Biopsychology Flashcards
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Nervous system
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A complex network of nerve cells that carry messages that originate both inside the body and outside the body, it involves the brain and spinal cord transmitting information to different parts of the body
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Central nervous system
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Consists of the brain and spinal cord, the brain has 3 functions, 1. take information from senses, 2.interpret it and 3.respond to it. The brains outer layer is called the cortex and helps with problem solving. The spinal cord receives and transmits information from and to the brain to the peripheral nervous system. It also helps with reflex reaction e.g moving your hand from hot surfaces
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Peripheral nervous system
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- Somatic NS these are the nerves we actively control, the SNS gets info from sensory receptors and sends it to the CNS which relays it to the motor neurone. 2. Automatic nervous system these nerves connect to the CNS to internal organs which we do not control. This system works automatically as we don’t have to tell our nerves to do things e.g telling our heart to beat, it also consists of two sub devisions SYMPATHETIC and PARASYMPATHETIC nervous systems.
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Parasympathetic nervous system
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It relaxes a person after emergency has passed to conserve body’s energy. E.g when your heart rate increase the PNS slows it down to help you rest and digest and directs tissue repair(active when relaxed)
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Sympathetic nervous system
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Prepares the body to expend energy in an emergency situation. It increases heart rate and also releases sugar from liver into blood (for energy). The goal is to supply more blood to the brain and muscles by reducing blood flow to the digestive system. It also tells the endocrine system to release hormones.
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Differences between automatic and somatic nervous systems
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- Somatic under control(automatic involuntary)
2. Somatic controls skeletal muscles(automatic controls smooth muscles)
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Structure of neurons
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- Dendrites are on the end of the neuron and receive signals from other neurons
- Dendrites are part of the cell body which includes the nucleus
- Signal carried away from cell body along the axon which is covered in a myelin sheath(to protect the axon and speeds up impulse)
- At the end of axons are terminal buttons which communicate with the next neuron in the chain across the synapse
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Function of a neuron
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Its purpose is to receive and send messages. Message sent by axons are called action potentials.
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Action potential(neurons)
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When and impulse is sent from the cell body this electric charge sends signals down the axon
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Sensory neurons
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They carry messages from the sensory receptors to the CNS, the sensory receptors can be found in the eyes, they convert information from the receptors into neural impulses.
THEY HAVE LONG DENDRITES AND SHORT AXONS.
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Relay neuron
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They connect the sensory neurons to the motor or other relay neurons. THEY HAVE SHORT DENDRITES AND SHORT AXONS.
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Motor neuron
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They connect the CNS to the muscles and glands.When stimulated they release neurotransmitters that bind to the receptors on the muscle and trigger a muscle movement. THEY HAVE SHORT DENDRITES AND LONG AXONS
13
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Synapse
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When action potential reaches the terminal buttons it need to pass through the synapse to reach the next neuron. The synapse is a gap between two neurons.
14
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Neurotransmitters
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When action potential reaches the end of a neuron, the presynaptic neuron releases neurotransmitter which are chemicals that diffuse across the synapse to the next neuron. They bind to the post synaptic receptor sites(they are specific shape of neurotransmitters)
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Re-uptake
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When neurotransmitters return to the presynaptic neuron, the quicker the re-uptake the shorter the effect of the neurotransmitters.
16
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Excitation
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Neuron is positively charged and more likely to fire,e.g Adrenaline(causes excitement)
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Inhibition
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Neuron becomes negatively charged and is less likely to fire,e.g Serotonin(causes inhibition)
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‘Firing’ of neurons
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The decision to fire or not depends on the summed effects of all neurons . If the number of excitatory and inhibitory neurotransmitters are the same they cancel each other out.
