the central nervous system, involved in the maintenance and defense against pathogens, but do not produce or circulate cerebrospinal fluid. Therefore, ependymal cells are uniquely specialized for this crucial role in the structure and function of the central nervous system.