Biological Rhythms

Front 1

What is the duration of: ultradian rhythms?

Back 1

Less than every 24 hours

Front 2

What is the duration of: circadian rhythms

Back 2

24 hour cycle

Front 3

What is the duration of: infradian rhythms

Back 3

More than every 24 hours

Front 4

What is an example(s) of: an ultradian rhythm

Back 4

Sleep stages, eating

Front 5

What is an example(s) of: a circadian rhythm

Back 5

Sleep/wake cycle

Front 6

What is an example(s) of: an infradian rhythm

Back 6

Menstrual cycle, SAD, hibernation

Front 7

Who studied circadian rhythms and what did they find?

Back 7

Siffre: Spent 6 months in a cave. Only had artificial light and a phone connected to the outside world. He had enough provisions for his stay and was monitored by a camera.
Sleep cycles first were completely off, but settled into a 25 hour day subsequent to that

Front 8

What are the issues with research into circadian rhythms?

Back 8

Siffre's research cannot be generalised due to it being a one-man case study.
Artificial light may have impacted on his sleep/wake cycle (EXT variable)
Other factors such as loneliness may have had more of an important role than availability of natural light.

Front 9

What research support is there for Siffre's study?

Back 9

Folkard et al: 12 participants lived in a cave for 3 weeks. They had to wake when their clock said 7:45 and sleep when it said 11:45. The clock was gradually sped up over the 3 week period and their day reduced from 24 to 22 hours.
None of the participants reacted well to the shift in sleep pattern, suggesting we do have a strong internal circdian rhythm

Front 10

What are the applications of research into circadian rhythms?

Back 10

Shift work: more likely to suffer from health problems, sleep disorders and catch illnesses
Drug therapy: certain medications work better at day/night depending on the drug

Front 11

Who studied ultradian rhythms and what were their findings?

Back 11

Dement and Kleitman: sleep occurs in four stages.
1- light sleep, alpha and theta waves, easily woken, blood pressure starts to slow
2- moving towards a deeper sleep, slow breathing and heart rate
3- deep sleep begins, delta waves, slow brain waves
4-deepest sleep, REM, dreams most likely to occur, very groggy if woken

Front 12

What and how was research carried out on ultradian rhythms?

Back 12

EEG monitoring. Patients were woken during each stage of sleep and had to report feelings, experiences and emotions. 80-90% of the time, when woken during REM sleep, participants claimed to remember dreams.
Only 7% of wakening in NREM sleep led to dream recall.

Front 13

What is SAD?

Back 13

Seasonal Affective Disorder.
Caused by increased levels of melatonin (due to a lack of vitamin d) being secreted from the hypothalamus, this reduces serotonin production and causes depression

Front 14

How long does SAD last and what are the symptoms?

Back 14

From September to November, it has to last for 2 consecutive winters to be diagnosed. Symptoms are irritability, restlessness, tension, fatigue and sleeping problems (insomnia and hypersomnia)

Front 15

What is the menstrual cycle and how long does it last?

Back 15

Ovulation that occurs once a month due to rising oestrogen levels, progesterone is then used to make the womb grow thicker. If pregnancy does not occur, then the womb lining is shed in a period. It occurs roughly every 28 days.

Front 16

What research has been done into the menstrual cycle?

Back 16

Pheromones. Women with irregular periods were given pheromones from women with consistent periods to see if it would make their cycle predictable.
Donor women wor pads uder their armpits to collect their pheromones, these were then frozen and rubbed on the upper lip of the irregular women.
Rearchers found that the women with irregular periods began synching with their pheromone "donor"

Front 17

What are exogenous zeitgebers?

Back 17

Outside influences, such as light and temperature, that impact on our internal body clock

Front 18

What are endogenous pacemakers?

Back 18

Internal influences, such as hormones and biological structures, that impact on our internal body clock

Front 19

What research has been conducted into the role of endogenous pacemakers?

Back 19

DeCoursey: removed the SCN from 30 chipmunks and then released them back into the wild. After 80 days, he found that nearly all the chipmunks had died due to the disruption to their normal biological rhythm, when compared to a control group with their SCN in tact

Front 20

Where does the SCN receive information from?

Back 20

The optic nerves

Front 21

Evaluation: DeCoursey

Back 21

Animals used therefore it cannot be generalised to humans
It was a natural study, meaning it has a real life application

Front 22

What is the SCN?

Back 22

The Superchiasmatic Nucleus

Front 23

Where is the SCN located?

Back 23

In the hypothalamus

Front 24

What is the SCN connected to and what hormones does it cause the release of?

Back 24

The pineal gland which produces cortisol and melatonin

Front 25

What studies, other than Decoursey, can be used to support the role of endogenous pacemakers?

Back 25

Siffre

Front 26

What is the role of melatonin in our internal bodyclock?

Back 26

To inhibit hormones that cause us to feel awake and instead, make us feel tired. It is released in low light- hence why we become tired at night time.

Front 27

What did Morgan do in his experiments on animals?

Back 27

Mutant hamsters were bred with 20 hour circadian rhythms. When the SCN from a normal hamster was removed and implanted into the mutant hamsters, their circadian rhythm returned to normal

Front 28

What are the issues with animal studies?

Back 28

Removal of parts of the brain and endangering the lives of animals has many ethical issues, do the costs out-weigh the benefits?
DeCoursey knew that the chipmunks would be in danger by changing their circadian rhythms.
The mammals tested are unlike humans and their circadian rhythms are the opposite to humans- making us question the validity and generalisability of the studies