Biological rhythms Flashcards
What are the 4 types of biological rhythms?
Circadian, Diurnal, Infradian & Ultradian
Define circadian rhythms and give an example
Circadian is a type of biological rhythm that occurs within a 24 time period, e.g., the sleep-wake cycle, these are endogenously regulated
Define infradian rhythms and give an example
These are a type of biological rhythms in a cycle occur greater than a 24hr period, e.g., menstruation (28 day cycle) & seasons
Define Ultradian rhythms and give an example
A biological rhythm that occurs within a period shorter than 24hrs
e.g., eating habits and hormone cycle
Define diurnal rhythms and give an example
A type of biological rhythm that is synchronized with a day and night cycle, it is influenced by external cues.
e.g., closing/ opening of flowers during day/night or cortisol levels
What is an endogenous pacemaker?
Is an internal cue that occurs within the body that regulates circadian rhythms
e.g., SCN
What is an exogenous zeitgeber?
Environmental cues that influence our circadian rhythms e.g., light
Tend to synchronize with EP to external time
this enables coordination between physiology and behavior for outside world
Describe the Kleitman study and the conclusions
Kleitman et al stayed in a cave for 32 days, without natural sunlight,
urine, temperature, eating & sleeping habits were measured
They found that despite darkness, they were able to keep a sleep-wake cycle to some degree
Richardson experienced a 27hr cycle, whereas Kleitman had just 24hr+ cycle
What causes differences in people’s circadian rhythms?
People’s chronotypes may cause differences. Some people are considered morning people & others as night owls
Cultural differences may also influence circadian rhythms as people eat at different meal times and sleep at different times
What helps our circadian rhythms adjust?
The main factor is sunlight, it causes us to adjust our rhythm to a 24hr period
Temperature & eating can also have an effect
SCN is closely associated with optic nerves (behind eyes) can make adjustments based on incoming light
Describe the location and function of the SCN
The SCN known as the suprachiasmatic nucleus is located in the hypothalamus in the brain. It is made of a bundle of neurons, damage to this area can disrupt the circadian rhythm. Its intrinsic rhythm is separate from the rest of the brain.
It stimulates the release of melatonin from the pineal gland, does not cause sleep, but stimulates the beginning of the process.
Melatonin peaks during sleep and then reduces, abolished by wakeup time
Describe the procedure and conclusion of the mutant hamster study
Ralph et al, swapped mutant hamsters ‘ SCNs with a cycle of 21 hrs and implanted them into normal hamsters’ hypothalamus which had a 24-hour cycle
They found that the normal hamsters took on the 21hr day/night cycle
concluding that the SCN is the dominant endogenous pacemaker
What are the effects of shift work on circadian rhythms?
It can cause irritability, lack of concentration, attention to detail, impaired judgement and ability to make decisions.
It can lead to an increase in workplace conflict, workplace accidents and mistakes being made
Is having permanent night shifts beneficial for our circadian rhythm?
Whilst our body is eventually able to adjust to night shifts it can still lead to poor sleep quality, as it is difficult to fall asleep during the day due to light, noise etc, leading to overall less sleep being had.
This leads to a reduced social life and reduces family time
How does jet lag effect out circadian rhythm?
If we are travelling from east or west, jet lag causes our endogenous pacemaker to come out of sync with the exogenous zeitgeber of light. EP needs time to adjust. EZ can make small adjustments daily, which occur gradually
Our body clock can fall behind or ahead of time depending on where we are travelling to
