biological rhythms : circaidian rhythms ao1

Question 1

what is a biological rhythm

Answer 1

repeated patterns of changes in the body which are regulates by an internal body clock

Question 2

3 types of biological rhythms

Answer 2

ultra radian
infra radian
circadian

Question 3

2 things which control and maintain biological rhythms

Answer 3

endogenous pacemakers
exogenous zeitgebers

Question 4

Define endogenous pacemakers

Answer 4

Internal body clocks that regulate biological rhythms such as regular times of sleep linked to levels of light
Eg suprachiasmatic nucleus and pineal gland

Question 5

scn (superchiasmatic nucleus) found in … and is an example of a …

Answer 5

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

Question 6

how does scn work in maintaining circ rhythm

Answer 6

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

Question 7

Ralph et al 1990 procedure

Answer 7

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

Question 8

Findings of Ralph et al 1990

Answer 8

They found the rats cycle shortened to 20h showing that the SCN is determining the length of the cycle

Question 9

Define exogenous zeitgebers

Answer 9

An environmental/external cue such as light that helps to regulate and reset our internal biological clock

Question 10

2 Types of exogenous zeitgebers

Answer 10

Light
Social cues

Question 11

Explain how exogenous zeitgebers work in terms of light

Answer 11

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

Question 12

who studied exogenous zeitgebers using chipmunks

Answer 12

DeCoursery et al 2000

Question 13

de coursey et al procedure

Answer 13

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

Question 14

de coursey et al findings and conclusions

Answer 14

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

Question 15

Define Entrainment

Answer 15

An adjustment of the body clock in line with the environment

Question 16

Exogenous zeitgebers - social cues

Answer 16

Infants sleep wake cycle is random at first
6 weeks - circadian rhythms begin
16 weeks entertained rhythms

Question 17

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)

Answer 17

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

Question 18

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.

Answer 18

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

Question 19

Circadian rhythms are

Answer 19

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)

Question 20

Infradian rhythms and give example

Answer 20

Last for more than 24h
Eg menstrual cycle - 28 days
SAD - seasonal affective disorder

Question 21

describe menstrual cycle as an infradian rhythm

Answer 21

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

Question 22

who investigated if there are any exogenous zeitgebers which affect the menstrual cycle

Answer 22

martha mclintock 1971

Question 23

martha mclinktok procedure

Answer 23

investigated 35 females who went to same college and lived together in dormitories - seeing how in sync menstrual cycles would become

Question 24

mcclintok findings

Answer 24

a significant factor in synchrony is the time the individuals of the group spent together

Question 25

mc clintok conclusionssh

Answer 25

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

Question 26

who conducted another study to investigate if the menstrual cycle had a pheremonal basis

Answer 26

stern and mc clintok 1998

Question 27

stern mc clintock 1998 procedure

Answer 27

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

Question 28

stern mclinktok findings

Answer 28

68% of the womens menstrual cycle were more synchronised with women whos pheremones were shared compared to the start of the study

Question 29

stern n mclintok conclusions

Answer 29

findings suggest that pheremones may be an exogenous zeitgeber that can influence the internal biological clock of the menstrual cycle

Question 30

what is s.a.d

Answer 30

depressive disorder - low mood lack of activty w seasonal pattern symptoms triggered during winter where hours of daylight shorter yearly cycle

Question 31

s.a.d caused by

Answer 31

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

Question 32

Ultraradian rhythm

Answer 32

Biological rhythms that last less than 24h - whereby you have more than one cycle within 24h eg stages of sleep

Question 33

how did scientists figure out that stages of sleep was an ultradian rhythm

Answer 33

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

Question 34

stages 1 and 2 of sleep

Answer 34

peroson easily awoken during light sleep - alpha waves which get slower and become beta waves

Question 35

stages 3, 4 of sleep

Answer 35

difficult to awake sm1 deep sleep - delta waves which are slower but w higher amp

Question 36

stage 5 of sleep

Answer 36

rem sleep rapid eye movement body paralysed yet increase speed of brain activity

Question 37

who studied stages of sleep in terms of ultradian rhythm

Answer 37

dement and kleitman 1957

Question 38

dement and kleitman procedure

Answer 38

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

Question 39

dement and kleitman findings

Answer 39

when woken up during non rem sleep 7% of dreams were recalled, when woken up during rem sleep 80% of dreams were recalledp0

Question 40

Circadian rhythms sleep wake cycle

Answer 40

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

Question 41

what can disturb sleep wake cycle

Answer 41

major changes eg shift work or jet lag biological clock and phisiological systems dependent on body clock become out of balance

Question 42

who and when studies exogenous pacemakers in humans

Answer 42

michelle sifree 1962

Question 43

michelle Sifree procedure

Answer 43

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

Question 44

sifree findings

Answer 44

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

Question 45

sifree conclusions

Answer 45

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

Question 46

How does core body temp vary across the day and what impact does this have on our behaviour

Answer 46

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. 1. 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.

Question 47

What endogenous pacemakers and exogenous zeitgebers are likely to influence sleep wake cycle and how

Answer 47

**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.

Question 48

shift work ao1

Answer 48

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.

Question 49

consequences of shift work - sleep deprivation

Answer 49

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).

Question 50

consequnces of shift work - heart disease

Answer 50

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.

Question 51

consequnces of shift work - social consequnces

Answer 51

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.

Question 52

shift work - ao3 practical applications

Answer 52

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.