Suprachiasmatic Nucleus

The suprachiasmatic nucleus (SCN) is a tiny region located in the hypothalamus of the brain. It serves as a key component of the circadian rhythm regulation system, also known as the body’s internal clock.

Anatomy and Location

The suprachiasmatic nucleus is a pair of small, distinct structures located in the anterolateral region of the hypothalamus, just above the optic chiasm. It is situated near the midline, close to the third ventricle.


The primary function of the suprachiasmatic nucleus is to regulate the timing and synchronization of various physiological and behavioral processes within the body. It plays a crucial role in maintaining and coordinating the circadian rhythms of organisms. These rhythms include the sleep-wake cycle, hormone release, body temperature, and metabolism, among others.

Circadian Rhythm Regulation

The suprachiasmatic nucleus receives direct input from the retina of the eye, which allows it to perceive light and monitor changes in the external environment. This light input helps the SCN to synchronize the internal biological clock with the 24-hour light-dark cycle of the day.

The SCN then functions as a master pacemaker, generating electrical and chemical signals that influence various peripheral clocks throughout the body. These peripheral clocks, found in tissues and organs, play a role in adjusting the body’s physiology to align with the central circadian clock.

Internal Clock Disorders

Disruptions to the suprachiasmatic nucleus or its input pathways can lead to various circadian rhythm disorders, such as advanced sleep phase syndrome or delayed sleep phase syndrome. These disorders affect the timing of sleep and wakefulness, leading to difficulties in maintaining a regular sleep-wake schedule.

Additionally, disruptions in the suprachiasmatic nucleus have been implicated in conditions like jet lag, shift work sleep disorder, and certain mood disorders, emphasizing the crucial role of this nucleus in overall well-being and functioning.