4.2.2 Biopsychology

Question 1

the nervous system

Answer 1

• the main system that controls the mind and body
• divided into two parts;
• the central nervous system (CNS)
• the peripheral nervous system (PNS)

Question 2

the central nervous system (CNS)

Answer 2

• made up of the brain and the spinal cord
• the brain is central to maintaining life and has many functions, including;
• language production and understanding
• co-ordinating movement
• coding sensory data from sensory organs
• regulates bodily processes based on info from the peripheral nervous system
• sleep
• the spinal cord connects the brain with the peripheral nervous system;
• it ensures that signals from the brain are transmitted to the rest of the body via the PNS
• it’s also involved in unconscious movements, i.e. reflex actions

Question 3

the peripheral nervous system

Answer 3

• consists of nerves which branch out from the brain and spinal cord, forming the communication network between the CNS and the rest of the body
• transmits messages throughout the whole body from the brain and relays messages back to the brain
• divided into two sections;
• the somatic nervous system
• the autonomic nervous system

Question 4

the somatic nervous system

Answer 4

• transmits and receives messages from the senses
• responsible for voluntary movement and is under conscious control

Question 5

the autonomic nervous system

Answer 5

• transmits and receives info from the organs
• responsible for involuntary movement and isn’t under conscious control
• divided into two further sections;
• the sympathetic system (increases activity)
• the parasympathetic system (decreases activity to conserve the body’s energy)

Question 6

neurons

Answer 6

• these are cells within the nervous system that transmit info as electrical impulses throughout the body
• thought to be around 100 billion neurons in the brain and over 1 billion in the spinal cord
• there are 3 main types of neuron;
• sensory
• relay
• motor

Question 7

structure of neurons

Answer 7

• all 3 types of neuron have the same general structure;
• the dendrite (receptor) receives a signal
• the signal is carried towards a cell body (which contains the nucleus)
• the signal travels along an axon towards the axon terminal
• synaptic terminals / ending at the end of the axon pass the electrical signal to the next neuron
• sensory and motor neurons are myelinated; they have myelin sheath (an insulating layer) which protects axons and allows impulses to jump between the nodes of ranvier (gaps in the myelin sheath), therefore it speeds up transmission of an impulse

Question 8

sensory neurons

Answer 8

• diagram 1
• they carry info from receptors in the PNS towards the CNS
• they keep the brain informed about the external and internal environment via processing info coming from sense organs
• dendrites, cell body and axon in the PNS and synaptic terminals in the CNS where they connect to relay neurons
• myelinated neurons
• they’re unipolar as they can only transmit messages

Question 9

relay neurons

Answer 9

• diagram 2
• they connect sensory neurons to motor neurons
• they’re based in the CNS
• unmyelinated neurons
• they’re multipolar as they can both transmit and receive messages

Question 10

motor neurons

Answer 10

• diagram 3
• they carry signals from the CNS to organs, muscles and glands in the body (effectors)
• cell body in the CNS and the rest of the nerve in PNS
• myelinated neurons
• multipolar neurons as they can both transmit and receive messages

Question 11

reflex arc

Answer 11

• a neural pathway that controls a reflex action
• stages of a reflex arc;
• a stimulus is detected by sense organs in the PNS, e.g. change in temperature if we touch something hot
• sense organs convey a message along a sensory neuron
• message reaches CNS
• CNS connects with a relay neuron
• relay neuron transfers message to a motor neuron
• motor neuron carries message to an effector, e.g. a muscle
• this causes a reflex response, e.g. muscle contracts to move hand away from hot object

Question 12

synapses

Answer 12

• the gap between two neurons
• consists of a pre-synaptic membrane, synaptic cleft and post-synaptic membrane
• signals within neurons are transmitted electronically, but signals between neurons are transmitted chemically, as electrical impulses can’t jump across synapses

