Biopsychology - Paper 2 Flashcards
Paper 2
1
Q
What do dendrites do?
A
receive signals
2
Q
What does the axon do?
A
carries impulses away from the cell body
3
Q
What does the Myelin sheath do?
A
protects the axon
4
Q
What do terminal buttons do?
A
Communicate with next neuron
5
Q
What do the Nodes of ranvier do?
A
Speed up transmission of impulse
6
Q
What do Motor neurons do?
A
Carry messages from CNS to muscles and glands. SHORT dendrites, LONG axons
7
Q
What do Sensory neurons do?
A
Carry messages from PNS to CNS. When they reach the brain, they are translated into sensations. LONG Dendrites, SHORT axons
8
Q
What do Relay neurons do?
A
Carry messages from sensory to motor neurons, or other relay neurons. SHORT dendrites, SHORT axons
9
Q
What is the process of the reflex arc?
A
- Stimulus presented
- Sensory neurons send a message through peripheral nervous system
- Message reaches the spinal cord, where it’s passed to a relay neuron
- The message is either passed to a motor neuron or sent to the brain for further processing
- Motor neuron carries the message to an effector
10
Q
What is the process of synaptic transmission?
A
- The nerve impulse travels down the axon of the presynaptic neuron
- When it reaches the end of the axon, chemical messengers called neurotransmitters are released from vesicles within the presynaptic neuron
- These diffuse across the synapse
- The neurotransmitters then behind to the receptors on the postsynaptic neuron
- This stimulates the postsynaptic neuron to transmit a nerve impulse down its axon, to the next neuron
- The neurotransmitters are deactivated by being reabsorbed back into the presynaptic neuron or by being broken down by enzymes in the synapse
11
Q
What are neurotransmitters?
A
Each neurotransmitter has its own specific molecular structure that fits perfectly into the postsynaptic site, like a lock and key. Neurotransmitters also have specialist functions
12
Q
What is excitaiton?
A
Some neurotransmitters have an excitatory effect on the neighbouring neuron. If a synapse is more likely to cause the postsynaptic neuron to fire, it is an excitatory synapse. This is like the accelerator
13
Q
What is inhibition?
A
Some neurotransmitters have an inhibitory effect on the neighbouring neuron. If the message is likely to be stopped at the postsynaptic neuron it is an inhibitory synapse
14
Q
What is summation?
A
A neuron can receive both types of neurotransmitter at the same time. Likelihood of the cell firing is determined by adding up excitatory and inhibitory synaptic input which is summation. If the net effect on the postsynaptic neuron is inhibitory it will be less likely to fire. If the net effect is excitatory the neuron will be more likely to fire
15
Q
What is the nervous system?
A
A complex system of nerve cells that carry messages to and from the brain and spinal cord to different parts of the body to help parts of the body communicate with each other. It is divided into the central NS and the Peripheral NS
16
Q
What is the Central Nervous System?
A
Made of brain and spinal cord
Brain - involved in psychological processes and is the centre of all conscious awareness
Spinal cord - an extension of the brain responsible for the reflex action and relaying information between the brain and rest of the body
17
Q
What is the peripheral nervous system?
A
Transmits messages via neurons to and from the CNS. Function is to relay nerve impulses from the CNS to rest of the body back to CNS. It is subdivided into the somatic and autonomic nervous system
18
Q
What is the somatic nervous system?
A
Controls voluntary actions achieved by receiving information from the sense and carrying sensory and motor information to and from the CNS
19
Q
What is the autonomic nervous system?
A
Governs vital functions to the body such as breathing, heart rate etc. It controls involuntary actions and only carries motor information to and from the CNS. Subdivided into the parasympathetic and sympathetic.
20
Q
What is the symapathetic nervous system?
A
Involved in responses that help us deal with emergencies (fight or flight). Neurons travel to organs and glands to prepare body for rapid action. Causes the body to release stored energy and inhibits less important bodily processes e.g., digestion.
21
Q
What is the parasympathetic nervous system?
A
Involved in returning the body to a rest state once the emergency has passed. Bodily processes that are inhibited by the sympathetic branch are returned to normal
22
Q
What is the endocrine system?
