EP & EZ

• (AO1) Give the functions of endogenous pacemakers

  The body's internal biological clock

  Regulate biological rhythms

  Govern biological rhythms, e.g. circadian sleep/wale cycle
• (AO1) Give the functions of endogenous pacemakers

  The body's internal biological clock

  Regulate biological rhythms

  Govern biological rhythms, e.g. circadian sleep/wale cycle
• (AO1) Describe the SCN's job within endogenous pacemakers 


  SCN = most important EP

  • Maintains sleep/wake cycle AND located in hypothalamus
  • Controls other biological rhythms - links 2 other areas of the brain responsible for sleep + arousal
  • Receives info about light levels (EX) from optic nerve, which sets the circadian rhythm, is then synchronised with outside world e.g. day/night.
  • Sends signals to pineal gland which leads to increase in melatonin production at night to induce sleep.
  • SCN + pineal gland work together as EPs, however their activity is responsive to the external cue of light.
• (AO1) Give the functions of exogenous zeitgebers

  Influence biological rhythms

  Can be described as environmental events that are responsible for resetting the biological clock or an organism.

  Can include social cues e.g. mealtimes / social activities.

  Most important zeitgeber = light (external cue) which is responsible for resetting body clock each day, keeping it on a 24 hour cycle.
• (AO1) Describe the SCN's jobs within exogenous zeitgerber

  Contains receptors sensitive to light

  This external cue is used to synchronise the body's internal organs and glands.

  Melanopsin = protein in eye = sensitive to light + carries the signal to the SCN to set 24 hour daily body cycle.
• (AO3) Give a strength of EP & EX

  Point: Support from Morgan 1995

  Evidence: Aimed to explore the importance of the SCN. Bred hamsters so circadian rhythms were 20h. The SCN neurons from abnormal hamsters were transplanted into brains of normal ones.

  Evaluate: Demonstrates significance of SCN and how EPs are important biological circadian rhythms.
• (AO3) Give a counter limitation point to Morgan

  Point: Use of hamsters

  Evidence: Humans would respond differently to manipulations of their biological rhythm because we are different biologically and different biological contexts.

  Evaluate: This makes research carried out on other animals unable explain role of EPs in research in biological process of humans.
• (AO3) Give a limitation of EP & EX

  Point: Biologically reductionist

  Evidence: Behaviourist approach suggests bodily rhythms are influenced by other people/social norms e.g. sleep occurs when dark = socially unacceptable for a person to conduct daily routines at night.

  Evaluate: The research is criticised for being reductionist as it only considers a singular biological mechanism and thus fails to consider the other widely divergent viewpoints.
• (AO3) Give a strength of EP & EX

  Point: Support for the role of melanopsin

  Evidence: Researchers claimed that majority of blind people who still have some light perception have normal circadian rhythms. Whereas, those without any light perception show abnormal circadian rhythms.

  Conclusion: Demonstrates importance of EX as a biological mechanism & impact on biological circadian rhythms.