Biopsychology Flashcards
1
Q
Nervous system definition
A
A specialised network of cells in the human body and is our primary communication system .
2
Q
Main functions of the nervous system
A
1) to collect, process and respond to information in the environment
2) to coordinate the working of different organs and cells in the body
3
Q
What are the two sub systems of the nervous system
A
1) central nervous system
2) peripheral nervous system
4
Q
What is the Central nervous system
A
It is made up of the brain and spinal cord. The brain is the centre of all conscious awareness and the spinal cord is an extension of the brain.
5
Q
What is the peripheral nervous system
A
It transmits messages via neurons to and from the CNS. The PNS is further divided into :
- the autonomic nervous system (ANS)
- the somatic nervous system (SNS)
6
Q
What is the role of the Somatic nervous system
A
It carries sensory information from the outside world to the brain and provides muscle responses via the motor pathways.
7
Q
What is the role of the autonomic nervous
A
It plays an important role is homeostasis, which maintains internal processes such as body temperature, heart rate and blood pressure. It consists of two components
- the sympathetic nervous system
- the parasympathetic nervous system
8
Q
Role of the sympathetic nervous system
A
It is typically involved in responses that prepare the body for fight or flight. Impulses travel from the sympathetic nervous system to organs to prepare us for action. For example heart rate and blood pressure increase, and digestion and salivation are suppressed.
9
Q
What is the role of the parasympathetic nervous system
A
The role is to relax the body and Return us to our normal resting state. It slows down heart and breathing rate and reduces blood pressure. Processes such as digestion and salivation are started again.
10
Q
Nervous system structure
A
1) Split into central nervous system and peripheral nervous system.
2) central nervous system split into brain and spinal cord
3) peripheral nervous system split into somatic and autonomic nervous system.
4) autonomic nervous system split into the sympathetic and parasympathetic nervous system.
11
Q
Similarities in the central nervous system
A
Both the Brain stem and spinal cord control involuntary processes. Brain controls breathing and spinal cord controls involuntary reflexes.
12
Q
Differences in the central nervous system
A
1) Brain provides conscious awareness whereas the spinal cord allows for simple reflex responses
2) the brain consists of multiple regions responsible for different functions, whereas the spinal cord has one main function.
13
Q
Similarities in the peripheral nervous system
A
Both the sympathetic nervous system and somatic nervous system respond to external stimuli. Sympathetic nervous system responds by preparing the body for fight or flight. The somatic nervous system respons to external stimuli by carrying information from sensory receptors to the spinal cord and brain.
14
Q
Differences in the peripheral nervous system
A
1) the autonomic nervous system consists of 2 components whereas the somatic only has one.
2) the somatic nervous system has sensory and motor pathways but the autonomic nervous system only has motor pathways.
3) the autonomic nervous system controls internal organs and glands, while the somatic nervous system controls muscles and movement.
15
Q
How many neurons are there in the human nervous system
A
100 billions and 80% are in the brain.
16
Q
Structure of typical neuron
A
The cell body contains the nucleus. Branch like structure called dendrimer hand out from the cell body. The axon carries Impulses away from the cell body down the length of the neuron. The axon is covered in a fatty layer of myelin sheath (protects and speeds up electrical transmission). The myelin sheath has gaps called nodes of ranvier.
17
Q
What are the three types of neurons
A
- sensory
-relay - motor
18
Q
What are sensory neurons
A
They Are found in receptors such as eyes, ears, tongue and skin, and carry nerve impulses to the spinal cord and brain. They have long dendrites and short axons. The cell body is in the middle of the neuron.
19
Q
What are relay neurons
A
They Are found in the Brain and spinal cord and allow sensory and motor neurones to communicate. They have short dendrites and short axons. They do not have a myelin sheath
20
Q
What are Motor neurons
A
They Are found in the central nervous system and control muscle movements. When stimulated, they release neurotransmitters that bind to the receptors on muscles to trigger a response, which lead to movement. They have short dendrites and long axons.
21
Q
Process of synaptic transmission
A
- a neuron is activated by a stimulus, the inside of the cell becomes Positively charged causing an action potential.
- this creates an electrical impulse that travels down the axon towards the end of the neuron.
