Biopsychology - Biological rhythms

Question 1

Define endogenous pacemakers

Answer 1

Internal body clocks that keep biological processes to time

Question 2

Define exognenous zeitgebers

Answer 2

External cues that entrain internal body clocks, meaning altering body clocks to match the environment

Question 3

What is a circadian rhythm?

Answer 3

A biological rhythm that lasts around 24 hours

Question 4

What do we have circadian rhythms for?

Answer 4

Regulating sleep and wake, the release of hormones, and varying our body temperature and blood pressure

Question 5

What is the sleep wake cycle? What does the cycle require?

Answer 5

A pattern of sleep and wakefulness that repeats every 24 hours. There must be an endogenous pacemaker that keeps this pattern and we are aware of conflicts between the EP and exognenous zeitgebers like light and social cues in situations like jet lag. The EP will be entrained by the EZ’s to the new time zone, but it can take several days.

Question 6

What is the endogenous pacemaker for the sleep-wake cycle?

Answer 6

Suprachiasmatic Nucleus (SCN)

Question 7

What is the SCN , location and function?

Answer 7

It is known as the master clock. It is part of the hypothalamus within the limbic system. It is located at the optic chiasm, the point on the optic nerves where they cross. When light is detected by the SCN it sends light to the pineal gland, stopping the production of melatonin, a hormone that results in a sleep response.

Question 8

What is the main exogenous zeitgeber in the sleep wake cycle?

Answer 8

Light

Question 9

Apart from light, name other exogneous zeitgebers in the sleep wake cycle.

Answer 9

Social cues like, meal times, exercise, when others go to bed, or environmental cues like clocks

Question 10

What did Siffre test?

Answer 10

The circadian sleep wake cycle endogenous pacemaker is thought to be free running, maintaining a predictable cycle without constant entrainment by exogenous zeitgebers.

Question 11

How did Siffre test if the circadian rhythm was free running? Findings?

Answer 11

Siffre spent 179 days (6 months) in a cave with no natural light or other potential EZ’s such as clocks or social cues.

Siffre’s body clock (EP) maintained a regular cycle of around 25 hours without EZs, longer than the expected 24-hour cycle. Suggesting the EP for the sleep wake cycle is free running but needs entrainment to keep to the 24-hour day/night cycle.

Question 12

Explain criticism of natural light isolation studies. What did Czeisler find ?

Answer 12

Psychologists have criticised the use of artificial lights in isolation experiments on the sleep wake cycle, suggesting the artificial lights disrupted measurements of the free-running circadian rhythm by acting as an EZ. In a study controlling for artificial light, Czeisler found the circadian rhythm was closer to 24 hours, with little drift.

Question 13

What was Vetter’s procedure and findings?

Answer 13

27 office workers in an experimental group were exposed to strong blue light, their circadian rhythms would shift to match the office lighting. A control group of 27 office workers with normal office lighting, rhythm’s matched the shifting time of the natural light of dawn.

Strongly suggests that light is an EZ and artificial lights can disrupt the endogenous pacemaker by over-riding natural light as the primary EZ.

Question 14

What was Ralph’s procedure and findings?

Answer 14

Golden hamsters with the Tau mutation have a circadian rhythm of 20 hours compared with 24 hours for normal golden hamsters.

The SCN from normal hamsters was transplanted into the brain of Tau mutant hamsters, these hamsters gained a sleep wake cycle of 24 hours.

The normal hamsters gained a 20- hour cycle when given the SCN from Tau mutant hamsters. This suggests the SCN is the main endogenous pacemaker in the sleep wake cycle.

Question 15

Strengths of the circadian rhythm

Answer 15

+ Sleep pattern disruption can lead to anxiety and decreased alertness. Therefore, having an understanding will lead to solutions to the negative effects of jet lag and shift work which will result in psychology having a positive effect on the wider economy.

