what systems and structures are of interest to biopsychologists

1. A-level Psychology
2. Biopsychology A-level

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What do the examiners await for?

• Accurate and detailed knowledge
• Clear, coherent and focused answers
• Effective use of terminology (use the "technical terms")

In application questions, examiners expect for "constructive application to the scenario" which ways that you need to describe the theory and explicate the scenario using the theory making the links between the two very clear. If there is more than one individual in the scenario you must mention all of the characters to go to the top band.

Difference betwixt AS and A level answers

The descriptions follow the aforementioned criteria; still y'all take to employ the issues and debates effectively in your answers. "Effectively" means that it needs to be clearly linked and explained in the context of the answer.

Read the model answers to get a clearer idea of what is needed.

Divisions of the Nervous System

Central

The nervous system is our primary internal communication system, a specialised network of cells in our body. The primal nervous organisation receives information from the senses and controls the behavior and regulation of the torso's psychological processes.

The primal nervous system (CNS) is made up of the encephalon and spinal string.

The brain receives information from sensory receptors and sends messages to muscles and glands. It is the centre of all conscious awareness and is divided into different lobes with different functions. It contains the cerebrum which makes up about 85% of the full mass.

The forebrain is divided into two parts.

The diencephalon contains the:

• Thalamus: concerned with relaying sensory information from the brainstem to the cortex.
• Hypothalamus: controls basic functions such every bit hunger, thirst, sexual behavior; also controls the pituitary gland.

The cerebral hemispheres command higher level cognitive and emotional processes:

• The limbic organisation is involved in learning, retentivity and emotions
• The basal ganglia is involved in motor activities and movement
• The neocortex/cerebral cortex is involved with planning, problem-solving, language, consciousness and personality

The spinal string is an extension of the brain that is responsible for reflex actions. It allows the encephalon to monitor processes such every bit breathing and to control voluntary movements.

The hindbrain (pons, medulla, cerebellum) is a continuation of the spinal string carrying on into the lesser of the encephalon – the brain stem – mainly composed of sensory and motor neurons. The cerebellum controls motility and motor coordination.

Peripheral (autonomic and somatic)

The portion of the nervous system that is outside the brain and spinal cord. The primary function of the peripheral nervous arrangement is to connect the brain and spinal cord to the residual of the trunk and the external environment.

The peripheral nervous organisation transmits information to and from the CNS.

This is accomplished through nerves that comport information from sensory receptors in the eyes, ears, skin, olfactory organ and natural language, as well as stretch receptors and nociceptors in muscles, glands and other internal organs.

The PNS is made up of 31 spinal nerves which radiate out from the spinal string and tin can be divided into the:

Somatic Nervous System

The somatic nervous system controls voluntary movements, transmits and receives messages from the senses and is involved in reflex deportment without the involvement of the CNS so the reflex can occur very chop-chop.

Somatic Nervous System (SNS) connects the central nervous arrangement with the senses and is equanimous of:

• Sensory nerve pathways bring information to the CNS from sensory receptors, dealing with touch, pain, pressure, temperature etc.
• Motor nerve pathways which control actual movement by carrying instructions towards muscles

Autonomic Nervous Arrangement

Autonomic Nervous Organisation (ANS) regulates involuntary actions such as actual arousal (how 'excited' or relaxed we are), trunk temperature, homeostasis, heart rate, digestion and blood pressure. Composed of ii parts:

• The sympathetic nervous system that is involved in responses which help u.s. bargain with emergencies. It slows actual processes that are less important in emergencies such as digestion. The sympathetic ANS leads to increased arousal: e.g. increase in center rate and blood pressure, pupil dilation, reduction in digestion and salivation.
• The parasympathetic nervous system that relaxes the private one time the emergency has passed (eg. slows the center rate down and reduces claret pressure) and conserves the trunk's natural action past decreasing activity/maintaining it. The parasympathetic ANS leads to decreased arousal.

The structure and role of sensory, relay and motor neurons

• Sensory neurones – convey information well-nigh sensory stimuli: vision, affect, taste, etc. towards the encephalon.
• Motor neurones – convey instructions for physical operations: due east.g. release of hormones from glands, muscle move, digestion, etc.
• Relay neurons – connect different parts of the cardinal nervous organisation (CNS).

The process of synaptic transmission

Neurotransmitters (excitation and inhibition)

The nervous system is composed of 100 billion cells called neurons. Although different types of neurons vary in size and function they all operate in the same way – passing on messages via electrical and chemical (neurotransmitter) signals.

