Biospychology- Circadian rhythms

Question 1

What is a biological rhythm?

Answer 1

Cyclical patterns within biological systems.

Question 2

What is a circadian rhythm?

Answer 2

Sleep-wake cycle.

Question 3

What is an endogenous pacemaker?

Answer 3

Internal mechanisms that govern biological rhythms E.G.peal gland.

Question 4

What is an exogenous zeitgeber?

Answer 4

External mechanisms that govern biological rhythms E.G.light/dark.

Question 5

How long does a circadian rhythm last for?

Answer 5

Around 24 hours.

Question 6

What is the sleepWake cycle?

Answer 6

A free running cycle controlled by endogenous pacemakers working as a body clock which is internal to our biological systems.

Question 7

What controls the sleep wake cycle?

Answer 7

The supracharismatic nucleus is a major endogenous pacemaker in mammals that controls the sleep cycle. It is in the hypothalamus where the optic nerves from the eyes crossover it gets stimulated by light that penetrate our eyelids and the SCN then regulates our sleep wake cycle.

Question 8

What is an important exogenous zeitgeber in the sleep-wake cycle and why?

Answer 8

Light and dark.
The suprachiasmatic nucleus receives information directly from the retina of the eye.

Question 9

What does the SCN do?
(Suprachiasmatic nucleus).

Answer 9

-The SCN passes the information on day length and light that it receives to the penal gland. (SCN sends messages to the pineal gland).
- During the night the Pio gland increases the production of melatonin which we know induces sleep. (Dark -night equals increases melatonin).
-Sunlight in the morning stops the production of melatonin increasing the production of cortisol which increases wakefulness. (Induces sleep).

Question 10

What is the role of homeostasis in the sleep wake cycle?

Answer 10

When an individual has been awake for a long time, homeostasis tells the body that there is a need for sleep because of energy consumption this homeostatic drive for sleep increases throughout the day.

Question 11

Explain body temperature as another example of a circadian rhythm.

Answer 11

– This is another example of a circadian rhythm. It is at its lowest at 36° at 4:30 am and at its highest at 38° at around 6 pm.
– Sleep occurs when the core temperature begins to drop and body temperatures start to rise during the last few hours of sleep promoting a feeling of alertness in the morning.

Question 12

What was the aim of Siffre’s cave study into circadian rhythms?

Answer 12

Aim: to investigate how the human body is natural circadian rhythms behave in the absence of external cues such as natural light sound and temperature fluctuations.

Question 13

What was the procedure of Siffre’s cave study into circadian rhythms?

Answer 13

Procedure:
- Siffre isolated himself in a cave for six months he had no access to natural light or external time queues.
- The cave environment was kept constant with control temperature and humidity levels he communicated with researchers outside of the cave.
– He recorded his sleep cycles body temperature and psychological state while external researchers monitored his activities remotely.

Question 14

What was the findings of Siffre’s cave study into circadian rhythms?

Answer 14

Findings:
– In the absence of external time queues , Siffre’s sleep cycle extended beyond the typical 24 hour period period to around 25 hours.
– This meant that each day lasted about an hour longer.
– When he returned, he believed the date to be a month earlier than it was.
– Despite the absence of external cues, his body maintained a regular pattern of sleeping and waking.

Question 15

What was the conclusion of Siffre’s cave study into circadian rhythms?

Answer 15

Conclusion:

– The study concluded that the human body has an intrinsic circadian rhythm which is naturally slightly longer than 24 hours typically around 25 hours.
– External cues like natural light play crucial role in resetting this internal clock to align with the 24 hour day.

Question 16

What is the further research in two circadian rhythms?

Answer 16

• Ascoff and Wever (1976) convince participants to spend four weeks in World War II bunkers derived of light.

All but one participant displayed a circadian rhythm of around 24:25 hours the other extended to 29 hours.

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-folkard conducted the study of a circadian rhythm similar to Sifre in a cave this time they had a clock to enforce strict bed and waking times what participants didn’t know was research as sped up the clock so their days but only 22 hours instead of 24

Only one participant was able to comfortably adjust to the new regime.

Question 17

What is meant by synchronisation?

Answer 17

When an individuals internal body clock is out of sync with the external environment.

Question 18

What are the consequences of synchronisation and the impact of social cues?

Answer 18

– Jetlag: this is caused by travelling across several time zones. The internal clock is not synchronised with the day and time night time rhythm so if your queues are involved adapting to local times for eating and sleeping jetlag can cause insomnia fatigue irritability and poor concentration.
– Shift work causes desynchronisation in circadian rhythm which leads to negative health effects. Regulated by social cues such as social interactions with others, mealtimes work schedules.

