Biopsychology-Biological rhythms- TB Flashcards
What are biological rhythms?
Patterns of change in body activity that conforms to a cyclical period
What is a circadian rhythm?
A biological rhythm that lasts around 24 hours
What is the main circadian rhythm?
Sleep-wake cycle
What drives biological rhythms?
Internal body clock
What is the internal body clock that drives biological rhythms?
Endogenous pacemaker
What are external changes in the environment that drives biological rhythms?
Exogenous zeitgebers
What synchronises circadian rhythms?
Master circadian pacemaker= Suprachiasmatic nuclei (SCN) in the hypothalamus
What is photoentrainment?
Light providing the main input to the body clock
How does light impact the body clock?
Light sensitive cells in eyes detect brightness & send messages to SCN, which uses info to coordinate activity of circadian rhythm (e.g. more awake)
How many points are there when explaining the sleep-wake cycle as a circadian rhythm?
6
What is the first point of the sleep-wake cycle?
Light & dark= main external signals for sleep/wake
What is the second point of the sleep-wake cycle?
Dips and rises in key times- strong sleep = 2-4am & 1-3pm
What is the third point of the sleep-wake cycle?
Homeostatic control- tells us to sleep if awake for long
What is the fourth point of the sleep-wake cycle?
Circadian system helps keep us awake in daylight but homeostatic=sleepier
What is the fifth point of the sleep-wake cycle?
Influenced by daylight too
What is the sixth point of the sleep-wake cycle?
If left to own devices & no external cues present, it is “free running” e.g. Michel Siffre
What are two other circadian rhythms?
1) Core body temperature- lowest at 4:30am, highest at 6pm, sleep starts as temp drops
2) Hormone production- Pineal gland in brain produces & releases melatonin- peak during dark & encourages sleep
What was the aim of Michel Siffre’s study?
To study the influences on circadian rhythms
What was Michel Siffre’s procedure?
2nd study- lived in a cave (no light) for 6 month, so that the only thing influencing him was his internal body clock
What were Michel Siffre’s findings?
His natural circadian rhythm was 48 hours when young, and just over 24 hours when older (66) but with dramatic variations
What does the homeostatic drive do?
Causes increase in need for sleep, throughout the day
When is sleep drive strongest?
Between 2-4am and between 1-3pm
What is melatonin?
Produced by the pineal gland in the brain in response to darkness (sleepier)
How long are ‘free running’ circadian rhythms?
24-25 hrs
What do some suggest is the most important factor in circadian rhythms other than light?
Body temperature more important as it sets timings for cells