6.8.1 Circadian Rhythms

• What are circadian rhythms?

  Biological cycles every 24 hours
• Circadian rhythms are influenced by external cues called zeitgebers
• Match the circadian rhythm with its description:

  Sleep-Wake Cycle ↔️ Regulates sleep and wakefulness

  Hormone Release ↔️ Controls the timing of hormone secretion

  Body Temperature ↔️ Influences core body temperature fluctuations
• What external cue helps synchronize circadian rhythms?

  Sunlight
• Circadian rhythms occur approximately every 24 hours.
• The suprachiasmatic nucleus (SCN) is located in the hypothalamus
• Steps in the biological mechanisms regulating circadian rhythms:

  1️⃣ Zeitgebers such as light exposure detected by the retina

  2️⃣ Signals sent to the suprachiasmatic nucleus (SCN)

  3️⃣ SCN generates the 24-hour cycle
• Which hormone is regulated by the SCN to promote sleep?

  Melatonin
• Light exposure helps synchronize the SCN to maintain regular circadian rhythms.
• Match the component with its function:

  Suprachiasmatic Nucleus (SCN) ↔️ Main control center for circadian rhythms

  Zeitgebers ↔️ External cues that synchronize the SCN

  Retina ↔️ Detects light and sends signals to the SCN
• The SCN is located in the hypothalamus
• Steps in the synchronization process of circadian rhythms:

  1️⃣ Light exposure is detected

  2️⃣ Retina sends signals to the SCN

  3️⃣ SCN aligns the 24-hour cycle
• Circadian rhythms can be influenced by sunlight.
• Match the circadian rhythm with its description:

  Sleep-Wake Cycle ↔️ Regulates sleep and wakefulness

  Hormone Release ↔️ Controls the timing of hormone secretion

  Body Temperature ↔️ Influences core body temperature fluctuations
• What is the approximate periodicity of circadian rhythms?

  $24 hours$
• Zeitgebers, such as sunlight, are external cues that synchronize circadian rhythms.
• Circadian rhythms continue even without external stimuli.
• What is the main control center for circadian rhythms in the brain?

  Suprachiasmatic Nucleus (SCN)
• Zeitgebers, like light, synchronize circadian rhythms by sending signals to the SCN.
• Melatonin is a hormone regulated by the SCN to promote sleep.
• Steps in the influence of light on circadian rhythms

  1️⃣ Light detected by retina

  2️⃣ Signals sent to SCN

  3️⃣ SCN adjusts 24-hour cycle

  4️⃣ Melatonin production suppressed
• Darkness promotes the release of melatonin, which induces sleepiness.sleepiness.
• What effect does light have on melatonin release?

  Suppresses it
• Disruptions to circadian rhythms can lead to health issues.
• What is one strategy for mitigating jet lag symptoms?

  Maximize light exposure
• For shift work, maintaining consistent sleep schedules and taking naps can help mitigate effects like insomnia.
• Match the circadian rhythm disruption with its cause:

  Jet Lag ↔️ Crossing time zones

  Shift Work ↔️ Working unusual hours
• Exposure to natural light in the morning helps synchronize your internal clock.
• Reducing exposure to blue light from screens before sleep can improve melatonin production.
• What is the primary zeitgeber that aligns circadian rhythms?

  Light