Biological Systems MCAT Practice Exam

Which types of cells are responsible for detecting shapes and boundaries?

1. Rods

2. Parvocellular cells

3. Magnocellular cells

4. Ganglion cells

The correct answer is: Parvocellular cells

Parvocellular cells play a crucial role in the visual processing system by detecting shapes, colors, and boundaries. These cells are a type of ganglion cell found in the retina and are characterized by their small cell bodies. They have high spatial resolution, enabling them to discern fine details and identify static objects and their contours. Parvocellular cells integrate signals from cone photoreceptors, which are responsible for color vision, allowing them to contribute significantly to the perception of shapes and the recognition of patterns. In contrast, rods are primarily involved in low-light conditions and do not contribute to color vision, focusing instead on detecting brightness rather than shape. Magnocellular cells, while also part of the ganglion cell population, are more tuned to detecting motion and providing information about the movement of objects rather than their precise shapes. Ganglion cells serve as the output neurons of the retina, transmitting information to the brain but encompass a diverse set of cell types beyond just the parvocellular and magnocellular categories. Thus, parvocellular cells are specifically designed for shape and boundary detection, making them the correct response in this context.