Biopsychology

Question 1

The nervous system

Answer 1

> Biopsychologists assume that behaviour and experiences are caused by activity in the nervous system/
The nervous system is a specialised network of cells in the human body.
Our primary internal communication system.
Two main functions: to collect, process and, respond to information in the environment and to coordinate the working of different organs and cells

Question 2

The central nervous system

Answer 2

> The CNS is made up of the brain and the spinal cord. >The brain is the centre of all conscious awareness. The brain’s outer layer, the cerebral cortex, is highly developed in humans.
The brain is divided in two hemispheres .
The spinal cord is an extension of the brain. It is responsible for reflex actions.

Question 3

The peripheral nervous system

Answer 3

> The PNS transmits messages via millions of neurons (nerve cells), to and from the central nervous system.
The PNS is further subdivided into: the somatic nervous system (SNS) and the autonomic nervous system (ANS)

Question 4

The somatic nervous system

Answer 4

> This is the part of the PNS that is responsible for carrying sensory and motor information to and from the spinal cord.
It is made up of 12 pairs of cranial nerves from the brain, 31 pairs of spinal nerves from the spinal cord, and all of their branches.

Question 5

The autonomic nervous system

Answer 5

> This governs vital functions in the body such as breathing, heart rate, digestion, sexual arousal and stress responses.
There are two main divisions of the ANS which are: the sympathetic nervous system and the parasympathetic nervous system.
Their actions are mostly antagonistic - that is they usefully work in opposition to each other.

Question 6

Fight or flight

Answer 6

> The sympathetic nervous system controls what has been called the “Fight or Flight” phenomenon

Question 7

the endocrine system

Answer 7

> this system is in charge of body processes that happen slowly such as cell growth.
faster processes such as breathing and body movement are controlled by the nervous system.
The endocrine system and nervous system are separate but they often work together to help the body function properly

Question 8

Endocrine system - adrenal glands

Answer 8

These release adrenaline directly into the bloodstream which prepares the body for fight or flight by constricting blood vessels in the stomach. this inhibits digestion and gives you that sick feeling as well as increasing your heart rate.

Question 9

endocrine system - pituitary gland

Answer 9

This controls the regulation of hormones from all other endocrine glands

Question 10

endocrine system - ovaries

Answer 10

This facilitates the release of the female hormones - oestrogen and progesterone

Question 11

endocrine system- testes

Answer 11

This facilitates the release of the male hormone - testosterone

Question 12

neurons and synaptic transmission

Answer 12

Biopsychologists assume that behavior and experiences are caused by activity in the nervous system. The nervous system transmits signals for communication via the billions of nerve cells (neurons) it houses. These nerve cells communicate with each other, through electrical and chemical messages, within the body and the brain.

Question 13

neurons and synaptic transfusion - neurons

Answer 13

Cells that conduct nerve impulses are called neurons. The things that people think and feel, say and do are cause, one way or another, by electrochemical events occurring within and between the neurons that make up the nervous system, particularly those in the brain.

Question 14

neurons and synaptic transfusion - nucleus

Answer 14

The control centre of a cell, which contains the cells chromosomal DNA.

Question 15

neurons and synaptic transfusion - dendrite

Answer 15

Receives the nerve impulse or signals from adjacent neurons

Question 16

neurons and synaptic transfusion - axon

Answer 16

Where the electrical signals pass along

Question 17

neurons and synaptic transfusion - myelin sheath

Answer 17

insulates/protects the axon from external influences that might affect the transmission of the nerve impulse down the axon

Question 18

neurons and synaptic transfusion - nodes of ranvier

Answer 18

These speed up the transmission of the impulse by forcing it to ‘jump’

Question 19

neurons and synaptic transfusion - terminal buttons

Answer 19

terminal buttons send signals to an adjacent cell

Question 20

neurons and synaptic transfusion - motor neuron

Answer 20

function - carries messages from the CNS to effectors such as muscles and glands.

length of fibres - short dendrites and long axons

Question 21

neurons and synaptic transfusion - relay neuron

Answer 21

function - transfers messages from sensory neurons to other interconnecting neurons or motor neurons

length of fibres - short dendrites and short or long axons

Question 22

neurons and synaptic transfusion - sensory neurons

Answer 22

function - carries messages from the PNS to the brain and spinal cord

length of fibres - long dendrites and short axons

Question 23

neurons and synaptic transfusion - knee jerk reflex

Answer 23

In a reflex arc, like the knee jerk reflex, a stimulus, such as a hammer hitting the knee, is detected by sense organs in the peripheral nervous system, which conveys a message along a sensory neuron. The message reaches the central nervous system where it connects with a relay neuron. This then transfers the message to a motor neuron. This then carries the message to an effector such as a muscle, which causes the muscle to contract and, hence, the knee to move or jerk.