A
Works with nervous system to regulate physiological processes. Endocrine communicates chemical messages which are hormones to organs. Regulate body’s growth, metabolism and function. Hormones released by glands
23
Q
What are glands?
A
Organs secrete hormones to regulate bodily functions. Major gland is pituitary gland located in the brain. It controls the release of hormones from all other endocrine glands
24
Q
What are hormones?
A
Chemicals that circulate in the bloodstream and influence target organs to regulate bodily activity. They are produced in large amounts but disappear quickly and have powerful effected. Incorrect timing of hormone release can result in dysfunction of bodily systems
25
What is the adrenal gland and adrenaline?
Triggers fight or flight by increasing heart rate, blood pressure etc
26
What are the testes and testosterone?
Causes the development of tests in the womb. A surge during puberty causes secondary sexual characteristics such as facial hair and deepening of the voice
27
What are ovaries and Oestrogen and Progensterone?
Help to regulate the menstrual cycle. Oestrogen is involved in repairing and thickening the uterus lining, progesterone maintains the lining
28
What is the Pineal gland and Melatonin?
Regulates the sleep-wake cycle, high levels cause drowsiness when daylight is low
29
What is the fight or flight response?
We experience an acute stressor which activates the hypothalamus which activates the sympathetic branch of the ANS which activates the Adrenal Medulla to release adrenaline and noradrenaline
These reactions can include activation of emergency functions like increased heart rate and blood pressure so O2 is pumped to the muscles for physical activity. Non emergency bodily processes are suppressed
30
What is the body like when in a sympathetic state?
- Increased heart rate
- Increased breathing rate
- Dilates pupils
- Inhibits digestion
- Inhibits saliva production
- Contracts rectum
31
What is the body like in a parasympathetic state?
- Decreased heart rate
- Decreased breathing rate
- Constricts pupils
- Stimulates digestion
- Stimulates saliva production
- Relaxes rectum
32
What do adrenaline and noradrenaline do?
Increases: heart rate, blood pressure, glucose released, respiration, perspiration and blood coagulation.
Decreases: digestion
33
What is an AO3 point of the fight or flight response?
It may be different in females. Taylor et al found that females adopt a 'tend and befriend' response in stressful or dangerous situations. Women are more likely to protect their offspring and form alliances with other women, rather than fighting or fleeing.
Fight or flight response is gender bias as it only applies to males
34
What is localisation of function?
Specific functions have specific locations within the brain. If a certain area is damaged, the associated function will also pe affected.
35
What is the auditory cortex?
Processes auditory information. Damage to this area may produce hearing loss
36
What is the Broca's area?
Responsible for speech production. Broca's aphasia is where speech is slow, laborious and lacking in fluency
37
What is the frontal lobe?
associated with ‘higher’ cognitive functions, including decision-making, problem-solving, thought, and attention.
38
What is the motor cortex?
Responsible for fine motor movements. Involved in the planning, control, and execution of voluntary movements. Damage may result in a loss of control over fine movements
39
What is the somatosensory cortex?
Responsible for processing sensory information. The somatosensory cortex on one side of the brain receives sensory information from the opposite side of the body
40
What is the visual cortex?
Responsible for processing visual information. Each eye sends information from the right visual field to the left visual cortex
41
What is the Wernicke's area?
It is responsible for what we hear - understanding language and accessing words
42
What are the positive evaluation points of localisation of function?
+ Brain scan research - Peterson et al used brain scans to demonstrate how Wernicke's area was active during a listening task and the Broca's during a reading task
+ Tulving et al have shown that episodic and semantic memories were recalled from different sides of the prefrontal cortex whilst procedural memory is associated with the cerebellum.
43
What are the negative evaluation points of localisation of function?
- Animal research - Lashley removed between 10-50% of the cortex in rats that were learning a maze and found that no area was more important than the other in terms of ability to learn the maze. This suggests that higher cognitive processes are not localised but distributed more holistically reducing the validity
HOWEVER, difficult to generalise from animals to humans
- Plasticity - when the brain is damaged and a particular function has been lost, the rest of the brain is able to reorganise itself to recover the function. Turk et al discovered a patient who suffered damage to the left hemisphere but developed the capacity to speak in the right
44
What is hemispheric lateralisation?
