Biopsych Flashcards
Endogenous Pacemaker
Internal body clocks that regulate many of our biological rhythms, such as the influence of the SCN on the sleep/wake cycle
Exogenous Zeitgeber
External cues that may affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle
EXO – outside Zeitgeber – time give
sleep wake cyle
a daily cycle of biological activity based on a 24-hour period (circadian rhythm) that is influenced by variatiosin the environment such as night and day
cicradian ryhtym
A type of biological rhythm, subject to 24-hour cycle, which regulates a number of the body processes such as the sleep/wake cycle
CIRCA - about
DIEM – day
Circadian – about a day
suprachiasmatic nucleus
The most important endogenous pacemaker closely linked to the pineal gland, both of which are influential in maintaining the circadian sleep/wake cycle.
master clock
scn and exogenous zietbergeer
SCN receives information about light levels (an exogenous zeitgeber) from the optic nerve. The SNC sends signals to the pineal gland, which leads to an increase in the production of melatonin at night, helping to induce sleep, and supresses the production of melatonin during the day (when there is a lot of light), thus making you feel more awake and alert. It has also been suggested as a causal factor in seasonal affective disorder. (SAD)
low levels of light
melanopsin carries signals to scn
axon pathway to pineal gland
melatonin
induced sleep
decoursey
destroyed the SCN connections in the brains of 30 chipmunks who were then returned to their natural habitat and observed for 80 days.
Their sleep/wake cycle of the chipmunks who had their SCNs destroyed disappeared, and by the end of the study a significant number of chipmunks were killed by predators.
martin ralph
Bred ‘mutant’ hamsters with a 20-hour sleep/wake cycle.
When the SCN cells from the foetal tissue of mutant hamsters were transplanted to the brains of normal hamsters, the cycles of sleep/wake defaulted to 20 hours.
campbell and murphey
demonstrated that light may be detected by skin receptor sites on the body even when the same information is not received by the eyes. They had 15 participants who they woke up at various times and a light pad was shone at the back of their knees. The researchers managed to produce a deviation in the participants usual sleep/wake cycle by up to three hours.
This suggests that light is a powerful exogenous zeitgeber that does not necessarily need to rely on the eyes to exert its influence on the brain.
exogenous zeitberger- social cues
We are able to compensate for the absence of natural zeitgebers (e.g. light) by responding to social cues, such as mealtimes and social activities.
klein wegmann
found the circadian rhythms of air travellers adjusted more quickly if they went outside more and right after landing at their destination, possibly because they were exposed to social cues that acted as zeitgebers.
he importance of the SCN has been demonstrated in research.
E: Morgan (1955) bred hamsters so that they had circadian rhythms of 20 hours rather than 24.
E: SCN neurons from these abnormal hamsters were transplanted into the brains of normal hamsters, which subsequently displayed the same abnormal circadian rhythm of 20 hours, showing that the transplanted SCN had imposed its pattern onto the hamsters.
L: This research demonstrates the significance of the SCN and how endogenous pacemakers are important for biological circadian rhythms.
However, this research is flawed because of its use of hamsters. Humans would respond very differently to manipulations of their biological rhythms, not only because we are different biologically, but also because of the vast differences between environmental contexts. This makes research carried out on other animals unable to explain the role of endogenous pacemakers in the biological processes of humans
Consequences of changes to endogenous pacemakers and exogenous zeitgebers ?
disrupted sleep patterns,
increased anxiety and irritability
and decreased alertness and vigilance
Lowered productivity
ETHICAL ISSUES end and exo
P: There are ethical issues in the way some animal issues are conducted
E: Particularly in relation to Decoursey et al. study, the chipmunks were exposed to considerable harm and subsequent risk
E: A significant amount of the chipmunks were killed as a result of being returned to their natural habitat
L: Whether what we learn from these investigations justifies the negative procedures involved is a matter of debate.
siffre
two months living in total isolation in a subterranean cave without access to a clock, calendar, or the natural sun light, sleeping and eating only when his body told him to
findings of siffre
He went into the cave on 16 July 1962 and came out of the cave on 14 September 1962. However, Siffre thought the day he came out – two months after he had entered the cave was the 20th of August, showing how his time in the cave had warped his sense of time.
Siffre’s ‘free-running’ biological rhythm had settled into a sleep-wake cycle of around 24 hours and 30 minutes. Although he did continue to fall asleep and wake up on a regular schedule
He settled into a sleep/wake cycle usually just beyond the usual 24-hour cycle – 24.5hours
aschoff and wever
A group of participants spent four weeks in a bunker deprived of natural light during WWII
All participants except one (who displayed an extended sleep/wake cycle of 29 hours) displayed a circadian rhythm of between 24 and 25 hours.
folkard
studied a group of 12 people who agreed to live in a dark cave for 3 weeks – going to bed when the clock said 11:45pm and waking up when it said 7:45am. Over the course of the study, the researchers gradually speeded up the clock (the participants were not aware of this). So, an apparent 24-hour day was instead only 22 hours.
folkard findings
It was revealed that only one of the 12 participants were able to comfortable adjust to this new 22-hour day suggesting the existence of a strong free-running circadian rhythm that cannot be overridden by changes in the external environment
Practical application to drug treatment circadian
P: Circadian rhythms co-ordinate a number of the body’s basic processes such as heart rate, digestion and hormone levels
E: This in turn has had an effect on pharmacokinetics, that is, the action of drugs on the body and how well they are absorbed and distributed
E: Research into circadian rhythms has revealed that there are peak times during the day or night when drugs are most likely to be effective
L: This has led to the development of guidelines to do with the timing of drug dosing for a whole range of medications including anticancer, respiratory and cardiovascular (Baraldo 2008)
Research Support:circadian
p: Research has been conducted to investigate circadian rhythms and the effect of external cues like light on this system.
E: Siffre (1975) found that the absence of external cues significantly altered his circadian rhythm:
E: When he returned from an underground stay with no clocks or light, he believed the date to be a month earlier than it was.
L: This suggests that 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.
However,
Siffre’s case study has been the subject of criticism. As the researcher and sole participant in his case study, there are severe issues with generalisability.
However, further research by Aschoff & Weber (1962) provides additional support for Siffre’s findings. Aschoff & Weber studied participants living in a bunker. The bunker had no windows and only artificial light, which the participants were free to turn on and off as they pleased. Aschoff & Weber found that the participants settled into a longer sleep/wake cycle of between 25-27 hours. These results, along with Siffre’s findings, suggest that humans use natural light (exogenous zeitgebers) to regulate a 24-hour circadian sleep-wake cycle, demonstrating the importance of light for this circadian rhythm.
what is the nervous system
specialised netowkr of cells in the human body
two main functions of nervous systems
1) collwct process and repsond to i fo in the environment
2) coordinate thw wroking of different organs and cells in the body
two componens of cns
spinal chord and brain
peripheral nervous system
its role is to transmit infromation from the environemnt to the central nervous system and from the cns to other parts of the body
symphatehtic
increases bodily functions to prepare for action flight or fights
