6.8.3 Ultradian Rhythms

• Ultradian rhythms are biological cycles that repeat more than once within a 24-hour day
• The sleep cycle is an example of an ultradian rhythm.
• Match the rhythm type with its cycle length and control mechanisms:

  Ultradian Rhythms ↔️ Less than 24 hours, Internal processes

  Circadian Rhythms ↔️ 24 hours, Environmental cues
• Circadian rhythms are influenced by environmental cues like light
• The menstrual cycle is an example of an infradian rhythm.
• What is the approximate cycle length of the sleep cycle in humans?

  90-120 minutes
• Heart rate is an example of an ultradian rhythm regulated by the autonomic nervous system
• Fluctuations in hormone levels like cortisol are examples of ultradian rhythms.
• Which ultradian rhythm governs the sleep cycle?

  Sleep stages
• Order the stages of the sleep cycle:

  1️⃣ N1 (Light sleep)

  2️⃣ N2 (Deeper sleep)

  3️⃣ N3 (Deepest sleep)

  4️⃣ REM (Dream state)
• Which hormone regulates sleep onset and duration?

  Melatonin
• The suprachiasmatic nucleus (SCN) in the hypothalamus coordinates biological rhythms
• The brainstem controls sleep stages and transitions through NREM and REM sleep.
• The biological mechanisms underlying ultradian rhythms primarily involve neurotransmitters and hormones
• Which neurotransmitter regulates sleep onset and duration?

  Melatonin
• The suprachiasmatic nucleus (SCN) in the hypothalamus coordinates biological rhythms.
• Match the brain region with its function in ultradian rhythms:

  Hypothalamus ↔️ Coordinates biological rhythms

  Brainstem ↔️ Controls sleep stages
• Unlike circadian rhythms, which have a 24-hour cycle, ultradian rhythms occur frequently throughout the day
• What is an example of an ultradian rhythm in humans?

  Sleep cycle
• Order the rhythm types by their cycle length from shortest to longest:

  1️⃣ Ultradian rhythms

  2️⃣ Circadian rhythms

  3️⃣ Infradian rhythms
• Circadian rhythms are influenced by environmental cues like light and temperature.
• What is an example of an infradian rhythm?

  Menstrual cycle
• Match the rhythm type with its characteristics:

  Ultradian ↔️ Less than 24 hours

  Circadian ↔️ 24 hours

  Infradian ↔️ Longer than 24 hours
• The sleep cycle, an example of an ultradian rhythm, lasts approximately 90-120
• Which system regulates heart rate as an example of an ultradian rhythm?

  Autonomic nervous system
• Ultradian rhythms govern the sleep cycle, which repeats roughly every 90 minutes.
• Order the stages of the sleep cycle from lightest to deepest:

  1️⃣ N1

  2️⃣ N2

  3️⃣ N3

  4️⃣ REM
• What characterizes N1 sleep?

  Light sleep
• REM sleep is characterized by vivid dreams and rapid eye movements
• Match the neurotransmitter or hormone with its function:

  Melatonin ↔️ Regulates sleep onset

  Cortisol ↔️ Influences alertness

  Growth Hormone ↔️ Repair and growth
• The suprachiasmatic nucleus (SCN), located in the hypothalamus, is crucial for coordinating biological rhythms
• Regular meal times and balanced nutrition support stable hormone levels, improving sleep quality.
• What can chronic stress disrupt in relation to ultradian rhythms?

  Hormone regulation
• Match the research study with its findings:

  Dement & Kleitman (1957) ↔️ Identified distinct sleep stages

  Born et al. (1999) ↔️ Demonstrated pulsatile cortisol secretion

  Wehr (1991) ↔️ Found shorter sleep cycles in winter
• Understanding ultradian rhythms can enhance workplace performance by timing breaks during 90-minute cycles
• Aligning medication administration with hormone secretion peaks can improve treatment effectiveness.