Neurons lie adjacent to each other but are non connected. When an electric indicate reaches the axon terminals, molecules of neurotransmitters are released across the synaptic gap (the gap separating one neuron from another) and and so adhere to post-synaptic receptors on the side by side neuron. This will then trigger an electrical impulse in the side by side prison cell.

During synaptic transmission, the action potential (an electrical impulse) triggers the synaptic vesicles of the pre-synaptic neuron to release neurotransmitters (a chemical message).

These neurotransmitters lengthened beyond the synaptic gap (the gap between the pre and post-synaptic neurons) and bind to specialised receptor sites on the mail-synaptic neuron.

The action of neurotransmitters at synapses tin can be:

• Excitatory – make a nerve impulse more likely to be triggered: for example, dopamine or serotonin which produce states of excitement/activeness in the nervous organisation and in our mental state/behavior.
• Inhibitory - brand a nerve impulse less likely to be triggered: for example, GABA calms activeness in the nervous organization and produces states of relaxation (as with anti-anxiety medication such as Valium).

The function of the endocrine arrangement: glands and hormones

Hormones are chemical messengers secreted from structures (glands) in the body which pass through the bloodstream to cause changes in our torso or behavior. The network of glands is chosen the endocrine system.

Endocrine Gland	Main Hormones	Effects
Thyroid	Thyroxine	Regulates metabolic rate and protein synthesis
Adrenal medulla	Adrenaline and noradrenaline	Fight or flight response: increased heart charge per unit, blood pressure, release of glucose and fats (for free energy)
Adrenal cortex	Corticosteroids	Release of glucose and fats for energy; suppression of the immune system
Testes	Testosterone	Male sexual characteristics, muscle mass
Ovaries	Oestrogen	Female sexual characteristics, flow, pregnancy
Pineal	Melatonin	Sleep-wake cycle

The pituitary gland is the primary gland and controls release of hormones from many of the glands described above. The pituitary is divided into the inductive and posterior.

• ANTERIOUR PITUITARY (Hormones released)
• ACTH: Stimulates release of corticosteroids during flying-flying response.
• Prolactin: Stimulates product of milk from mammary glands (breasts).
• Growth Hormone: Prison cell growth and multiplication.

• POSTERIOUR PITUITARY (Hormones released)
• Vasopressin: Regulates water balance.
• Oxytocin: Uterine contractions during childbirth .

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The fight or flight response including the function of adrenaline

The fight or flight response is a sequence of activity within the trunk that is triggered when the body prepares itself for defending or attacking (fight) or running away to safe (flight).

Stress is experienced when a person'south perceived environmental, social and/or physical demands exceed their perceived ability to cope.

The stress response (otherwise known as the 'fight or flight' response) is difficult-wired into our brains and represents an evolutionary adaptation designed to increase an organism's chances of survival in life-threatening situations.

The fight or flight response involves 2 major systems

• The Sympathomedullary Pathway – deals with astute (short-term, immediate) stressors such as personal attack.
• The Pituitary-Adrenal System – deals with chronic (long-term, on-going) stressors such as a stressful chore.

The Sympathomedullary Pathway (SAM)

The hypothalamus besides activates the adrenal medulla. The adrenal medulla is part of the autonomic nervous system (ANS).

The ANS is the part of the peripheral nervous system that acts as a control system, maintaining homeostasis in the body. These activities are by and large performed without conscious control.

The adrenal medulla secretes the hormone adrenaline. This hormone gets the body prepare for a fight or flying response. Physiological reaction includes increased heart charge per unit.

Adrenaline lead to the arousal of the sympathetic nervous organization and reduced activity in the parasympathetic nervous organization.

Adrenaline creates changes in the body such as decreases (in digestion) and increases (sweating, increased pulse and blood pressure level).

Once the 'threat' is over the parasympathetic branch takes command and brings the body back into a balanced state.

No ill effects are experienced from the short-term response to stress and information technology farther has survival value in an evolutionary context.

