AQA A-LEVEL PSYCHOLOGY REVISION NOTES: BIOPSYCHOLOGY

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PSYCHOLOGY AQA A-LEVEL UNIT 2 (7182/2)

THE SYLLABUS

NEURONS, THE NERVOUS SYSTEM, THE ENDOCRINE SYSTEM, FIGHT OR FLIGHT RESPONSE

• The structure and function of sensory, relay and motor neurons. The process of synaptic transmission, including reference to neurotransmitters, excitation and inhibition
• The divisions of the nervous system: central and peripheral (somatic and autonomic)
• The function of the endocrine system: glands and hormones
• The fight or flight response including the role of adrenaline

LOCALISATION OF FUNCTION IN THE BRAIN AND HEMISPHERIC LATERALISATION

• Motor, somatosensory, visual, auditory and language centres including Broca’s and Wernicke’s areas
• Split brain research
• Plasticity and functional recovery of the brain after trauma

WAYS OF STUDYING THE BRAIN

• Scanning techniques, including functional magnetic resonance imaging (fMRI); electroencephalogram (EEGs) and event-related potentials (ERPs); post-mortem examinations

BIOLOGICAL RHYTHMS

• Circadian, infradian and ultradian and the difference between these rhythms
• The effect of endogenous pacemakers and exogenous zeitgebers on the sleep/wake cycle

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INTRODUCTION

Humans are biological organisms, thus from a biological perspective all aspects of human psychology must derive from internal biological structures and processes.

Major fields of focus for biopsychologists have been:

• The role of genetic inheritability on traits such as intelligence, personality type and mental illness
• The anatomy of the brain in relation to which brain sites are responsible for particular abilities and how parts of the brain interact with each other
• The role of neurotransmitters and hormones – both biologically produced chemicals – on motivation, emotion and behaviour. For example, the influence of the neurotransmitter dopamine on schizophrenia or the influence of the hormone testosterone on male gender role and aggression.

Biological psychology employs highly scientific methods and shares much in common with biology and chemistry.

The brain is connected to and receives and passes on messages from the nervous system. The brain and nervous system are composed of cells called neurons which communicate with each other via electrical and chemical (neurotransmitter) signals. It is this neuronal activity which is responsible for all human cognitive abilities and psychological states.

The syllabus covers the structure and function of neurons, the various divisions of the nervous system, the endocrine system (which controls the release of hormones) and the fight-flight response – how the human body responds when faced with stress.

You will also study basic brain anatomy – looking at brain sites concerned with visual and auditory perception, and the comprehension and production of language. Research has focused on how the left and right hemispheres of the brain interact with each other and how brains change as we grow and heal after damage.

Lastly, you will study the natural rhythms of the body examining research on the sleep-waking cycle, nightly patterns of rapid and non-rapid eye movement sleep and dreaming, and menstruation. You will also cover the physically and psychologically detrimental effects of disrupting the body’s natural rhythms.

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THE PROCESS OF SYNAPTIC TRANSMISSION, INCLUDING REFERENCE TO NEUROTRANSMITTERS, EXCITATION AND INHIBITION (AQA A-level Psychology revision)

NEURONS, SYNAPTIC TRANSMISSION & NEUROTRANSMITTERS

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.

Electrical nerve impulses (action potentials) travel from the dendrites along the cell body and the axon to the axon terminals. These action potentials are the basic units of information processing in the nervous system and control all aspects of human behaviour (e.g. perception, memory, emotion, etc.)

Neurons lie adjacent to each other but are not connected. When an electrical signal reaches the axon terminals, molecules of neurotransmitters are released across the synaptic gap/synapse (the gap separating one neuron from another) and then attach to post-synaptic receptors on the adjacent neuron. This will then trigger an electrical impulse in the adjacent cell.

The action of neurotransmitters at synapses can be

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

THE STRUCTURE AND FUNCTION OF SENSORY, RELAY AND MOTOR NEURONS

• Sensory neurones – convey information about sensory stimuli: vision, touch, taste, etc. towards the brain
• Motor neurones – convey instructions for physical operations: e.g. release of hormones from glands, muscle movement, digestion, etc.
• Relay neurons – connect different parts of the central nervous system (CNS).

THE DIVISIONS OF THE NERVOUS SYSTEM: CENTRAL AND PERIPHERAL (SOMATIC AND AUTONOMIC)

The central nervous system (CNS) is made up of the brain and spinal cord.