Two hemispheres of the brain are functionally different, certain mental processes and behaviours are mainly controlled by one hemisphere rather than the other
45
What are the two hemispheres connected by?
Corpus callosum which is a bundle of fibres which help the two hemispheres to exchange information
46
What does the left hemisphere do?
Language processing - Broca's and Wernicke's areas are here
47
What does the right hemisphere do?
Dominant for facial recognition. A case study of a woman who had right hemisphere damage highlighted that the right hemisphere also seems more adept at spatial relationships. The woman would get lost even in familiar situations
48
What is the supporting evaluation points for hemispheric lateralisation?
Fink used PET scans to identify which brain regions were active during a visual processing task. Ps were asked to attend to global elements of an image, regions of the right hemisphere were more active. When required to focus on finer detail, left was more dominant
49
What are the negative evaluation points of hemispheric lateralisation?
- Plasticity - Turk et al
- Animal research - Lashley (However, animals)
- Lateralisation may be complicated by age - Szflarski found that language became more lateralised to the left as children developed into adolescents, but after the age of 25, lateralisation decreased with each decade. Suggest HL is a much more complex process
50
Who did split-brain research?
Sperry
51
What was Sperry's sample?
11 patients who had had their corpus callosum cut to cure severe eplilepsy.
52
What was Sperry's procedure?
Verbal recognition - visual image presented to left visual field via tachistoscope. Ps asked to describe what they saw, repeated using right visual field (processed by left)
Touch recognition - ps couldn't see objects in front of them. Ps asked to pick up an object using their right hand (left hemisphere) and asked to describe what they felt. Repeated using left hand
53
What were Sperry's findings about verbal recognition?
Picture shown to right visual field - could easily describe what was seen. Picture shown to left visual field - couldn't describe what was seen, said there was nothing there.
Language was processed by the right hemisphere when shown to left visual field, language is doesn't process language so difficulty describing
54
What were Sperry's findings about touch recognition?
Although they couldn't verbally describe the objects presented to left visual field, they were able to select a matching object using their left hand
55
What are the positive evaluation points of split-brain research?
Well controlled. The methodology can be praised for using highly standardised procedures which was conducted in a controlled environment
56
What are the negative evaluation points of split-brain research?
Unusual and limited sample. Only 11 took part all of whom had a history of epileptic seizures and had received drug therapy for different amounts of time which may have caused unique brain changes. Some may have experienced more disconnection of the hemispheres. The control group had no history of epilepsy
57
What is fMRI?
Measures brain activity in specific areas by detecting associated changed in blood flow
58
How does fMRI work?
Detects brain changes in blood oxygenation and flow in the brain. When a brain is more active, it consumes more O2 and to meet this increased demand blood flow id directed to the active area. It produces 3D images showing which part of the brain is involved in a process. They show 1-4s after an event occurs and are thought to be accurate within 1-2mm
59
What are the positive evaluation points of fMRI?
+Less invasive - less invasive than other techniques such as PET scans which used radiation or require instruments to be inserted into the brain. It is virtually risk free
+ Spatial resolution - good spatial resolution of 1-2mm which helps researchers pinpoint specific responses and the exact source of brain activity
60
What is spatial resolution?
The smallest measurement that a scanner can detect. Greater spatial resolution allows researchers pinpoint specific responses and the exact source of brain activity
61
What are the negative evaluation points of fMRI?
- Expensive - to buy and maintain and they require trained operators. This makes research expensive and difficult to organise
- Temporal resolution - 1-4 seconds which is worse than EEG/ERP which have a temporal resolution of 1-10milliseconds. Psychologists are then unable to predict with a high degree of accuracy
62
What is temporal resolution?
The accuracy of the scanner in relation to time
63
What is EEG?
A record of the brain wave patterns produced by millions of neurons, producing characteristic patterns
64
How does EEG work?