The Hypothalamic Pituitary-Adrenal (HPA) Arrangement

• The stressor activates the Hypothalamic Pituitary Axis
• The hypothalamus stimulates the pituitary gland
• The pituitary gland secretes adrenocorticotropic hormone (ACTH)
• ACTH stimulates the adrenal glands to produce the hormone corticosteroid
• The adrenal cortex releases stress hormones called cortisol. This have a number of functions including releasing stored glucose from the liver (for energy) and controlling swelling later on injury. The immune organization is suppressed while this happens.
• Adequate and steady blood saccharide levels help person to cope with prolonged stressor, and helps the body to render to normal
  

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Localisation of function in the brain and hemispheric lateralisation:

Hemispheric lateralisation: motor, somatosensory, visual, auditory and language centres; Broca's and Wernicke's areas

Localisation of function is the theory that dissimilar areas of the brain are responsible for different behaviors, processes or activities. Information technology contrasts with the holistic theory of the brain. If a certain area of the encephalon becomes damaged, the role associated with that area will also be affected.

The link between brain structures and their functions (e.g. language, memory, etc.) is referred to every bit encephalon localisation.

The brain is divided into 2 hemispheres – left and correct.

Motor and Somatosensory Areas

The motor cortex controls voluntary movements. Both hemispheres have a motor cortex with each side controlling muscles on the opposite side of the body (i.eastward. left hemisphere controls muscles on right side of body).

Different areas of the motor cortex control dissimilar parts of the trunk and these are in the same sequence every bit in the body (e.g. the office of the cortex controlling the human foot is next to the part decision-making the leg, etc.)

Visual Centers

Processing of visual information starts when calorie-free enters the eye and strikes photoreceptors on the retina at the back of the eye. Nerve impulses so travel upward the optic nerve to the thalamus and are then passed on to the visual cortex in the hindbrain.

The correct hemisphere'south visual cortex processes visual data received past the left eye and vice-versa. The visual cortex contains different regions to do with color, shape, movement, etc.

Auditory Centers

Processing of auditory information (audio) begins in the inner ear'southward cochlea where sound waves are converted into nerve impulses which travel forth the auditory nervus to the encephalon stem (which decodes duration and intensity of sound) then to the auditory cortex which recognises the sound and may form an advisable response to that audio.

Language Centers

Broca's Expanse is more often than not considered to exist the main heart of speech communication production. The neuroscientist later whom this brain expanse is named plant that patients with speech production bug had lesions (harm) to this area in their left hemisphere but lesions in the right hemisphere did not crusade this problem. More than recent research indicates Broca's area is besides involved with performing complex cognitive tasks (e.one thousand. solving maths problems).

Wernicke's expanse is likewise in the left hemisphere and is concerned with speech comprehension. The neuroscientist subsequently whom this encephalon expanse is named found that lesions in this encephalon area could produce but not understand/comprehend language. Wernicke's area is divided into the motor region (which controls movements of the mouth, tongue and vocal cords) and the sensory area (where sounds are recognised as language with significant).

Broca's and Wernicke's areas are connected by a loop which ties together language production and comprehension.

Evaluation AO3

Research support from case studies – Phineas Gage was in an blow which caused him to lose part of his frontal lobe which altered his personality – The frontal lobe may play a role in mood regulation therefore localisation theory is correct.

Equipotentiality theory argues that although basic brain functions such as the motor cortex and sensory functions are controlled by localised encephalon areas, higher cerebral functions (such as problem-solving and decision-making) are non localised. Research has plant that damage to brains can event in other areas of the brain taking over control of functions that were previously controlled by the role of the encephalon that has been damaged. Therefore, the severity of encephalon damage is determined by the amount of damage to the brain rather than the particular area which has been damaged.

The way in which encephalon areas are connected with each other may be as important for normal cerebral function as particular brain sites themselves. Brain sites are interdependent and damage to connections betwixt sites may atomic number 82 to the brain site not being able to part unremarkably. For instance, Dejerine (1892) found that damage to the connectedness betwixt the visual cortex and Wernicke's area lead to an disability to read (vision + comprehension).

Gender differences take been found with women possessing larger Broca's and Wernicke'due south areas than men, presumably as a result of women'southward greater utilize of linguistic communication.

Hemispheric lateralisation: Split Brain Research

Hemispheric lateralisation concerns the fact that the brain'due south ii hemispheres are non exactly alike and have different specialisms. For example, the left hemisphere is mainly concerned with speech and language and the correct with visual-motor tasks. Broca (1861) found that damage to the left hemisphere led to dumb language but damage to the same expanse on the right hemisphere did non.

The encephalon'south two hemispheres are connected by a bundle of nerve fibres – the corpus callosum – which allows information received past 1 hemisphere to be transferred to the other hemisphere.