Question 24

neurons and synaptic transfusion - neurotransmitters

Answer 24

Chemicals that are released from a synaptic vesicle into the synapse by neurons. They affect the transfer of an impulse to another nerve or muscle. These neurotransmitters are “taken back up” into the terminal buttons of neurons through the process of reuptake. Or they are broken down by an enzyme

Question 25

neurons and synaptic transfusion - action potential

Answer 25

An action potential occurs when a neuron sends information down an axon, away from the cell body. The action potential is an explosion of electrical activity - this means that some event (a stimulus) causes the resting potential to move forward.

Question 26

neurons and synaptic transfusion - excitation and inhibition

Answer 26

Synaptic connections can be excitatory or inhibitory – the difference lies in the action of the neurotransmitter at the postsynaptic receptor.
>Excitatory - they make it more likely the next neuron will fire (such as acetylcholine).
>Inhibitory - they make it less likely the next neuron will fire (such as GABA). Normal brain function depends upon a regulated balance between excitatory and inhibitory influences.

Question 27

Localisation of Function in the Brain

Answer 27

He theory that different areas of the brain are responsible for different behaviours, processes and activities.

Question 28

Localisation of Function in the Brain - motoring area

Answer 28

A region of the frontal lobe involved in regulating movement.

Question 29

Localisation of Function in the Brain - Somatosensory area

Answer 29

An area of the parietal lobe that processes sensory information such as touch.

Question 30

Localisation of Function in the Brain - Visual area

Answer 30

Part of the occipital lobe that receives and processes visual information.

Question 31

Localisation of Function in the Brain - Auditory area

Answer 31

Located in the temporal lobe and concerned with the analysis of speech-based information.

Question 32

Localisation of Function in the Brain - Broca’s area.

Answer 32

An area of the frontal lobe of the brain in the left hemisphere (in most people) responsible for speech production.

Question 33

Localisation of Function in the Brain - Wernicke’s area.

Answer 33

An area of the temporal lobe (encircling the auditory cortex) in the left hemisphere (in most people) responsible for language comprehension.

Question 34

Localisation of Function in the Brain - Hemispheres

Answer 34

In most respects , the left and the right sides of the brain are very similar. One difference however is the presence of the language areas, which are only found on the left hand side.

Question 35

Localisation of Function in the Brain - Damage to Broca’s or Wernicke’s

Answer 35

Damage to the wernicke’s area or the broca’s area would result in aphasia - inability (or impaired ability) to understand or produce speech.

Question 36

Localisation of Function in the Brain - The Brain’s Three Layers

Answer 36

The brain can be viewed as having three concentric layers: the central core, the limbic system, the cerebrum.

Question 37

Localisation of Function in the Brain - The Brain’s Three Layers - Central core

Answer 37

> This regulates our most primitive and involuntary behaviours such as breathing, sleeping or sneezing.
It is also known as the brain stem. It includes structures such as the hypothalamus – in the midbrain;
It regulates eating and drinking as well as regulating the endocrine system in order to maintain homeostasis. Homeostasis: the process by which the body maintains a constant physiological state

Question 38

Localisation of Function in the Brain - The Brain’s Three Layers - The limbic system

Answer 38

This controls our emotions. Around the central core of the brain, interconnected with hypothalamus, it contains structures such as the hippocampus; key roles in memory.

Question 39

Localisation of Function in the Brain - The Brain’s Three Layers - The cerebrum

Answer 39

> This regulates our higher intellectual processes. It has an outermost layer known as the cerebral cortex; appears grey because of the location of cell bodies (hence “grey-matter”).
Each of our sensory systems send messages to and from this cerebral cortex. The cerebrum is made up of the left and right hemispheres which are connected by a bundle of fibres called the corpus callosum.

