Biopsychology - rhythms Flashcards
(17 cards)
What are biological rhythms and what are they governed by?
all living organisms are subject to biological rhythms and these exert an influence on the way in which body systems behave.
they are governed by:
the body’s internal clocks (endogenous pacemakers)
external changes in environment (exogenous zeitgebers)
What are the four types of biological rhythm
ultradian (many)
circadian (about once a day)
infradian (infrequent than a day)
circadian (about a year)
Ultradian rhythms
occur many times during the day e.g: sleep cycle
Circadian rhythms
last for around 24 hours e.g: sleep wake cycle
Infradian
take longer than a day to complete e.g: menstrual cycle
Circannual
type of infradian rhythm that take much longer to complete e,g: hibernation or SAD
What is the sleep wake cycle
the alternative stages of sleep and waking that are dependent on the 24 hour circadian cycle
Exogenous zeitgebers in sleep wake cycle
exogenous zeitgebers - the fact we feel drowsy when its night and alert during the day shows the effect of daylight as an external signal for when we need to be awake
Endogenous pacemakers in sleep wake cycle
biological clock without influence of external stimuli is called free running.
the basic rhythm is governed by the suprachiasmatic nucleus (SCN) which is a bundle of nerves in the hypothalmus.
exogenous zeitgeber of light can reset the scn which passes info onto the pineal gland increasing melatonin production
What is melatonin and what is its function
melatonin is a hormone that induces sleep and is inhibited during periods of waking and stimulated during periods of sleep.
the circadian rhythm dips and rises during the day and the sleepiness in these troughs is more intense when we’re sleep deprived
Homeostatic control on sleep and wake
when we have been awake for a long time, homeostasis tells us that we need sleep because wakefulness is using up a lot of energy. Homeostatic drive for sleep increases all day and peaks at late evening when most fall asleep
Alterations to sleep cycle
the circadian clock is described as free running and will maintain a cycle of around 24-25 hours even in the abscence of external cues.
but it is intolerant of major alterations in sleep wake schedules because it causes biological clock to become out of balance (jet lag)
Studies into circadian rhythms (MS)
Michael siffre (1962,1970) demonstrated free running circadian rhythm of about 25 hours.
French caver spent long periods in dark caves to examine effects of free running biological rhythms.
He spent two months in caves of southern alps (1962) and six months in Texan cave (1970)
He had no external cues to guide rhythms, no daylight or clocks. the only thing influencing his behaviour was his internal body clock
in both caste studies his free running circadian rhythm settled down to just above 24 hours so he did have a regular sleep/wake cycle.
in later study his clock ticked slowly as he was older
Aschoff and Wever (1976)
Group of participants spent four weeks in WW2 bunker deprived of natural light
all but one (whose sleep wake cycle extended to 29 hours) displayed a circadian rhythm between 24-25 hours
Endogenous pacemakers may have stronger influence than exogenous zeitgebers
Folkard et al (1985) studied a group of 12 people living in dark cave for three weeks going to bed when clock said 1145 and wkaing up at 745
Researcher gradually sped up clock so 24 hour day lasted 22 hours
only one adjusted to the new regime comfortably which suggests existence of strong free running circadian rhythm can’t be overridden by external environment changes
Strength of circadian rhythm research (practical applications)
Bolvin et al found shift workers experience a lapse of concentration around 6am (circadian trough) so mistakes and accidents are more likely
research also suggests link between shift work and poor health
research into sleep wake cycle may have economic implications in terms of how best to manage worker productivity and safety
Limitation of circadian rhythm research (use of case studies and small samples)
Aschoff and Wever/Schiffre used small groups or individual participants. Participants may not be representative of wider population which limits generalusability. At a later age, Siffre’s internal clock ticked much slowly which suggests that even with the same person, factors can prevent general conclusions being drawn
