Circadian Rhythm -
Controlled biologically by:
Pineal gland- secretes melatonin
SCN-supra-chiasmatic nuclei: group of pacemaker cells in the hypothalamus in the brain
Light exposed to
Lowest levels=high melatonin=sleepiness
Highest levels=low melatonin
Synchronises the circadian clock to local time (sensitive to the external environment). Priniciple zeitgeber is sunlight.
Term that describes the capture and regulation of timing of the circadian rhythm by a zeitgeber.
What is circadian rhythm?
cycle of behavioural and physiological changes in the body during a 24 hour period
e.g arousal state, body tempo, hormone secretion
Core body tempo drops during sleep at 3-5 am/Tempo at peak at mid afternoon
If exposed to light before core body tempo minimum, may shift circadian clock to later time, vice versa.
If tempo increases 1 degree-alertness/decreses-sleepiness
Causes of biological rhythms
Rhythm driven internally such as SCN
e.g SCN/pineal gland
Also affected by pacemaker-collection of cells that generate rhythmic signal e.g heart rate/SCZ
Rhythms driven by external environment-sunlight
occurs due to the exogenous cues being altered compare to endogenous (internal cues)
e.g affected by jetlag-different time zones
e.g being forced awake at night
Types of waves
Periodic state that alters awareness and is accompanied by physiological effects
Brain waves measure by EEG