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Direction of travel
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Information can only travel one direction; from pre-synaptic neuron to post synaptic. Because:
- Receptors for neurotransmitter are only present on the postsynaptic membrane
- The synaptic vesicles are only present on the postsynaptic neuron
- Its the binding of neurotransmitters to receptors that enables signals to be passed on
20
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Endocrine system
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Another system that works with the nervous system.Its made up of a network of specialist glands. These glands release hormones, and these hormones transmit information via the blood.
21
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Function of endocrine system
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Its to secrete hormones which are needed to regulate many bodily functions and provides a chemical system of communication via blood. Its regulated by the hypothalamus.
22
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Flight or fight response
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Its generated from the endocrine system and autonomic nervous system. The ANS activates the sympathetic branch, this response helps an individual to react quicker than normal and facilitate optimal functioning. When threat passes the parasympathetic nervous system returns the body to resting state.
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Q
Flight or fight evaluation
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✅We have come up with strategies to try and counteract this effect, e.g learning relaxation techniques to counter the fight or flight response. This is important as modern society doesn’t experience life or death situations that often and these release of hormones can damage health, thus application can reduce this and benefit the economy.
❌Human behaviour isn’t limited to just two responses, a psychologist suggests that first encounter of danger could prompt a ‘freeze’ response, during this faze humans are hyper-vigilant. This suggests that fight or flight is limited and doesn’t fully explain the complex cognitive and biological factors that underpin danger
❌There is gender bias as females experience a different response called the ‘tend or befriend’ in dangerous situations e.g woman are more likely to protect their child and alliance with other women rather than fight or flee. This highlights a beta bias as psychologist assume females respond the same way males do therefore limiting generalisation of fight and flight
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Q
Motor cortex
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Responsible for all voluntary muscle movement, e.g getting glass of water. Its located in the frontal lobe.
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Somatosensory cortex
The somatosensory cortex produces sensations of touch pressure, pain and temperature. Its located in the parietal lobe
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Visual cortex
Information from the eyes are transmitted to this are of the brain. Its located in the occipital lobe
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Auditory cortex
It processes sound as information from the inner ear travels via nerve impulses. Its located in the temporal lobe.
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Wernicke's area
Patients with damage to this area could not form coherent sentences and were unable to understand language, this area involves language comprehension. Its located in the left temporal lobe of the left hemisphere.
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Broca's area
Patients with damage to this area could understand spoken language normally but were unable to speak or express their thoughts in writing, this area involves speech production. Its located in the frontal lobe of the left hemisphere.
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Localisation
Refers to different areas of the brain being responsible for specific functions. In this case; Broca's ares is responsible for production of speech whereas Wernicke's area is responsible for understanding speech.
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Lateralisation
Different hemispheres of the brain might have different specialisations. Referring to Broca's and Wernicke's areas it suggests that language is located in the left hemisphere
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Broca's Alphasia
Inability to articulate speech fluently and writing is also disrupted. Understanding language is normal.
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Broca's Alphasia
Inability to articulate speech fluently and writing is also disrupted. Understanding language is normal.
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Wernicke's Alphasia
Breakdown in the ability to understand speech and to formulate coherent sentences. Patients can utter words but sentences are deficient in meaning.
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Advantages of localisation of function
✅There is supporting research that demonstrates localisation of function, a psychologist used brain scans to demonstrate that Wernicke's area was active during listening tasks and Broca's area was active during a reasoning task. This supports localisation as different areas of the brain have different tasks.
✅Further supporting research that supports localisation, a psychologist found that individuals who can express themselves using both spoken and sign language, fMRIs showed that regardless of which type of language used Broca's area was active. Another psychologists found patients with Wernicke's aphasia have disrupt understanding sound and sign language. This supports localisation as it suggest that sigh and spoken language are in similar areas.
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Disadvantages of localisation of function
❌There is evidence to contradict localisation as it was reported a boy at the age of 2 had most of his left hemisphere removed due to a tumour. At that time he lost all linguistic abilities but after undergoing intensive rehabilitation at the age of 17 his language was almost normal. It was found that his right hemisphere has compensated for the loss of the left and shows that brain plasticity can occur and that language is not fully localised to just 2 areas.