Investigations into the corpus callosum began when doctors severed patients' corpus callosum in an try to prevent violent epileptic seizures. Sperry (1968) tested such split-encephalon patients to assess the abilities of separated encephalon hemispheres.

Sperry (1968)

Aim: To appraise the abilities of separated brain hemispheres.

Procedure

Participants sat in forepart of a board with a horizontal rows of lights and were asked to stare at the heart bespeak. The lights then flashed beyond their correct and left visual field. Participants reported lights had only flashed upwards on the right side of the board.

FindingsWhen their right middle was covered and the lights were flashed to the left side of their visual field they claimed not to have seen whatever lights at all. However, when asked to point at which lights had lit upwards they could do.

DecisionThis shows that participants had seen the lights in both hemispheres but that fabric presented to the left middle could not exist spoken virtually as the right hemisphere (which receives information from the left eye) has no language centre and thus cannot speak nearly the visual data it has received. It can communicate about this in different non-visual ways, yet – e.g. participants could bespeak at what they had seen.

This proves that in lodge to say that ane has seen something the region of the brain associated with speech must be able to communicate with areas of the brain that procedure visual information.

Evaluation AO3

Considering separate-brain patients are so rare, findings equally described higher up were often based on samples of 2 or 3, and these patients often had other neurological problems which might have acted as a misreckoning variable. As well, patients did not always have a consummate splitting of the 2 hemispheres. These factors mean findings should be generalised with care.

More contempo research has contradicted Sperry's original claim that the right hemisphere could non process fifty-fifty basic language. For example, the case study of JW establish that later a dissever-brain process he developed the ability to speak out of his correct hemisphere which means that he tin speak virtually information presented to either his left or his correct visual field.

Brain lateralisation is assumed to be evolutionarily adaptive as devoting just i hemisphere of the brain to tasks leaves the other hemisphere gratis to handle other tasks. For example, in chickens, encephalon lateralisation allows birds to use 1 hemisphere for locating food, the other hemisphere to watch for predators. Thus, encephalon lateralisation allows for cerebral multi-tasking which would increase chances of survival.

Individuals with high level mathematical skills tend to take superior right hemisphere abilities, are more likely to be left handed, and are more than likely to suffer allergies and other immune system wellness bug. This suggests a relationship between encephalon lateralisation and the immune system.

Research also indicates that the brain become less lateralised as we historic period. It is possible that as we historic period and face declining mental abilities the brain compensates by allocating more resources to cognitive tasks.

Test Questions

Plasticity and functional recovery of the brain after trauma

Plasticity

Plasticity is the brains trend to change and adapt (functionally and physically) equally a effect of feel and new learning. During infancy, the brain experiences a rapid growth in the number of synaptic connections. As we age, rarely used connections are deleted and frequently used connections are strengthened (synaptic pruning).

Although this was traditionally associated with changes in childhood, recent research indicates that mature brains continue to evidence plasticity every bit a result of learning.

Learning and new experiences cause new neural pathways to strengthen whereas neural pathways which are used infrequently get weak and somewhen die. Thus brains conform to changed environments and experiences. Boyke ('08) found that even at lx+, learning of a new skill (juggling) resulted in increased neural growth in the visual cortex.

Kuhn ('xiv) found that playing video games for thirty+ minutes per twenty-four hour period resulted in increased brain affair in the cortex, hippocampus and cerebellum. Thus, the complex cerebral demands involved in mastering a video games caused the formation of new synaptic connections in brain sites controlling spatial navigation, planning, controlling, etc.

Davidson ('04) matched 8 experienced practitioners of Tibetan Buddhist meditation against ten participants with no meditation experience. Levels of gamma brain waves were far college in the experienced meditation group both before and during meditation. Gamma waves are associated with the coordination of neural activity in the encephalon. This implies that meditation tin increase encephalon plasticity and cause permanent and positive changes to the brain.

Kempermann ('98) found that rats housed in more complex environments showed an increase in neurons compared to a control grouping living in simple cages, Changes were especially articulate in the hippocampus – associated with memory and spatial navigation.

A similar miracle was shown in a study of London taxi drivers. MRI scans revealed that the posterior portion of the hippocampus was significantly larger than a control group, and size of difference was positively correlated with amount of time spent as a taxi commuter (i.e. greater demands on retentiveness = more neurons in this portion of hippocampus).

