Biologic Rhythms Flashcards
Define Biological rhythms
Body Rhythms are biological processes that show cyclical variation over time
Define Circadian
Around 24 Hours, it is the sleep/wake cycle
Define Endogenous Pacemaker
Internal Clock
Is spontaneously generated from an indivuduals internal state.
Define Exogenous Zeitgeber
External Factors
Light levs such as sun night and day as well as clocks tells the time of day.
Explain Circadian Rhythms
Often referred to as the “body clock,” the circadian rhythm is a cycle that tells our bodies when to sleep, rise, eat—regulating many physiological processes. This internal body clock is affected by environmental cues, like sunlight and temperature
The Role Of The Suprachiasmatic Nuceaus in The Sleep/Wake Cycle
Light enters the retina even when eyes are closed.
Information sent via neural pathway to the SC.
The SCN is located in the hypothalamus.
Information is then sent via another neural pathway to the pineal gland.
The pineal gland is located deep within the brain.
Low light cues are detected in the SCN which triggers the pineal gland to release melatonin
Levels of melatonin rise
Sleep
The Role Of The Suprachiasmatic Nucleus
Melatonin is released by the Pineal gland in the absence of light cue, but the circadian cycle disappears if the SCN is destroyed.
Sleep Study - Siffre
Michel Siffre (1972) was a french cave explorer He spent Seven months underground with no cues as to the time of day He organised his life into a fairly normal pattern of alternating periods of activity and sleep He was linked upto a computer and video camera, to scientists on the surface, to monitor his physiological functions and state of mind For every day that passed he rose an hour later, the clock in his brain was running a little slower. He developed a 2 hour day (Not 24H)
What does the study of Siffre suggest about biological rhythms?
Physical activity (Sleep/Wake) providing support for endogenous
What does the study of Siffre suggest about biological rhythms?
Physical activity (Sleep/Wake) providing support for endogenous pacemaker. Exogenous Zeitgeber can influence pacemaker
Evaluation of Siffre Study
- Case Study:
- Rich Data
- Individual Differences
- Cant Generalise
- Control Environment:
- Control Extraneous variables
- Establish Cause and Effects
Lacks Mundane Realism
The Tale Of The Mutant Hamsters
There is strong evidence for the importance of the SCN in maintaining the circadian rhythm.
When the SCN cells are removed from the brin and kept in the laboratory, they follow a cycle of neural activity lasting approximately 24.5 hours.
Breds of mutant Hamsters with a 20 hour rhythm had transplanted SCN cells from normal hamster foetuses who were born displaying the mutant 20 hour cycle. They also transplanted normal SCN tissue into the mutant hamsters who started to sow a 24 hour cycle within a week.
Practical Application To Shift Work
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 into the relationship between shift work and poor health show shift workers are three times more likely to develop heart disease, which may be due to the stress of adjusting to different sleep/wake patterns and the lack of poor quality of sleep.
Thus, research into the sleep/wake cycle may have economic implications in terms of how best to manage worker productivity.
Weakness of Circadian Rhythms - Individual Differences
A case for individual differences in circadian rhythms. Morning people preferred to rise early and go to bed early (6am and 10pm) while evening people prefer going to sleep and wake up late (10am and 1am) showing peoples circadian rhythms could vary from one another.
Real World Application
One real world application of circadian rhythms is chronotherapeutics - the study of how timing affects drug treatments.
The specific time that patients take their medication is very important as it can have a significant impact on treatment success. It is essential that the right concentration of a drug is released in the target are of the body at the time that the drug is most needed.
For example, the risk of heart attack is greatest during the early morning hours after awakening, and so chronotherapeutic medications have been developed with a novel drug delivery system. These medications can be administered before the person goes to sleep at 10pm, but the actual drug is not released until the vulnerable period of 6am to noon.
Discuss and Research Into The Circadian Rhythm
A01: Sleep Wake Cycle - Example of Circadian Rhythm) SCN - Endogynous pace maker A03: Mutant Hamster
A01: Outline Siffre's Research A03: Evaluation of Siffre: Sample Bias, Individual Differences
Define Infradian Rhythms
an infradian rhythm is a rhythm with a period longer than the period of a circadian rhythm
Two Examples of Infradian Rhythms
Menstrual Cycle
Hibernation
Endogenous Pacemaker and the Menstrual Cycle
The Pituitary Gland governs the phrases of the menstrual cycle by influencing changes in the endometrium (Wall of the uterus)
Briefly Explain the Hormones in the menstrual cycle
The hormone LH causes the mature egg to be released from the ovary. This image shows how the level of oestrogen changes during the menstrual cycle. Progesterone is another hormone secreted by ovaries: it maintains the lining of the uterus and stays high during pregnancy.
Explain Pre-Menstrual Syndrome
is used to describe a variety of behavioural and emotional effects which occur at several phases of the cycle.
PMT occurs in all cultures suggesting a physiological cycle rather than an environmental influence.
Deterministic View - Infradian Rhythm
Ms. English Drove a car into her husbands house, and blamed it on PMS. Supported by Dr Katherina who said ‘Women are not responsible for their actions on PMS’
Free Will View- Infradian Rhythms
One Study Found people who were told to wake up earlier had higher levels of the stress hormone ACTH, which contributes to them waking up, causing them to wake earlier
Research Into Exogenous Zeitgebers - Russell (1980)
It was found that female menstrual cycles became synchronised with other females through odour exposure.
In one study, sweat samples from one group of women were rubbed onto the upper lip of another group. Despite the fact that the two groups were separate, their menstrual cycles synchronised.
This suggests that the synchronisation of menstrual cycles can be affected by pheromones, which have an effect on people nearby rather than on the person producing them.
These findings indicate that external factors must be taken into consideration when investigating infradian rhythms and that perhaps a more holistic approach should be taken, as opposed to a reductionist approach that considers only endogenous influences.
