Biological rhythms and EP and EZS

• Circadian rhythms occur every 24 hours. An example of this is the sleep wake cycle. If we aim to sleep for around 8 hours a day, in a 24 hour period we would be awake for 16 hours.
• Infradian rhythm occurs over longer periods than 24 Hours. For example menstrual cycles are an example of an infradian rhythm as they last approximately 28 days
• Sabbagh and Barnard found that menstrual cycles between females who live together and become synchronised due to pheromones linked to evolution.
• Ultradian rhythms occur more than once everyday. This lasts less than 24 hours. For example; light and deep sleep cycle can be defected through electroencephalograms(EEGS).
• A strength of a EEG is a objective measure. All the participant are monitored in the same scientific way so this increases the reliability and increases validity of the findings from each participant brainwaves during their sleep
• A strength of a EEG is that they collective quantative data that can be analysed stastically which makes its easier to draw conclusions from data
• A weaknesses of a EEG is measuring sleep and dreaming in a laboratory is the way participant behave may be different than at home.
• A weaknesses of a EEG is that sample sizes tend to be very difficult to generalise.
• A weaknesses of a EEG is that it does not explain electrical activity taking place.
• Exogenous Zeitgebers and Endogenous Pacemakers are These both have an influence on human behaviour. You need to know what they are and you need to be able to explain how they influence behaviour and how they interact with each

  other.
• Exogenous Zeitgebers (EZs)-These are external influences /cues that trigger a biological rhythm. An external time-giver For example…When light or social cues lead us to understand time

  and therefore influence our internal systems and

  behaviour, our body becomes entrained
• Endogenous Pacemakers (EPs)-These are biological structures

  For example…The suprachiasmatic nucleus (SCN) is part of the hypothalamus and is thought to act as an internal clock

  to control the sleep/wake cycle.When light is detected through the

  retina (in the eye), the pineal gland,secretes (produces and discharges)or inhibits a hormone calledmelatonin which induces sleep (moremelatonin makes us sleepy, less melatonin wakes us up)
• When EPs and EZs interact. Sometimes EPs are in full control. Other times, they are more flexible an therefore get influenced. For example, we can make ourselves stay up late if we are going out or watching a film
• Jet lag-Travelling to different parts of the world for some days after the journey the sleep/wake cycle is disrupted (body temperature fails/body arousal may increase or decrease)
• Shift work-Employees required to do shift work, normally go

  to sleep when others are awake. When biological rhythm is disrupted (endogenous pacemakers/exogenous zeitgebers), sleep/wake cycle is disrupted too