From: hubermanlab
The circadian clock is an internal mechanism present in virtually all living organisms, from cyanobacteria to humans, that regulates various physiological processes in accordance with a roughly 24-hour period. Circadian rhythms are essential for synchronizing biological processes with the external environment, notably the cycle of day and night.
Discoveries in Circadian Biology
Dr. David Berson, a leading expert in neurobiology, has contributed significantly to our understanding of the circadian clock, particularly regarding how the brain and body synchronize with daylight cycles. Dr. Berson’s lab is renowned for the discovery of intrinsically photosensitive melanopsin cells, special ganglion cells in the retina that are adept at sensing overall light intensity and thereby play a pivotal role in setting circadian rhythms ([00:00:22]([00:00:22])).
Function of Circadian Clocks
Synchronization with Daylight
These melanopsin cells communicate with the brain to adjust circadian rhythms according to the intensity of ambient light. This process is crucial for understanding how we perceive the time of day and adjust our biological clocks accordingly ([00:22:02]([00:22:02])).
The Suprachiasmatic Nucleus
Central to circadian regulation is the suprachiasmatic nucleus (SCN), a small cluster of nerve cells in the hypothalamus. The SCN acts as the central pacemaker of the circadian timing system, coordinating rhythms across the body ([00:27:01]([00:27:01])).
Suprachiasmatic Nucleus (SCN)
The SCN is strategically positioned to control sleep-wake cycles, hormone release, temperature regulation, and other circadian-controlled functions. It achieves synchronization through neuronal and hormonal signals.
The Role of Light
Light exposure, especially during the day, is critical for maintaining circadian rhythms. Melanopsin cells signal to the SCN, which in turn can adjust melatonin secretion by the pineal gland. This pathway modulates alertness and sleep ([00:31:28]([00:31:28])).
Disruption and Synchronization of the Clock
Jet Lag and Adaptation
Circadian rhythms can be disrupted by changes in our light environment, such as during travel across time zones, leading to jet lag. The adjustment period involves resetting the clock by exposure to natural light at the destination to realign the internal clock with the external environment ([00:23:05]([00:23:05])).
Lack of Synchronization
In cases such as blindness, where normal light perception is impaired, synchronization becomes challenging. Individuals with retinal blindness may suffer from insomnia due to drift in their circadian rhythms, emphasizing the need for a light-based synchronizer ([00:24:14]([00:24:14])).
Impacts on Health
Regular disruption of circadian rhythms has been linked to several health issues, including sleep disorders, depression (notably Seasonal Affective Disorder), metabolic dysfunction, and cardiovascular diseases. The SCN coordinates various bodily functions to maintain homeostasis and health.
Conclusion
Understanding and maintaining circadian rhythms is vital for health and wellbeing. As discoveries in circadian biology advance, they hold promise for treating disorders linked to circadian dysfunction. Dr. Berson’s contributions underline the complexity and importance of circadian systems in aligning our internal timekeeping with the external world ([00:29:03]([00:29:03])).