Functional Recovery

Functional recovery is the idea that following physical injury or other forms of trauma, unaffected areas of the brain can accommodate to compensate for those that are damaged.

Case studies of stroke victims who have experienced brain damage and thus lost some brain functions have shown that the brain has an power to re-wire itself with undamaged brain sites taking over the functions of damaged brain sites. Thus, neurons next to damaged brain sites tin can take over at least some of the functions that have been lost.

Functional recovery is an effect of encephalon plasticity which is thought to operate in 2 principal ways.

1. Neuronal unmasking. Wall ('77) noticed the brain contained 'dormant synapses' – neural connections which take no function. Yet, when brain damage occurs these synapses tin become activated and open upwards connections to regions of the brain that are not normally active and have over the neural part that has been lost every bit a result of damage.
2. Stem cells are unspecialised cells which can become specialised to carry out different types of task: for example, taking on the behavior of neurons in the encephalon. Electric current enquiry is examining ways in which stem cells might be used to help recovery from brain trauma: for example, they could be implanted to supercede dead cells or to release substances which encourage growth or recovery of damaged cells.

There is a negative correlation betwixt functional recovery and historic period: i.e. immature people have a high power to recover which declines as we age.

Level of education (associated with a more active, neurologically well-connected brain) is positively correlated with speed of recovery from traumatic encephalon injuries. Schneider found that patients with a college education were x7 times more likely to than those who did non finish college to recover from their disability after 1 year.

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Means of Studying the Brain

Functional magnetic resonance imaging (fMRI)

A brain scanner which measures increased claret flow to brain sites when individuals are asked to perform cognitive/concrete tasks. Increased blood menstruation indicates increased need for oxygen in that area.

This produces 3D images showing which parts of the encephalon are involved in a detail mental process, important for our understanding of localisation of function.

Thus, fMRI tin help build upwards a map of brain localisation. For example, an fMRI scan could identify encephalon sites which received increased oxygen when a participant is asked to solve maths problems.

Strengths

• Non-invasive – No insertion of instruments unlike PET and no exposure to radiation – Beneficial to the economy every bit there is no recovery fourth dimension then people don't accept to be off work.

Limitations

• fMRI only measures blood flow – it cannot home in on the activity of individual neurons therefore it's hard to tell exactly what brain activity is being represented on the screen – Loftier likelihood that the findings will be misinterpreted as information technology doesn't show action similar EEG/ERP. •

• fMRI may overlook the interconnectivity of brain sites. By just focusing on brain sites receiving increased blood menstruation, information technology fails to business relationship for the importance of brain sites connecting/communicating with each other.

• Expensive – Other neuroimaging techniques such as EEG may be cheaper and it can only capture a clear paradigm if the person stays still – May not be worthwhile for the NHS to fund it.

Electroencephalogram (EEGs)

Measures electrical activity in the encephalon using electrodes attached to the scalp, and measures how electric activeness in the encephalon varies over time/in different states (due east.thou. waking vs. asleep). EEG readings can detect epilepsy and Alzheimer'southward.

four basic brain moving ridge patterns are (i) alpha – awake and relaxed, (ii) beta – awake and highly aroused or in REM (rapid center movement sleep), (three) delta – deep sleep, (four) theta – low-cal sleep.

Strengths

• Records encephalon action over time and can, therefore, monitor changes every bit a person switches from chore to job or one state to another (e.1000. falling asleep).

• EEGs have medical applications in diagnosing disorders such as epilepsy and Alzheimer's.

• Not-invasive - No insertion of instruments different PET and no exposure to radiation – EEGs are nigh take chances free and is avoidant of any danger to the brain itself.

• Cheaper than fMRI thus making them more bachelor – Psychologists can get together more data on the functioning of the human encephalon thus contributing to our understanding of dissimilar psychological phenomena.

Limitations

• EEGs only monitor electrical activity in outer layers of the brain, therefore, cannot reveal electrical activity in deeper brain sites.

• Not highly accurate – electrical activity detected in several regions of the brains simultaneously – Very hard to pinpoint exactly which expanse is producing this activity. therefore cannot distinguish differences in activity between 2 closely adjacent areas.

• Uncomfortable – Difficult for the patients equally electrodes are attached to their head – Could event in an unrepresentative reading as the patients discomfort could trigger cognitive responses to the existent fourth dimension situation.

Event-related potentials (ERPs)

ERP'southward are very small voltage changes in the brain triggered by specific events or stimuli which are measured using an EEG.