+ Understanding the circadian blood pressure rhythm, helps with timing drug treatments and health treatments

+ Knowing the psychological effects of exposure to light, particularly blue light has had implications as technology changes, we are exposed to more blue light late at night from personal devices and LED road lighting. This provides people with advice on how to maintain a healthy sleep pattern.

+ There is an evolutionary explanation for the day/night cycle of humans and other animals specialised for day time activity. We are not specialised for night time activity, so we have a sleep period at night to protect us from accidental harm and predators.

Question 16

Limitations of circadian rhythms

Answer 16

• Use of case studies and small samples in isolation investigations - Siffre’s results may not be able to be generalised to the wider population, especially as individual differences in the duration and stages of circadian rhythms have been shown, hence his results may lack ecological validity. Even Siffre himself noted that as he grew older, his endogenous pacemaker ticked at a slower rate, which may have acted as an uncontrolled confounding variable in his investigations.
• Confounding effect of artificial light - Psychologists have criticised the use of artificial lights in isolation experiments on the sleep wake cycle, suggesting the artificial lights disrupted measurements of the free-running circadian rhythm by acting as an EZ. In a study controlling for artificial light, Czeisler found the circadian rhythm was closer to 24 hours, with little drift.

Question 17

What is an infradian rhythm?

Answer 17

A biological process that repeats less frequently than once every 24 hours (e.g weeks/months)

Question 18

What is an ultradian rhythm?

Answer 18

A ultradian rhythm is a biological process that repeats more frequently than once every 24 hours (e.g minutes/ hours)

Question 19

What is an ultradian rhythm?

Answer 19

A ultradian rhythm is a biological process that repeats more frequently than once every 24 hours (e.g minutes/ hours)

Question 20

Give examples of infradian rhythms

Answer 20

Menstrual cycle of fertility
Seasonal affective disorder (SAD)

Question 21

What is seasonal affective disorder

Answer 21

An infradian rhythm that takes a year to complete. Emotional mood lowers in winter and improves in summer. It is suspected this is due to the lack of bright sunlight in winter.

Question 22

Describe the menstrual cycle

Answer 22

A 28 day cycle with a 6 day period of fertility, however cycles can be shorter or longer ranging between 24 and 35 days

Question 23

Name some of the biological aspects of the menstrual cycle

Answer 23

Releasing the egg (ovulation), thickening of the womb lining and losing the womb lining during menstruation.

Question 24

What regulates the biological changes that happen during the menstrual cycle?

Answer 24

Regulated by the hormones: oestrogen (pre ovulation) and progesterone (post ovulation) . The levels of these hormones act as endogenous pacemakers keeping the biological processes to time, acting as an internal body clock for the menstrual cycle

Question 25

Strengths of research about the menstrual cycle/ infradian rhythms

Answer 25

+ McClintock = studied 135 women who lived in the same dorm at uni, recorded period onset and duration. Found that women appeared to synchronise their cycles with their friendship groups . Russel found similar findings when women cohabitate.

+ Stern and McClintock = investigated if synchronisation was due to women sharing pheromones. 20 women were given pads to wipe on their top lip each day. The pads had been taken from the armpits of 9 donor women at different stages of their MC. Found that the women would either shorten or extend their MC to match the donor , depending on when in the donor’s MC the pad had been collected. Suggests synchronisation due to the presence of pheromones, acting as an exogenous zeitgeber, an external cue.

+ Evolutionary theories suggest that synchronisation is advantageous, a way to stop one male dominating a group and having all the children, being unable to impregnate all the women at once due to synchronisation, leading to genetic diversity in small human groups.

Question 26

Limitations of Infradian rhythm

Answer 26

• Pheromones as chemical messengers are not accepted widely as a process that happens in humans.
• There have been some replications of McClintock study with positive results there have been a number showing no sychronisation, including Trevathan showing cohabiting lesbian couples did not synchronise, the optimal conditions for possible synchronisation.
• As menstrual cycles can vary in length, women can appear to synchronise just due to their variability in their cycles, something not taken into consideration in all of the studies showing positive results.
• Some evolutionists argue that sychronisation of MCs is not an advantageous adaption but instead it is maladaptive due to women wanting to be fertilised by the male with the best genes, and needing to compete with other women for him if they sychnronised.