Question 40

Localisation of Function in the Brain - Corpus callosum

Answer 40

The corpus callosum enables messages to enter the right hemisphere to be conveyed to the left hemisphere and vice versa.

Question 41

Localisation of Function in the Brain - The hemispheres

Answer 41

Each hemisphere is further divided into four lobes:
>The frontal lobe (The location for awareness of what we are doing within our environment),
>The parietal lobe (Location for sensory and motor movements),
>The temporal lobe (Location for the auditory ability and memory acquisition)
>The occipital lobe (Location for vision).

Question 42

Localisation of Function in the Brain - Brain scan evidence

Answer 42

> There is a wealth of evidence providing support for the idea that many neurological functions are localised, particularly in relation to language and memory.
Peterson (1988) used brain scans to demonstrate how Wernicke’s area was active during a listening task and Broca’s area was active during a reading task, suggesting that these areas.
There now exists a number of highly sophisticated and objective methods for measuring activity in the brain which provide sound scientific evidence for the localisation of brain function.

Question 43

Localisation of Function in the Brain - Neurosurgical evidence

Answer 43

> This is by far the most extreme treatment as it involves the destruction of healthy brain tissue: Lobotomy: removal of the brain tissue.
Leucotomy: cutting the connections to a particular part of the brain. Controversially, neurosurgery is still used today for treatment-resistant severe depressives and extreme cases of OCD. The success of these procedures strongly suggests that symptoms and behaviours associated with serious mental disorders are localised

Question 44

Localisation of Function in the Brain Case Study - Aim

Answer 44

To explain the cause of Gage’s change of personality.

Question 45

Localisation of Function in the Brain Case Study - Method

Answer 45

Whist working on the railroad, 25 year old Gage was preparing to blast a section of rock using explosives. He dropped his tamping iron onto the rock, which caused the
explosive to ignite. The explosion hurled the meter length iron pole, point first through his left cheek. It passed behind his left eye, and exited his brain and skull from the top of his head. It was found 25 to 30 yards behind him covered in bits of his brain. He was knocked over but is not believed to have lost consciousness.

Question 46

Localisation of Function in the Brain Case Study - Results

Answer 46

He survived, and after months of recovery wanted to regain his job. Before the accident he had been a most capable and efficient foreman, one with a well-balanced mind, and who was looked on as a shrewd smart business man. However, no one would employ him as his personality had changed from someone who was kind and reserved to someone who was now boisterous, rude and grossly blasphemous. His friends said he was “No longer Gage.”

Question 47

Localisation of Function in the Brain Case Study - Conclusion

Answer 47

As Damasio et al. stated; although his accident was horrific, it has taught us a great deal about the complexity of psychological processes that occur in the human brain.

Question 48

Localisation of Function in the Brain Case Study - Evaluation

Answer 48

We must be careful about generalising these findings, as they are based on one very rare case of an unfortunate individual.

Question 49

Localisation of Function in the Brain - Higher cognitive functions are not localised

Answer 49

Not all researchers agree with the view that cognitive functions are localised in the brain. The work of Karl Lashley (1950) suggests that the basic motor and sensory functions were localised, but that higher mental functions were not. Lashley claimed that intact areas of the cortex could take over responsibility for specific cognitive functions following injury to the area normally responsible for that function. According to this point of view, the effects of damage to the brain would be determined by the extent rather than the location of the damage. This view received some support from the discovery that humans were able to regain some of their cognitive abilities following damage to specific areas of the brain.

Question 50

Split brain research into hemispheric lateralisation - Left brain

Answer 50

Analytic thought, logic, language, science and maths. Is the language centre of the brain. Controls the right hand. Receives information from the right visual field.

Question 51

Split brain research into hemispheric lateralisation - Right brain

Answer 51

Holistic thought, intuition, creativity, art and music. Focuses on visuo-spatial tasks. Controls the left hand. Receives information from the left visual field.

Question 52

Split brain research into hemispheric lateralisation - Sperrys split brain experiment - Aim

Answer 52

The aim of their research was to examine the extent to which the two hemispheres are specialised for certain functions.