Measures pocket-size voltages of electric activeness when a stimulus is presented. Because these minor voltages are difficult to pick out from other electrical signals in the brain, the stimulus needs to be repeatedly presented, and only signals which occur every time the stimulus is presented will be considered an ERP for that stimulus.

ERPS are of 2 types: (i) sensory ERPS - those that occur within 100 milliseconds of stimulus presentation; (ii) cognitive ERPS – those that occur 100 milliseconds or more after stimulus presentation. Sensory ERPS indicate the brain's 1st recognition of a stimulus. Cognitive ERPS correspond information processing and evaluation of the stimulus.

Strengths

• ERPS provide a continuous measure of neural activity in response to a stimulus. Therefore, changes to the stimulus tin be directly recorded: eastward.yard. if a blue coloured slide turned light-green.

• Derived from EEG – Excellent temporal resolution compared to fMRI – Much more specificity has led to their widespread employ in the measurement of cognitive functions and deficits.

• Non-invasive - No insertion of instruments dissimilar PET and no exposure to radiation – Virtually take chances free and is avoidant of any danger to the brain itself.

Limitations

• ERPS just monitor electrical activity in outer layers of the brain, therefore, cannot reveal electrical activity in deeper encephalon sites.

• Extraneous stimuli must exist eliminated in guild to collect pure data, the participant may react to background noise or a difference in temperature – For experiments where these variables tin can't exist controlled, it's hard to draw conclusions.

• Lack of standardisation in methodology betwixt studies – Different groups will use varying averages on what neural activity they decide to filter out – Hard to replicate experiments and ostend findings in a peer review study.

Post-mortem examinations

Brains from expressionless individuals who displayed cerebral abnormalities whilst live can be dissected to cheque for structural abnormalities/damage: e.g. Broca's expanse was discovered subsequently dissections of patients who displayed speech abnormalities, and HM'due south (Memory Topic) inability to store new memories was linked to lesions in his hippocampus. Neurological abnormalities have been linked to depression, schizophrenia, anti-social personality disorder, etc.

Strengths

• Allow for detailed examinations and measurement of deep brain structures (due east.g. the hypothalamus) not measurable by encephalon scans.

• Brain tissue can be examined in particular – Deep structures of the encephalon tin can be investigated later on decease – PM is more appropriate than EEG or ERP when examining any brain construction other than the neocortex.

• Highly applicable – Broca and Wernicke both relied on post mortem studies in establishing links betwixt language, encephalon and behavior decades before neuroimaging ever became a possibility – Evidence has improved medical cognition and less money can be used by the NHS on less efficient techniques which generates a positive impact on the economy.

Limitations

• The issue of causation – The deficit a patient displays during their lifetime may non be linked to the deficits establish in the brain, they may be the result of another illness – Psychologists are unable to conclude that the arrears is acquired by the harm found in the brain. Various factors can act as misreckoning variables and might confuse findings/conclusions. For example, length of time between death and post-mortem, other damage acquired to the encephalon either during death or equally a result of disease, age at death, drugs given in months prior to death, etc.

• Ethical bug – Deceased people are not able to provide informed consent such as HM because of his lack of brusque term abilities – There will be problems with replicability considering future ethical guidelines will be stricter.

Test Questions

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Biological Rhythms

Circadian, infradian and ultradian and the difference between these rhythms

The physiological processes of living organisms follow repetitive cyclical variations over certain periods of fourth dimension. These bodily rhythms have implications for behavior, emotion and mental processes.

There are three types of bodily rhythms:

1. Cyclic rhythms: follow a 24-hour cycle: e.g. the sleep-waking cycle
2. Ultradian rhythms: occur more than once a 24-hour interval: e.chiliad. the cycles of REM and NREM sleep in a unmarried night'due south sleep
3. Infradian rhythms: occur less than in one case a mean solar day: e.yard. menstruation (monthly) or hibernation (yearly)

All bodily rhythms are controlled by an interaction of:

1. Endogenous pacemakers (EP's). Internal biological structures that command and regulate the rhythm.
2. Exogenous zeitgebers (fourth dimension givers) (EZ's). External ecology factors that influence the rhythm.

