Biological Rythems

Question 1

Define biological rhythms

Answer 1

Cyclical changes in the way biological systems behave

Question 2

3 types biological rhythms

Answer 2

• circadian
• infradian
• ultradian

Question 3

What control biological rhythms

Answer 3

• endogenous pacemakers
• exogenous zeitgebergs

Question 4

Endogenous pacemakers

Answer 4

Internal body clocks that regulate biological rhythms such as regular sleep times

Eg SCN/ pineal gland

Question 5

Exogenous zeitgebers

Answer 5

External stimuli that influence biological rhythms

Eg daylight/ noise

Question 6

Circadian rhythms

Answer 6

• Biological rhythms that last approximately 24 hours
• sleep/wake cycle

Question 7

Types of endogenous pacemakers in the circadian rythems

Answer 7

Suprachiasmatic nucleus (SCN) and pineal gland

Question 8

Describe SCN in circadian rythems

Answer 8

• optic nerve that receives and acts on info about the amount of daylight
• as daylight decreases the SCN instructs the pineal gland to release the hormone melatonin

Question 9

Evaluation of endogenous pacemakers

Answer 9

Strength:
- supporting evidence, Ralph et al, removed SCN from hamsters who had abnormal circadian rhythms of only 20 hours and implanted them into hamster with normal 24hr cycle there cycles decreased to 20 hrs shows SCN has important role in the sleep/wake cycle

• although not possible to carry out similar studies in humans involving removal and transplant of SCN
  Sack et al shows how a dose of melatonin can be used to entrain the free running circadian rhythms of blind ppl so they become synchronised with 24 hr cycle, demonstrates important role o melatonin release from the pineal gland in te sleep wake cycle

Question 10

Evaluation of exogenous zeitebers

Answer 10

Case study: siffre
- spent 6 months in a cave , separated from natural light-dark cycles he was wired up so his bodily functions could be recorded
- when he was awake lights where switched on by researchers when he as asleep lights turned off
- at first sleep wake patterns was erratic however it settled down to a pattern of 25-30hrs
- not healthy as sleep wake cycle ties to her body function if one out of sink others function become out of sink causes weaken immune system and digestive patterns
- when he emerged from the cave it was the 179th day but in his days 151st day
- suggest we need exogenous zeitgebers to keep our sleep wake cycle on track

• low ecological validity, conducted in artificial conditions with artificial light therefore resulting behaviour could be argued to tell us little about real life influences

Question 11

Limitation of endogenous pacemakers and exogenous zeitgebers

Answer 11

Thinks of endogenous acemakers and exogenous zeitgebers as separate perhaps we should thin of them as a blended system, running of the biological clock is a combination of the both

Question 12

Infradian rythems

Answer 12

• last mor than 24hrs
  Eg menstrual cycle

Question 13

Describe the infradian rhythm the menstrul cycle

Answer 13

Controlled by hormone level (endogenous PM) or pheromones and mating pattern (exogenous)

Question 14

Evaluation of infradian rhythms

Answer 14

McClintock&stern:
- investigated synchronisation of the menstrual cycle of 29 women age 20-35yrs
- did this by gathering pheromones from 9 women by placing pas o cotton under their arms, each cotton pad was frozen and treated with alcohol(disguise the smell) and paced under the other women nose on a daily basis
- fund 68% women respond to pheromones with their cycle shortening to 1-14 days or lengthening by 1-12 days to be similar to the donors
- shoes mens menstrual cycle can be altered by the communication of pheromones (exogenous)

Evolutionary advantage
- synchronised of the menstrual cycle as this means that there could be potentially synchronised pregnancies which means child care could be shared when babies are born around the same time

Unclear
- how close women have to live together and for how long for menstrual synchronisation to occur and to ht extent to which pheromones can have still requires more research

Question 15

Ultradian rhythms

Answer 15

• Last less than 24 hours
• eg stages of sleep

Question 16

Stages of sleep in ultradian rhythms

Answer 16

Stage 1&2: light sleep stages, brain waves patterns slower an more rhythms starting with alpha waves an progresses to that

Stages 3&4: deep sleep stage, difficult to wake someone up associated with slower delta waves , high amplitude low frequency

REM: active stage, body paralysed to stop person acting out their dream and brain activity resembles that of an awake person low amplitude and high frequency

Question 17

How long is spent in sleep stage

Answer 17

90mins

Question 18

How many ultradian rhythms can a person go through in one night

Answer 18

5

Question 19

Evaluation of ultradian rhythms

Answer 19

Dement and kleitman:
- monitored electrical activity in the brain during sleep using EEG recordings and so could wake ppts during different stages of sleep
- ppts reported their feelings, experiences and emotions
- ppl awakened during REM reported dreaming 90% of the time
- dreams recalled in detail
-7% of awakenings from NREM sleep led to dream recall

Objective measures such as EEGS, research is scientific and allows replicability, high reliability as finding have been replicated many times

Limitations
- lacks ecological validity, artificial setting tells us little about real life
- demand characteristics, lab experiment as they know the are being observed
- lacks population validity not representative, lower validity