- once the action potential reaches the axon terminal, it has to cross the gap between the pre and post synaptic neuron.
- on the axon terminal there are synaptic vesicles that contain neurotransmitters , so when the action potential reaches the vesicles, they release their contents via exocytosis,
- the neurotransmitter diffuses across the synaptic gap where it binds to receptors on the dendrites of the post synaptic neuron.
22
Q
What are the two types of neurotransmitters
A
Excitatory
Inhibitory
23
Q
How do excitatory neurotransmitters work + examples
A
The Neurotransmitter Binds to the post synaptic neuron creating an excitatory post -synaptic potential, meaning the post synaptic cell is more likely to fire. Examples include adrenaline and dopamine.
24
Q
How does an inhibitory neurotransmitter work
A
The Neurotransmitter binds to the Post synaptic neuron receptors resulting in an inhibitory post-synaptic potential, making it less likely the neuron will Fire. Examples include serotonin and GABA.
25
What is summation
The likelihood a cell will Fire by adding up excitatory and the inhibitory synaptic input. If the net effect is excitatory, the cell is likely to fire. If the net effect is inhibitory, the cell is less likely to fire.
26
What is the function of the endocrine system
-It is a network of glands that secrete hormones and works alongside the nervous system to control vital functions,
-release hormones/chemical messengers from glands into the bloodstream which then bind with
specific receptors in order to regulate the activity of cells or organs in the body
- for example the thyroid gland releases thyroxine which affects metabolic rates which in turn affects growth rates.
- dysfunctions in hormone secretion can have serious consequences eg not being able to enter the fight or flight response due to lack of adrenaline.
27
3 glands, the hormones they secrete and their effects
Thyroid gland - releases thyroxine - regulates the body’s metabolic rate and protein synthesis
Pineal gland - releases melatonin - regulation of biological rhythms and the sleep-wake cycle
adrenal glands- secretes adrenaline/controls the sympathetic division in the fight or flight response
28
What is the fight or flight response
This is where an individual experiences a threatening or stressful situation and causes adrenaline to be secreted from the adrenal medulla.
29
Response to acute (sudden) stressors
When the SNS is triggered, it sends a signal to the adrenal medulla to secret adrenaline into the bloodstream. As adrenaline circulates, it causes a number of physiological changes.
When the threat has passed, the PNS dampens down the stress response, by slowing down heartbeat, reducing blood pressure and starting digestion again.
30
Affects of adrenaline
1) increased heart rate- increase blood flow to organs and movement of adrenaline around the body
2) increased breathing rate. - to increase oxygen intake
3) pupil dilation- to increase light entry into the eye to enhance vision
3) sweat production - to regulate temperature
5) reduction of non-essential functions eg digestion/urination- to increase energy for other essential functions.
31
Strengths of fight or flight
1) It makes sense from an evolutionary point of view because it would have also helped an individual to survive by fighting or fleeing a threat.
32
Weaknesses of fight or flight
1) one weakness is that it doesn’t take into account other responses. Gray suggests that the first response to danger is to avoid confrontation altogether, which is demonstrated by a freeze response where animals and humans are hyper-vigilant to decide what is the best course of action.
2) the fight or flight response is typically a male response to danger and recent research suggests that females adopt a “tend and befriend” response. Taylor et al suggested women are more likely to protect their offspring and form alliances with other women rather than fight an adversary or flee.
3) while the fight or flight response may have been Good for our ancestors who faced life threatening situations eg predators, modern day life rarely requires such an intense biological response. Humans who face a lot of stress continually activate the SNS, which continually raises blood pressure causing heart disease.
33
What is localisation of function?
The principle that specific functions such as language, memory etc have specific locations in the brain.
34
What is the motor cortex located?
It is located in the back of the frontal lobe. Both hemispheres of the brain have a motor cortex that control the muscles on the opposite side of the body.
35
What is the function of the motor cortex?
The motor cortex is responsive for the generation of voluntary movements. Damage to this area can cause muscle dysfunction and paralysis
36
Where is the somatosensory cortex located?
It is located in the parietal lobe of both hemispheres of the brain.
37
What is the function of the somatosensory cortex?
