Circadian Rhythm

Definition

Circadian rhythm is the internal 24-hour clock that regulates many physiological and behavioral processes in the body. It is a natural, internal system that cycles between sleepiness and alertness at regular intervals, aligning with the day-night cycle.

5 Must Know Facts For Your Next Test

1. Disruption of the circadian rhythm can lead to sleep disorders, metabolic issues, and increased risk of certain diseases.
2. Light exposure is the primary zeitgeber that resets the circadian clock, signaling the brain to adjust hormone release and other physiological functions.
3. Melatonin production is a key marker of the circadian rhythm, with levels rising in the evening to promote sleepiness and falling in the morning to facilitate wakefulness.
4. The suprachiasmatic nucleus (SCN) in the hypothalamus acts as the body's 'master clock', synchronizing various circadian rhythms.
5. Irregular work schedules, jet lag, and certain medications can all disrupt normal circadian rhythms and lead to health problems.

Review Questions

• Explain how the circadian rhythm is influenced by external cues and environmental factors
  • The circadian rhythm is primarily entrained by light exposure, which acts as the primary zeitgeber or external cue. When sunlight hits the retina, it triggers the suprachiasmatic nucleus (SCN) in the hypothalamus to adjust the body's internal clock, regulating the release of hormones like melatonin and cortisol. Other environmental factors like temperature, meal times, and social cues can also influence and synchronize the circadian rhythm to the 24-hour day-night cycle.
• Describe the role of the suprachiasmatic nucleus (SCN) in regulating the circadian rhythm
  • The suprachiasmatic nucleus (SCN) in the hypothalamus acts as the body's 'master clock', coordinating various physiological and behavioral processes to align with the 24-hour day-night cycle. The SCN receives light information from the retina and uses this input to synchronize the internal circadian rhythms, including the sleep-wake cycle, hormone release, body temperature, and other metabolic functions. Damage or disruption to the SCN can lead to desynchronization of these circadian rhythms and associated health problems.
• Evaluate the potential consequences of disrupting the normal circadian rhythm
  • Disruption of the circadian rhythm can have far-reaching consequences for physical and mental health. Irregular sleep-wake patterns, jet lag, and shift work can lead to sleep disorders, increased risk of obesity, diabetes, and cardiovascular disease. Circadian disruption has also been linked to mood disorders, cognitive impairment, and increased susceptibility to certain types of cancer. Maintaining a consistent, healthy circadian rhythm is crucial for overall well-being, as it ensures the proper timing and coordination of essential physiological processes.

Related terms

Suprachiasmatic Nucleus (SCN): The part of the brain's hypothalamus that acts as the body's 'master clock', synchronizing circadian rhythms with external cues like sunlight.

Melatonin:

A hormone produced by the pineal gland that helps regulate the sleep-wake cycle and other circadian processes.

Zeitgeber: An external cue, such as daylight or temperature, that entrains and synchronizes the body's internal circadian clock.