ultradian and circadian rhythms

• How can oscillators be divided based on rhythm period?

  Ultradian, circadian, infradian
• What are the classifications of oscillators based on autonomy?

  Autonomous, semi-autonomous, subordinate
• Which rhythms do many hormones follow?

  Circadian and ultradian rhythms
• What is the role of the SCN in rhythmicity?

  It is vital for circadian rhythms
• What happens to ultradian rhythms in SCN-lesioned animals?

  They persist despite the lesion
• What is food anticipatory activity (FAA) associated with?

  Food-entrainable oscillator (FEO)
• Is FAA dependent on the SCN clock?

  No, it is independent of the SCN
• What do we lack regarding the food clock?

  A clear understanding of its neural underpinnings
• What does the current hypothesis suggest about the FEO?

  It comprises a network of connected oscillators
• What type of oscillators are infradian oscillators?

  Intrinsic
• What is the role of the pars tuberalis?

  It acts as a circadian oscillator
• What is the frequency of ultradian rhythms?

  More frequent than every 24 hours
• What physiological phenomena fall under ultradian rhythms?

  From milliseconds to hours
• How is each wave within a sleep cycle classified?

  As an ultradian rhythm within an ultradian rhythm
• What characterizes circadian rhythms?

  They occur in 24-hour cycles
• What controls circadian rhythms in constant conditions?

  Intrinsic 24-hour long mechanisms
• What happens to intrinsic rhythms in constant conditions?

  They are slightly longer than 24 hours
• What causes jet lag?

  Disruption of normal circadian rhythm
• What characterizes infradian rhythms?

  Less frequent than every 24 hours
• What physiological processes are associated with infradian rhythms?

  Repeating every few days, months, or years
• What defines autonomous oscillators?

  Single neurons connected to drive oscillations
• How do semi-autonomous oscillators function?

  Poorly connected and fire at different times
• What can synchronize semi-autonomous oscillators?

  An input can synchronize their oscillations
• What characterizes subordinate oscillators?

  They lack a molecular clock themselves
• How do subordinate oscillators produce synchronized oscillations?

  By receiving input from the SCN
• What pattern do corticosterone levels follow?

  An ultradian (pulsatile) pattern
• What is the role of the SCN in corticosterone rhythms?

  It is responsible for the circadian rhythm
• What generates ultradian rhythmicity in CORT release?

  The HPA axis
• Do ultradian oscillations rely on clock gene expression?

  No, they do not rely on it
• What is unique about the food-entrainable oscillator (FEO)?

  It is not modulated by the SCN
• What is the input-output pattern of the FEO?

  Input → pacemaker → output pattern
• What triggers food anticipatory activity (FAA)?

  Restricted food availability at specific times
• Is FAA dependent on calorie deficiency?

  No, it is not dependent on calories
• What happens to FAA after SCN lesions?

  It persists after complete bilateral lesions
• What does FEO consist of?

  A network of interconnected brain structures
• What do infradian rhythms generate?

  Seasonal rhythms like fur coat changes
• How does the SCN function as a calendar?

  By interacting with other body parts
• What drives rhythmic melatonin production?

  The photic input pathway from retina to SCN
• How does melatonin signal interact with photoperiod?

  It provides an internal endocrine representation
• What is the only conserved site of melatonin binding in mammals?

  The pars tuberalis in the pituitary