Biological rhythms Flashcards
what is an endogenous pacemaker
internal body clocks that play a main role in controlled biological rhythms
what is an exogenous zeitgeber
environmental factors that synchronise biological rhythms with the outside world
e.g light
what is a circadian rhythm
a bodily rhythm that lasts 24 hours e.g sleep wake cycle
what is an ultradian rhythm
a rhythm that lasts less than 24v hours
e.g sleep pattern
what is an infradian rhythm
a rhythm that lasts longer than 24 hours
e.g SAD (season affectiveness disorder)
How does the sleep wake cycle work when you’re tired
When no light (exogenous zeitgeber) is perceived by the eyes.
A message is sent to the SCN (endogenous pacemaker) to produce melatonin
The SCN instructs the pineal gland to produce melatonin
When melatonin is produced it makes us feel tired inducing sleep
Explain the sleep wake cycle when awake
Light is perceived by the retina within the eye. A message is sent to the SCN so as not to produce melatonin the SCN obstructs the pineal gland not to produce melatonin so we stay awake
What are desynchronised rhythms
Cycle is out of sync
E.g Jet lag
What are desynchronised rhythms
Cycle is out of sync
E.g Jet lag
What are symptoms of desynchronization?
Constant tiredness
Attention worsens
Memory is poor
Agitated
Who researched circadian rhythms
(2 separate researchers 2 separate studies)
Siffre
Ralph et al
What did Siffre study
The human body clock by spending time in a cave with no external cues (clocks,light etc)
What happened during Siffres stays in the caves
He ate, slept, awoke when he felt like it with nothing influencing him apart from his internal body clock
What did Siffre find after his first stay in the cave
He resurfaced on September 17th thinking it was August 20th
What did Siffre find after his second stay in the cave
His natural circadian rhythm had settled down to just over 24 hours but sometimes changed to 48 hours
He also found his internal body clicked slowly compared to when he was a young man (from the first cave)
What animal did Ralph et al mutate for his experiment into circadian rhythms
Hamsters 🐹
What did Ralph ET al do to the hamsters in his study into circadian rhythmes
He gave the hamster a SCN that lasts 20 hours
What did Ralph find after transplanting the new SCN to the hamster
He going that the hamsters rhythm changed from 24 hours to 20 hours suggesting SCN governs cycle length
What is SAD (season affectiveness disorder)
This is where people become depressed in the winter — due to it being dark therefore produce more melatonin leading to less seretonin being produced
Lack of seretonin can cause depression
Who researched infradian rhythms
Eastman
What was the procedure of Eastmans research into people with SAD
96 p.t with SAD
Randomly assigned to one of three groups
1hr 30 mins of bright light in the morning
1hr 30 mins of bright light in the evening
Morning placebo ‘light’
What did Eastman find when researching infradian cycles such as SAD
Those with the morning treatment showed significantly more complete remission of their symptoms
Response to evening light was better than placebo but not same level of significance as morning light
How is our sleep pattern an ultaradian rhythm
Our sleep pattern is made up of 5 stages lasting 90-100 minutes
What are characteristics of stage 1 and 2 of our sleep cycle
Alpha, theta waves
Slow heart rate
Low temperature
What are characteristics of stage 3 and 4 of our sleep cycle
Slow wave sleep with delta waves
Metabolic rate slows
Growth hormone is released
Deep sleep
What are characteristics of REM sleep
Shows awake brain traits with the eye and brain being active but body is paralyzed
Who researched ultradian rhythms
Dement and Klietman
Who researched ultradian rhythms
Dement and Klietman
What was the aim of Dement and Klietmans investigation into ultradian rhythms
Investigate the change in brain with the different stages of sleep
What was the procedure of Dement and Klietmans research into ultradian rhythms
Monitored 9 adults sleep patterns in a sleep lab — EEG recorded brainwave activity
What were the findings of Dement and Klietmans research into ultradian rhythms
REM highly correlated with dreaming
Brain activity varied according to how vivid the dreams were p.t were woken during REM had the most accurate recall
What is a limitation of biological rhythms
P: a limitation of circadian rhythms is it’s based on case studies
E: in 1999, Siffre repeated his study and found that his internal body clock was slower therefore different results could be produced by the same person
E: suggesting circadian rhythms may not be representative of the wider population
L: therefore we should show caution when generalizing findings
What is a strength of biological rhythms
P: A strength of circadian rhythms is the supporting research
E: for example Ralph et Al’s research using a mutated hamster that had a SCN that lasted 20 hours instead of 24
E: they found its rhythm change suggesting the SCN governs cycle length
L; this is a strength of SCB as a determiner of circadian rhythms may as an explanation for why we sleep