Question 13

synaptic transmission

Answer 13

• diagram 4
• the process of sending info from one neuron to another
• info is passed down the axon of a neuron as an electrical impulse (action potential)
• the pre-synaptic membrane contains vesicles, which release neurotransmitters (chemical messengers) that diffuse across the synaptic cleft and bind to receptors in the post-synaptic membrane
• this stimulates the post-synaptic membrane to generate an electrical impulse that then travels down the axon of the post-synaptic neuron
• to prevent continued stimulation of the second neurone, the neurotransmitters are then recycled as they’re released from receptors, taken back up by the pre-synaptic membrane and repackaged into vesicles, or they may be destroyed by being degraded by enzymes in the synapse

Question 14

excitation and inhibition

Answer 14

• neurotransmitters can have either excitatory (positive) or inhibitory (negative) effects
• excitatory; increases the likelihood of the neuron firing an impulse (depolarisation), e.g. dopamine
• inhibitory; decreases the likelihood of the neuron firing an impulse (hyperpolarisation), e.g. serotonin

Question 15

summation

Answer 15

• the process of adding (‘summating’) the excitatory and inhibitory signals from the neurotransmitters to determine the net effect and therefore whether or not an action potential will be generated
• spatial summation; involves simultaneous signals from multiple presynaptic neurons being received by a postsynaptic neuron
• temporal summation; involves a single presynaptic neuron rapid-firing signals to a postsynaptic neuron

Question 16

the endocrine system

Answer 16

• diagram 5
• a system of glands that secrete hormones into the bloodstream, which produces an effect upon reaching a target cell / organ
• transmits info chemically
• operates much slower than the nervous system

Question 17

structures in the endocrine system

Answer 17

• hypothalamus; stimulates and controls release of hormones from pituitary gland
• pituitary gland; ‘master gland’ which produces hormones that control the release of hormones from other glands, e.g. FSH and LH
• pineal gland; melatonin for sleep regulation
• thyroid gland; thyroxine to control metabolism
• pancreas; insulin (decreases) and glucagon (increases) to control blood sugar levels and digestive enzymes, e.g. amylase and lipase
• adrenal gland; adrenaline for fight or flight response
• ovaries (female); oestrogen, i.e. female sex hormone, and progesterone which regulates uterus for pregnancy and is also made by the placenta
• testes (male); testosterone, i.e. male sex hormone

Question 18

pituitary gland

Answer 18

• connects the endocrine system to the nervous system via the hypothalamus
• secretes hormones which act on other glands to stimulate the release of other hormones to bring about certain effects
• split into anterior (front) and posterior (rear) lobes
• anterior lobes produce peptide hormones, e.g. FSH, LH, growth hormone, thyroid -stimulating hormone (TSH) which stimulates the thyroid to release thyroxine, and adrenocortical trophic hormone (ACTH) which stimulates the adrenal cortex and the release of cortisol
• posterior lobes produce vasopressin (regulates blood pressure) and release oxytocin (responsible for uterus contractions during childbirth)

Question 19

fight or flight response

Answer 19

• preparing the body for action (either fighting or fleeing) upon sensing a threat;
• the body senses a threat
• through sensory neurons in the PNS, this info is sent to the hypothalamus in the brain which coordinates a response and triggers increased levels of activity in the sympathetic branch of the ANS
• this stimulates the adrenal medulla within the adrenal glands to release adrenaline and noradrenaline which is transported to target effectors via the bloodstream
• different bodily activities are increased to either fight or flee from the threat
• once the brain senses that the threat has passed, the parasympathetic nervous system kicks in to reduce these activities and returns the body to a resting state (rest and digest response)

Question 20

adrenaline in the fight or flight response

Answer 20

• adrenaline increases bodily activities to either fight or flee from the threat, e.g;
• blood pressure and heart rate increase to supply blood to the muscles at a faster rate
• breathing rate increases so more oxygen can be sent to muscles
• muscles become more tense so the body is physically responsive
• salivation decreases as the digestion system decreases so that more blood can be directed to the muscles
• pupil size increases so more light can enter the eyes, allowing for clearer vision