❌Another weakness is that evidence is based on case studies which are usually of individuals who have suffered a severe trauma e.g stroke, thus are idiographic. Therefore the exact parts of the brain that are damaged are unlikely to be exactly the same and therefore cannot be generalisable to non-damaged brain.
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Brain lateralisation
Refers to the fact that each hemisphere is different and that they have functional specialism e.g the left hemisphere is dominant for language.
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Corpus collosum
The large band of neural fibres connecting the two brain hemispheres and carrying messages between them.
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Split brain research
Individuals has all undergone the same surgical procedure, which involved cutting the corpus callosum down the middle to separate the hemispheres( treat epilepsy).
👁🗨The procedure: Sperry took advantage of the fact that information from the left eye goes to the right hemisphere and vise-versa.
Split brain patient had to focus on a dot in the centre of a screen. At the same time information was presented either to the left or right. Results were compared against normal controls.
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Describing what was seen(Split brain research)
Words being presented on the right visual field was immediately reported however the patient was unaware when a word flashed on their left side. This is because the right visual field passes information to the left hemisphere which deals with language. Thus the patient did not recognise the word in his left visual field as the right hemisphere doesn't have a language system.
👁🗨Conclusion- the left hemisphere is dominant in terms of language.
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Recognition by touch(Split brain research)
When the left hand is behind the screen among a number of objects and a word flashed in the right hemisphere the left hand would correctly select the object. This shows that the right hemisphere understand basic nouns.
👁🗨Conclusion- the right hemisphere has some basic language ability.
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Advantages of split brain research
✅There is research to support split brain research in normal functioning brains. A psychologist who found that the left hemisphere was more concerned with language and the right hemisphere was more concerned with spatial functions. Ornstein reinforced this by stating that the right side of the brain is the creative side whereas the left side is more logical. this is a strength as it supports Sperry's split brain research as it shows that the brain is lateralised.
✅Another strength is the high levels of control, e.g Sperry stopped the natural tendency of participants to move both eyes to the stimulus so the stimulus was only presented for 200 milliseconds. This isolates the visual field that is tested, this is a strength as it allows Sperry to carry out a wide range of variations on the original procedure which has helped us understand lateralisation.
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Disadvantages of split brain research
❌The research has low population validity because only 11 males underwent the original surgical procedure. Moreover there were differences in the operations carried out, in some patients a smaller pathway which connected the who hemispheres was also cut. We cannot develop a model of hemisphere lateralisation using only split brain research due to generalising issues
❌The research also lacks ecological validity as the task that participants were given were very controlled. By Sperry ensuring patients couldn't move their eyes in time does not reflect how the participants would use their brains in everyday life. It is likely they will use both eyes to compensate for the cut corpus collosum. therefore it is difficult to make generalisations with just split brain research.
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Plasticity
Refers to the ability of the brain to change and adapt. It occurs at the beginning of life in brain development and after brain injury to compensate for lost function.
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Synaptic pruning
Pathways and networks that are not used therefore die off.
| Counter- Any connections that are frequently used are strengthened.
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Apoptosis
Neuron death(or cell death)
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Plasticity research evidence
1. Research was done on London taxi drivers, 16 male taxi drivers and 50 male non-taxi drivers. MRI scans were carried out to analyse amount of grey matter in the brain. The posterior hippocampus of the taxi drivers was significantly larger in comparison to control group. (Learning induced plasticity)
2. A 2 year old boy had most of his left hemisphere removed due to a tumour, losing all linguistic abilities. After undergoing extensive rehabilitation he was able to speak almost normally at the age of 17. It was found his right hemisphere has compensated for the loss of the left. This shows brain plasticity can occur.
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Functional recovery
A form of plasticity whereby other areas of the brain take over the functions of the damaged area.
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Spontaneous recovery
Can happen quickly after trauma whereby the brain starts adapting.This slows down after weeks.