Question 27

What are the five distinctive patterns of brain wave?

Answer 27

Delta, theta, alpha, beta, and gamma

Question 28

What type of brain waves distinguish sleep stages?

Answer 28

Theta and Delta

Question 29

How many stages of sleep are there?

Answer 29

Four stages

Question 30

What are the first three stages of sleep called?

Answer 30

Non-REM or NREM, termed N1, N2 and N3

Question 31

What is the fourth stage of sleep called ?

Answer 31

REM (rapie-eye-movement) where most dreams occur

Question 32

How long does one sleep cycle take? How many times does it repeat?

Answer 32

Once cycles takes about 90 minutes and repeats 4-5 times over the course of a night’s sleep

Question 33

Describe what happens in N1?

Answer 33

'’falling asleep sensation. Easy to wake and the body may move suddenly (hypnic jerks) . There may be a sensation of falling, mild auditory or visual hallucinations.

Question 34

What does the EEG show for N1?

Answer 34

Theta waves, slow frequency , but high amplitude in comparison to being awake

Question 35

Describes what happens in N2

Answer 35

Deeper than N1. Harder to wake, the body is relaxed, heart rate and body temperature are lowered and the eyes are still.

Question 36

What does the EEG show for N2?

Answer 36

Shows slow Theta, but occasional activity called sleep spindles and K complexes

Question 37

Describe what happens in N3

Answer 37

Deepest sleep. Very difficult to wake, body at its most relaxed with heart rate at its lowest .

Question 38

What does N3 look like on the EEG ?

Answer 38

Slow frequency and large amplitude delta waves (slow wave sleep)

Question 39

Describe REM stage of sleep

Answer 39

Brain returns to active state passing back through N2 and N1, REM is similar to wakefulness as seen on the EEG however the body is paralysed. Characterised by rapid eye movement, and associated with dreaming, as when woken people will report vivid dreams in this stage.

Question 40

After the REM stage, what happens to the brain?

Answer 40

The brain returns to N1 after REM, repeating the cycle up to 5 times in one night. Each cycle tends to include a larger proportion of REM sleep and shorter duration of N3.

Question 41

strengths of Stages of sleep

Answer 41

+ Dermot and Kleitman
Study 1 =EEG recordings of 33 ppts over a night’s sleep. Brain waves followed a cyclic pattern of activation, with bodily relaxation occurring during slow wave sleep and REM during periods of high activation.
Study 2= 9 ppts woken at different stages in their sleep cycle reported dreaming more frequently when woken in the REM stage.

+ Shapiro
Found ultramarathon runners showed longer sleep after intense physical activity . Also an increased proportion in slow wave sleep, suggesting N3 is for physical recovery of the body

+ Haider
EEG of 10 patients recovering from drug overdose showed increased REM sleep, suggesting REM is for mental recovery

+ Technology and devices based on understanding sleep stages have been developed. These track sleep and help individuals improve sleep. Avoiding waking in REM stage stops people feeling groggy and disorientated. This technology leads to happier, healthier and a more economically productive population

+ The development of more sophisticated EEGs , and other techniques is improving our understanding of the new sleep cycle, leading in 2007 to combining stages 3&4 into the new N3 stage.

Question 42

Limitations of sleep stages

Answer 42

• The overall pattern of sleep stages is consistent however there are more individual differences e.g newborn babies spend 80% of sleep in REM compared to 20-25% in adults. Suggests stages of sleep are not a simple process but adapt to the developmental needs of the individual.
• Circadian and ultradian rhythms seem to be connected and perhaps shouldn’t be seen as separate processes, Czeilser showed the longest period of REM sleep coincides with the lowest point in the circadian body temperature cycle. Could mean both processes could use the same internal body clock also know as the as the endogenous pacemaker (SCN)