It receives input from receptors in the skin, including touch, pain, pressure and temperature from all areas of the body surface.
38
Where is the visual cortex located?
It is located in the occipital lobe in both hemispheres of the brain.
39
What is the function of the visual cortex?
It processes information such as colour and shape. Damage to this area can cause blindness and loss of visual perception.
Visual processing starts in the retina where light enters and strikes the photoreceptors. Nerve impulses from the retina are transmitted to the brain via the optic nerve. The majority terminate in the thalamus, which acts as a relay station, passing the information onto the visual cortex
40
Where is the auditory centre located?
In both hemispheres of the temporal lobe
41
What is the function of the auditory cortex?
It is concenrned with hearing eg volume and pitch.
The auditory pathways begin in the inner ear, where sound waves are concerted to nerve impulses, which travel via the auditory nerve to the auditory cortex in the brain.
42
What is the Broca’s area?
– This area is named after Paul Broca who treated patients who had difficulty producing speech. He found that they had lesions to the left hemisphere of the frontal lobe.
Damage to the broca’s Area causes Expressive Aphasia. This disorder affects language production but not understanding. Speech lacks fluency and patients have difficulty with certain words which help
sentences function (e.g. ‘it’ and ‘the’)
43
What is Wernicke’s area?
This area is in the left hemisphere of the temporal lobe. Carl Wernicke found that patients with a lesion to this area could speak but were unable to understand language. Wernicke concluded that this area is responsible for the processing of spoken language.
The Wernicke Area is connected to the Broca’s Area by a neural loop. Damage to the Wernicke’s Area
causes Receptive Aphasia. This disorder leads to an impaired ability to understand language.
44
Strengths of localisation of function
1) Peterson et Al used brain scans to show how Wernicke’s area was active during a listening task and Broca’s area was active during a reading task. This suggests language is localised to these two areas. Brain scans are also highly scientific and objective.
2) a study was conducted on Phineas Gage who had an accident on the railway tracks in 1848, ans suffered from brain damage as a pole was forced through his temporal lobe. Gage suffered a complete change in personality after the accident suggesting that personality is localised to the temporal lobe.
45
Weaknesses of localisation of function
1) Karl Lashley found that higher cognitive functions such as learning are not localised to specific areas of the brain. He removed areas of the cortex in rat’s brains ans found that no area was more important in terms of the rat’s ability to run the maze. This suggests that the study of brain localisation is reductionist as it simplifies our behaviour to specific areas rather than the working of the brain as a whole.
2) Bavelier et al found a large variability in individual patterns of activation across individuals. For example he observed activation in the right and left temporal lobe and occipital lobe when individuals were reading silently. Therefore there are individual differences in response to various activities and localisation of function.
46
What is hemispheric lateralisation?
Hemispheric lateralisation refers to the notion that certain functions are principally controlled by one side of the brain
47
What has Research shown about the left hemisphere?
It is dominant for language.
48
What has Research shown about the right hemisphere?
It is dominant for visuo-spatial functions and facial recognition.
49
Why is the brain described as contralateral?
The left hemisphere deals with the right side of the body and the right hemisphere controls the left side of the body.
50
How are the two hemispheres connected?
They are connected by a bundle of nerve fibres called the corpus callosum. This enables informations to be communicated between the two hemispheres
51
Strengths of brain lateralisation?
1) one advantage of hemispheric lateralisation is that it makes sense from an evolutionary standpoint. It increases neural processing capacity, which is adaptive. Rogers eg al (2005) found that hemispheric lateralisation in chickens is associated with na ability to perform two tasks simultaneously (finding food and being vigilant for predators).
2) lateralisation means we can study people who are left handed, and why they are more prone to illness. Tonnessen et al found a relationship between handedness and immune disorders suggesting a link between brain lateralisation and development of the immune system.
52
Weaknesses of brain lateralisation?
1) lateralisation changes with age. Szaflarski et al found that language became more lateralised to the left hemisphere up to age 25 but decreased after that.
2) lateralisation does not explain brain plasticity research. Danelli et al used a case study of an Italian boy EB, who had a large tumour removed from the left hemisphere. After the operation, he lost all linguistic abilities. He was put into a rehabilitation programme and his language abilities improved. When they tested him at age 17, they found his right hemisphere has compensated the loss of his left hemisphere
53
Why did past surgeons cut the corpus callosum?