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

The forebrain is divided into 2 parts.

• The diencephalon contains the
  • Thalamus: concerned with relaying sensory information from the brainstem to the cortex.
  • Hypothalamus: controls basic functions such as hunger, thirst, sexual behaviour; also controls the pituitary gland.
• The cerebral hemispheres control higher level cognitive and emotional processes
  • The limbic system is involved in learning, memory 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 peripheral nervous system (PNS)

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

• Somatic Nervous System (SNS) connects the central nervous system with the senses and is composed of
  • sensory pathways which deal with touch, pain, pressure, temperature
  • motor pathways which control bodily movement
• Autonomic Nervous System (ANS). Controls bodily arousal (how ‘excited’ or relaxed we are), body temperature, homeostasis, heart rate and blood pressure. Composed of 2 parts
  • The sympathetic ANS leads to increased arousal: e.g. increase in heart rate and blood pressure, pupil dilation, reduction in digestion and salivation.
  • The parasympathetic ANS leads to decreased arousal.

(See Fight-Flight response below).

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THE FUNCTION OF THE ENDOCRINE SYSTEM: GLANDS AND HORMONES (AQA A-level Psychology revision guide)

Hormones are chemical messengers secreted from structures (glands) in the body which pass through the bloodstream to cause changes in our body or behaviour. The network of glands is called 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 rate, blood pressure, release of glucose and fats (for 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, menstruation, pregnancy
Pineal	Melatonin	Sleep-wake cycle

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

ANTERIOR PITUITARY (Hormones released)
ACTH	Stimulates release of corticosteroids during flight-flight response
Prolactin	Stimulates production of milk from mammary glands (breasts)
Growth Hormone	Cell growth and multiplication
POSTERIOR PITUITARY (Hormones released)
Vasopressin	Regulates water balance
Oxytocin	Uterine contractions during childbirth

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THE FIGHT OR FLIGHT RESPONSE INCLUDING THE ROLE OF ADRENALINE (A-level Psychology resources)

Stress is experienced when a person’s 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 hard-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 two major systems

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

THE BODY’S RESPONSE TO ACUTE (IMMEDIATE) STRESS

 

THE BODY’S RESPONSE TO CHRONIC (LONG-TERM) STRESS

THE SYMPATHOMEDULLARY (SAM) PATHWAY

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LOCALISATION OF FUNCTION IN THE BRAIN AND HEMISPHERIC LATERALISATION: MOTOR, SOMATOSENSORY, VISUAL, AUDITORY AND LANGUAGE CENTRES; BROCA’S AND WERNICKE’S AREAS, SPLIT BRAIN RESEARCH. PLASTICITY AND FUNCTIONAL RECOVERY OF THE BRAIN AFTER TRAUMA (AQA A-level Psychology resources)

LOCALISATION OF FUNCTION IN THE BRAIN AND HEMISPHERIC LATERALISATION: MOTOR, SOMATOSENSORY, VISUAL, AUDITORY AND LANGUAGE CENTRES; BROCA’S AND WERNICKE’S AREAS

 

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

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

MOTOR AND SENSORIMOTOR AREAS

• The motor cortex controls voluntary Both hemispheres have a motor cortex with each side controlling muscles on the opposite side of the body (i.e. left hemisphere controls muscles on right side of body). Different areas of the motor cortex control different parts of the body and these are in the same sequence as in the body (e.g. the part of the cortex controlling the foot is next to the part controlling the leg, etc.)
• The sensorimotor cortex registers sensory information from different areas of the body: e.g. pain, temperature, pressure. Both hemispheres have a sensorimotor cortex with each side receiving information from the opposite side of the body.

VISUAL CENTRES

• Processing of visual information starts when light enters the eye and strikes photoreceptors on the retina at the back of the eye. Nerve impulses then travel up the optic nerve to the thalamus and are then passed on to the visual cortex in the hindbrain. The right hemisphere’s visual cortex processes visual information received by the left eye and vice-versa.

The visual cortex contains different regions to do with colour, shape, movement, etc.

AUDITORY CENTRES

• Processing of auditory information (sound) begins in the inner ear’s cochlea where sound waves are converted into nerve impulses which travel along the auditory nerve to the brain stem (which decodes duration and intensity of sound) then to the auditory cortex which recognises the sound and may form an appropriate response to that sound.

