(P1) biological psychology Flashcards
what is lateralisation
If we look at a human brain, or the brains of most other animals, we can see that there are two distinct halves, and that the organ is roughly symmetrical. In technical terms, there are two hemispheres in the human brain. ‘Lateralisation’ refers to the tendency of the different hemispheres of the brain to take care of slightly different functions. For example, the language areas are found in the left hemisphere in the majority of people.
The most basic manifestation of lateralisation is that, broadly, the left hemisphere corresponds to the functioning of the right side of the body and vice versa (this ‘crossover’ is sometimes called ‘contralateralisation’). If you tread on something sharp with your right foot, it is in your left hemisphere that the damage is registered and the sensation of pain is produced (to alert you to the fact that something bad has happened and to do something about it). Conversely, if you reach out with your left hand to pick something up, it is your right hemisphere which is sending out the signals to the muscles that cause your arm to move. If one hemisphere of the brain is damaged, then the first sign is often a change in the functioning of the opposite side of the body.
Lateralisation goes beyond sensing and moving the body. Many other psychological processes show some degree of lateralisation. For example, in 90% of right handed people, language processing (speaking and understanding the speech of others) is done by the left hemisphere of the brain. There is also evidence that, generally, the left hemisphere deals with information by breaking it down into simpler parts, whereas the right hemisphere prefers to process information in a holistic way. That said, the two hemispheres are in constant communication with each other through a ‘bridge’ between the two hemispheres called corpus callosum.
what is localisation?
‘Localisation’ refers to the tendency of different areas within the brain to be responsible for different functions. In the outside layer of a mammal’s brain (the cerebral cortex) we can identify many different small areas that take care of different psychological processes. At the front of the cortex there are areas responsible for planning and problem solving. Further back we find areas responsible for moving and sensing the body. Around the sides we can identify areas that are important for memory, and, at the back, there are the areas that process visual information from the eyes.
what is the nervous system?
The nervous system is a network of specialised cells capable of transmitting information around the body. It co-ordinates the behaviour of the organism.
what is the central nervous system?
The central nervous system processes information. It consists of the brain and spinal cord.
overview of neurons and neural transmission
The nervous system is made up of several types of cell. The most important type is the neuron. Neurons generate electrical signals called action potentials. These signals start at one end (the dendrites) and finish at the other (the terminals). A neuron generates action potentials all the time. The number of action potentials generated each second is called its firing rate.
Although all action potentials are identical, the neuron can vary its firing rate to be faster or slower. It does this in response to the signals it receives from other neurons that connect to it. In turn, the firing rate of the receiving neuron influences the firing rates of other neurons it is connected to.
neuron
the main cell of the nervous system
role/function of the neuron
the neuron’s role is to pass messages between other neurons using neurotransmitters to enable behaviour, thinking and emotions to be transmitted and to enable the working of the brain.
the electrical impulses travelling down the axon trigger the release of neurotransmitters from the terminal at the end of the axon.
the neurotransmitters are then released into the synaptic gap to be picked up by receptors on the dendrites of other neurons or to be re-uptaken for reuse. this is known as synaptic transmission.
action potential
the electrical signals that are sent from the dendrites to the terminals of a neuron.
dendrites
the tree-like structures that receive signals from other neurons.
axon
the long, branching structure that transmits the action potential to the terminal, allowing neural signals to be sent over (potentially) long distances.
terminal
the structure where action potentials finish, and chemical signals are sent to other neurons.
myelin sheath
a fatty substance wrapped around the axons of some neurons. It allows action potentials to travel faster.
ions
charged particles. The movement of ions allows the action potential to happen.
firing rate
the frequency with which a neuron produces action potentials. A neuron’s firing rate increases or decreases in response to the signals it receives from other neurons at its dendrites
role/function of neurotransmitters
role of neurotransmitters is to carry messages from one neuron to another.
- if the neurotransmitter released from the terminal of an axon is not taken up by the dendrites of an adjacent neuron, the message stops.
process of neural transmission
The nervous system, which gives rise to and organises our thinking, emotion and behaviours, is a network of specialised cells called neurons. A neuron is specialised in two ways. First, it can transmit electro-chemical signals, called action potentials, from one end (its dendrites) to the other (its terminals). Second, it can form connections with other neurons. These connections are called synapses.