This is to prevent violent electrical activity caused by epileptic seizures crossing from one hemisphere to the other. Patients who underwent this surgery are referred to as split-brain patients.
54
Who conducted research into split-brain patients?
Sperry and Gazzaniga (1968)
55
What was Sperry and Gazzaniga’s research?
Patients were asked to stare at a dot in the centre of a screen and then information is presented in either the left or right visual field. They were either asked to describe what they saw, in either field or they had to draw what they saw.
56
Findings of split brain research?
1) the picture presented to the right visual field (processed by left hemisphere), the patient could describe verbally what they saw, as the left hemisphere controls language. However when presented in the left visual field, they could not describe what was shown.
2) in the drawing task, when a picture was presented in the right visual field (processed by left hemisphere) , the picture was never as clear as the left hand showing how right hemisphere controls visual motor tasks.
57
Strengths of split-brain research?
1) split brain research has allowed us to prove that there is hemispheric lateralisation, and different hemispheres have different roles. It has also shown that connectivity between the two areas is as important as the operation of the different parts.
2) experiments on split-brain patients are high controlled and scientific. Each participant in sperry’s study was tested in the same conditions, and they all were epileptic patients who had split brain surgery so it reduces individual differences.
58
Weaknesses of split brain research?
1) one issue with split brain research is that there are very few patients and only between 10-15 have been subjected to extensive study meaning there is a small sample size. The samples often were varied in terms of age and gender so different results occurred, making it difficult to generalise findings
2) the data from the research is very artificial. In the real world, a severed corpus callosum can be compensated for by the unrestricted use of both visual fields. This means the research lacks ecological validity.
59
What is brain plasticity?
Brain plasticity is the ability of the brain to modify the structure and function based on experience.
Plasticity allows the brain to cope better with the indirect effects of brain damage, such as swelling or haemorrhage following a road accident, or the damage resulting from inadequate blood supply following a stroke.
60
Strengths of brain plasticity?
1) Blakemore and Mitchell were studying the development of the visual cortex in cats. They were able to show that characteristics of visual neurons were permanently changed by exposure to specific environments after birth. Kittens reared in an environment with black vertical stripes did not respond to horizontal black stripes, showing how exposure to certain stimuli affects brain development.
2) Davidson et al. (2004) demonstrated the permanent change in the brain generated by prolonged meditation. Buddhist monks who meditated frequently had a much greater activation of gamma waves, which coordinate neural activity, than students who had no experience of meditation.
61
Weaknesses of brain plasticity?
1) one Limitation of plasticity is that it may be negative behaviourial consequences. Evidence has shown that the brain’s adaptation to prolonged drug use leads to poorer cognitive functioning as well as increased risk of dementia as found by medina et Al. This shows that brain plasticity is not always beneficial.
2) one weakness is that studies carried out on animals eg blakemore and Mitchell used kittens, which have very different brain development to humans. This means we have to be cautious when generalising findings from animals studies to humans.
62
What is functional recovery?
Functional recovery is where the brain recovers abilities previously lost due to brain damage, it is an example of plasticity. Research suggests that young brains are more plastic, however, the brain is capable of plasticity and functional recovery at any age. Studies have suggested that women recover
from a brain injury quicker than men do.
63
What are the mechanisms for recovery?
1) axonal sprouting
2) denervation super sensitivity
3) recruitment of homologous areas
4) neuronal unmasking
64
What is axonal sprouting?
the growth of new nerve endings which connect with other undamaged nerve cells to form new neuronal pathways
65
What is denervation supersensitivity?
this occurs when axons that do a similar job become aroused to a higher level to compensate for the ones that are lost. However, it can have the negative consequence of oversensitivity to messages such as pain
66
What is recruitment of homologous areas?
Opposite sides of the brain will now perform the specific tasks. For example if the Broca’s area on the left side of the brain was damaged, the right side would carry out its functions for a period of time.
67
What is Neuronal unmasking?