Measures electrical activity within the brain via electrodes. The scan recording represents the brainwave patterns that are generated from the action of millions of neurons, providing an overall account of brain activity. Electrodes measure the activity of the cells so using more electrodes gives a fuller picture. Real time recording of brain activity
65
What is ERPs?
Isolating specific responses of neurons to specific stimuli or tasks
66
How do ERPs work?
A stimulus s presented many times to a participant. Using statistical averaging technique, random or background brain activity from the original recording is filtered out, leaving only event-related potentials. ERPs are one of the most widely used methods.
67
What are the positive evaluation points of EEG/ERPs?
+ Cheaper - in comparison to fMRI and therefore more widely available to researchers. This could help psychologists to gather further data on the functioning human brain, leading to greater understanding of sleeping and Alzheimer's
+ Temporal resolution - good as it takes readings every millisecond, meaning it can record the brain activity in real time. This leads to an accurate measurement of electrical activity when undertaking a specific task
+ Less invasive - virtually risk free
68
What are the negative evaluation points of EEG/ERPs?
- General data EEG - only provides a measure of general brain activity meaning brain response to a single stimulus or event of interest is not usually visible in the EEG recording
- Spatial resolution - EEG/ERPs have poor spatial resolution. Only detect activity in superficial regions of the brain. Unable to provide info on what is happening in the deeper regions of the brain, making it limited in comparison to fMRI
69
What are post mortem examinations?
correlating behaviours before death with brain structures after death
70
How do post mortem techniques work?
Analysing a person's brain following their death. Individuals whose brains are subject to a post-mortem are likely to be those who have a rare disorder and have experienced unusual deficits.
71
What are the positive evaluation points of post-mortem examinations?
Provide a detailed examination of the structure of the brain that isn't possible with other scanning techniques. They can access areas such as the hypothalamus and hippocampus which other scanning techniques struggle to reach so provide an insight into deeper brain regions which provide a basis for further research
72
What are the negative evaluation points of post-mortem examinations?
- Ethical issues - informed consent and whether a patient provides consent before their death. Many examinations are carried out on patients with severe psychological deficits who would be unable to provide consent.
- Causation - the deficit a patient displays during their lifetime may not be linked to deficits found in the brain. The deficits reported could have been the result of another illness, so cannot conclude that the deficit is cause by the damage found int he brain/ Confounding factors include medication, time between death and post-mortem and age at death
73
What is plasticity?
The brain's capacity to change or adapt because of new learning or brain trauma. The brain doesn't stop changing in childhood, new neural connections can be made at any time
74
What is functional recovery?
Form of plasticity, ability to redistribute functions following damage through trauma. The brain can rewire itself by forming new synaptic connections: axonal sprouting, recruitment of homologous areas, neuronal unmasking
75
What is axonal sprouting?
The growth of new nerve endings which connect with other undamaged nerve cells to form new neuronal pathways. When an axon is damaged its connection with a neighbouring neuron is lost. Other axons will sprout extra connections . The brain can rewire itself by forming new synaptic connections close to the area of damage.
76
What is recruitment of homologous area?
Areas on the opposite side of the brain perform specific tasks. If the Broca's area was damaged on the left side of the brain, a similar area on the right side of the brain would carry out its function
77
What is neuronal unmasking?
Some of the brain's neurons are dormant. These neurons are alive but are not doing their specific function e.g., they may fail to send messages to a muscle. When a brain area becomes damaged, these dormant areas become unmasked. The unmasking of dormant neurons opens connections in regions of the brain that are not normally activated which leads to the development of new structures
78
What are the factors affecting recovery after brain trauma?
Age, Gender, Physical exhaustion, stress and alcohol consumption
79
How does age affect recovery of the brain after trauma?
There is deterioration of the brain in old age, and this therefore affects the extent and speed of recovery. Marquez de la Plata et al found that following brain trauma, older patients regained less function in treatment than younger and were more likely to decline in terms of function for the 5 years following the trauma
80
How does gender affect recovery of the brain after trauma?
