Circadian rhythm +exogenous pacemakers etc

Question 1

Endogenous pacemakers

Answer 1

-Endogenous pacemakers are internal body clocks that keep our biological processes to time

Question 2

Exogenous zeitgebers

Answer 2

-Exogenous zeitgebers are external cues that entrain our internal clocks (alternating internal body clocks to match the environment)

Question 3

Circadian rhythms

Answer 3

-Circadian rhythms are biological rhythms that last about 24 hours
-We have a circadian rhythm for regulating our sleep-wake cycle

Question 4

The sleep wake cycle and endogenous pacemakers

Answer 4

-The sleep-wake cycle is the pattern of sleep and wakefulness that repeats every 24 hours
-This pattern is controlled by endogenous pacemakers, but these can be affected by external cues (exogenous zeitgebers) such as changes in light

Question 5

The suprachiasmatic nucleus (SCN) as the endogenous pacemaker of the sleep-wake-cycle and its effect on the pineal gland+ production of melatonin

Answer 5

-The suprachiasmatic nucleus (SCN) is the endogenous pacemaker of the sleep-wake-cycle, located in a part of the hypothalamus (in the limbic system) called the optic chiasm
-When the SCN detects light, it sends light to the pineal gland; this prevents the production of melatonin, which is a hormone that results in the sleep response
-This therefore makes the individual feel less sleepy

Question 6

Light as the main exogenous zeitgeber for the sleep-wake cycle

Answer 6

-Therefore light is thought to be the extraneous zeitgeber for the sleep-wake cycle
-However, research has shown that other factors, such as when we time our meals, what time other people go to bed, and environmental cues such as clocks, also act as exogenous zeitgebers on our sleep-wake-cycle

Question 7

Evaluation of circadian rhythm endogenous pacemakers being free running Siffre (1975)
-However psychologists argue use of artificial life + Cseizler (1999)

Answer 7

-Circadian sleep-wake cycles endogenous pacemakers are thought to be free running, meaning that they maintain a predictable cycle without constant entrainment by exogenous zeitgebers
-Siffre (1975) investigated this by living in a cave for 179 days without natural light and any other potential exogenous zeitgebers such as clocks or social cues
-It was found that his internal body clock maintained a consistent 25-hour cycle without EZ’s,larger than the predicted 24 hour cycle
-This suggests that the endogenous pacemaker for the sleep wake cycle is free-running, but needs entrainment by exogenous zeitgebers to keep to the 24 hours day night cycle
HOWEVER, psychologists criticise the use of artificial light in isolation experiments on the circadian sleep wake cycle (e.g Siffre 1975), suggesting that it disrupts the measurements of the free running circadian cycle
-In an experiment that controls for artificial light, Czeisler (1999), it was found that the sleep-wake cycle was closer to 24 hours, with a little drift

Question 8

Vetter (2011) office worker blue light vs natural light

Answer 8

-Vetter (2011) when an experimental group of 27 office workers were exposed to strong blue light in the office, their circadian rhythms shifted to match the lights of the office
-Compared to a control group of 27 office workers who who’s circadian rhythm continued to match the natural light of dawn
-These results not only suggest that light is an exogenous zeitgeber, but also suggests that artificial light can affect the endogenous pacemaker of the sleep-wake cycle by overriding natural light as the primary exogenous zeitgeber

Question 9

Ralph (1990) tau hamsters mutation removed SCN

Answer 9

-Ralph (1990) destroyed the SCN of hamsters with the tau mutation (this mutation causes hamsters to have a 20-hour sleep-wake cycle as opposed to the 24-hour cycle of normal hamsters)
-He then replaced the destroyed SCN with the SCN of a normal hamster
-After this procedure, he found that these hamsters gained a 24-hour sleep-wake cycle
-Additionally, when normal hamsters were given the SCN of hamsters with the tau mutation, they gained a 24-hour sleep-wake cycle
-This suggests that the suprachiasmatic nucleus is the main endogenous pacemaker of the sleep-wake cycle

Question 10

Economic implications of Circadian Rhythms (STRENGTH)

Answer 10

-Research into circadian rhythms has economic implications as it can be useful in helping psychologists develop treatments for jet lag (e.g improving the performance of athletes on the road) and improve the productivity of shift workers; increasing their contributions to the economy