Biological rhythms

Question 1

What are biological rhythms

Answer 1

Distinct patterns of changes in the body activity that conform to cyclical time periods. Biological rhythms are influenced by internal body clocks (endogenous pacemakers) as well as external changes to the environment (exogenous zeitgebers)

Question 2

Biorhythms are governed by..

Answer 2

Endogenous pacemakers
and
Exogenous zeitgebers

Question 3

Circadian:
What are endogenous pacemakers?

Answer 3

INTERNAL body clock - biological clock ‘left to its own devices’ without the influence of external stimuli i.e light -> free running

Question 4

Circadian:
What are exogenous zeitgebers?

Answer 4

EXTERNAL changes in the environment - time giver (light) - sunlight

Question 5

Circadian:
What is the basic rhythm governed by?

Answer 5

Suprachiasmatic nucleus (SCN). The SCN lies just above the optic chiasm which provides information from the eyes about light

Exogenous zeitgebers (light) can reset the SCN

Question 6

State the 4 types of bio-rhythms

Answer 6

Ultradian rhythms
Circadian rhythms
Infradian rhythms
Circannual rythms

Question 7

Describe an ultradian rhythms

Answer 7

Occur MORE OFTEN THAN ONCE A DAY and occur in most mammals. An example can be found in sleep, as it is divided into several very separate stages

Question 8

Describe circadian rhythms

Answer 8

DAILY - These types of bio rhythm repeat themselves roughly every 24 hours, such as the sleep/wake cycle, or body temp cycle

Green:
- Mammals possess about 100 different biological circadian rhythms

Question 9

Describe infradian rhythms

Answer 9

Occur LESS OFTEN THAN ONCE A DAY and MORE OFTEN THAN ONCE A YEAR e.g a month such as the menstrual cycle

Control mechanisms range from the influence of pheromones, the influence of the day/night cycle and the direct influence of an internal body clock (SCN)

Question 10

Describe Circannual rhythms

Answer 10

Occur roughly ONCE A YEAR and are very rarely seen in humans. They occur in several species of mammal e.g Hibernation

S.A.D has been suggested as a possible human example

Question 11

Aschoff and Wever evidence to circadian rhythm

Answer 11

A group of participants spent four weeks in a WW2 bunker deprived of natural light

All but one (whose sleep/wake cycle extended to 29hrs) displayed a circadian rhythm between 24 and 25hrs

Siffre’s experience and the bunker study suggest that the ‘natural’ sleep/wake cycle may be slightly longer than 24hfs but is entrained by exogenous zeitgebers associated with our 2hr day (e.g daylight hours, mealtimes e.g)

Question 12

EVALUATION of circadian rhythms (Research evidence: Siffre)

Answer 12

Studies on circadian rhythms and how external stimuli, such as light, affect this system have been carried out.

According to Siffre (1975), when he returned from an underground stay without light or clocks, he mistakenly thought the date was a month earlier than it actually was. This is an example of how the lack of external cues dramatically affected his circadian rhythm.

This implies that the lack of outside stimuli prolonged his 24-hour sleep-wake cycle, giving him the impression that fewer days had passed and that one day was longer than it actually was.

Question 13

EVALUATION of circadian rhythms with a counterpoint

Answer 13

Biological rhythms become desynchronised as a result of shift work.

According to Bolivn et al., shift workers have a circadian trough about 6 a.m., which results in a break in concentration that increases the risk of accidents. Studies also point to a connection between shift work and ill health; shift workers have a 3 timesincreased risk of heart disease (Knutsson).

Therefore, studying the sleep-wake cycle may have economic implications for managing shift work arrangements.

COUNTERPOINT: As correlational research is used, dysynchronisation might not be the cause of the problems that have been reported. Solomon, for instance, came to the conclusion that shift workers’ high divorce rates may be caused by their inability to attend significant family occasions. This implies that the negative effects of shift work might not be caused by biological causes.

Question 14

EVALUATION of circadian rhythms (generalisations)

Answer 14

Studies of the sleep/wake cycle often use small groups of participants (e.g Aschoff and Wever) or even single individuals (e.g Siffre). Participants may not be representative of the wider population and this limits making meaningful generalisations.

Siffre observed that his internal clock ticked much more slowly at 60 than when he was younger.