Research to suggest that women recover better from brain injury as their function is not as lateralised. Ratcliffe et al examined 325 patients with brain trauma for their level of response for cognitive skills. Patients were 16-45 at injury, received rehabilitation and completed a follow-up a year later. None of them had learning problems prior to the trauma. When assessed for cognitive skills, women performed significantly better than men on tests of attention.working memory and language whereas men outperformed females in visual analytic skills.
81
How does physical exhaustion, stress and alcohol consumption affect recovery of the brain after trauma?
When function is recovered in an individual it is important to remember that often the function is sued with considerable effect and although the person can do a task, they are often fatigued by the effort. Other factors such as stress and alcohol consumption can effect ability to use any function that has been regained
82
What are the positive evaluation points of functional recovery?
+ Evidence: Maguire et al used an MRI scanner to scan the brains of London taxi drivers and found they had significantly more volume of grey matter in the posterior hippocampus than a matched control group. The volume of this area was also positively correlated with the amount of time they had been a taxi driver. This is positive as it supports the idea that human brain can adapt as a result of learning and experience
+ Animal studies: Early evidence of neuroplasticity comes from an animal study conducted by Hubel and Wiesel. Kittens had one of their eyes sewn up and the brain's cortical responses were analysed. It was found that the area of the visual cortex associated with the shut eye was not as predicted but continued to process information from the open eye. This is positive as it supports the idea that the brain can change or adapt as a result of experience
+ Practical applications: Understanding the processes involved in plasticity has contributed to the treatment and rehabilitation of brain injury patients. Following illness or injury to the brain, recovery tends to slow down after a few weeks so forms of physical therapy are usually performed to maintain improvement in functioning. This shows that the brain may have the capacity to fix itself to a point, this process requires further intervention if it is to be completely successful
83
What are the negative evaluation points of functional recovery?
- Individual differences: certain individuals may have more of an ability to recover from brain trauma than others. Elbert et al showed that adults require far more intensive training than children after brain trauma and Schneider et al found that patients with college education were 7x more likely than those who didn't finish high school to be disability-free one year after brain injury suggesting a number of factors contribute to brain plasticity and recovery from brain trauma, which makes it a complex area to study
- Negative consequences: Ramachandram and Herstein found that 60-80% of amputees have been known to develop phantom limb syndrome - the continued experience of sensations in the missing limb as if it were still there. These sensations are usually unpleasant, painful and are thought to be due to cortical reorganisation in the somatosensory cortex because of limb loss. Negative plasticity is a problem as it shows the brain's ability to adopt to changes doesn't always have positive effects
84
What are biological ryhthms?
The natural cycle of change in our body's chemicals or functions. These rhythms are governed by the body's internal clocks and external changes to the environment
85
What are circadian rhythms?
A cycle in biological or psychological activity that occurs once every 24 hours. An example is the sleep-wake cycle which occurs once every day and core body temperature - it is the highest around 4pm and lowest at 4am and hormone production
86
What is hormone production?
Hormone release follows a circadian rhythm. The production and release of melatonin from the pineal gland in the brain follows a circadian rhythm, with peak levels occurring during the hours of darkness. By activating chemical receptors in the brain, melatonin encourages feelings of sleep. When its dark, more melatonin is produced, and when it is light again, the production of melatonin drops and the person wakes up
87
What is the sleep-wake cycle?
The circadian rhythm not only dictates when we should be sleeping, but also when we should be awake. Light and darkness are the external signals that determine when we feel the need to sleep and wake up. The circadian rhythm also dips and rises at different times of the day, so our strongest sleep drive usually occurs in two 'dips' between 2-4am and 1-3pm
88
What is the positive evaluation point of circadian rhythms?
Practical applications: research into the circadian rhythms provides an understanding of the consequences that occur when they are disrupted. Bolvin found that night workers experience reduced concentration around 6am, leading to an increase in mistakes and accidents
89
What is the negative evaluation point of circadian rhythms?
Samples - research on circadian rhythms usually involve small samples. For example Siffre was the only person in his study. This is an issue because results cannot be generalised
90
What happened in Siffre's study?
