Anatomy Practice Exam

What occurs during the photopupillary reflex?

1. Pupils dilate in response to darkness

2. Pupils constrict when exposed to bright light

3. Pupils remain unchanged regardless of light

4. Pupils widen to allow more light in

The correct answer is: Pupils constrict when exposed to bright light

During the photopupillary reflex, pupils constrict when exposed to bright light. This response is a protective mechanism that helps to regulate the amount of light entering the eye, preventing damage to the retina and enhancing visual acuity in bright conditions. The reflex is mediated by photoreceptors in the retina that detect increased light levels and signal the brain, leading to activation of the parasympathetic nervous system. This system causes the circular muscles of the iris to contract, resulting in a smaller pupil size. The reflex serves an important role in vision, as it increases depth of field and improves the eye's ability to focus on close objects. It is an involuntary response and occurs almost instantaneously when the light intensity changes. Understanding this reflex is crucial for comprehending how the eye adapts to varying lighting conditions, which is a vital component of visual function.