Question 53

Split brain research into hemispheric lateralisation - Sperrys split brain experiment - Procedure

Answer 53

An image/word is projected to the patient’s left visual field (which is processed by the right hemisphere) or the right visual field (which is processed by the left hemisphere). When information is presented to one hemisphere in a split-brain patient, the information is not transferred to the other hemisphere (as the corpus callosum is cut).

Question 54

Split brain research into hemispheric lateralisation - Sperry’s split brain experiment - Visual findings

Answer 54

Participants would only recognise stimuli if the stimuli was presented again to the same visual field.
Information presented to the right visual field could be described in speech and writing (with the right hand). If the same information is presented to the left visual field, the participant insisted he either did not see anything or that there was only a flash of light on the left side, that is, the information could not be described in speech or writing. However the participant could point with his left hand to a matching picture / object presented among a collection of pictures / objects.

Question 55

Split brain research into hemispheric lateralisation - Sperry’s split brain experiment - Tactile findings

Answer 55

Objects placed in the right hand could be described in speech or writing. If the same objects were placed in the left hand participants could only make wild guesses and often seemed unaware they were holding anything. Objects felt by one hand were only recognised again by the same hand for example objects first sensed by the right hand could not be retrieved by the left. When two objects were placed simultaneously in each hand and then hidden in a pile of objects, both hands selected their own object and ignored the other hand’s object.

Question 56

Split brain research into hemispheric lateralisation - Sperry’s split brain experiment - Conclusion

Answer 56

> People with split brains have two separate visual inner worlds, each with its own train of visual images.
Split-brain patients have a lack of cross-integration where the second hemisphere does not know what the first hemisphere has been doing.
Split-brain patients seem to have two independent streams of consciousness, each with its own memories, perceptions and impulses ie two minds in one bod

Question 57

Split brain research into hemispheric lateralisation - Sperry’s split brain experiment - Evaluation 1 +

Answer 57

Ethics – as the study used a quasi methodology, Sperry did not need to manipulate anything, which is more ethical than studies which manipulate variables.

Question 58

Split brain research into hemispheric lateralisation - Sperry’s split brain experiment - Evaluation 2 X

Answer 58

Quasi study – as the there was no manipulation by the experimenter, establishing cause and effect becomes more difficult than a traditional experiment.

Question 59

Split brain research into hemispheric lateralisation - Sperry’s split brain experiment - Evaluation 3 X

Answer 59

No control group, Sperry did not use a control group, which makes it difficult to truly establish cause and effect. However, it is important to note that in this study a control group was not needed as the results of the tasks for people without split corpus callosums were already known.

Question 60

Split brain research into hemispheric lateralisation - Sperry’s split brain experiment - Evaluation 4 X

Answer 60

External validity – the external validity in this study may be considered low because the stimuli was selectively delivered to one hemisphere. This does not happen in real life and thus is not representative of the everyday experience of ‘split-brain’ patients. However this selective presentation of stimuli increased the internal validity because there is an increased likelihood that Sperry measured the effects of hemisphere deconnection.

Question 61

Brain plasticity

Answer 61

> Our brains have the ability to change throughout life. During infancy the brain grows in the number of synaptic connections (peaks to 15 000 by 3 years old ish - Gopnik et al 1999). This is twice as many as in the adult brain.
As we age, rarely connections are deleted and frequently used connections are strengthened (synaptic pruning).
Originally it was thought that changes were restricted to developing the brain within childhood and that the adult brain, having moved beyond a critical period, would remain fixed and static in terms of function and structure. >More recent research suggests that at any time in life existing neural connections can change and new ones can be formed as a result of learning(plasticity).

Question 62

Brain plasticity - Eleanor Maguire et al

Answer 62

> Studied the brains of London taxi drivers using an MRI and found significantly more grey matter in the posterior hippocampus than in the matched control group.
This part of the brain is associated with the development of spatial and navigational skills in humans and other animals.
As part of their training London Cabbies must take a complex test called ‘the knowledge’, which assesses their recall of the city streets and possible routes.
It is also noteworthy that the longer they had been doing the job the more pronounced was the structural difference (a positive correlation).