• Circadian RHYTHMS
• Centre rate, metabolic rate, breathing rate and torso temperature all achieve maximum values in the tardily afternoon/early on evening and minimum values in the early hours of the morning. If we reverse our sleep-waking pattern these rhythms persist. This indicates human bodies are evolved for action in the day and balance at night and, indeed, being nocturnal or disrupting the circadian cycle is highly stressful and physiologically and psychologically harmful.
• The EP decision-making the sleep-waking cycle is located in the hypothalamus. Patterns of light and darkness are registered by the retina, travel up the optic nerves to where these fretfulness join (optic chiasma), then laissez passer into the superchiasmatic nucleus (SCN) of the hypothalamus. If this nerve connection is severed circadian rhythms become random. The same consequence is produced by damaging the SCN of rats, and people born without eyes cannot regulate bodily rhythms.
• Ralph bred a group of hamsters to follow a (shortened) 20-hour cyclic cycle. SCN cells were removed and transplanted into the brains of rat foetuses with normal rhythms. In one case born, these rats adopted a 20-hr cycle. Their brains were and so transplanted with SCN cells from 24-hr cycle hamsters and within a week their cycles had adopted this new 24 cycle.
• When cells from the SCN were removed from rats the 24-hour cycle of neural activity persisted in the isolated cells. Recent inquiry past Yakazaki found that isolated lungs and livers, and other tissues grown in a lab still persist in showing circadian rhythms. This suggests cells are capable of maintaining a circadian rhythm even when they are not under the control of any brain structures and that about actual cells are tuned in to following a daily circadian rhythm.
• All of this evidence points to the fact that circadian rhythms are primarily controlled past evolutionarily-adamant, biological structures that exert a strong influence on us to maintain normal sleep-waking patterns.
• However, circadian rhythms are also influenced past EZ's - 'cues' in the surround- about what time of solar day or night it is. In 1975 Siffre spent half-dozen months underground in an surround completely cutting off from all EZ'due south. Although he organised his time in regular patterns of sleeping and waking his torso seemed to take a preference for a 25 hour rather than a 24-hour cycle. This implies that circadian rhythms are mainly controlled by EP'southward rather than EZ's.
• Another piece of bear witness in back up of this idea is that Innuit Indians who alive in the Chill Circle inhabit an environment that has hardly whatsoever darkness in summer and hardly any light in winter. If the sleep-waking bicycle was primarily controlled past EZ's they would tend to sleep a huge amount in wintertime and inappreciably at all in summer. Notwithstanding, this is not the case - they maintain a adequately regular pattern of sleeping and waking all twelvemonth around.

• ULTRADIAN RHYTHMS
• With the development of certain scientific equipment, it became possible to written report slumber more considerately.• The electroencephalogram (EEG) measures electrical brain activity.

  • The electrooculogram (EOG) measures centre movement.

  • The electromyogram (EMG) measures muscle tension.

• These instruments signal that during a single night'south sleep we experience a cyclical ultradian rhythm of different stages and types of sleep which tin can be roughly divided into REM (rapid centre movement) and NREM (non-rapid eye movement). REM is strongly associated with dreaming: for example, 80% of sleepers awoken from REM will report that they have been dreaming, whilst the NREM charge per unit is simply 15%, and dreams from NREM are reported as less vivid and visual. NREM can be sub-divided into stages 1-4.
• Once asleep we enter phase 1 NREM so, over the next half-hour, rapidly descend through stages 2, 3 and iv. As we descend through the stages muscles progressively relax, EEGs go less active, pulse, respiration and blood pressure level become slower, and information technology is progressively more difficult to wake the sleeper. After spending about 30 mins in phase 4 NREM the bike reverses and we ascend back through the NREM stages iii, two and 1. Still, instead of waking up we enter our 1st menses of REM sleep. During REM, pulse, respiration and blood force per unit area increase but become less regular and EEG's resemble those of the waking state - showing the encephalon to be highly agile in terms of blood catamenia, oxygen consumption and neural firing.
• Major characteristics of REM are that backside the closed lids the eyeballs show rapid movement and the encephalon shows spontaneous action that is strongly associated with the experience of dreaming. Firstly, hindbrain and midbrain structures commonly associated with relaying visual and auditory stimuli from the outside world spontaneously generate signals: i.due east. the encephalon is interim as if it is hearing and seeing things. Secondly, the motor cortex (responsible for bodily movement) spontaneously generates signals but these are 'cut off' at the acme of the spine, limb commands are blocked, and we are effectively paralysed from the neck down.
• As stated before it is more often than not assumed that we almost exclusively dream in REM and that NREM is not associated with dreaming. It is possible that nosotros dream in both NREM and REM, but we don't think dreams from NREM equally we are more 'deeply' asleep in this state and dream memories cannot be recalled.
• Patterns of NREM and REM alter as we age.