Wall (1977) first identified ‘dormant synapses’ in the brain. This unmasking of dormant synapses can open connections to regions of the brain that are not normally activated creating a lateral spread of activation which then gives way to the development of new structures.
68
Strength of functional recovery after trauma?
1) one strength of understanding the processes involved in functional recovery is its practical application. It has contributed to the field of neuro-rehabilitation. This is when doctors provide therapy and electrical stimulation of the brain to counter the deficits in motor and/or cognitive functioning that may have been experienced following a stroke for example.
69
Weaknesses of functional recovery after trauma?
1) Elbert et al (2001) concluded that the capacity for neural reorganisation is much greater in children than adults as shown by the extended practice that adults require in order to produce changes, so findings cannot be generalised.
2) There are have studies to show there is are gender differences when it comes functional recovery. Ratcliffe et al (2007) examined 325 patients with brain trauma for their level of response for cognitive skills to rehabilitation. The patients were 16-45 years old at injury, received rehabilitation at a care facility, and completed a follow-up one year later. It was found that women performed significantly better than men on tests of attention/working memory and language whereas men outperformed females in visual analytical skills.
70
What is fMRI?
1) Functional magnetic resonance imaging provides an indirect measure of neural activity.
2) it uses magnetic fields and radio waves to monitor blood flow to the brain.
3) It measures the change in energy released by Haemoglobin, reflecting activity of the brain to give a moving picture of the brain.
4) activity can be measured by comparing brain activity during a base line task and during a specific activity.
71
Strengths of fMRI?
1) fMRIs capture dynamic brain activity as opposed to a post-mortem examination which purely show the physiology of the brain.
2) fMRIs have good spatial resolution.
72
Weaknesses of fMRIs?
1) interpretation of fMRI is complex and is affected by poor temporal resolution, biased interpretation and by the base line task used.
2) fMRI research is expensive leading to reduced sample sizes which negatively impact the validity of the research.
73
What is an electroencephalogram (EEG)?
1) an EEG directly measures general neural activity in the brain, usually linked to states such as sleep and arousal.
2) electrodes are placed on the scalp and detect neuronal activity below where they are placed.
3) when electrical signals from the different electrodes are graphed over a period of time, the resulting representation is called an EEG pattern.
4) a patient with epilepsy has spikes in their EEG pattern, a patient with a brain injury show a slowing of electrical activity.
74
Strengths of EEGs?
1) an EEG provides a recording of the brain’s activity in real time rather than a still image. This means a researcher can accurately compare activity during different tasks while the test is happening, so good temporal resolution.
2) EEGs is useful in clinical diagnosis of conditions such as epilepsy. It has also contributed to our understanding of the stages involved in sleep especially ultradian rhythms.
75
Weaknesses of EEGs?
1) EEGs can only detect the activity in superficial regions of the brain so cannot reveal what is happening in the deeper regions such as the hippocampus, so difficult to understand the functioning of LTM through EEGs.
2) EEG signal is not useful for pinpointing the exact area of neural activity so has poor spatial resolution.
76
What are Event related potentials (ERPs)?
1) electrodes are placed on the scalp and directly measure neural activity in response to a specific stimulus introduced by the researcher.
2) to establish a specific response to a target response to a target stimulus required many presentations of the stimulus and the responses are averaged together so that any extraneous neural activity cancels itself out.
77
Strengths of ERPs?
1) ERPs are cheaper than an fMRI so can be used more widely in research.
2) ERPs can measure the processing of a stimulus even in absence of a behavioural response. Therefore it is possible to measure “covertly” the processing of a stimulus.
78
Weaknesses of ERPs?
1) ERPs like EEGs have poor spatial resolution. So w cannot be sure which areas of the brain are responsible for specific behaviours.
2) there is a lack of standardisation in ERP methodology beween different Research studies so findings cannot be generalised.
79
What is Post-mortem examinations?
1)When an individual dies, the psychologists look for abnormailties in the brain that might explain their behaviour.
2) post mortem studies have found a link between brain abnormalities and psychiatric disorders for instance there is evidence of reduced glial cells in the Frontal lobe of patients with depression .
80
Strengths of post-mortem examinations?