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How does functional recovery occur?
1. Axon sprouting - Axons of surviving neurons grow new branches that make synapses in areas of the brain formerly supplied by the damaged neurons
2. Denervation super sensitivity- Occurs when axons that do a similar job are aroused to a higher level to compensate for the ones that are lost.
3. Recruitment of homologous areas, opposite side of the brain will perform specific tasks. e.g If Broca's area is damaged on the left hemisphere the right hemisphere might carry out the function instead.
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Advantages of functional recovery
✅One strength is practical application, for example after brain injury, therapy can be used to try to implement and retain spontaneous recovery. Techniques may include movement therapy and electric stimulation of the brain. As therapy works it shows that the brain can change via plasticity after trauma.
✅Another strength is that there is research evidence to support brain plasticity, for example a psychologist imaged the brains of medical students three months before and after their final exams. Learning-induces changes were observed in the posterior hippocampus as a result of leaning for the exam. Furthermore another psychologist found larger parietal cortex in brains of people that were bilingual compared to monolingual.Both studies support that changes in the brain can occur due to learning and experiences.
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Disadvantages of functional recovery
❌Its not always a smooth transition, when function is recovery in individuals it can require considerable effort although the person can do the task. This can leave the individual fatigued; other factors such as stress and alcohol can also affect the ability to use a function that was regained. Thus plasticity can be affected by other factors and individual differences.
❌Another weakness is gender difference as it can affect the extent to which plasticity occurs.A psychologist examined 325 patients with brain trauma who had received rehabilitation and completed a follow up a year later. When assessed for cognitive skills she found women performed significantly better than men on tests of attention and language. Males outperformed females in visual skills. Women also had a better recovery than men.Thus this questions the extent to which plasticity and recovery after trauma can occur in terms of gender.
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How does fMRi work?
It records the energy release by hemoglobin. When hemoglobin has oxygen it reacts differently to when it is without oxygen. It detects hemoglobin with and without oxygen so when an area of the brain is active and is therefore using more oxygen, the fMRI scanner detects the amount of energy released.
This gives a moving picture and shows activity about one seconds after it occurs. They produce 3D images and can produce maps showing which part of the brain are involves in particular abilities. Activity is represented in different colors, e.g red is high activity and blue is low activity. Patient will have their brain actively measures when resting and then again when completing different tasks to allow for comparing brain activity.
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Advantages of fMRI
✅One strength is that its non-invasive because it doesn't not require anything to be inserted in the body nor does it expose the body to harmful radiation(PET scans). This is an advantage as it means its more ethical and participant are more willing to participate. It also makes repeatedly testing one participant much easier.
✅They also have high spatial resolution, meaning that the location that shows up on the scan is very accurate. This is unlike EEG which does not tell you which area of the brain is responsible for the activity picked up. This allows fMRIs to be used to research localisation of function very precisely.
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Disadvantages of fMRI
❌ An issue is that there is low temporal resolution as there is a time lag of about one second between brain activity and measurement. This means an fMRI is not accurate enough to distinguish between different stages of stimulus processing. In contrast to EEGs which have very high temporal resolution.
❌Another weakness is that they are not always practical. it is expensive compared to neuroimaging techniques and can only capture a image if the person is perfectly still. This is a problem as they can be uncomfortable and noisy so if a person is not still the image wont be produced right. Therefor this may result is a smaller sample size and the study lacking population validity.
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How do EEGs work
EEGs measure electrical activity in the brain as information in the brain is processed as electrical activity. Electrodes are places on the scalp and these detect small electrical changes resulting from the activity of the brain cells under the electrode.
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Advantages of EEGs
✅One advantage is that they have high temporal resolution which means they provide a recording of the brain in real time. The data is measured in milliseconds making the temporal resolution higher that fMRIs. This is a strength as it means EEGs are more accurate at detecting brain activity compared to fMRIs which give delayed responses and may be inaccurate
✅Another strength is the low running and buying cost of EEGs compared to fMRIs. Universities in the UK are more likely to have their own EEG whereas they have to go to a hospital to use a fMRI. This is a strength as it means its easier to carry out research using EEGs and give a larger samples which increases population validity.