Question 21

localisation of function in the brain

Answer 21

• diagram 6
• more modern approach as early scientists saw the brain in a holistic way (all areas used for all function)
• localisation suggests that certain functions have specific locations in the brain;
• motor cortex; responsible for voluntary movement and is located in the frontal lobes
• somatosensory cortex; responsible for sensing physical sensations on your skin (touch), i.e. pressure, heat, etc., and is located in the parietal lobes
• auditory cortex; responsible for processing sound and is located in the temporal lobes
• visual cortex; responsible for processing visual info from the eyes and is located in the occipital lobes

Question 22

hemispheric lateralisation

Answer 22

• diagram 7
• dividing the brain into two hemispheres; a left and right one
• the two hemispheres are connected by the corpus callosum (a bundle of nerve fibres) which acts as a bridge and allows them to send messages and work together. info passes through this to whichever side of the brain needs to deal with it
• each hemisphere has 4 brain lobes;
• frontal lobe; prefrontal area, motor cortex, Broca’s area
• temporal lobe; auditory cortex, Wernicke’s area
• parietal lobe; somatosensory cortex
• occipital lobe; visual cortex
• there is also a cerebellum which controls balance, coordination and the brain stem, which controls involuntary responses
• in general, the hemispheres are contralateral, i.e. info from the left side of the body is processed by the right hemisphere and vice versa
• e.g. damage to the motor cortex in the right hemisphere will affect the person’s ability to move their left side
• the left hemisphere is called the ‘dominant’ one as it’s generally responsible for language and speech, logic, analysis and problem solving
• the right hemisphere is generally more concerned with spatial reasoning, interpreting visual info and recognising emotions (facial expressions)

Question 23

language centres

Answer 23

there are two areas, located in the left hemisphere, particularly important for language; Broca’s area and Wernicke’s area

Question 24

Broca’s area

Answer 24

• responsible for speech production
• located in the frontal lobe of the left hemisphere (for most people)
• identified by and named after Paul Broca, who observed that patients who’d had difficulty producing words had lesions (damage) in this area of the brain
• damage to the Broca’s area causes Broca’s aphasia; a condition involving impaired speech production (slow speech and a lack of fluency) and an inability to find the right words

Question 25

Wernicke’s area

Answer 25

• responsible for language comprehension
• located in the temporal lobe of the left hemisphere (for most people)
• identified by and named after Wernicke, who found that patients who had damage near the auditory cortex had specific language impairments
• damage to the Wernicke’s area causes Wernicke’s aphasia; a condition involving the use of nonsensical words due to the inability to grasp the correct meaning of words, but no issues with actual speech production

Question 26

localisation of function - strengths

Answer 26

• Phineas Gage; he had an accident where an iron rod shot through his skull whilst at work, damaging the left frontal lobe of his brain. before the accident, he was calm and polite, but after it he became rude and violent, supporting the idea of localisation and that personality change can be explained by damage to a specific area of the brain
• fMRI scans demonstrate correlations between different mental activities and different areas of the brain, e.g. Ovaysikia et al. (2011) demonstrates increased blood flow in different areas of the brain depending on whether a person is reading words of recognising facial expressions

Question 27

localisation of function - limitations

Answer 27

• case studies, e.g. phineas gage, use a sample size of one so it may not be valid to generalise findings to the entire population
• higher cognitive processes, e.g. learning, language and memory, are too complex to be localised within a single area, and may be distributed in a holistic way within the brain instead
• e.g. Lashley’s (1950) equipotentiality theory; he removed different parts of rats brains while they were learning a maze but found no single area was more important in their ability to learn the maze, implying that higher cognitive processes aren’t localised as damage to the brain can result in other areas taking control of functions that were previously controlled by the damaged part
• neuroplasticity; the brain can recover functions after damage to areas associated with that function, suggesting mental activities aren’t localised in these areas, e.g. Danelli et al. (2013) describes the case study of a boy who had his entire left hemisphere removed and still learnt to speak