Question 63

Brain plasticity - functional recovery

Answer 63

> After physical injury, trauma (stroke) unaffected areas of the brain are able to adapt and compensate for damaged areas.
Functional recovery that many occur in the brain after trauma is an example of plasticity.
Healthy brain areas may take over functions of those that are damaged. Neuroscientists say this can happen very quickly (spontaneous recovery). It can then slow down which is when a patient may need rehab. Brains can rewire Doidge 2007. Forms new synaptic connections close to the area of damage (when there is roadworks we find a new route, we don’t just stop)
Structural changes in the brain:
Axonal sprouting
Reformation of blood vessels
Recruitment of homologous areas

Question 64

Brain plasticity - Evaluation 1

Answer 64

Negative Plasticity: Brain’s ability to rewire itself can have maladaptive behavioural consequences. Prolonged drug use for example have shown to result in poorer cognitive functioning as well as an increased risk of dementia (Medina et al 2007). 60-80% of amputees have developed phantom limb syndrome (sensations in the missing limb as if it were attached still)

Question 65

Brain plasticity - Evaluation 2

Answer 65

Age and Plasticity: Reduces with age, Brain has a greater propensity for reorganisation in childhood, Harder to learn when we are older, Ladina Bezzola et al (2012) said how 40 hours of golf, training produced changes in the neural representation of movement in participants aged 40-60. Using fMRI the researchers observed reduced motor cortex activity in the novice golfers compared to a control group suggesting more efficient neural representations after training. Plasticity does continue through lifespan

Question 66

Ways of investigating the brain - functional Magnetic Resonance Imaging

Answer 66

> Detects changes in blood oxygenation + flow due to neural activity - Brain area = more active, consumes more oxygen
Produces 3D images - Shows which parts are involved particular mental processes

Question 67

Ways of investigating the brain - fMRI strengths

Answer 67

> Doesn’t rely on use of radiation
If administered correctly, it is virtually risk-free, non-invasive + straightforward to use
Produces images that have very high spatial resolution, depicting detail by the millimetre + prodding a clear picture of how brain activity is localised

Question 68

Ways of investigating the brain - fMRI limitations

Answer 68

> Expensive compared to other neuroimaging techniques
Can only capture a clear image if the person stays perfectly still
Poor temporal resolution due to approx. 5 sec. time lag behind image on screen + initial firing of neuronal activity
Only measures blood flow in the brain - Cannot home in on activity of individual neurons + can be difficult to tell exactly what kind of brain activity is represented on screen

Question 69

Ways of investigating the brain - Electroencephalogram

Answer 69

> Measure electrical activity within brain via electrodes fixed to individual’s scalp using a skull cap - Scan recording represents brainwave patterns generated from action of millions of neurons - Provides overall account of brain activity
Used by clinicians as diagnostic tool - Unusual arrhythmic patterns of activity may indicate neurological abnormalities - E.g epilepsy, tumours or disorders of sleep
Many scientific + clinical applications

Question 70

Ways of investigating the brain - EEG strengths

Answer 70

> Invaluable in diagnosis of conditions such as epilepsy - Characterised by random bursts of activity in brain that can easily be detected on screen
Contributed to understanding of stages involved in sleep
Extremely high temporal resolution - Today’s tech can accurately detect brain activity with resolution of a single millisecond

Question 71

Ways of investigating the brain - EEG Limitations

Answer 71

> Generalised nature of information received
Signal not useful for pinpointing exact source of neural activity - Doesn’t allow researchers to distinguish between activities originating in different but adjacent locations

Question 72

Ways of investigating the brain - Event-related potentials

Answer 72

> EEG data contain all neural responses associated with specific sensory, cognitive + motor events - May be of interest to cognitive neuroscientists
Developed a way of isolating responses using statistical averaging technique - Extraneous brain activity from original EEG recording is filtered out - Leaves only responses that relate to presentation of specific stimulus/performance of specific task - What remains are event-related potentials - Types of brainwave triggered by particular events
Research revealed different forms of ERP

Question 73

Ways of investigating the brain - ERPs strengths

Answer 73

> Bring more specificity to measurement of neural processes than using raw EEG data
Have excellent temporal resolution, especially when compared to neuroimaging techniques such as fMRI - Led to widespread use in measurement of cognitive functions + deficits
Researchers been able to identify many different types of ERP + describe precise role of them in cognitive functioning - E.g P300 component is thought to be involved in the allocation of attentional resources + maintenance of working memory

