Biological Rhythms Flashcards
Give 3 examples of biological rhythms that govern behaviour.
Sleep-wake cycle
Pregnancy.
Reproductive behaviour, e.g. battery chickens.
Menstrual cycle.
Homeostasis, e.g. temperature.
Hibernation, e.g. bears.
Physical changes in plants, e.g. mimosa plants, prayer plants.
What are biological rhythms?
A biological rhythms is a change in body processes or behaviour in response to cyclical time periods.
What 2 things are biological rhythms influenced by?
Internal body clock (endogenous pacemakers)
External environment (exogenous zeitgebers)
How long does a biological rhythm last?
Some of these rhythms occur many times a day.
Some take longer than a day to complete.
In some cases, take a very long time.
What does ‘Circadian’ mean?
Circa: Circular
Diem: Day.
What is a Circadian rhythm?
Physical, mental, and behavioural changes that follow a roughly 24-hour cycle, responding primarily to light and darkness in an organism’s environment.
How long does a Circannual rhythm last? Give an example of one.
A year.
E.g. flowering, hibernation.
How long does a Circalunar rhythm last? Give an example of one.
A month.
E.g. Spawning of tropical corals
How long does a Circatidal rhythm last? Give an example of one.
A change of tide (2 high, 2 low (in 24hrs)).
E.g. clams.
How long does a Circadian rhythm last? Give an example of one.
A day.
E.g. Sleep-wake cycle.
The sleep-wake cycle is an example of a circadian rhythm, how is this usually measured?
By reading the time and regular events like when we eat and go to sleep.
What is the study of circadian rhythms called?
Chronobiology.
What is the main feature that the human body clock regulated by? What other factors also contribute?
Regulated by endogenous pacemakers
Including other factors such as:
Release of hormones like melatonin.
Cortisol.
Metabolic rate.
Body temperature.
Natural light, (exogenous zeitgebers).
Social time cues, (exogenous zeitgebers).
Give an example of how humans demonstrate the effect of daylight.
We feel drowsy when it’s night-time and alert during the day.
What is a Mimosa plant? What do they do?
A creeping annual flowering plant.
Its sensitive leaves fold inward and droop when touched or shaken.
Outline the 1729 study by Jacques d’Ortous de Mairan.
Demonstrated that endogenous pacemakers still function without the cues from the environment when placed in a box that let no light in.
What were the aims of Siffre’s 1975 study.
The aims of the study were to find out what it would be like for astronauts in space, where there were no exogenous zeitgebers such as daylight to affect our biological rhythms.
Siffre wanted to find out what his natural sleep-wake cycle would be without any exogenous zeitgebers.
What was the procedure of Siffre’s 1975 study.
He took a supply of frozen food and 780 gallons of water into the cave.
When Siffre woke up and thought it was daytime, he phoned the research team above ground, and they switched on the lights in the cave.
He conducted daily experiments, taking his blood pressure, memory, and physical tests.
When he felt tired, he thought it was then night time; he would phone the research team again, informing them he thought it was night and they would turn the lights off, and Siffre would go to sleep.
What were the findings of Siffre’s 1975 study.
After 9 weeks, his sleep-wake cycle became more varied and random again for 20 days.
When his sleep-wake cycle varied, the cycle could be from 18–52 hours.
On day 150, he returned to a 26-hour cycle that lasted until the experiment’s ended.
What was concluded from Siffre’s 1975 study.
Siffre concluded that time is not something humans could work with and understand without any external environmental cues.
What did Siffre think about astronauts, in reference to his study?
Siffre thought astronauts could manage their biological rhythm without exogenous zeitgebers; however, they would need companionship as the isolation would not be manageable.