Question 28

split brain research

Answer 28

• the left and right hemispheres are connected by the corpus callosum, which allows for quick communication between the two hemispheres
• in rare cases of extreme epilepsy, a surgeon may perform a corpus callosotomy (cutting the corpus callosum), separating the two hemispheres
• this stops the electric seizures bouncing between hemispheres, containing them to just one side of the brain, thus reducing their severity
• patients who’ve undergone a corpus callosotomy (split-brain patients) are able to live relatively normal lives, but there are some effects on functioning, as observed by Sperry

Question 29

Sperry’s split brain research

Answer 29

• Sperry (1968) studied 11 split-brain patients
• he projected info into each visual field and in a series of tests, ppts were asked to either say what they saw, draw it, or pick it out from hidden objects
• he found that when info was presented to the right visual field (left hemisphere) ppts could describe it in words, but when info shown to the left visual field (right hemisphere), they couldn’t describe what they saw
• this is likely because the visual cortex is contralateral, so visual data in the right hemisphere couldn’t be shared to the language processing areas in the left hemisphere in order for the ppt to describe what they saw
• however, ppts could use their left hand to draw or pick out an object associated with the image shown to the left visual field
• this can be explained by the fact that images shown to the left visual field would’ve been processed in the right hemisphere, which controls the left hand, as the motor cortex is also contralateral

Question 30

split brain research - strengths

Answer 30

• Sperry’s experiments demonstrate that the brain functions are lateralised, e.g. if images processed in the right hemisphere can’t be spoken of, it suggests image and language processing do happen in different hemispheres
• Gazzaniga (1983) found that when split-brain ppts had each of their hemispheres presented with faces, the right hemisphere was more capable of recognising them, supporting the idea that image processing happens in the right hemisphere

Question 31

split brain research - limitations

Answer 31

• Sperry’s sample size is quite small with just 11 ppts, so findings shouldn’t be generalised to the entire population
• split-brain patients are already rare prior to the corpus callosotomy due to their epileptic fits, so the effects seen in Sperry’s experiments may be effects of epilepsy itself or the drugs used to treat it, rather than effects of the corpus callosotomy
• conflicting case studies, e.g. Gazzaniga (1998) described how split-brain patient J.W. learned to speak about info presented to his right hemisphere 13 years after undergoing a corpus callosotomy
• his research often leads to the exaggeration of the different functions of the different hemispheres, as functions associated with one hemisphere can usually be carried out or shared by the other hemisphere when needed, e.g. as described by Danelli et al. (2013)

Question 32

brain plasticity

Answer 32

• the ability of the brain to alter its structure and functions in response to changes in the environment;
• new neural pathways can be formed when we’re presented with new info
• commonly used pathways are strengthened
• unused pathways become weaker and may be removed
• the brain is highly plastic in childhood, enabling children to quickly learn new skills, adapt to their environment, and recover from brain injury
• plasticity reduces with age, but still remains throughout adult life too
• aka neuroplasticity

Question 33

functional recovery after trauma

Answer 33

• brain damage can be caused by serious head injuries, strokes, tumours, etc. and can result in a loss of function
• plasticity enables people to recover function after brain damage by rewiring itself in the following ways;
• functional reorganisation; healthy areas of the brain can take over the functions of lost or damaged areas
• synaptic pruning; frequently used synapses grow stronger over time and unused ones have the connections lost
• Wall (1977) observed that unused neural pathways can activate and form new connections to compensate for damaged ones
• axon sprouting; damage to the axon of a neuron can break its connections to neighbouring neurons, so the intact neighbouring neurons may sprout (grow) extra nerve endings to reconnect with the damaged neurons
• constraint-induced movement therapy (CIMT) can also help recover function; after a stroke which has caused loss of function on one side of the body, patients may be prevented from using their non-affected side, forcing them to ‘re-learn’ how to use their affected side, e.g. their arm

Question 34

brain plasticity - strengths

Answer 34

• Maguire et al. (2000) found that London taxi drivers had a higher volume of grey matter in the posterior hippocampus (an area associated with spatial memory and navigation) compared to a control group, suggesting that the brain is plastic and able to rewire itself to adapt to its environment
• Bezzola et al. (2012) found evidence of neural changes in ppts aged 40-60 following 40 hours of golf training, suggesting plasticity still exists amongst older adults
• it has practical application as research in this area has helped improve the cognitive functions of people suffering from injuries, e.g. it’s led to the development of neurological rehab, which involves motor therapy and electrical stimulation to counter deficits to cognitive functioning
• it also occurs in animals; Hubbel and Wiesel (1963) sewed the right eye of kittens shut and found that the left visual cortex was still processing info from the open eye, suggesting loss of function leads to compensatory action in the brain