A neuron constantly transmits action potentials. Each action potential is the same as all the others, so a neuron cannot transmit action potentials of different strengths or speeds. However, a neuron can vary the frequency with which it transmits action potentials. This frequency is called the neuron’s firing rate. Variations in the firing rate are caused by chemical messages received at its synapses from other neurons (the upstream neurons). These messages may cause the neuron to increase or decrease its firing rate. As it varies its firing rate, the neuron can, in turn, influence the firing rates of all the neurons it sends messages to (the downstream neurons).
When a neuron is not transmitting an action potential it is ‘at resting potential’. During resting potential there is a difference in electrical charge between the inside and the outside of the neuron. The difference in charge is caused by there being different concentrations of ions (charged particles) on either side of the neuron’s cell membrane. The outside has a higher concentration of positive ions than the inside, so the membrane is polarised - there is a positive charge outside compared to the inside. Most of the time, the cell membrane is impermeable to these ions, so the difference in charge is maintained.
An action potential starts when the neuron is stimulated by chemical messages received from upstream neurons at its synapses. If enough stimulation occurs, the neuron opens tiny ion channels in its membrane. Because there is a higher concentration of positive ions outside the neuron, the opening of the ion channels causes positive ions to flood into the neuron by diffusion. Because of this influx of positive ions, the difference in charge across the cell membrane is reversed (depolarised) in that region. This local reversal of the charge across the cell membrane is the action potential.
As soon as the action potential has occurred in one area of the neural membrane, the membrane at the immediately adjacent site also becomes disturbed, and the ion channels open. This causes the membrane to depolarise and, through this process, the action potential propagates along the cell membrane in the direction of the terminal in a chain reaction, a bit like toppling dominoes. At the same time, where the membrane has been depolarised, the ion channels close, and tiny pumps start working, moving the ions back to where they started. While this is happening, another action potential cannot occur. This is called the refractory period.
Overall, the propagation of an action potential from the dendrites to the terminals is a bit like a ‘Mexican wave’ in a crowd at a sports event. People standing up and sitting down in a sequential way creates the appearance of a ‘wave’ in the crowd that travels around the stadium. What is important to appreciate is that the only movement that actually occurs is the people standing up and sitting down a moment later - but this creates the ‘wave’ that seems to move right around the crowd. By analogy, the people sitting down represent the neural membrane at the resting potential. The people standing up represent the depolarised portion of the neural membrane and the ‘wave’ represents the action potential as it propagates along the neuron.
Some neurons have a myelin sheath wrapped around their axon. The myelin is a fatty substance that prevents an action potential from propagating. However, there are little breaks in the myelin at regular intervals along the sheath. These are called the nodes of Ranvier. At each node, the neural membrane is exposed. This allows an action potential to ‘jump’ quickly from node to node in a process called saltatory conduction. Saltatory conduction speeds up the propagation of an action potential quite significantly, so a myelin sheath allows a neuron to send messages faster than an unmyelinated one. This is an advantage where axons have to stretch over long distances (e.g. in the arms and legs) so myelinated neurons are found more in the spinal cord and the peripheral nervous system than in the brain.
draw the structure of a neuron
explain the process of synaptic transmission
A synapse is the junction between two neurons. Neurons influence each others’ firing rates by sending chemical signals at their synapses. The action potentials reaching the terminals on the presynaptic neuron cause the release of a chemical called a neurotransmitter. The higher the firing rate, the more neurotransmitter is released. The neurotransmitter drifts across the synaptic gap and binds to receptors on the postsynaptic neuron. This causes its firing rate to change (either up or down).
