Final answer:
The client experiencing 'eyes rolled upward' is exhibiting an extrapyramidal side effect, specifically an oculogyric crisis, due to haloperidol's effect on the basal nuclei and its role in dopamine regulation within the extrapyramidal system.
Step-by-step explanation:
The client's symptom where "his eyes rolled upward" is recognized as an extrapyramidal side effect known as oculogyric crisis. This side effect results from haloperidol's impact on the nervous system, particularly in the basal nuclei region. Haloperidol affects dopamine activity, which plays a central role in motor control within the extrapyramidal system.
This system is involved in the coordination and control of posture and movement. An oculogyric crisis is characterized by involuntary upward deviation of the eyes and can be quite alarming for both patients and their families. These involuntary movements are one of the movement disorders that can occur with haloperidol treatment due to its dopamine blocking effects.