biopsychology: circadian rhythms Flashcards
(25 cards)
What are biological rhythms?
Distinct patterns of changes in body activity that conform to cyclical time periods. > they are influenced by both internal body clocks and external changes to the environment.
What influences biological rhythms?
Internal body clocks (endogenous pacemakers) and external changes (exogenous zeitgebers).
define endogenous pacemakers
internal mechanisms that regulate biological functions
define exogenous zeitgeibers
external cues that influence these rhythms
What are circadian rhythms?
Patterns of behaviour that occur or recur approximately every 24 hours. > these are set and reset by environmental light levels
What are the types of circadian rhythms?
- The sleep–wake cycle
- Core body temperature
- Hormone production
What external signals affect the sleep-wake cycle?
Light and darkness > These signals act as exogenous zeitgebers that help regulate the cycle.
Does light and darkness act as an endogenous pacemaker or exogenous zeitgebers?
Exogenous zeitgebers.
What is the role of the superchiasmatic nucleus (SCN)?
It acts as an endogenous pacemaker. > The SCN is a group of neurons in the hypothalamus that regulates circadian rhythms
Where is the superchiasmatic nucleus located?
In the hypothalamus.
How are circadian rhythms synchronized?
they are driven by our body clocks and synchronised by the master circadian pacemaker, the superchiasmatic nuclei (SCN).
What must the master pacemaker constantly do?
Be reset to keep our bodies in synchrony with the outside world.
What is the primary input to the circadian system?
Light
Light is crucial for regulating the body’s internal clock.
What is photoentrainment
a process that involves setting the body clock to the correct time > it is essential for aligning biological rhythms with the day-night cycle
What type of cells in mammals are sensitive to light?
Light-sensitive cells within the eye > they act as brightness detectors
What do light-sensitive cells do with the information they gather?
Send messages about environmental light levels directly to the SCN
What is the role of the SCN in the circadian system?
Coordinate the activity of the entire circadian system
outline Siffre’s cave study
he spent extended periods of time underground to study the effects on his own biological rhythms
* He was deprived of exposure to natural light and sound but with access to food and drink
* He re-surfaced in mid September after two months in the caves but he believed it was mid August.
* A decade later he spent 6 months in a cave again.
outline Siffre’s results
In each case, his ‘free running’ biological rhythm settled down to one that was just beyond the usual 24 hours though he did continue to fall asleep and wake up on a regular schedule > this suggets we do not need external factors like light to regulate our circadian rhythm
outline Folkhard’s research
12 people agreed to live in a dark cave for 3 weeks, going to bed at 11.45 and waking up at 7.45
Over the course of the study, the researchers gradually sped up the clock so a 24 hour day would only last 22 hours.
in Folkhard’s study how many ppts adjusted to the regime
only 1/12
what can we conclude from Folkhard’s research
This suggests that without external cues such as light our internal body clock feels uncomfortable. This illustrates how powerful our internal body clock is. > it’s a strong free-running circadian rhythm that cannot easily be overridden by exogenous zeitgebers
AO3: practical application > school
The understanding of circadian rhythms has led to suggestions to shift times of the school day.
A number of researchers have recommend that the school day start a couple of hours later to fit in with the typical teenage chronotype (sleep pattern). Hormonal shifts in the teenage body mean that getting to sleep becomes more difficult and therefore adolescent students tend to be rather sleepy at the start of the school day. > Research has shown benefits for academic and behavioural performance when lessons start later in the day, including reduced dependence on caffeine
STRENGTH as schools that are aiming to improve students performance should take circadian rhythms into account when setting the time of day.
COUNTER: However, shifting the start of the day is disruptive for parents and teachers, and it limits the number of extracurricular activities after school. Also, critics of the proposal suggest that a later school day would not actually reduce sleep deprivation, it would simply mean that teenagers would stay up later and still be exhausted!
AO3: practical application > shift work
Research on circadian rhythms has provided an understanding of the adverse consequences that occurs when they are disrupted.
For example, night workers engaged in shift work experience a period of reduced concentration around 6 in the morning meaning mistakes and accidents are more likely. Research has also pointed to a relationship between shift work and poor health. For example shift workers are three times more likely to develop heart disease than people who work more typical patterns.
STRENGTH as research into sleep-wake cycle may have economic implications in terms of how best to manage worker productivity
COUNTER: Studies investigating the effects of shift work tend to use correlational methods. This means it is difficult to establish whether desynchronization of the sleep wake cycle is actually a cause of negative effects. There may be other factors. For example Solomon concluded that high divorce rates in shift workers might be due to strain of deprived sleep and other influences such as missing out on important family events. This suggests that it may not be biological effects that create the adverse effects associated with shift work
