biological rhythms : circaidian rhythms ao1 Flashcards
what is a biological rhythm
repeated patterns of changes in the body which are regulates by an internal body clock
3 types of biological rhythms
ultra radian
infra radian
circadian
2 things which control and maintain biological rhythms
endogenous pacemakers
exogenous zeitgebers
Define endogenous pacemakers
Internal body clocks that regulate biological rhythms such as regular times of sleep linked to levels of light
Eg suprachiasmatic nucleus and pineal gland
scn (superchiasmatic nucleus) found in … and is an example of a …
cluster of nerve cells located in the hypothalamus and is an example of a endogenous pacemaker for our sleep wake cycle and it regualtes pineal gland - is an an example of an endogenous pacemaker
how does scn work in maintaining circ rhythm
pacemaker must be constantly re set to be kept in sync
light sensitive cells in eye send info about environment to scn which then coordinates the entire circ rhythm - photo entrainment
Ralph et al 1990 procedure
Took the SCN (superchiasmatic nuclues) out of genetically abnormal hamsters which only had a circadian rhythm of 20h and transplanted them into normal rats who had a 24h cycle
Findings of Ralph et al 1990
They found the rats cycle shortened to 20h showing that the SCN is determining the length of the cycle
Define exogenous zeitgebers
An environmental/external cue such as light that helps to regulate and reset our internal biological clock
2 Types of exogenous zeitgebers
Light
Social cues
Explain how exogenous zeitgebers work in terms of light
Light can reset the bodies main pace maker SCN
less light = scn stimulates the pineal gland to produce more melatonin to help us fall asleep
more light=scn stim pineal gland to release less melatonin making us feel more awake
who studied exogenous zeitgebers using chipmunks
DeCoursery et al 2000
de coursey et al procedure
control group - 20 chipmunks w (scn intact) vs experimental condition - 30 chipmunks (scn destroyed)
each chipmunk was radio collared for tracking purposes and then released back into natural habitat where they were observed for 80 days
de coursey et al findings and conclusions
more chipmunks w scn damaged were killed by weasels compared to the control group
thus suggesting damage to scn affected their sleep wake cycle - they didnt know when to sleep making them restless during the night and more vunerable to predation
thus this research implicates the importance of the scn in regulating our sleep wake cycle
Define Entrainment
An adjustment of the body clock in line with the environment
Exogenous zeitgebers - social cues
Infants sleep wake cycle is random at first
6 weeks - circadian rhythms begin
16 weeks entertained rhythms
Julia complains that her baby is sleeping all day and keeping her awake all night.
Using your knowledge of research into exogenous zeitgebers, discuss what Julia could do to encourage her baby to sleep more at night
(8)
Lower exposure to light near bedtime and more light during the day - decreased melatonin prod stim from pineal gland
Social cues like running a warm bath or giving her milk or giving high interaction during the day time and less at night signalling it’s time to go to sleep
Sam is a police officer. She has just started working the night shift and after a week, she finds that she has difficulty sleeping during the day and is becoming tense and iritable. Sam is also worried that she is less alert during the night shift itself.
In terms of exogenous zeitgebers (external factors eg light) she could decrease her exposure to light during the day which stimulates her pineal gland to produce more melatonin which could help her go to sleep during the day
Distruption of biological rjhtyms has been shown to lead to distrupted sleep patterns increased anxiety and decreased
Moving to night shift means endogenous pacemakers (internal biological Rthyms) try to impose inbuilt rhythm of sleep but are now out of synchrony
Circadian rhythms are
biological rhythm with a 24h cycle
optimises physiology and beh eg when to sleep eat release hormones body temp based on environment (light and dark)
Infradian rhythms and give example
Last for more than 24h
Eg menstrual cycle - 28 days
SAD - seasonal affective disorder
describe menstrual cycle as an infradian rhythm
in first half of menstrual cycle levels of the hormone oestrogen rise causing ovary to develop and release an egg, lining of womb thickens
in second half levels of progesterone rise which helps in maintaining the lining of the womb in prep for implantation of dev embryo
who investigated if there are any exogenous zeitgebers which affect the menstrual cycle
martha mclintock 1971
martha mclinktok procedure
investigated 35 females who went to same college and lived together in dormitories - seeing how in sync menstrual cycles would become
mcclintok findings
a significant factor in synchrony is the time the individuals of the group spent together
mc clintok conclusionssh
she questioned whether the findings could be explained by pheremones - odurless chemical we rel into environment that affects beh of others
perhaps these airborne chem signals are being detected by the women which shapes when their mentrual cycle starts
who conducted another study to investigate if the menstrual cycle had a pheremonal basis
stern and mc clintok 1998
stern mc clintock 1998 procedure
29 women
9 women wore a cotton pad under their armpit for 8h from which pheremones were taken from
pads rubbed on upper lip of the other women at different stages of their menstrual cycle
stern mclinktok findings
68% of the womens menstrual cycle were more synchronised with women whos pheremones were shared compared to the start of the study
stern n mclintok conclusions
findings suggest that pheremones may be an exogenous zeitgeber that can influence the internal biological clock of the menstrual cycle
what is s.a.d
depressive disorder - low mood lack of activty w seasonal pattern
symptoms triggered during winter where hours of daylight shorter
yearly cycle
s.a.d caused by
melatonin
in the night pineal gland secretes melatonin until increase in light
during winter the lack of light in the morning means more melationin secretion for longer
has knock on effect - low serotonin levels in brain linking to depressive symptoms
Ultraradian rhythm
Biological rhythms that last less than 24h - whereby you have more than one cycle within 24h eg stages of sleep
how did scientists figure out that stages of sleep was an ultradian rhythm
used eegs and found distinct brain wave patterns for 5 stages eg gamma and beta waves
90 min increments in non rem sleep w 3 levels that show increasing levels of being in a deep sleep, body temp and freq of brain waves shown by eeg decreases
rem sleep - brain waves look like sm1 whos awake although skeletal muscles paralysed w rapid eye movements - when we dream
stages 1 and 2 of sleep
peroson easily awoken during light sleep - alpha waves which get slower and become beta waves
stages 3, 4 of sleep
difficult to awake sm1
deep sleep - delta waves which are slower but w higher amp
stage 5 of sleep
rem sleep
rapid eye movement
body paralysed yet increase speed of brain activity
who studied stages of sleep in terms of ultradian rhythm
dement and kleitman 1957
dement and kleitman procedure
used eeg to record sleeping and dreaming - see differences in dreaming bet rem and non rem
9 ppts - pnly 5 studied in detail
ppts allowed to eat normally but no caffiene or alochol
would go to sleep in lab w electrodes placed on head
dement and kleitman findings
when woken up during non rem sleep 7% of dreams were recalled, when woken up during rem sleep 80% of dreams were recalledp0
Circadian rhythms sleep wake cycle
Melatonin- a hormone produced by the pineal gland that increases sleepiness. In humans it is usually produced at night and is regulated by the suprachiasmatic nucleus.