LANGUAGE CENTRES

• Broca’s Area is generally considered to be the main centre of speech production. The neuroscientist after whom this brain area is named found that patients with speech production problems had lesions (damage) to this area in their left hemisphere but lesions in the right hemisphere did not cause this problem. More recent research indicates Broca’s area is also involved with performing complex cognitive tasks (e.g. solving maths problems).
• Wernicke’s area is also in the left hemisphere and is concerned with speech comprehension. The neuroscientist after whom this brain area is named found that lesions in this brain 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 meaning).
• Broca’s and Wernicke’s areas are connected by a loop which ties together language production and comprehension.

 EVALUATION

• Equipotentiality theory argues that although basic brain functions such as the motor cortex and sensory functions are controlled by localised brain areas, higher cognitive functions (such as problem-solving and decision-making) are not localised. Research has found that damage to brains can result in other areas of the brain taking over control of functions that were previously controlled by the part of the brain that has been damaged. Therefore, the severity of brain damage is determined by the amount of damage to the brain rather than the particular area which has been damaged.
• The way in which brain areas are connected with each other may be as important for normal cognitive function as particular brain sites themselves. Brain sites are interdependent and damage to connections between sites may lead to the brain site not being able to function normally. For example, Dejerine (1892) found that damage to the connection between the visual cortex and Wernicke’s area lead to an inability to read (vision + comprehension).
• Gender differences have been found with women possessing larger Broca’s and Wernicke’s areas than men, presumably as a result of women’s greater use of language.

HEMISPHERIC LATERALISATION & SPLIT-BRAIN RESEARCH

Hemispheric lateralisation concerns the fact that the brain’s 2 hemispheres are not exactly alike and have different specialisms. For example, the left hemisphere is mainly concerned with speech and language and the right with visual-motor tasks. Broca (1861) found that damage to the left hemisphere led to impaired language but damage to the same area on the right hemisphere did not.

The brain’s 2 hemispheres are connected by a bundle of nerve fibres – the corpus callosum – which allows information received by one hemisphere to be transferred to the other hemisphere.

Investigations into the corpus callosum began when doctors severed patients’ corpus callosum in an attempt to prevent violent epileptic seizures.

Sperry (’68) tested such split-brain patients to assess the abilities of separated brain hemispheres.

• Participants sat in front of a board with a horizontal rows of lights and were asked to stare at the middle point. The lights then flashed across their right and left visual field. Participants reported lights had only flashed up on the right side of the board.
• When their right eye was covered and the lights were flashed to the left side of their visual field they claimed not to have seen any lights at all. However, when asked to point at which lights had lit up they could do.
• This shows that participants had seen the lights in both hemispheres but that material presented to the left eye could not be spoken about as the right hemisphere (which receives information from the left eye) has no language centre and thus cannot speak about the visual information it has received. It can communicate about this in different non-visual ways, however – e.g. participants could point at what they had seen.
• This proves that in order to say that one has seen something the region of the brain associated with speech must be able to communicate with areas of the brain that process visual information.

EVALUATION

• Because split-brain patients are so rare, findings as described above were often based on samples of 2 or 3, and these patients often had other neurological problems which might have acted as a confounding variable. Also, patients did not always have a complete splitting of the 2 hemispheres. These factors mean findings should be generalised with care.
• More recent research has contradicted Sperry’s original claim that the right hemisphere could not process even basic language. For example, the case study of JW found that after a split-brain procedure he developed the ability to speak out of his right hemisphere which means that he can speak about information presented to either his left or his right visual field.
• Brain lateralisation is assumed to be evolutionarily adaptive as devoting just one hemisphere of the brain to tasks leaves the other hemisphere free to handle other tasks. For example, in chickens, brain lateralisation allows birds to use one hemisphere for locating food, the other hemisphere to watch for predators. Thus, brain lateralisation allows for cognitive multi-tasking which would increase chances of survival.
• Individuals with high level mathematical skills tend to have superior right hemisphere abilities, are more likely to be left handed, and are more likely to suffer allergies and other immune system health problems. This suggests a relationship between brain lateralisation and the immune system.
• Research also indicates that the brain become less lateralised as we age. It is possible that as we age and face declining mental abilities the brain compensates by allocating more resources to cognitive tasks.

PLASTICITY AND FUNCTIONAL RECOVERY OF THE BRAIN AFTER TRAUMA

Plasticity refers to neurological changes as a result of learning and experience. Although this was traditionally associated with changes in childhood, recent research indicates that mature brains continue to show plasticity as a result of learning...

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