Biological Rhythms

Question 1

Morgan

Answer 1

Removed the SCN from hamsters and found this resulted in a disappearance of their circadian rhythm. The circadian rhythm could be re established by transplanting SCN cells from foetal hamsters, supporting the central role of the SCN as a pacemaker.

Question 2

Morgan and Ralph

Answer 2

Transplanted SCN cells from mutant hamsters ( those who were bred to have shorter cycles than 20 hours) and found that transplanted hamsters took the mutant rhythm. When transplanting SCN normal 24 hour cycle to mutants, the mutant hamsters took the 24 hour cycle within 6/7 days and the recipients rhythm no longer matched their own genes but the genes of SCN donors. Supports the central role of SCN as an endogenous pacemaker.

Question 3

Siffre

Answer 3

Spent 6 months in a cave with no natural sound or light. Initially he experienced a erratic sleep wake cycle, however settled into a regular pattern of a 25 hour circadian rhythm rather than a 24 one. Concluded that endogenous factors can influence sleep wake cycles in the absence of light. Main zeitgeber in the study was light, presence of light is necessary for the biological rhythm to be coordinated with the outside world - exogenous factors can also influence biological rhythms

Question 4

Aschoff and Weaver

Answer 4

Human endogenous pacemakers tend to run slightly slower than 24 hours and needs to be synchronised each day through exogenous zeitgebers

Question 5

Luce and Segal

Answer 5

People who live in arctic would sleep for 6 months if their cycle was only controlled by endogenous factors. However, they found that they slept for 7 hours a night and social customs have become their dominant zeitgeber.

Question 6

De Coursey

Answer 6

30 chipmunks had their SCN removed and then returned to their natural habitat. After 80 days, found that significantly more chipmunks had been killed compared to the control group with intact SCN. Suggesting that the chipmunks were killed as they stayed awake, therefore to rely solely on exogenous factors could threaten survival.

Question 7

Dement and klietman

Answer 7

When participants were woken from REM stage 5 sleep they reported dreams about 80% of the time. Whereas for NREM it was approx 20% where dreams were less vivid and fragmented. Consequently REM was referred to as the dreaming sleep.

Question 8

Dement

Answer 8

Experimental group were awoken every time they were entering REM sleep. The longer then experimental group were deprived of REM the more attempts were made to enter it. When allowed to sleep uninterrupted their REM increased over the next 5 days until they recovered what they had lost (REM Rebound). REM is essential stage of sleep and it’s nature is not just passive state but a sequence of highly organised stages that vary in importance .

Question 9

Oswald

Answer 9

Observed patients recovering from drug overdoses and found a significant increase in the amount of REM sleep suggesting it was indicative of brain restoration.

Question 10

Reinberg

Answer 10

Young woman spent 3 months in a cave relying on the dim light of the miners lamp, her days increased to 24.6 and her menstrual cycle decreased to 25 days and took a year to return to normal, implies infradian rhythms are influenced by exogenous factors.

Question 11

Mc Clintock

Answer 11

Suggested that synchrony in the menstrual cycle between women is produced by pheromones

Question 12

Reinberg

Answer 12

Young woman spent 3 months in a cave relying on the dim light of the miners lamp, her days increased to 24.6 and her menstrual cycle decreased to 25 days and took a year to return to normal, implies infradian rhythms are influenced by exogenous factors.

Question 13

Mc Clintock

Answer 13

Suggested that synchrony in the menstrual cycle between women is produced by pheromones

Question 14

Schank

Answer 14

Studied the occurrence of menstrual cycles in 186 Chinese women living in uni accommodation over one year. Found no evidence that women synchronised their cycles.

Question 15

Savage and West

Answer 15

The brains metabolic rate is the key variable. They found that in 96 species BMR was positively correlated with sleep, but a stronger positive relationship exists between Brian metabolic rate and sleep, in fact brain mass is positively correlated REM sleep.

Question 16

Zeppelin

Answer 16

Studied the relationship between sleep length and metabolic rate and found a negative correlation between body size and total sleep time.

Question 17

Morin

Answer 17

Although poor sleepers and good sleepers reported the same levels of minor stressful life events,insomniacs rated the impact of daily minor stressors and the intensity of major life events more highly than good sleepers. Insomniacs perceived lives to be more stressful and reported greater levels of pre sleep arousal than good sleepers. Suggesting that the key factor in insomnia is the way people perceive stressors and the perceived lack of control over stressful events rather than the number of stressful events.

Question 18

Vgontza

Answer 18

Found an association between insomnia and increased Stress related hormones (ACTH and cortisol). They suggest that for insomniacs a disorder of hyper arousal in the CNS caused by chronic activation of the hypothalamic pituitary gland which leads to increased risk of chronic anxiety. Consequently treatment should be based on decreasing psychological and emotional arousal not just treating sleep.

Question 19

Monti

Answer 19

Many cases of insomnia could be treated by treating the underlying cause suggesting that some forms of insomnia are a result of other illnesses and are not an illness in themselves as primary insomnia is.

Question 20

Lundh

Answer 20

Found the predominant factor in persistent insomnia patients is psychasthenia with high scores of anxiety, often have low self esteem and are over dependant on others. These factors suggest that personality factors play a role in causing and maintaining insomnia.

Question 21

Hublin

Answer 21

Found sleepwalking to be more common among children with up to 20% being affected. In adults it’s about 2% suggesting it’s to do with maturation and development.