circadian rhythm Flashcards
exogenous pacemaker
a rhythmically occurring natural phenomenon which acts as a cue in the regulation of the body’s circadian rhythms
endogenous pacemaker
the internal biological clock (circadian rhythm)
two key structures that control biological rhythms
SCN and the pineal gland
the electrical activity of the SCN has an
endogenous circadian rhythm
evidence for an internal pacemaker
michel siffre (1962), stephen and zucker (1972)
michel siffre (1962)
lived in total isolation for two months with no clocks or daylight to mark time, he would phone researchers every time he woke ate and slept, his erratic sleep patterns settled into a sleep wake cycle of roughly 24-25 hours
stephen and zucker (1972)
laboratory rats housed with 12 hours of darkness and 12 hours of light were more active during the dark period, when the SCN was damaged the normal circadian patterns of behaviour stopped, concluding that the SCN is a key pacemaker which controls circadian rhythms
the SCN sends
regular daily impulses via nerves to the pineal gland to produce melatonin
melatonin
the sleep hormone
light
the retina of the eye is also connected to the SCN via a nerve pathway therefore light also affects the SCN and the pineal gland
circadian rhythm
a body rhythm that cycles over 24 hours, sleep is a perfect example
the clock is used to
anticipate the differing demands of the 24-hour day and fine-tune physiology and behaviour in advance of changing conditions
in anticipation of going to bed
body temperate, blood pressure, and cognitive performance decreases
before dawn
metabolism is geared up in anticipation of increased activity when we wake
three determinants of the sleep wake cycle
endogenous pacemaker, endogenous sleep regulating substances, exogenous pacemaker