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Disadvantages of EEGs
❌One limitation is that EEGs only give a general overview of electrical activity. It cannot pinpoint the exact source of neural activity, It also only picks up activity close to the electrodes. Thus the spatial resolution is much lower than fMRI and cannot help with localisation of function. This is a limitation as it only allows limited amount of research questions.
❌A further problem with EEGs is that it can only detect the activity in superficial regions of the brain. This means it cannot reveal what is going on in the deeper regions such as the hippocampus.
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What are ERPs?
An event-related potential (ERP) is the measured brain response that is the direct result of a specific sensory, cognitive, or motor event. More formally, it is any stereotyped electrophysiological response to a stimulus. ... ERPs are measured by means of electroencephalography (EEG).
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Post mortem examination
The brain of a dead individual is sliced into very thin pieces and examined, this can be used to see where damage has occurred in the brain. These are likely to be carried out on brains that have a rare disorder and will be compared against a healthy control brain. E.g a post mortem was carried out on Tan's brain and it was found that he had a large lesion in the frontal lobe in the Broca's area.
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Advantages of Post mortem
✅Post mortem allows for a detailed analysis of the brain which would not be possible with other methods. e.g fMRIs and EEGs don't give full access to the entire brain like post mortem. This is a strength as it allows researchers to examine deeper areas of the brain such as the hippocampus.
✅As researchers have direct access to brain, they are very precise. E.g it allows researchers to see exactly the specific neural circuits. This is as benefit as post mortems have extremely high spacial resolution giving more detailed information.
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Disadvantages of Post mortem
❌A weakness is that there are a number of confounding variables that can influence the results. E.g the cause of death or drug treatment. This is a problem as any comparisons to controls may not be valid.
❌A further problem is that there are issues with establishing causation. This is because post mortem studies are retrospective. Furthermore, any observed damage may not be a result of the suspected cause. This is a problem as it means it is difficult to draw a firm conclusion.
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Circadian rhythm
A circadian rhythm lasts for 24 hours and the most obvious example is the sleep/wake cycle. The body clock is regulated by an internal system including external factors e.g body temperature.
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Variations of sleep/wake cycle
1. Night owls - People wake up slowly and reach their peak performance in the afternoon or late evening.
2. Young children tend to go to sleep early and wake early. As children hit adolescence their circadian rhythm changes and they prefer to go to bed later and wake up later.
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Advantages of circadian rhythm
✅A strength is that there is supporting research. Folkard studied 12 participates who lived in a dark cave for three weeks. They went to bed at 11.45pm and woke up at 7.45am. During the study the researcher gradually sped up the clock, this meant that a 24 hour day was reduced to 22 hours. None of the participants were able to adjust comfortably to the new regime. This supports research into circadian rhythms as it suggest our internal body clocks cannot be overridden by external cues.
✅Another strength is that there are practical applications. Shift work requires the worker to adjust their sleep/wake cycle on a regular basis, which has negative impacts on health. e.g shift workers are three times more likely to develop heart disease, which can be due to stress of adjusting sleep/wake cycle. This is a strength as this can have benefits for the economy and it means that employees can consider this impact on health which reduces the burden of NHS
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Disadvantages of circadian rhythm
❌One limitation is that circadian rhythms can have individual differences. e.g the cycle length can vary from 13 to 65 hours, the onset of the cycle also differs between people. For example. Duffy found that morning people prefer to rise early and go to bed early, whereas evening people preferred to wake and go to bed later. This is a problem as it shows that despite internal body clock being innate, there is some variation in them.