Question 35

brain plasticity - limitations

Answer 35

• functional recovery can deteriorate with age; Danelli et al. (2013) demonstrates that young people can recover function even after extensive damage to the brain, but it’s highly unlikely that an older patient could recover from such damage
• some research also suggests women are better able to recover function after brain damage than men, perhaps because female brains tend to have more neural connections between both hemispheres, resulting in reduced hemispheric lateralisation, so the hemispheres can better compensate for the damaged ones

Question 36

ways of studying the brain

Answer 36

• functional magnetic resonance imaging (fMRI)
• electroencephalogram (EEGs)
• event-related potentials (ERPs)
• post-mortem examinations

Question 37

functional magnetic resonance imaging (fMRI)

Answer 37

• a brain imagine technique (brain scan) which uses magnetic fields to measure blood flow and oxygenation in the brain to identify which areas of the brain are activated during certain tasks
• brain areas that are more active need more blood flow, which is oxygenated blood, and inactive / less active parts of the brain will show deoxygenated blood
• active areas can then be compared with less active areas and can be shown on the fMRI image

Question 38

fMRI - strengths

Answer 38

• high spatial resolution as fMRI scans can identify activity in the brain within 1mm, providing a more detailed picture of brain activity, e.g. more than EEGs
• dynamic as it identifies active brain regions over time, so it can pick up changes in brain activity and allows for comparisons
• can be used while a patient is carrying out a task, so we can make inferences about brain function and localisation
• non-invasive and safe for patients

Question 39

fMRI - limitations

Answer 39

• fMRI machines are expensive and hard to build
• the patient needs to remain very still throughout
• sample size is often very small due to availability and funding
• low temporal resolution as there’s approx. a 5 second difference between neuronal activity and the produced image

Question 40

electroencephalogram (EEGs)

Answer 40

• a scan of the brain’s electrical activity which is performed by attaching electrodes to the scalp or by using a hat with electrodes attached
• the electrodes detect electrical activity in the brain cells beneath them, so the more electrodes used in an EEG, the more complete the picture of brain activity will be
• usually between 22-34 electrodes are used, but there can be any from 2-100 placed
• the activity is displayed in brain waves (4 types), where the amplitude shows the brain intensity and the frequency shows the speed of activation
• commonly used in sleep studies

Question 41

4 types of brain waves

Answer 41

• alpha waves - state of relaxation
• theta waves - state of deep relaxation, i.e. when you’re falling asleep
• beta waves - state of alertness and mental activity
• delta waves - state of deep sleep

Question 42

event-related potential (ERPs)

Answer 42

• uses the same apparatus as EEGs, but use statistical techniques for measuring
• they record brain activity in response to a stimulus
• i.e. it initially records a baseline picture of brain activity, then the stimulus is presented many times, which provides data using statistical averaging
• the waveform’s peaks and dips show exactly when cognitive processes happen in the brain in response to when the stimulus is presented
• commonly used in memory research

Question 43

EEG and ERP - strengths

Answer 43

• both are cheaper than brain imaging techniques, e.g. fMRI
• dynamic as they enable researchers to measure changes in brain activity as they happen
• they’re useful to test reliability on self-report techniques, i.e. to avoid social desirability bias
• higher temporal resolution as EEGs can record several pictures of the brain per second, unlike fMRI
• ERPs allow researchers to isolate and study how individual cognitive processes take place in the brain

Question 44

EEG and ERP - limitations

Answer 44

• both have low spatial resolution, so are unable to provide a detailed view of brain activity, unlike fMRI
• expertise is needed to interpret the outcome from the experiment
• some cognitive processes can’t be studied using ERPs as they’re unable to be presented multiple times

