biopsychology - biological rhythms Flashcards
what is a circadian rhythm (2 examples)
biological rhythm that is subject to 24 hour cycle, regulates many body processes eg. sleep/wake cycle + body temperature./
what is an infradian rhythm (2 examples)
biological rhythm with a frequency of less than one cycle in 24 hours. eg. menstruation and seasonal effective disorder
what is an ultradian rhythm ( 2 examples)
frequency of more than one in 24 hours eg. sleep/wake cycle and heart rate
outline the flow diagram of how light affects the sleep wake cycle
light detected by retina in eye —> signal travels to optic chiasm —> signal to hypothalamus —> signal to suprachiasmatic nucleus —–> stimulates pineal gland to secrete either serotonin (if light present) or melatonin (if no light)
when is body temp at it’s lowest and highest (example of circadian rhythm) + what is link to sleep
is at its lowest in the early hours of the morning (4:30 am) and at its highest in the early evening (6 pm) . Sleep typically occurs when the core temperature starts to drop, and the body temperature starts to rise towards the end of a sleep cycle promoting feelings of alertness first thing in the morning.
what is the exogenous zeitgeber for sleep/wake cycle
most common is light, can be social cues such as mealtimes, activities
what is the endogenous zeitgeber for sleep/wake cycle
suprachiasmatic nucleus
what did Siffre investigate?
circadian rhythms and the effect of exogenous zeitgebers (light) on the system.
outline Siffre’s methodology
spent 6 months underground where he was derived of natural light. This was done to investigate the effect of lack of light on his biological rhythm. To achieve he measured brain waves, blood pressure and body temp at standardised times of the day.
What did Siffre find about his biological clock when exposed to a lack of natural light
His biological clock free ran, this was evident when he resurfaced and believed the date to be a month earlier than it was. His 24-hour sleep-wake cycle was increased by the lack of external cues, making him believe one day was longer than it was, and leading to his thinking that fewer days had passed
what conclusions can be made about circadian rhythms from Siffre’s research
in absence of exogenous zeitgebers the internal body clock free runs, there is a need for EZ to entrain our body clock
what is the methodology of Aschoff and Wever’s study
group of pps spend 4 weeks in world war 2 bunker deprived of natural light, all but one pps (whose cycle extended to 29 hours) stayed within 24 and 25 hours.
what conclusions can be made from Aschoff and Wever’s study
evidence of a strong free running circadian rhythm our natural sleep wake cycle may be slightly longer than 24 hours but is entrained by our 24 hour day, there are individual differences in the need for exogenous zeitgebers to entrain our internal body clock. Some people need them more than others.
what is the validity problem with both Aschoff and Wever’s study and siffre study
Pps are not 100% deprived of EZ. Siffre used an artificial light in the cave which would stimulate the production of serotonin. Aschoff - pps would be influenced by the sleep cycle of other people providing social cues of when to go to bed. As cannot fully remove effect of EZ this decreases the validity of the conclusions made.
what was the benefit of Siffre’s methodology
took valid measures for proof of circadian rhythms - (blood pressure, temperature ect.) this provides a comprehensive set of data used to validate the changes in the sleep wake cycle over months in the cave.