Question 74

Ways of investigating the brain - ERPs limitations

Answer 74

> Critics have pointed to a lack of standardisation in ERP methodology between different research studies - This makes it difficult to confirm findings
A further issue is that, in order to establish pure data in ERP studies, background noise + extraneous material must be completely eliminated - This may not always be easy to achieve

Question 75

Ways of investigating the brain - Post-mortem examinations

Answer 75

> Involves analysis of a person’s brain following death
Psychological research - individuals whose brains are subject to a post-mortem are likely to have a rare disorder + experienced unusual deficits in mental processes/behaviour during their lifetime - Areas of damage within the brain are examined after death to establishing likely cause of affliction the person suffered - May also involve comparison with neurotypical brain to ascertain extent of the differenc

Question 76

Ways of investigating the brain - Post-mortem examinations strengths

Answer 76

> Vital in providing foundation for early understanding of key brain processes - Karl Wernicke relied on post-mortem studies to make links between language, brain + behaviour
Improve medical knowledge + help generate hypotheses for further study

Question 77

Ways of investigating the brain - Post-mortem examinations limitations

Answer 77

> Causation is an issue within investigations. - Observed damage to brain may not be linked to deficits under review, but to some other unrelated trauma/decay
Ethical issues of consent from patient before death - May not be able to provide informed consent - E.g HM - lost ability to form memories + not able to provide consent

Question 78

Biological rhythms

Answer 78

Distinct patterns of change sin body activity that conform to cyclical time periods. Biological rhythms are influenced by internal body clocks (endogenous pacemakers) as well as external changes to the environment (exogenous zeitgebers).

Question 79

Biological rhythms - circadian rhythm

Answer 79

A type of biological rhythm, subject to a 24-hour cycle, which regulates a number of body processes such as the sleep/wake cycle and changes in core body temperature.

Question 80

Biological rhythms - siffre’s cave study procedure

Answer 80

On several occasions, he has spent long periods of time living underground in order to study his own biological rhythms. Underground, in a cave, he had no external cues to guide his rhythms - no daylight, no clocks, no radio. He simple woke, ate and slept when he felt like it. The only thing influencing his behaviour was his internal ‘clock’ or ‘free-running rhythm’.

Question 81

Biological rhythms - siffre’s cave study findings

Answer 81

> In his first underground sojourn of 61 days in the osuthern Alps in 1962, he resurfaced on 17th of September thinking the date was 20th of August.
On the 2nd occasion he spent 6 months in a Texan cave - his natural circadian rhythm settled down to just over 24 hours but sometimes this would change dramatically to as much as 48 hours.
On his final underground sojourn, he was 60 years old (1999). He was interested in the effects of ageing on biological rhythms. He found that his internal clock ticked more slowly than when he was a young man. He also found that his sleep patterns had changed

Question 82

Biological rhythms - infradian rhythms

Answer 82

A type of biological rhythm with a frequency of less than one cycle in 24 hours, such as menstruation and seasonal affective disorder.

Question 83

Biological rhythms - ultradian rhythms

Answer 83

A type of biological rhythm with a frequency of more than one cycle in 24 hours, such as the stages of sleep.

Question 84

Biological rhythms - endogenous pacemakers

Answer 84

Internal body clocks that regulate many of our biological rhythms, such as the influence of the suprachiasmatic nucleus (SCN) on the sleep/wake cycle.

Question 85

Biological rhythms - Exogenous zeitgebers

Answer 85

External cues that may affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle.

Question 86

Biological rhythms - sleep/wake cycle

Answer 86

A daily cycle of biological activity based on a 24-hour period (circadian rhythm) that is influenced by regular variations in the environment, such as the alternation of night and day.’

Question 87

Biological rhythms - circadian clock

Answer 87

The brain’s circadian clock regulates sleeping and feeding patterns, alertness, core body temperature, brain wave activity, hormone production, regulation of glucose and insulin levels, urine production, cell regeneration, and many other biological activities. The most important hormones affected by the circadian clock, at least insofar as they affect sleep, are melatonin (which is produced in the pineal gland in the brain, and which chemically causes drowsiness and lowers body temperature) and cortisol (produced in the adrenal gland, and used to form glucose or blood sugar and to enable anti-stress and anti-inflammatory functions in the body).