Question 45

post-mortem examinations

Answer 45

• a physical examination of a person’s body, including their brain, after they’ve died
• researchers will analyse a brain by weighing it, dissecting it and comparing it to neurotypical (‘normal’) brains
• this allows them to identify key functions of specific parts of the brain
• e.g. Broca’s area was discovered by post-mortem dissection as Broca found a lesion on the left temporal lobe of a patient with impaired speech production (he couldn’t say anything other than the word ‘tan’), and Broca’s aphasia is the term used today for patients with issues producing speech

Question 46

post-mortem examinations - strengths

Answer 46

• enables researchers to study deeper areas of the brain that can’t be reached
• fundamental in the development of understanding brains and how they function, including localisation of function, e.g. Broca’s research
• the individual isn’t alive so can’t experience any discomfort

Question 47

post-mortem examinations - weaknesses

Answer 47

• no brain activity can be measured as the research is conducted on a dead person
• brains could’ve been affected by the cause of death, thus affecting the results
• it’s hard to compare the brain after death with the functioning prior to death - any relationship found would be correlational and not causal

Question 48

biological rhythms

Answer 48

• various cycles which the activities of the mind and body follow;
• circadian
• infradian
• ultradian
• biological rhythms are controlled by endogenous pacemakers, which are influenced by exogenous zeitgebers

Question 49

endogenous pacemakers

Answer 49

• biological structures and mechanisms within the body that regulate biological rhythms
• e.g. the SCN seems to act as an internal clock to keep the body on a 24 hour sleep-wake cycle

Question 50

exogenous zeitgebers

Answer 50

• cues in the external environment that inform endogenous pacemakers to regulate biological rhythms
• the body can be entrained so its internal mechanisms are altered by these external cues
• e.g. sunlight and darkness prompt the body to release hormones such as melatonin which control sleep and wake cycles
• social cues can also act as exogenous zeitgebers, e.g. work schedules, meal timings, etc.

Question 51

research support for endogenous pacemakers and exogenous zeitgebers

Answer 51

• endogenous pacemakers; Morgan (1995) removed the SCN of hamsters and found that their sleep-wake cycle disappeared, but then re-appeared once ‘normal’ hamster SCN cells had been transported into their brains; however his use of animals may be unethical and the results can’t be generalised to humans as our biological systems work in different ways
• exogenous zeitgebers; Campbell and Murphy (1998) demonstrated that light in the form of a torch is a key exogenous zeitgeber for regulating circadian rhythms, even when shone on the back of ppt’s knees as it disrupted their sleep cycles by up to 3 hours; however, this study lacks external validity as the sample size was 15 which is too small to be able to generalise results

Question 52

circadian rhythms

Answer 52

• biological rhythms lasting approximately 24 hours, i.e. one cycle a day
• e.g. the sleep-wake cycle; you may cycle between sleeping for 8 hours when it gets dark and being awake for 16 hours in the day
• controlled by the SCN which is influenced by light
• shift work has been found to lead to desynchronisation of ‘pre-set’ circadian rhythms and can lead to adverse cognitive and physiological effects, e.g. memory lapses
• jet lag can also lead to desynchronisation of circadian rhythms

Question 53

the effect of endogenous pacemakers and exogenous zeitgebers on the sleep-wake cycle

Answer 53

• the main system (endogenous pacemaker) that controls circadian rhythms is a tiny cluster of nerve cells called the suprachiasmatic nucleus (SCN) in the hypothalamus
• it acts as a ‘master clock’ as it detects the level of light present then uses this info to coordinate the activity of the entire circadian rhythm
• the SCN regulates the pineal gland which secretes melatonin release at night which induces sleep by inhibiting the brain mechanisms that promote wakefulness, i.e. it makes you tired
• the most obvious exogenous zeitgeber that influences these internal processes would be sunlight, e.g. the darkness of the night is thought to trigger the melatonin release

