Studies done by Micheal Siffre where he spent prolonged time in underground caves without exogenous zitegibers like sunlight, noise, clocks, etc have supported the existence of endogenous pacemakers in our sleep wake cycle as his results showed that his sleep wake rhythm settled to an average 24 hour cycle. However this study could be criticized for lacking validity as it could be considered to be a case study hence it only describes the behavior of one individual ( Micheal Siffre) and cannot be generalized to the population. In addition to this, the conditions he faced in the caves such as reduced temperatures and the use of a dim light might have affected his sleep wake cycle. However Shiffre’s results are supported by various studies including Aschoff and Wever (1976) study where participants stayed in an underground WWII bunker without exogenous zitegibers and the results showed that most of the participants displayed a sleep wake cycle of 24 to 25 hours. The main endogenous pacemaker in mammals is the Suprachiasmatic Nucleus (SCN); a cluster of nerve cells located in the hypothalamus whose neurons have an in built circadian rhythm.
Essay 1: Outline and evaluate the role of endogenous pacemakers in the control of one or more biological rhythms (9+16 marks) Biological rhythms are regular patterns of physiological, behavioural or cognitive activities. They include the changes in levels of brain chemicals, increasing and decreasing body temperature over a single day, and also shifting between sleeping and waking. There are three main types of biological rhythms. They are “Infradian Rhythms”, “Circadian Rhythms” and “Ultradian Rhythms”. Infradian rhythms are cycles that have the longest duration, lasting more than 24 hours.
A circadian rhythm is a natural change in a biological process which occurs roughly every 24 hours. The most well known example would be the sleep wake cycle which occurs once every 24 hours. The sleep-wake cycle is known as an endogenous pacemaker which can be affected by external factors, also known as exogenous zeitgebers, such as noise, light, social cues and the temperature. The most dominant endogenous pacemaker (or central oscillator) we have is the Suprachiasmatic nucleus (SCN) which is located on top of the optic chiasm. It is a small bundle of cells found in the hypothalamus and is used to detect light.
Finally an ultradian rhythm has a cycle shorter than 24 hours, it changes within a 24 hour period, and an example of this would be heart rate. Endogenous pacemakers are the inherited mechanisms that work internally monitoring the exogenous zeitgebers that help to synchronise biological rhythms to external cues such as night and day. An example of an endogenous pacemaker is the supra-chiasmatic nucleus, which is a section of the brain above the optic chiasm that controls circadian rhythms by regulating body rhythms in line with environmental light levels. Research conducted on hamsters shows that removal of the supra-chiasmatic nucleus results in randomised sleep walking patterns, this demonstrates that endogenous pacemakers have a key role in controlling biological rhythms as the removal of one would begin to randomise and alter biological rhythms. Another example of an endogenous pacemaker is the reticular activating system found within the brainstem, its role is to regulate arousal levels from sleep to focused attention and to also filter any external stimuli.
Discuss the role of exogenous and endogenous pacemakers in biological rhythms: Endogenous: Most organisms have an internal biological ‘clock’ which controls the circadian rhythm. Your biological clock is endogenous (part of the internal organism). Biological clock helps us to realise an event, for example when it is night time. Darlington et al (1998) said that the ticking of the clock is created by reactions between proteins. He described it as continuous circle; Proteins ‘CLOCK & CYCLE’ bind together in the morning, which increases the production of ‘PER & TIM’ during the day.
Endogenous bodily clocks are influenced by external (exogenous zeitgebers) factors. One of these lies in the suprachiasmatic nuclei (SN), which is a small group of cells found in the hypothalamus. It receives information by the retina. Information about light and dark synchronises our biological rhythms with the 24-hour cycle of the outside world. If the SN is damaged, or the connection between it and the retina severed, circadian rhythms disappear completely, and the rhythmic behaviours would become random over the day.
It can be concluded that circadian rhythms persist despite the removal of exogenous zeitgebers. (AO1) Evaluation • Supported by research by Aschoff and Wever (1976) they placed participants in an underground WW2 bunker, in the absence of exogenous zeitgebers. They found the participants still had their 24/25-hour circadian rhythms, which provides evidence for the role of internal endogenous zeitgebers. (AO2) • Both studies use small sample sizes. In particular, Siffre’s study was a case study, which focused on one individual person.
Acetylcholine acts as a neuromodulator which engage in direct synaptic transmission between specific neurons. In the CNS acetylcholine plays a role in attention and arousal in the PNS it works as a major part of the autonomic nervous system and works to activate muscles (Waymire, 1997). Acetylcholine is involved in voluntary movement, learning, memory, and sleep. | | | | Pharmacological agent prescribed to increasethe neurotransmitter: | List three possible side effects linked to this agent: | To increase the neurotransmitter in the body the supplement choline bitartrate and CDP-Choline and herbal agents ginseng and ginkgo biloba (Moore, 2013). | 1) Low blood pressure | | 2) Stomach ache | | 3) Increase perspiration and salivation (Moore, 2013) | Example of a neurological disorder, disease, or condition where this agent occurs | List possible risks associated with not taking this agent for the disorder, disease, or condition: | A severe autoimmune muscular disease by varying progressions of defects of the skeletal muscles in the body is known as myasthenia gravis.
Melissa McDonald Blue Zone Reflection- Lab 2 5/21/2012 It was very interresting when he started to talk about the idea of doing physical activities that come naturally to humans rather than "pumping iron" and doing triathalons. I very much agree with this idea because I believe the world (especially here in America) have moved so far away from natural things. It is actually rare to do ANYTHING "natural" here in America anymore. From the foods we eat to the activities we participate in, we have moved to a completely robotic and unnatural society. I thought it was also interresting how he mentioned that doing some sort of physical activity for five minutes multiple times throughout the day rather then being immobile all day and then going to the gym for 45 minutes at the end is actually better for you.
Zimbardo aimed to investigate the difference between situational and dispositional factors in social roles by creating a mock prison in the basement of Stanford University. He recruited 12 participants to play the role of prison guards and 12 to play the role of prisoners from a pool of 75 male volunteers. All participants were screened for any psychological disorders, such as mental illness and drug taking, and only theses without any indications of instability or aggressive personalities were selected. The prison had 16 rules which prisoners were expected to obey and the guards were expected to enforce, such as eating meals at specific times of day, needing to ask permission to write letters, or needing to ask permission to use the toilet. The guards were given a uniform that consisted of a shirt and mirrored sunglasses.