light and dark are external signals that det when we sleep and wake up - this is under homeostatic control
they dip and rise at diff times - strongest sleep drive is bet 2 - 4 am and 1-3pm
what can disturb sleep wake cycle
major changes eg shift work or jet lag
biological clock and phisiological systems dependent on body clock become out of balance
who and when studies exogenous pacemakers in humans
michelle sifree 1962
michelle Sifree procedure
Entered a cave
No concept of time in the cave - no clock no sunlight - key exogenous zeitgeber
Spent 2 months alone in the dark
Revealed that our bodies interpreted time based on external cues
Perception of time warped when he came out
Would sleep for either 2 or 18h
2 months had passed but he was underground for Nearly double the time
Insight into psychological effects of sleep deprivation
Blood pressure brain waved body temp - recorded Also liquid intake and output
sifree findings
despite the absence of natural daylight he maintained a regular sleep wake cycle of around 25h
woke up and went to bed at regular and fixed times
lost track of time
sifree conclusions
1) we have an internal biological clock that controls our circadian rhythm
2) it appears that our sleep wake cycle is actually nearer to 25h rather than 24h
3) it shows the need we have for exogenous zeitgebers such as light to regulate our sleep wake cycle
How does core body temp vary across the day and what impact does this have on our behaviour
Core body temperature peaks in the afternoon (around 4-6 pm) and is lowest in the early morning (around 4-6 am).
Evening (Decline):
After peaking in the afternoon, core body temperature gradually declines in the evening.
As the body prepares for sleep, temperature continues to drop, signaling the body to begin the process of rest and recovery.
These fluctuations affect alertness, cognitive performance, sleep onset, and mood, with higher temperatures promoting wakefulness and performance.
- Alertness and Cognitive Performance
Morning (Low Point):
When core body temperature is at its lowest (early morning), people tend to feel the sleepiest and least alert. This is because the body’s systems are not yet fully activated.
Cognitive functions such as memory, attention, and problem-solving tend to be poorer during this period, contributing to the grogginess people feel after waking up.
What endogenous pacemakers and exogenous zeitgebers are likely to influence sleep wake cycle and how
Endogenous pacemakers like the suprachiasmatic nucleus (SCN) in the brain regulate the sleep-wake cycle by controlling the release of melatonin and maintaining circadian rhythms. Exogenous zeitgebers, such as light, help synchronize the SCN with the external environment, reinforcing the 24-hour cycle. Darkness promotes melatonin release, signaling sleep, while light exposure in the morning helps reset the internal clock, influencing wakefulness and sleep patterns.
shift work ao1
People who work at night (shift work) often experience symptoms similar to jet lag.
This is because the person’s work schedule (exogenous zeitgeber) is at odds with their
circadian sleep-wave cycle, which is governed by powerful biological factors
(endogenous pacemakers). Not surprisingly, people who work shift work often feel
sleepy at work and suffer from insomnia at home.
consequences of shift work - sleep deprivation
Sleep Deprivation: People who work at night and have to sleep during the day
often experience difficulties in sleeping. This is because their biological clocks
(endogenous pacemakers) do not adjust completely. Furthermore, the daytime is
associated with significantly more noise and other disturbances that can also affect
sleep.
o Research suggests that daytime sleep is shorter than night-time sleep. Tilley
and Wilkinson (1982) suggest that REM is particularly affected and this
reduction in sleep results in sleep deprivation, which produces lower levels
of energy and reduces alertness during the night time (awake period).
consequnces of shift work - heart disease
Knutsson (1986) found that people who worked shift patterns for more
than 15 years were significantly more likely to develop heart disease. This
research highlights the negative health consequences of disrupting
biological rhythms, in particular the sleep-wake cycle. However, it is worth
noting that these findings are purely correlational and while the findings
might indicate a link between the disruption of biological rhythms and
heart disease, other factors may also play a significant role. For example, it
may be that jobs that require night time working are inherently more
stressful and it is the stress that is the major factor and not the shift work.
consequnces of shift work - social consequnces
Another issue that people who work shift patterns
experience is social disruption. People who work hours that are at odds with the
hours worked by their family and friends find it difficult to spend quality time with
significant others.
shift work - ao3 practical applications
While the research above highlights a series of negative
consequences associated with disrupting biological rhythms, Czeisler et al. (1982)
used research on shift work to improve the health and performance of shift
workers. They found that by using a phase system to make shift changes slower,
workers reported increased satisfaction and increase productivity. This suggests
that the negative impact of disrupting biological rhythms can be overcome by
slowly introduce people to night work.