❌Another problem is that many circadian rhythm studies have poor controls. For example, most studies participants are isolated from variables that can affect their CR e.g clock, radios and daylight. However they were NOT isolated from artificial dim light because it was generally though that it wont affect their CR. A psychologist found that they can adjust participants CR from 22 to 28 hours using dim light. This is a weakness as Artificial light may affect the CR acting as a exogenous zeitgeber, becoming a confounding variable.
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Endogenous pacemakers
Are our internal body clocks that regulate many of our biological rhythms such as the influence of the suprechiasmatic nuclei (SCN) and the pineal gland on the sleep/wake cycle. They are affected by the environment but can function fine without external cues.
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Research evidence for Circadian rhythm
1.Siffre spent 6 months in a cave. He measured his sleep/wake cycle without any clues as to the time of day.His main finding was that his daily rhythm lengthened to 25 hours.
2.Participants spent four weeks in a WWII bunker deprived of natural light. But they did have access to electric lights. They found that for the majority of participants their body clock settled into a sleep/wake cycle of 24-25 hours.
👁🗨Conclusion - Both studies show the existence of endogenous pacemakers because participants kept to a steady circadian rhythm without external cues. They also show that the exogenous zeitgeber of light is need to keep our cycle to 24 hours. Without external cues the sleep/wake cycle increases.
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Suprechiasmatic nuclei
Its located in the hypothalamus and is regulated by light. The SCN receives light even when the eyes are closes, so that the biological clock can adjust to changing patters of daylight whilst we are still asleep.
👩🔬Research - Ralph removed the SCN out of genetically abnormal hamsters that only had a 20 hour CR rather than 24 hour. Researchers transplanted the SCN from those hamsters into adult hamsters with a normal 24 hour CR. They found that the adult hamster's cycle changed to 20 hours. This suggest that the SCN is pivotal in regulating the sleep/wake cycle.
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Advantages of the effects of endogenous pacemakers on sleep/wake cycle
✅A strength is that there is supporting research. Folkard studied 12 participates who lived in a dark cave for three weeks. They went to bed at 11.45pm and woke up at 7.45am. During the study the researcher gradually sped up the clock, this meant that a 24 hour day was reduced to 22 hours. None of the participants were able to adjust comfortably to the new regime. This supports research into circadian rhythms as it suggest our internal body clocks cannot be overridden by external cues.
✅Another strength is that if we know that melatonin is key to making us feel tired(which is activated by the SCN), we can use medication to increase the amount of melatonin in people that struggle with their sleep/wake cycle e.g suffering from jet lag. Hoebert found that long term melatonin treatment was effective in sleep problems in 90% of cases in children with ADHD. This supports that endogenous pacemakers do play a key role in sleep/wake cycle
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Entrainment
When environmental cues adjust the body clock in line with the environment.
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Disadvantages of the effects of endogenous pacemakers on sleep/wake cycle
❌One limitation is that there is research evidence from Vetter to show that exogenous zeigebers are important in entraining sleep/wake cycle. Participants that all worked in the same office were either exposed to blue light or cool white light for five weeks between January and February. Participants exposed to the white light changed their sleep and activity in parallel to the seasonal changes in sunrise on non-work days. Those exposed to blue light remained entrained to office hours on non-work days. This supports that light is a zeitgeber that can influence sleep/wake cycle showing endogenous pacemakers are not the only influencing factor.
❌Another limitation is that its a reductionist explanation. To only look at the role of the SCN and melatonin levels ignores the importance of external factors on the sleep cycle such as light and social cues. Burgess shows that exogenous zeitgebers can change the sleep/wake cycle. This suggests that the sleep/wake cycle is more likely to be due to an interaction between internal and external factors.
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Exogenous zeitgebers
They are cues from the environment that play an important role in regulating time and our internal clock e.g sunlight.
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Light
Is seen as the most important zeitgeber(time keeper) as it resets the SCN every morning.
👩🔬Research - Burgess aimed to investigate whether the sleep cycle could be more forward to reduced jet lag.
