biopsych - biological rhythms - y13

Question 1

what are biological rhythms?

Answer 1

-they are distinct patterns of change in body activity that conform to cyclical time periods.
-these rhythms are influence by internal body clocks (endogenous pacemakers) as well as external changes to the environment (exogenous pacemakers)

Question 2

which gland produces melatonin in order to regulate sleep?

Answer 2

pineal gland.

Question 3

our core body temperature and IQ be correlated?

Answer 3

-as our body warms us, the better our cognitive performance.
-for example, during 6-7pm our body is at its hottest at 38 degrees C.

Question 4

Sunita Gupta (1991)

Answer 4

found improved performance on IQ tests when participants were assessed at 7pm as apposed to 2pm or 9am.

Question 5

what is the main endogenous pacemaker?

Answer 5

-the suprachiasmatic nucleus (SCN)
- a cluster of nerve cells located in the hypothalamus

Question 6

what are the main exogenous zeitgebers?

Answer 6

light, temperature and social cues.

Question 7

what is a circadian rhythm?

Answer 7

a biological rhythm which is subject to a 24 hour cycle, which regulate numerous bodily processes such as the sleep/wake cycle, blood pressure, metabolism, body temperature.

Question 8

how long is an ultradian rhythm?

Answer 8

occurs many times within a 24 hour period such as sleep.

Question 9

how long is an infradian rhythm?

Answer 9

takes more than a day to complete such as the menstrual cycle.

Question 10

how long is a circannual rhythm?

Answer 10

yearly such as hibernation.

Question 11

Siffres cave study (1975)

Answer 11

-isolated himself from all daylight with weak artificial light for 6 months with no clock or reference to time.
-his sleep-wake cycle settled naturally at around 25 hours although sometimes it would range up to 48
-concluded that the absence of natural light allowed his biological clock to run at its natural rate, and that normally daylight acted as an exogenous zeitgeber to resynchronise the cycle.

Question 12

two issues with Siffres cave study?

Answer 12

-it was a case study so it cannot be generalised to others.
-questionable internal validity as siffre was not isolated from all exogenous zeitgebers as he still had contact with the outside world.

Question 13

Aschoff and Wever (1976)

Answer 13

-studied participants who spent four weeks in a WWII bunker deprived of natural light.
-all but one displayed a circadiam rhythm of 24-25 hours, the other one had a circadian rhythm of 29 hours.
-suggetss that the ‘natural’ sleep/wake cycle may be slightly longer than 24 hours but become entrained (exogenous zeitgeber resetting the biological clock) through mealtimes, daylight hours etc.

Question 14

Folkard et al (1985)

Answer 14

-studied 12 people who lived in a dark cave for 3 weeks who went to bed when the clock showed 11:45pm and rose when it showed 7:45am.
-over 3 weeks, the researchers gradually sped up the clock so it was running at 22 hours.
-none of the participants comfortably adjusted to the 22 hour clock
-suggesting that the circadian rhythm may be ‘free-running’ and is not easily overriden by environmental influence.

Question 15

practical application of (disrupted) circadian rhythms?

Answer 15

-the concentration of night workers is reduced at about 6am (circadian trough) so mistakes and accidents are more likely (Boivin et al 1996)
-shift workers are also 3x more likely to develop heart disease (Knutsson 2003) perhaps because of the stress to readjusting to different patterns of the sleep/wake cycle, and poor quality sleep during the day
-this research has economic implications in terms of how best to manage worker productivity.

Question 16

what is a counterpoint to the practical application of ‘disrupted’ circadian rhythms?

Answer 16

-however, studies investigating the effects of shift work tend to use correlational methods
-this means it is difficult to establish whether desynchronisation of the sleep/wake cycle is actually a cause of negative effect.

Question 17

what is an issue with the studies used to investigate circadian rhythms?

Answer 17

the studies carried out involve small samples who may not be representative of the wider population, limiting meaningful generalisations which can be made.

Question 18

practical application to drug treatments?

Answer 18

-circadian rhythms coordinate many basic processes such as heart rate, digestion and hormones.
-these then have an effect on pharmacokinetics (absorption and distribution of drugs in the body)
-there are peak times in which drugs are more likely to be effective, which has led to guidelines as to timing and dosage in drugs for cancer, cardiovascular issues, epilepsy etc.
-medical treatments can be administered in a way that supports biological rhythms
-research has supported this (Bonten et al 2013)

Question 19

an issue with the length of time Siffre conducted his cave studies?

Answer 19

-at the age of 60, siffre carried out another cave study and found that his internal clock was slower than when he was younger.
-there were different findings even when looking at the same person
-showing how hard it is for researchers to draw general conclusions in attempt to support the idea of circadian rhythms.

Question 20

control issues in studies?

Answer 20

-P’s were deprived of natural light, but had artificial light
-Czeisler et al (1999) adjusted participants CR from 22 hours to 28 hours using dim lighting, therefore the use of light may have reset their biological clock meaning the study lacked validity as it was not measuring the true absence of exogenous zeitgebers.

Question 21

Czeisler et al (1999)

Answer 21

individual cycles can vary from 13 hours to 65 hours.

Question 22

Duffy et al (2001)

Answer 22

-some people naturally prefer going to bed early and rising early - larks
-while some sleep late and wake up late - owls.