EP's and EZ's

• Define Endogenous Pacemakers

  -Internal body clocks that regulate many of our biological rhythms such as the influence of the suprachiasmatic nucleus (SCN) on the sleep wake cycle.
• what is the superchiasmatic nucleus

  -A tiny bundle of nerve cells located in the hypothalamus in each hemisphere of the brain. ​

  -The SCN receives information about light levels from the optic nerve.​

  This happens even when our eyes are closed.
• The SCN passes information

  -that it receives about day length and light to the pineal gland.​

  -During the night, the pineal gland increases production of melatonin – a chemical that induces sleep.​

  -Melatonin is inhibited during periods of wakefulness.
• Define exogenous zeitgebers

  -External cues that may affect or entrain our biological rhythms , such as the influence of light on the sleep wake cycle.
• define entrainment

  -is the process by which circadian clock activity becomes synchronized to a 24-hour periodic environmental cue called zeitgeber
• how does light act as exogenous zeitgebers

  -A key zeitgeber in maintenance of the sleep wake cycle. ​

  -Works closely with the SCN in this process. ​

  -Melanopsin, a protein in the eye, is sensitive to light and carries signals to the SCN to set the 24h cycle.
• how do social cues act as exogenous zeitgebers

  -like meal-times, can also act as zeitgebers, and can maintain the sleep-wake cycle in the absence of light. ​

  -Newborn babies have irregular, random sleep wake cycles, until around 16wks when they are entrained by schedules imposed by parents e.g., meal-times, bed-times.
• define Desynchronisation

  -endogenous pacemakers and exogenous zeitgebers do not match.
• what are the effects of desynchronisation

  -Anxiety, feeling irritable, fatigue, decreased alertness, health problems