What is the primary function of the suprachiasmatic nucleus (SCN)?

• A. To regulate digestion and metabolism
• B. To receive and process sensory information
• C. To adjust biological clocks to daylight patterns
• D. To control heart rate and blood pressure

Answer: (C)

The suprachiasmatic nucleus (SCN) plays a crucial role in circadian rhythms, which are the physical, mental, and behavioral changes that follow a daily cycle. Its primary function is to synchronize the body’s internal biological clocks to the external environment, particularly by responding to light cues received through the eyes. This synchronization allows the SCN to regulate various physiological processes in accordance with the day-night cycle, such as sleep-wake patterns, hormone release, and body temperature.

The SCN achieves this by receiving direct input from retinal cells that are sensitive to light, which helps it interpret the light-dark cycles. As a result, the SCN controls the timing of numerous biological rhythms, ensuring that they align with the external environment, thereby maintaining homeostasis. This function is essential for optimizing the performance of biological processes according to the time of day.

The other options refer to functions typically managed by different systems or parts of the brain. For instance, digestion and metabolism regulation involves areas such as the hypothalamus but is not the primary role of the SCN. Sensory information processing occurs predominantly in the sensory cortices of the brain. Heart rate and blood pressure control are functions associated with the autonomic nervous system and regulated by areas such as the