Question 54

circadian rhythms - strengths

Answer 54

• Siffre (1973) spent 2 months in a cave without any natural light or a clock and he found that the absence of these external cues interfered with his sleep-wake cycle, because when he came out he believed the date to be a month earlier than it was
• understanding circadian rhythms can improve the sleep and health of shift workers, e.g. Czeisler et al. (1982) found that employees whose shifts were stable for over 21 days had more positive attitudes to their job and greater health, perhaps because their circadian rhythms could adjust to their work schedules during the 21 / more days, so firms can use this knowledge to improve employee satisfaction and reduce employee turnover

Question 55

circadian rhythms - limitations

Answer 55

• case studies such as Siffre can’t be generalised beyond the single participant, and Siffre may have also entrained his own circadian rhythm through signalling sleep and wake-up times by using artificial light
• Folkard et al.’s research lacks ecological validity due to its lab setting
• doesn’t account for individual differences, as some people won’t necessarily conform to a pre-determined sleep-wake cycle
• some cases show that exogenous zeitgebers and endogenous pacemakers
  have failed to entrain / alter circadian rhythms; Miles et al. (1977) reported
  the case of a man with a sleep-wake cycle of 24.9 hours which couldn’t be changed by using stimulants or sedatives, suggesting the influence of exogenous and endogenous factors may be overestimated
• it may be overly reductionist to ignore other factors that may be involved in something so complex like the sleep-wake cycle

Question 56

infradian rhythms

Answer 56

• biological rhythms lasting more than 24 hours, i.e. less than one cycle everyday
• e.g the human menstrual cycle; it typically takes around 28 days to complete
• they’re also controlled by endogenous pacemakers, e.g. hormones such as oestrogen and progesterone are crucial to the menstrual cycle
• they can be influenced by exogenous zeitgebers, e.g. Stern and McClintock (1998) found that women’s menstrual cycles may synchronise when they live together, perhaps as they’re exposed to pheromones (chemicals that can affect the behaviour or physiology of others) from the other women
• another example is seasonal affective disorder (SAD) which commonly occurs in the darker months of winter when more melatonin is secreted which brings energy levels down and leads to feelings of loneliness and depression

Question 57

ultradian rhythms

Answer 57

• biological rhythms lasting under 24 hours, i.e. cycles occur more than once everyday
• e.g. the different stages of sleep; a person typically cycles between 5 stages during the night, as demonstrated by Dement and Kleitman (1957);
• stages 1and 2; sleep escalators, light sleep, alpha waves increase and progress to theta waves, brain activity reduces, heart rate slows and muscles relax
• stages 3 and 4; deep sleep, delta brain waves increase (and peak in stage 4) and brain activity is greatly reduced (at its lowest level in stage 4)
• stage 5; rapid eye movement (REM) sleep, high level of brain activity, dreams are likely to occur, body is completely relaxed
• stages 1-4 are considered NREM sleep
• one complete sleep cycle through all stages typically takes around 90 minutes, so during a full night’s sleep, this cycle may be repeated 4/5 times

Question 58

infradian and ultradian rhythms - strengths

Answer 58

• research support from Stern and McClintock (infradian) and Dement and Kleitman (ultradian)
• Terman (1988) found the rate of SAD is higher in Northern countries where winter nights are longer, e.g. it affects about 10% of people living in New Hampshire (North of the US) but only 2% of residents in southern Florida, suggesting that SAD is affected by light (an exogenous zeitgeber) that results in increased levels of melatonin

Question 59

infradian and ultradian rhythms - limitations

Answer 59

• McLintock et al.’s research was a field study so there may be an array of extraneous variables, e.g. diet, exercise, etc. may have interfered with the findings
• Dement and Kleitman carried out their research in the 1950s, so it may lack temporal validity, and modern factors such as digital technology may now interfere with people’s ultradian rhythms, so new research should be undertaken on this topic
• Tucker et al. (2007) found significant differences between participants in terms of the duration of each sleep stage, suggesting there may be individual differences in ultradian rhythms
• there may be a lack of internal validity in Dement and Kleitman’s study as the lab setting and monitors attached to ppt’s heads while sleeping may affect their ordinary sleeping patterns