  • New-born - 16 hours' sleep, 50% REM (patterns of REM are observed in foetuses).

  • 3-year-former - 12 hours' sleep, 25% REM.

  • Adult - viii hours' sleep, 22% REM.

  • 70+- 6 hours' sleep, 14% REM.

  This changing design of REM has led researchers to believe ane office of REM is the growth and repair of the brain - needed a lot when young and less equally we age.

• The EP controlling REM appears to be the locus coeruleus (LC) (a patch of cells located in a brain structure called the pons) which produces noradrenaline and acetylcholine. Destruction of the LC causes REM to disappear. If neurons in a unlike office of the pons are destroyed, REM remains merely muscle paralysis in REM disappears- this results in a cat moving around although it is completely asleep. This may prevarication behind 'behavioral sleep disorder' in humans where sleepers may human activity out their dreams.

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

Circadian rhythms follow a 24-hour cycle (e.g. the sleep-waking bicycle) and are controlled by an interaction of:

1. Endogenous pacemakers (EP'south). Internal biological structures that control and regulate the rhythm.
2. Exogenous zeitgebers (time-givers) (EZ'southward). External environmental factors that influence the rhythm.

The EP controlling the sleep-waking cycle is located in the hypothalamus. Patterns of light and darkness are registered past the retina, travel up the optic nerves to where these fretfulness join (optic chiasma), and then pass into the suprachiasmatic nucleus (SCN) of the hypothalamus. If this nerve connexion is severed circadian rhythms become random. The same outcome is produced by damaging the SCN of rats, and people born without eyes cannot regulate bodily rhythms.

However, circadian rhythms are as well influenced by EZ's - 'cues' in the environment - about what time of twenty-four hour period or night it is. Siffre spent half dozen months hugger-mugger in an surroundings completely cut off from all EZ'due south. Although he organised his time in regular patterns of sleeping and waking his body seemed to accept a preference for a 25 hour rather than a 24-hour cycle. This implies that circadian rhythms are mainly controlled by EP's rather than EZ's.

Another piece of evidence in support of this idea is that Innuit Indians who live in the Arctic Circle inhabit an environment that has hardly any darkness in summer and hardly whatever light in winter. If the slumber-waking bike was primarily controlled past EZ's they would tend to sleep a huge amount in winter and hardly at all in summer. However, this is not the case- they maintain a fairly regular pattern of sleeping and waking all year effectually.

Disruption of the circadian sleep-waking cycle (east.thou. jet lag and shift work) has been shown to cause negative concrete and psychological effects.

Jet Lag occurs when we cantankerous several world time zones rapidly. Circadian rhythms volition be disrupted as although our endogenous pacemakers stay the aforementioned, the exogenous zeitgebers (patterns of light and dark in the new environment) have changed.

For example: Flight from London to New York. Leave London viii a.m. - spend 8 hours flight – arrive NYC iv p.m. Although our endogenous pacemaker 'feels' equally though it is iv p.thou., we must take account of the fact that NYC is 5 hours 'backside' London time. When nosotros arrive in NYC it volition in fact exist 11 a.m. (four p.grand. minus five hours). Therefore, our endogenous pacemaker has become desynchronised with the local exogenous zeitgebers.

The event of this is that we volition have an artificially lengthened day. For example, nosotros may exist ready to sleep by 6 p.m. NYC time, and afterward 8 hours' sleep might wake up at 2 a.m. ready to start a new day. The overall effect of crossing time zones in this fashion is that our trunk will feel every bit if it is daytime during the nighttime, and that it is night-time during the day. The more than fourth dimension zones we travel through the more severe this effect will exist.

Symptoms of Jet lag/shift piece of work include:

1. Tiredness during the new daytime and indisposition at night
2. Decreased mental performance and lack of concentration
3. Decreased concrete performance
4. Loss of appetite, indigestion and nausea
5. Irritability, headaches and mental confusion

The symptoms of Jet Lag are commonly described as more severe when travelling in a W-East direction (east.k. from NYC to London). When we travel in an Eastward-West management the solar day is diffuse. Every bit the Siffre written report proves, our body has a preference for a longer 25-hour circadian rhythm, and thus prefers a diffuse to a shortened day (equally occurs when we travel Westward-East).

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