28 participants followed a strict baseline sleep schedule for a week, they were exposed to light for the first 3.5 hours of waking over three days. There were three different conditions; continuous bright light, intermittent bright light or ordinary dim indoor light. Melatonin levels in dim light were measured before and after three days.
The change in CR were .6 hours for dim light group, 1.5 hours for intermittent group and 2.1 hours for continuous light group. This shows that light is an important exogenous zeitgeber that helps set our sleep/wake cycle.
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Social cues
Mealtime or social activities may also have a role as zeitgebers, Adapting a local time for eating and sleeping can be effective way to change ones CR when travelling.
👩🔬Research - Psychologist investigated jet lag and found that the CR or travellers adjusted quicker if they were outside more at their destination, this could be because they were exposed to social cues in the new time zone which acted as a zeitgeber, this shows that they can shift their internal body clock.
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Advantages of the effects of exogenous zeitgebers on sleep/wake cycle
✅One strength is that there is research evidence from Vetter to support that exogenous zeitgebers do help to entrain the sleep/wake cycle. Participants that worked at the same office were either exposed to a blue light or a cool white light for five weeks between January and February. It was found that participants exposed to the white light changed their sleep and activity in parallel to the seasonal changed in sunrise on non-working days. However those exposed to blue light remained entrained to office hours on non-woring days. This supports that light is a zeitgeber that can influence the sleep/wake cycle.
✅Another strength is practical application. For example, the relationship between exogenous zeitgebers can help explain jet lag and the effects of shift work. Night shift work is linked to an increased frequency of car accidents and also shift workers are three times more likely to develop heart disease. Understanding this can help to reduce problems. For example by having longer periods on the same shift pattern allowing pacemakers and zeitgebers to re-synchronise thus improving health and benefiting the economy.
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Disadvantages of the effects of exogenous zeitgebers on sleep/wake cycle
❌One limitation is conflicting research. Ralph removed the SCN out of genetically abnormal hamsters that only had a 20 hour CR rather than 24 hour. Researchers transplanted the SCN from those hamsters into adult hamsters with a normal 24 hour CR. They found that the adult hamster's cycle changed to 20 hours. This suggest that the SCN is pivotal in regulating the sleep/wake cycle not exogenous zeitgebers.
❌Another limitation is more conflicting research. Miles reported on a case study of a blind man with CR of 24.9 hours. Despite efforts to use social cues to regulate this rhythm, the rhythm did not change and he had to take stimulants and sedatives to maintain a 24 hours cycle. This contradicts the importance of external factors and shows that our endogenous pacemakers are integral to maintaining our CR.
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How is the SCN affected by light?
1. SCN detects changes in light via the optic nerve, this can happen while our eyes are closed.
2. The SCN then sends a message to the pineal gland to convert serotonin into melatonin.
3. These increased levels of melatonin cause drowsiness and also counter the stress hormone cortisol.
4. When light increases in the morning the SCN detects it and the pineal gland stops production of melatonin, this leads to the stress hormone cortisol increasing in the morning.
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Infradian rhythm
A rhythm that has a duration longer than 24 hours e.g weekly, monthly, annually menstrual cycle
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Monthly- The menstrual cycle
This is controlled mainly by endogenous pacemakers (hormones) but also zeitgebers (cycles of other women).
Female cycle lasts one month and its due to changes of hormone levels. Hormone oestrogen leads the ovary to develop an egg and release it. This occurs halfway through the cycle. Progesterone levels then rise, which allows womb lining to grow thicker, if pregnancy doesn't occur it breaks down and the cycle repeats.
👩🔬Research - McClintock took pheromones from 9 women via a cotton pad from their armpit. This was wiped onto the upper lip of 20 other women and their menstrual cycle changed. In 70% of women their cycle became closer to the 'odour donor'. This shows that exogenous zeitgebers affect out pacemakers.
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Annual- Seasonal affective disorder
This is controlled by endogenous pacemakers(melatonin) and zeitgebers(light).
