Biopsychology- endogenous pacemakers & exogenous zeitgebers

Question 1

Define Endogenous pacemakers.

Answer 1

internal mechanisms which determine the biological rhythms of the body

Question 2

Give an example of Endogenous pacemakers

Answer 2

the circadian sleep-wake cycle

Question 3

What are endogenous pacemakers affected by?

Answer 3

-The external environment

Question 4

How does light affect endogenous pacemakers?

Answer 4

-light is required to reset the sleep-wake cycle every 24 hours

Question 5

What is the primary endogenous pacemaker?

Answer 5

The suprachiasmatic nucleus (SCN)

Question 6

What is the SCN closely associated with?

Answer 6

The pineal gland

Question 7

What is the function of the SCN?

Answer 7

-responsible for sleep and arousal (e.g. the pineal gland, the optic nerve and the photosensitive ganglion cells of the retina)
-The SCN also receives information about light levels to ensure that biorhythms synchronise with the outside world, e.g. day and night
-The SNC sends signals to the pineal gland, which increases production of melatonin secretion at night, helping to induce sleep

Question 8

Where is the SCN located?

Answer 8

-In the anterior hypothalamus

Question 9

How does the SCN link to the sleep-wake cycle?

Answer 9

-Eye detects low light levels
-This information is then sent to the SCN
-The SCN then alerts the pineal gland to secrete melatonin
-Melatonin levels increase which induces sleep

Question 10

What are Exogenous zeitgebers?

Answer 10

any factors in the sleep-wake cycle which act as external cues to either wakefulness or sleepiness

Question 11

Give some examples of any exogenous zeitgebers in the sleep-wake cycle.

Answer 11

-going to bed with the light on or a digital device placed next to the bed may keep levels of light unnaturally high ,impacts negatively on sleep
-trying to sleep during the day - even if the person is very tired - may not happen due to light levels
-someone may sleep through their alarm clock if it has been set to an unusually early time (their body is not used to waking at this time so their sleep may be very deep)

Question 12

What are the functions of exogenous zeitgebers?

Answer 12

resetting the biological clock of an organism

Question 13

What are the important exogenous zeitgebers?

Answer 13

-Light
-Social cues (the timing of meals,work schedules,
exercise sessions)

Question 14

What is meant by synchrony?

Answer 14

The interactions between the internal clock (endogenous pacemakers) and external cues (exogenous zeitgebers) to set circadian rhythms

Question 15

Define entrainment

Answer 15

the alignment of behaviours such as waking, eating meals, working etc. to a regular sleep-wake cycle

Question 16

Siffre found that the absence of external cues significantly altered the circadian rhythem, when he returned from an underground stay in the caves with no clocks or light, he belived the date was a month earler, what does this suggest?

Answer 16

-The 24 hour sleep wake cycle was increased by the lack of external cues (exogeneuous zeitgebers) makinh him belive one day was longer than it actually was

Question 17

Aschoff and weber studied participants living in a bunker. The bunker had no windows and only artificial light, where the participants were freeto turn on and off as they please. Found that participants settled into a longer sleep wake cycle of between 25-27 hours. What does this suggest?

Answer 17

-Humans use natural light (exogenuous zeitgebers) to regulate a 24 hour circaidian rhythm - sleep wake cycle, demonstrating the importance of light for the circadian rhythm

Question 18

Duffy- Morning people prefer to rise and go to bed earlier and rise earlier whereas evening people are the complete opposite?

Answer 18

Demonstrates that there may be innate individual differences in circadian rhythms which suggests that researchers should focus on these differences

Question 19

Morgan-bred hamsters so that they had circadian rhythms of 20 hours rather than 24. SCN neurons from these abnormal hamsters and where transplanted into the brains of normal hamsters which then displayed the same abnormal rhythms

Answer 19

-Transported SCN imposed its patterns onto the hamsters and demonstrates the significance and how endogenous pacemakers are important for biological circadian rhythms

Question 20

Give an evaluation point (Research support)- Morgan

Answer 20

-Research support for the importance of endogenous pacemakers in particular the SCN in relation to the sleep wake cycle
-Morgan bred hamsters so that they had circadian rhythms of 20 hours rather than 24
-SCN neurons were transplanted from abnormal to normal hamsters who then had circadian rhythms of 20 hours (the pattern had been imposed)
-However it is difficult to generalise because hamsters do not respond in the same way as humans
-Humans would respond very differently to manipulations of their biological rhythms not only because we are biologically different but also there are vast differences in environment
-Therefore this research demonstrates the significance of the SCN and how endogenous pacemakers impact biological rhythms (such as the sleep wake cycle)
-Research carried out on animals may be unable to explain the role of endogenous pacemakers on the sleep wake cycle in humans

Question 21

Give an evaluation point (Resaerch support- siffre)

Answer 21

-Research support for the role of exogenous zeitgebers on the sleep wake cycle
-Siffre stayed in an underground stay with no clocks or light, he believed that the date was a month earlier than it actually was which demonstrates the importance of exogenous zeitgebers (light) on the sleep wake cycle
-Researcher was the only participant in his own study , severe issues with potential researcher bias and lack of generealisbilty to a wider population
-Results suggest that the 24 hour sleep wake cycle was increased by the lack of exogenous zeitgebers showing the impact of such factors on he bodily rhythms, these finding should be treated with caution as we are unable to conclude whether the role of exogeneous zeitgebers effects the sleep wake cycle in a wider population on the basis of this case study alone

Question 22

Give an evaluation point (Reductionist)

Answer 22

-Despite research support the role of endogeneous pacemakers and exogenous zeitgebers, the argument culd be considred reuctionsit
-The sleep wake cycle is influenced by other people and social norms
-Sleep occurs when it is dark because that is the social norm and it wouldnt be socially acceptable for a person to conduct their daily routine during the night
-Researched previously discussed could be considred reductionist as it only considers a limited range of factors (SCN and light)

Question 23

Give an evaluation point (application to real world)

Answer 23

-Research on exogenous zeitgebers carried out by Burgess et al
-Found that exposure to bright light prior to an east- west flight decreased the time needed to adjust to local time
-3 conditions: continuous bright light (2.1 hours ), intermittent bright light (1.5 hours) and dim light (0.6 hours)
-Each shifted their sleep wake cycle back by an hour over 3 days
-Suggests that light exposure prior to a flight would allow travellers to arrive with their circadian rhythms already partially retrained to local time (avoids jet lag)