Biological rhythms

    Cards (16)

    • Biological rhythms?

      Cyclical changes in the way that biological systems behave
      • Have evolved due to the environment in which organisms live have cyclic changes
      • E.G. day/night, summer/winter etc.
    • Circadian rhythms?

      A pattern of behaviour that occurs or reoccurs approx. every 24 hours, and which is set or reset by the environmental light levels
    • Sleep-wake cycle?

      Refers to alternating states of sleep and waking that are dependent on the 24 hour circadian cycle
      • is an example of circadian rhythms
    • How do circadian rhythms work?

      -Light provides primary input into the system
      -->first detected by the eye, which sends messages to the suprachiasmatic nuclei (SCN) found in the hypothalamus
      -The SCN uses this info to coordinate the activity if the entire circadian system
      -Sleeping + wakefulness are not determined by the circadian rhythm alone, but also by homoeostasis
    • Endogenous pacemakers?

      -Internal mechanisms/cues
      -e.g. body clocks
      -Regulate biological rhythms
    • Exogenous Zeitgebers?

      -External cues
      -e.g. social cues, light
      -Environmental events that are responsible for resetting the biological clock
      --Regulate biological rhythms
    • The SCN + pineal gland work together as endogenous pacemakers; however, their activity is responsive to external cues of light (EX Z)
    • SCN?

      -Found in the hypothalamus
      -Closely linked to the pineal gland
      -->responsible for the release of melatonin
      -Known as the master clock
      -Receives info about light (EX Z) via the optic nerve
      -->sends signals to t he pineal gland which increases melatonin
    • Light levels -> Eyes (optic nerve) -> Brain -> SCN (hypothalamus) -> Pineal gland -> Melatonin -> Sleep-wake cycle
    • Case study - Siffre's cave study?

      -Spent long period of time (2 + 6 months) in dark caves to examine the effects of 'free running'/'body clock' biological rhythms
      -In each case, Siffre's free running circadian rhythm settled down to just above the usual 24 (about 25 hours)
      -He DID have a regular sleep/wake cycle
    • Infradian rhythms?

      Biological rhythms that occur less often than once a day, meaning the cycle periods are a lot longer than 24 hours
      ->e.g. Menstrual cycle, SAD
    • Menstrual cycle?

      -Female menstrual cycle that is approximately 28 day with consideration of variation of 23-36 days
      -Regulated by hormones and can be affected by stress and excessive exercise
      -Ovulation occurs roughly halfway through the cycle when estrogen levels are highest
      -After ovulation, progesterone levels increase, ready for possible embryo plantation
    • Seasonal affective disorder (SAD)?

      -An infradian rhythm related to the seasons (yearly cycle)
      -Melatonin is secreted by the pineal gland at night, therefore longer nights increase melatonin secretion
      -Linked to an increase in depressive symptoms
    • Ultradian rhythms?
      Biological rhythms that occur more often than 24 hours, meaning the cycles are shorter than 24 hours
      ->e.g. human sleep patterns, meal patterns, hunger/appetite
    • What are the different stages of human sleep patterns?

      1. 4-5%, light sleep with muscle activity slowing down
      2. 45-55%, Breathing patterns and heart rate slows, decrease in body temperature
      3. 4-6%, Deep sleep, brain begins to generate, slow delta waves
      4. 12-55%, Very deep sleep, rhythmic breathing, limited muscle act
      5. 20-25%, Rapid eye movements, brain waves speed up + dreams occur, muscles relax + heart rate increase, breathing is rapid
    • Appetite/meal patterns?
      -Ultradian rhythm
      -Most humans eat 3 meals a day + appetite rise + fall because of food consumption
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