Siffre lived underground in a cave in Texas for 6 months, without external cues, such as daylight. It was found that his sleep-wake cycle settled into a ‘free-running’ rhythm of around 25 hours. This study suggests endogenous pacemakers, such as the SCN, are important in controlling the sleep-wake cycle. Despite the absence of any exogenous zeitgebers, Siffre was able to maintain a relatively normal cycle.
91
What are infradian rhythms (longest)?
Last more than 24 hours e.g., menstrual cycle, hibernation.
Menstrual cycle - monthly infradian rhythm that is governed by monthly changes in hormones that regulate ovulation. Rising levels of oestrogen causes ovulation. After ovulation progesterone helps the womb lining grow thicker, readying the womb for pregnancy, if it doesn't occur the womb lining comes away and leaves the body
92
Who did research into infradian rhythms?
McClintock
93
What was McClintock's research into infradian rhythms?
29 women with irregular periods were studies. Samples of pheromones were gathered from 9 of the women at different stages of their menstrual cycles, via cotton pad placed on their armpits/ The pads were then rubbed on the upper lip of the other participants. They found that 68% of women experienced changes to their cycle which brought them close to the cycle of their 'odour donor'
94
What are the positive evaluation points of infradian rhythms?
Research, particularly into menstruation is supported by the theory of evolution. It may have been advantageous for women to menstruate together and become pregnant at the same time. In a social group, this would allow babies who had lost their mothers to have access to breast milk, improving their chances of survival suggesting that synchronisation is an adaptive strategy
95
What are the negative evaluation points of infradian rhythms?
There are many factors that may cause the menstrual cycle to change including stress, extreme dieting and exercising
96
What are ultradian rhythms?
The shortest lasting less than 24 hours e.g., blinking, heartbeats, sleep patterns.
97
What are the stages in the sleep cycle?
Ultradian
We go through 5 distinct stages that span about 90 minutes.
Stage 1: Light sleep where a person may easily be woken, alpha brain waves occur
Stage 2: Light sleep continues, sleep spindles also occasionally occur
Stage 3: Deep sleep, delta waves occur with lower frequency and higher amplitude. It is difficult to wake someone at this point
Stage 5: REM sleep, body is paralysed yet brain activity closely resembles that of the awake brain. Produces theta waves and eyes move, dreams are most often experienced here
98
What are the positive evaluation points of ultradian rhythms?
Research into ultradian rhythms have improved the understanding of age-related changes in sleep. Sleep scientists have observed that SWS reduces with ages, leading to reduced alertness in the elderly. This suggests that knowledge of ultradian rhythms has practical value
99
What are the negative evaluation points of ultradian rhythms?
Tucker found large differences in the duration of each sleep stage in many participants. Researchers into ultradian rhythms often ignore individual differences making it difficult to describe 'normal' sleep
100
What is the SCN?
The most important pacemaker in human beings is the SCN. It is a tiny bundle of nerve cells located in the hypothalamus. It maintains circadian rhythms such as ht sleep-wake cycle. If it is damaged, sleep becomes erratic. It receives info about light from the optic chiasm. If our biological clock is running slow, then morning light automatically adjusts the clock. This synchronisation of the SCN by light changes is known as entrainment
101
How do the pineal gland and melatonin with the SCN?
The SCN passes info on day length and light to the pineal gland. During the night, the pineal gland increases production of melatonin - a chemical that induces sleep and is inhibited during periods of wakefulness. Melatonin has also been linked to seasonal affective disorder
102
What is Morgan's positive evaluation point of endogenous pacemakers and the sleep-wake cycle?
+ Supporting evidence: Morgan studied hamsters, it was found that if the SCN was removed, the circadian sleep-wake cycle completely disappeared. Transplanting SCN cells from foetal hamsters into these masters, helped to re-establish the sleep-wake cycle. If a hamster was given a transplanted SCN from a mutant strain with a short sleep-wake cycle, it will adopt the same patterns as the mutant donor. Supporting the view that the SCN is vital in maintaining the sleep-wake cycle
103
What is the counter-argument of Morgan's hamster study about endogenous pacemakers?