This suggests that, even when the same person s involved, there are factors that may prevent general conclusions from being drawn

Question 15

EVALUATION of circadian rhythms (teen circadian rhythms)

Answer 15

Research shows benefits for teen’s academic and behavioural performance when lessons start later in the day (adolescent sleep working group 2014) However a later start is disruptive for parents and teachers, teens may simply stay up later and still be exhausted. This implies that although modifying the school day could be desired, it might not be pratical

Question 16

Intro to the stages of sleep

Answer 16

Derment and Kleitman claim sleep is an ultradian bio-rhythm with five stages which together last around 90 mins, and a cycle of all five is repeated about five or six times a night.

In each stage heart rate, blood pressure and body temp continue to fall

Question 17

Stages 1 and 2 of sleep

Answer 17

Light sleep where a person may be easily woken

Stage 1 (15 mins) - brainwaves are high frequency and have a short amplitude (alpha waves) Hypogenic jerks (body moves suddenly)
Stage 2 ( 20mins) - alpha waves continue but there are occasional random changes in pattern called sleep spindles

Question 18

Stages 3 and 4 of sleep

Answer 18

This is known as deep sleep or slow wave sleep. The individual waves now have lowered frequency and higher amplitude. It is difficult to wake someone at this point

Stage 4 - growth hormone secreted
Sleep walking and sleep talking most likely to occur

Question 19

Stage 5 (REM sleep) of sleep

Answer 19

The body is paralysed yet brain activity closely resembles that of the awake brain. During this time, the brain produces theta waves and the eyes occasionally move around, thus rapid eye movement (REM)

Dreams most often experienced during REM sleep, but may also occur in deep sleep

Question 20

Menstrual cycle - infradian rythm

Answer 20

The human female menstrual cycle is about 28 days

Rising levels of oestrogen cause the ovary to release an egg (ovulation). Then progesterone helps the womb lining thicken , readying the womb for pregnancy. If pregnancy does not occur, the egg is absorbed and the womb lining comes away (menstrual flow)

Question 21

Evidence of the menstrual cycle

Answer 21

Stren and McClintock

• Studied 29 women with irregular periods
• Pheromones were taken from some at different stages of their cycles via a cotton pad under the armpits
• These pads were cleaned with alcohol and later rubbed on upper lips of the other participants
• 68% of women experienced changes to their cycle, brought them closer to the ccler of their ‘odour donor’

Question 22

Explain SAD as an infradian rhythm

Answer 22

Seasonal affective disorder is a depressive disorder (low mood, lack of activity) with a seasonal pattern

Often called the winter blues because the symptoms are triggered during the winter months when the number of daylight hours becomes shorter

Question 23

Why has the hormone melatonin related to SAD

Answer 23

During the night, pineal gland secretes melatonin until dawn when there is an increase in daylight

Winter= less light = secretion goes on for longer

Knock on effect on the production of serotonin in the brain (low -> depressive symptoms)

Question 24

EVALUATION of infradian and ultradian rhythms (individual differences)

Answer 24

Studying sleep patterns can be challenging by the individual differences among people.

The length of each stage varied significantly, according to Tucker et al., especially in stages 3 and 4 (which are right before REM sleep). Because this study was conducted in a controlled laboratory environment, situational circumstances could not be blamed for the variations in sleep patterns; instead, individual biological differences might be the only explanation.

This indicates that in order to effectively understand ultradian rhythms, a variety of elements need be taken into account in studies.

Question 25

EVALUATION of infradian and ultradian rhythms (issues with research)

Answer 25

However, the methods used in study may not provide much information regarding human ultradian rhythms.

Participants must be exposed to a certain degree of control and have monitors attached to them in order to study sleep patterns. The participants may find this invasive, causing them to sleep in a manner inconsistent with their typical sleep cycle.

This makes examining ultradian rhythms, such asthe sleep cycle, very challenging because it increases the possibility of drawing incorrect results and because the ecological validity of these research is often low.

Question 26

EVALUATION of infradian and ultradian rhythms (evolutionary basis)

Answer 26

According to evolutionary psychologists, groups of women benefit from synchronous menstrual cycles since several moms can share childcare when their children are born at the same time due to the synchronicity of pregnancies.

Studies indicate that infradian rhythms, like the menstrual cycle, are also significant behavioural regulators. According to research by Penton-Volk et al. (1999), women preferred more masculine faces when they were most fertile and more feminised ones when they were least fertile.

These results highlight the significance of researching infradian rhythms in connection to human behaviour by showing that women’s sexual behaviour is driven by these rhythms.