1) post mortem examinations allow for more detailed examinations of anatomical and neurochemical aspects of the brain compared to other methods of studying the brain. this allows for researchers to examine certain areas such as the hippocampus and hypothalamus.
2) Harrison claims that post-mortem studies have plaued a central part in our understanding of the origins in schizophrenia and other mental illnesses. For example iverson found that high levels of dopamine correlated to schizophrenia.
81
Weaknesses of post-mortem examinations?
1) studies using post mortem examinations lack validity because people die in a variety of circumstances and at varying stages of disease. Similarly, the length of time between death and the examination can affect results.
2) post mortem studies have very samall sample sizes. This means the sample cannot be said to be representative of the target population and so it is problematic to generalise the findings to the wider population.
82
What are biological rhythms?
Biological rhythms are cyclical changes in physiological systems. They evolved because the environments in which the organisms live have cyclical changes eg day/night , summer/winter.
83
What are circadian rhythms?
Circadian rhythms are any cycle that lasts 24 hours. Nearly all organisms possess a biological representation of the 24 hour day. These optimise an organism’s physiology and behaviour to best meet the varying demands of the day/night cycle.
84
How do circadian rhythms work?
1) Circadian rhythms are driven by the suprachiasmatic nuclei (SCN) in the hypothalamus.
2) This pacemaker (controls the rate at which something occurs) must constantly be reset so that our bodies are in synchrony with the outside world.
3)Natural light provides the input to this system, setting the SCN to the correct time in a process called photoentrainment.
4) The SCN then uses this information to coordinate activity of circadian rhythms throughout the body.
85
What is the sleep-wake cycle?
1) light and darkness are external signals that determine when we need to sleep and wake up. Our strongest sleep drive occurs 2-4 am and 1-3pm.
2)the release of melatonin from pineal gland is highest during hours of darkness. Melatonin indices sleep by inhibiting neural mechanisms that promote wakefulness. Light suppresses production of melatonin.
3) sleep and wakefulness are also under homeostatic control. When we are awake for a long time, homeostasis drive for sleep gradually increases, reaching its maximum in the late evening.
4) circadian rhythms keep up awake as long as there is daylight, prompting us to sleep when it’s dark. The internal circadian Rhythm maintains a cycle of 24-25 hours even without natural light.
86
Strengths of circadian rhythms?
1) one practical application of circadian rhythms is chronotherapeutics. The time that patients take medication is very important for treatment success. Medications have been developed that are taken before the person goes to sleep but are not released until the vulnerable time of 6:00 am.
87
Weaknesses of circadian rhythms?
1) there are individual differences in the length of circadian rhythms. One research study found that cycles vary from 13-165 hours.
2) another individual difference in circadian rhythms is when they reach their peak. Morning people prefer to rise easily and go to bed early whereas “evening people” prefer to rise late.
3) studies of individuals in the arctic regions where the sun does not set in summer months show normal sleeping patterns despite prolonged exposure to light. This suggests that exogenous Zeitgeber of light has little effect on internal biological rhythms.
88
What are ultradian rhythms?
Ultradian rhythms span a period of less than 24 hours.
89
Example of an ultradian rhythm?
An example is the five sleep stages. Human sleep follows a pattern alternating between Rapid Eye Movement (REM) sleep (which is stage five) and Non-Rapid Eye Movement (NREM) sleep (which consists of stages one, two, three and four). The cycle repeats itself every 90 minutes.
90
What are the EEG patterns of sleep stages?
1) Each stage shows a distinct EEG pattern. As the person enters deep sleep, their brainwaves slow and their breathing and heart rate decreases. During the fifth stage (REM sleep), the EEG pattern resembles that of an awake person. It is during this stage that dreaming occurs.
91
What is the basic rest activity cycle (BRAC)?
Kleitman (1969) referred to the 90 minute cycle found during sleep as the Basic Rest Activity Cycle (BRAC). He suggested that this 90 minute cycle continues when we are awake. During the day, rather than moving through the sleep stages, we move progressively from a state of alertness into a state of physiological fatigue. Studies suggest that the human mind can focus for about 90 minutes, and towards the end of those 90 minutes the body begins to run out of resources, resulting in loss of concentration, fatigue and hunger.
92
Evaluation of ultradian rhythms?