Question 19

What is the animal evidence relating to circadian rhythms?

Answer 19

Ralph (1990):
-Ralph bread group of hamsters to follow a shortened rhythm of 20 hour circadian cycle.
– SCN cells were removed and transplanted into the brains of a rat fetus with normal rhythms .
– When the hamsters had adopted the 20 hour cycle, their brains were then transplanted with SCN cells from the 24 hour cycle hamsters.
– When cells from the SCN were removed from rats 24 hour cycle of new activity persisted in the isolated cell.
– This shows circadian rhythms are primarily controlled by evolutionary determined biological structures.

Question 20

What is the tissue evidence for circadian rhythms?

Answer 20

Yamazaki (2001)
– Found that isolated lungs and livers and other tissues grown in a lab still persist in showing circadian rhythms.
– This suggests cells are capable of maintaining a circadian rhythm even when they are not under the control of any brain structures and that most bodily cells tuned into following a daily circadian rhythm.

Question 21

What is the innuit sleep cycle?

Answer 21

Innuit Indians who live in the Arctic Circle inhabit an environment that has hardly any darkness in the summer and hardly any light in winter.
The sleep waking cycle was primarily controlled by EZ’s they would tend to sleep a huge amount in winter and hardly at time in summer.
However, this is not the case – they maintain a fairly regular pattern of sleeping and waking all year round.

Question 22

What are the two strengths of the theory of circadian rhythms?

Answer 22

Impact of light through skin receptors
Negative impact of shift work.

Question 23

What are the limitations of the theory of circadian rhythms?

Answer 23

Methodological problems in Siffre’s study
Balancing the effect of light and temperature

Question 24

What is impact of light through skin receptors as a strength of the theory of circadian rhythms?(PEEL).

Answer 24

P: A strength of the argument that light is a powerful exogenous zeitgeber that can influence the sleep cycle comes from evidence that this occurs when detected by skin receptors rather than through the eyes.
E: Campbell and Murphy (1998) exposed 15 participants to light by having a light pad on the back of their knees at various times. This intervention managed to shift their sleep-wake cycle up to 3 hours.
E: these findings highlight the significant role that light plays in regulating biological rhythms underscoring the idea that light exposure can reset the bodies internal clock.
C: this study has been criticised because of the possible confounding varies of unintended light exposure.
L: therefore while the study provides intriguing insights its conclusions must be interpreted with caution due to these methodological concerns which could undermine the internal validity.

Question 25

Explain the negative impact of shift work as a strength of circadian rhythms.(PEEL)

Answer 25

P: a strength of research into circadian rhythms is it contribution to understanding the negative effect of sleep/weight cycle distribution.
E: Boivin et al (1996) investigated the sleep/wake cycle of Night Shift workers around 6 am he noticed decrease in concentration.
E: furthermore shift workers are three times more likely to develop heart disease (Knutson) highlighting the serious health risks associated with the circadian rhythm disruption.
L: this research has practical applications for health and safety policies in the workplace and offers economic insights into optimising work up productivity.

Question 26

What are the methodological problems in Siffre’s study as a limitation of the theory of circadian rhythms? (PEEL).

Answer 26

P: A limitation of Siffre’s cave study into the sleep wake cycle is the methodological issues presented in the study.
E: in Siffre’s there was a lack of control as he used an artificial light when in the cave this could have confounded the results as other research has shown circadian rhythms can be adjusted as a result of dim lighting.
E: he was also the researcher and the participant which means experimented by us could have been presented with the researcher influencing the result of the study.
L: this methodological issue reduces the internal validity of the results as the impact of extraneous variables means it is hard to isolate the effect of the independent variable on the dependent variable.

Question 27

What is balancing the effect of light and temperature as a limitation of circadian rhythm theories?(PEEL).

Answer 27

P: ill limitation of the argument that light is the main exogenous zeitgeber for the sleep cycle is that temperature maybe more important than light in determining circadian rhythms.
E: Buhr et al. (2010) found that fluctuations in temperature set the timing of cells in the body and caused tissues and organs to become active or inactive.
E: body temperature fluctuate on a 24 hour circadian rhythm and even small changes in it can send a powerful signal to our body clocks.
L: this shows that circadian rhythms are controlled and affected by several factors and undermines the validity of the theory that light is the only external zeitgeber for the sleep wake cycle.