Question 88

Biological rhythms - Endogenous Pacemakers and Exogenous Zeitgebers - Suprachiasmatic nucleus (SCN)

Answer 88

In mammals, the main endogenous pacemaker is located in the tiny cluster of nerve cells called the suprachiasmatic nucleus (SCN), which lies in the hypothalamus, the SCN is actually a pair of structures. One half sits in the left hemisphere of the brain and one on the right, just above where the optic nerves from each eye cross over (the optic chiasm). The SCN obtains information on light from the optic nerve, even when our eyes are shut. Light penetrates the eyelids, and special photoreceptors in the eyes pick up light signals and carry them to the SCN

Question 89

Biological rhythms - Endogenous Pacemakers and Exogenous Zeitgebers - Pineal Gland

Answer 89

The SCN passes information on day length and light that it receives to the pineal gland (a pea like structure in the brain just behind the hypothalamus). during the night when it is dark, the pineal gland increases production of melatonin- a chemical that induces sleep. During the day, when it is light the production of melatonin is inhibited. The pineal gland and the SCN function jointly as endogenous pacemakers in the brain. The sensitivity of the pineal gland and the SCN to light, and the role of melatonin in controlling sleep and activity, mean that, despite the endogenous nature of these clocks, their activity must be synchronised with the light-dark rhythm of the world outside.

Question 90

Biological rhythms - Endogenous Pacemakers and Exogenous Zeitgebers - Light

Answer 90

This is the key zeitgeber in humans. It can reset the body’s main endogenous pacemaker the SCN, and thus plays a role in the maintenance of the sleep/wake cycle. Light has an impact upon melatonin production and therefore sleep/wakefulness. Light also has an indirect influence on key processes in the body that control such functions as hormone circulation and blood circulation (but our focus is sleep).

Question 91

Biological rhythms - Endogenous Pacemakers and Exogenous Zeitgebers - Social cues

Answer 91

> Social stimuli, such as mealtimes and social activities, may also have a role as zeitgebers.
Ascoff et al (1971) showed that individuals are able to compensate for the absence of zeitgebers such as natural light by responding to social zeitgebers instead. >One of the earliest studies on jet lag (Klein and Wegmann, 1974) found that the circadian rhythms of air travellers adjusted more quickly if they went outside more at their destination. This was thought to be because they were exposed to the social cues of their new time zone, which acted as a zeitgeber.
Research has suggested that adapting to local times for eating and sleeping (rather than responding to one’s own feelings of hunger and fatigue), is an effective way of entrainment circadian rhythms and beating jet lag when travelling long distances. How light (an e.g. of an EZ) can be used to beat jet lag. Using light Exposure to Avoid Jet Lag: Practical application of EZs!
Burgess et al (2003): found that exposure to bright light prior to an east-west flight decreased the time needed to readjust to local time on arrival

Question 92

Biological rhythms - Endogenous Pacemakers and Exogenous Zeitgebers - Animal studies into the role of the SCN (DeCoursay)

Answer 92

The role of exogenous zeitgebers may have been exaggerated, as there is evidence that although external environmental cues may vary, some individual’s pacemakers are set to withstand their influence. DeCoursay destroyed the SCN connections in 30 chipmunks and returned them to their natural habitats for 80 days. She noted that many of them were killed by predation not long after, as they had ventured out of their nests at the wrong time of day, suggesting their normal sleep wake cycle had been impaired.

Question 93

Biological rhythms - Endogenous Pacemakers and Exogenous Zeitgebers - Animal studies into the role of the SCN (Ralph)

Answer 93

Furthermore Ralph implanted SCN cells from from mutant hamsters with a normal cycle. He discovered that for the hamsters who received the transplant their cycles changed to that of their mutant donors. Both these studies provide support for the importance of the SCN in regulating the sleep wake cycle. The strengths of both of these animal studies is that manipulation of the SCN (IV) was conducted under controlled conditions so the results can be replicated, and show a clear cause and effect relationship; i.e. damage/change to SCN alters sleep wake cycle.