1) Ericsson et al found support for ultradian rhythms. They studied a group of violinists and found that amount this group practise sessions were limited to 90 mins at a time. Violinists frequently slept to recover from oractice. The same pattern found amongst athletes, chess players and writers, which fits with BRAC.
2) Tucker et Al suggests that there are individual differences in ultradian rhythms which are biologically determined. Participants were studied for 11 days and nights in a lab environment. The researchers asssesed sleep duration, time taken to fall asleep and the amount of time in each stage and found differences in all characteristics.
93
What are infradian rhythms?
Infradian rhythms span a period longer than 24 hours. They may last weeks, months of even a year.
94
Example of infradian rhythms?
1) One example of an infradian rhythm is the menstrual cycle, which lasts for about a month. There are considerable variations in the length of this cycle, with some women experiencing a 23 day cycle and others a 36 day cycle (Refinetti, 2006). The average is 28 days.
2) Hormones regulate the menstrual cycle. Ovulation occurs roughly halfway through the menstrual cycle, when oestrogen levels are at their peak, and usually lasts for 16-32 hours. After ovulation, progesterone levels increase in preparation for the possible implantation of an embryo in the uterus.
95
Evaluation of infradian rhythms?
1) infradian rhythms can affect behaviour. Penton-voak found that women expired a preference for feminised male faces when choosing a long term partner. However, they showed preference for masculinised faces during ovulation.
2) the menstrual cycle is not only governed by infradian rhythms. When women of childbearing age live together, their menstrual cycles synchronise. In one study, the sweat from the upper lip of another group of women was rubbed onto a group of women and their menstrual cycles became in sync. Suggestion synchronisation is affected by pheromones.
96
What are endogenous pacemakers?
They are internal body clocks that regulate biological rhythms.
97
Example of endogenous pacemaker + function?
1) The suprachiasmatic nuclei (SCN). A tiny cluster of nerve cells in the hypothalamus that acts as a master clock controlling circadian rhythms.
2) neurons in the SCN synchronise so that neurons elsewhere receive time-coordinated signals. SCN’s built in circadian rhythms resets when external light levels change, and receives information about light levels from the optic nerve.
3) SCN also regulates the manufacture and secretion of melatonin in the pineal gland. SCN send signals to pineal gland to increase melatonin production and night and decrease it as light levels rise in the morning.
98
Evaluation of endogenous pacemakers?
1) Folkard studied a uni student Kate aldcroft who spent 25 days in a lab. She had no access to exogenous zeitgebers of light to reset the SCN. However, at the end of the 25 days her core temperature rhythm was still at 24 hours indicating we do not need exogenous zeitgebers of light to maintain our internal biological rhythms.
2) Kate aldcroft’s sleep-wake cycle extended to 30 hours, with periods of sleep as long as 16 hours. This suggests that we do need exogenous zeitgebers of light to maintain internal biological rhythms.
99
What are exogenous zeitgebers?
Exogenous zeitgebers are environmental events that are responsible for maintaining the biological clock of an organism.
100
Example of exogenous zeitgeber + function?
1) The most important zeitgeber is light. Receptors in the SCN are sensitive to changes in light levels during the day and use this to synchronise the activity of the bidy’s organs and glands.
2) light resets the internal biological clock. A protein in the retina if the eye called melanopsin which is sensitive to natural light is important to this system.
3) when people move to Night Shift or to another country with different time zone, the endogenous zeitgebers are out of synchrony with the exogenous zeitgeber of light. This leads to disrupted sleep patterns, increased anxiety and decreased alertness.
101
Evaluation of exogenous zeitgebers?
1) the vast majority of blind people who still have light perception have normal circadian rhythms. Blind people without light perceptions show abnormal circadian rhythms which shows the vital role exogenous zeitgebers of light play in maintains internal biological rhythms.
2) burgess et Al found that exposure to bright light prior to an east west flight decreased the time needed to adjust circadian rhythms to local time.
3) studies show individuals who live in artic regions where the sun doesn’t set in summer months still have normal sleep patterns despite prolonged exposure to light. This suggests there are occasions where exogenous zeitgebers of light are not as important to internal biological rhythms.