We need to be careful applying the results to human sleep-wake cycles. There are many factors such as social cues which will influence human cycles, making it difficult to generalise results. Hamsters are nocturnal so sleep-wake cycles and biological rhythms are different. We have social cues which influence sleep-wake cycle so cannot generalise to humans
104
What is Siffre's positive evaluation point of endogenous pacemakers and the sleep-wake cycle?
Siffre lived underground in a cave for 6 months, without external cues, such as daylight. It was found that his sleep-wake cycle settled int o a 'free-running' rhythm of around 25 hours. This suggest endogenous pacemakers such as the SCN are important in controlling the cycle. Despite the absence of any exogenous zeitgebers, Siffre was able to maintain a relatively normal cycle
105
What is the counter-argument of Siffre's study about endogenous pacemakers?
It is based in an individual case so is limited. His sleep-wake cycle may be very different to those of the general population, reducing the external validity of this study. Siffre's use of artificial lighting may have acted as an extraneous variable reducing internal validity
106
What is the positive evaluation point of endogenous pacemakers and the sleep-wake cycle?
There is real world application for the role of endogenous pacemakers in circadian rhythms. Our circadian rhythms affect when drugs are most effective, therefore when prescribed drugs it is not advise that they are taken at different times of the day to maximise their effects. This suggests that we have an internal clock that controls our 24 hour sleep wake cycle as medication is advised to be taken around this cycle
107
What is the negative evaluation point of endogenous pacemakers and the sleep-wake cycle?
Folkard studied Kate Aldcroft, who volunteered to spend 25 days in the controlled environment lab. During her time, she had no access to daylight or other zeitgebers that might have reset the SCN. At the end of the 25 days, her sleep-wake cycle had extended to 30 hours. This reduces the validity of the role of endogenous pacemakers in the sleep-wake cycle as it appears that exogenous zeitgebers (light) are required to synchronise the SCN
108
What are exogenous zeitgebers?
Environmental events that are responsible for entraining the SCN
109
What are some examples of exogenous zeitgebers?
Light and social cues
110
How does light (exogenous zeitgeber) work?
The most important one. It helps to maintain the sleep-wake cycle by resetting the SCN. Receptors in the SCN are sensitive to changes in light levels during the day and use this information to synchronise the activity of the body's organs and glands. Light resets the internal body clock each day, keeping it on a 24-hour cycle
111
How doe social cues (exogenous zeitgebers) work?
E.g., mealtimes, bedtimes and social events. Research also suggests that adapting to local times for eating and sleeping is an effective way of entraining circadian rhythms and beating jet lag when travelling long distances.
Reduction in light --> optic nerve --> stimulate SCN --> stimulates pineal gland --> melatonin increases --> less brain activity --> sleep
112
What are the positive evaluation points of exogenous zeitgebers?
- Campbell and Murphy found that shining a light on the back of participant's knees shifted the circadian rhythm. This implies that natural light plays a role in 'entraining' or biological clocks, to keep the sleep-wake cycle in synchrony with the outside world. Evidence of exogenous zeitgebers in circadian rhythm control
- Research has led to treatments for jet lag. Burgess et al found that exposure to bright light prior to an east-west flight reduced jet lag. Participants who were exposed to bright light felt sleepier 2 hours earlier in the evening and woke 2 hours earlier in the morning closer to the local times conditions they would find after an east-west flight. This has huge benefits to the economy as preventing jet lag increases productivity so people are more likely to return to work earlier if they are less tired
113
What are the negative evaluation points of exogenous zeitgebers?
Miles studied a young man who was blind from birth. Despite exposure to social cues, such as regular mealtimes, his sleep-wake cycle remained abnormal. This suggests that social cues alone are not effective in resetting the biological rhythm
114
How is the interactionist a better explanation of exogenous zeitgebers and endogenous pacemakers?
A reasonable conclusion to the discussion of the sleep-wake cycle is that both endogenous and exogenous factors influence its operation. It appears that pacemakers and zeitgebers interact therefore it makes little sense to separate the two fro the purpose of research