SAD(seasonal affective disorder) tends to occur in the winter months. It is similar to depression in that the symptoms are persistent low mood.
It is thought that lack of sunlight affects the hypothalamus.This in turn can lead to increased melatonin which makes you feel sleepy, lowering levels of serotonin which can affect mood as its linked to depression.
👩🔬Research - Terman found that SAD was five times more common in New Hampshire then Florida because it wasn't as sunny. Golden carried out a meta-analysis and found that use of bright light as treatment for SAD was effective in reducing the symptoms. Both studies show that light is an important zeitgeber.
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Ultradian rhythms
A rhythm that lasts less than one day. e.g Sleep cycle and our Basic rest activity cycle which last 90 minutes
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Sleep stages
The sleep cycle lasts 90 minutes. Each stage of sleep has a different brainwave activity( as monitored on an EEG). The sleep cycle alternates between REM and NREM. Sleep patterns can be affected by zeitgebers such as the amount of recent sleep, temperature or stress.
Image: Sleep stages
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Basic rest activity cycle(BRAC)
Kleitman suggests that the 90 minutes ultradian rhythm continues during the day, even when awake. During the day we move from a period of alertness into a state of physiological fatigue approximately every 90 minutes. Research suggest that humans can focus for 90 minutes and towards the end of these 90 minutes the body begins to run out of resources, resulting in fatigue and loss of concentration. Daily routines tend to match this.
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Advantages of infradian and ultradian rhythms
✅One strength is that there is research to support ultradian rhythm of sleep cycle. Kleitman monitored sleep patters of 9 adults in a sleep lab. Brainwave activity was recorded on an EEG and researchers controlled for the effects of caffeine and alcohol. Everyone had a period of REM sleep and those woken during REM sleep were more likely to recall dreams than in any other sleep cycle. This study supports that the sleep cycle is an ultradian rhythm that goes thought different stages.
✅Another strength is that there is practical application that can occur from research. For example, in relation to SAD one of the most effective treatments in phototherapy. This is a light box that stimulates very strong light in the morning and evening and is thought to reset melatonin levels. Eastman found that this relieved depressive symptoms in 60%of sufferers. This supports information on the infradian rhythm is likely to be accurate.
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Disadvantages of infradian and ultradian rhythms
❌However, its hard to draw conclusions from Kleitman's research as the research was carried out in tightly controlled conditions. For example, the participants pre-sleep routine differs to at home, as does where they sleep. This limits the external validity of the results, making it difficult to state that we all go though these stages for the same amount of time. For example in a longitudinal study some psychologists found that the amount of time spent in stage 2 of sleep increased by 20% from age 10 to age 13. Therefore there are individual differences in the ultradina rhythm of the sleep cycle.
❌However, Eastman's study also recorded a placebo effect on 30% when participants were given a fake generator and were told it was another form of treatment. This questions the extent to which light is a factor in causing SAD if depressive symptoms can improve without any changes to melatonin and whether SAD is an infradian rhythm.
87
Differences between rhythms
| Circadian vs Infradian
Time: Circadian= 24h whereas Infradian= more than 24h
Endogenous pacemakers: SCN, Penal gland and melatonin whereas oestrogen and progesterone
Exogenous zeitgebers: Light, social cues and temp. whereas cycles of other women and light
88
Differences between rhythms Circadian vs Ultradian
Time: Circadian= 24h whereas Ultradian= less than 24h
Endogenous pacemakers: SCN, Penal gland and melatonin whereas Acetylcholine increased and seratonin decreased
Exogenous zeitgebers: Light, social cues and temp. whereas Exercise and stress
89
Differences between rhythms
| Infradian vs Ultradian
Time: Infradian= more than 24h whereas Ultradian= less than 24h
Endogenous pacemakers: Oeastrogen and melatonin whereas Acetylcholine increased and seratonin decreased
Exogenous zeitgebers: cycles of other women and light whereas exercise and stress