Following release, neurotransmitter in the synaptic gap is broken down by enzymes or recycled by a reuptake pump. Some important neurotransmitters are dopamine, serotonin and GABA.
synapse
junction between two neurons*
synaptic transmission
(short definition)
the process in which one neuron signals to another neuron to increase or decrease its firing rate.
presynaptic membrane
the end structure of a neuron, where action potentials stop, and chemical signals are sent out.
postsynaptic membrane
the areas on a neuron’s dendrites, where chemical signals are received from other neurons.
synaptic gap
the space between the presynaptic and postsynaptic membrane. It is filled with fluid.
neurotransmitters
chemicals that convey a message from the presynaptic to the postsynaptic neuron.
vesicles
tiny ‘bubbles’ inside the presynaptic terminal where neurotransmitter is held before release.
reuptake
a process in which excess neurotransmitter it taken back into the presynaptic terminal and recycled.
evidence for neurotransmitters (link to schizophrenia/depression)
Abnormal levels of different neurotransmitters are implicated in a range of atypical behaviours. Having too much or too little of a particular neurotransmitter could cause activity to increase or decrease in the brain structures that used that neurotransmitter.
In clinical psychology, schizophrenia (a disorder in which a person experiences hallucinations and delusions) has been linked with excessive dopamine activity. Depression (a disorder where the person experiences low mood and negative thinking) has been linked with too little serotonin activity.
hindbrain
a set of brain structures at the top of the spinal cord, mainly dealing with survival functions like breathing, heartbeat and consciousness.
midbrain
a set of brain structures above the hindbrain, mainly responsible for movement and for homeostasis (keeping the internal environment stable).
limbic system
a set of brain structures linking the midbrain and the forebrain, mainly responsible for emotional responses including fear and anger. It plays an important role in aggression.
forebrain
a set of brain structures in the upper and outermost parts of the brain. It includes areas important for ‘higher’ mental functions like thinking, language and memory.
what is brain scanning?
Brain scanning refers to a set of technologies for producing images of the structure and functioning of the brain. Three important ones are CAT/CT, PET and fMRI. All of them generate cross-sectional images of the brain but they do so in different ways so they have different strengths and weaknesses. CAT scans are fast and cheap, but they only show brain structure, not activity. PET and fMRI show brain activity, but take longer and cost more than CAT scans.
A researcher wanting to investigate the brain needs to select the best technique to fulfil the aim of her study; there is no automatic ‘best’ technique to use. What turns out to be the best technique depends on what the research is trying to find out, who she is doing this with and under what conditions.
brain scanning/imaging
using technology to produce images of brain structure and/or activity without needing to open up the skull.
CAT scan
an imaging technology that uses X-rays to generate pictures of brain structure.
- x-rays
- greyscale image showing high level of detail of structures in the brain (0.5mm spatial resolution)
- temporal resolution: N/A as it DOES NOT show function/brain activity
- can image bone, soft tissue and blood vessels simultaneously
- CT scanner relatively cheap (£1 million for the scanner) and quick (5 mins)
PET scan
an imaging technology that generates images of brain activity by tracing the uptake of glucose in different brain areas.
- radioactive tracer is injected
- records brain activity
- non-invasive (nothing enters the body)
- spatial resolution 6mm (not very refined detail in images)
- PET has a temporal resolution of 5-15 mins (longer than fMRI)
- PET scanners are expensive (£2-3 million) and running costs are higher because you need facilities to make short-lived radioactive isotopes.
fMRI scan
an imaging technology that generates images of brain structure and activity by tracking the movement of water/blood in different brain areas.
- tracks brain activity
- response of brain tissues to a strong magnetic field
- spatial resolution of 1.5mm
- temporal resolution of 20 seconds
- very succeptible to motion-related artifacts (errors) as it is sensitive to movement, meaning images may blur.
- fMRI scanner costs £1.9 million and scan takes longer (30-40mins)
spatial resolution
how much fine detail is presented in the scan image. A scanner with a higher spatial resolution shows a more detailed image.
temporal resolution
how well the scanner tracks changes in brain activity over time. A scanner with a higher temporal resolution is more responsive to short-term changes in brain activity.
evidence for brain scanning techniques
Raine et al. (1997) used PET scans to compare murderers with ordinary people. They found that the murderers had different patterns of brain activity in the forebrain and the limbic system.
Hirvonen et al. (2011) used PET scans to show that long-term users of cannabinoid drugs show changes to the brain.
Gazer et al. (2000) used MRI scans to show that schizophrenia patients had reduced volumes of brain tissue compared to a comparison group.
Carlsson et al. (2000) used a range of studies, including brain imaging to show that schizophrenia is related to abnormalities in brain systems that use dopamine and glutamate as their main neurotransmitter.
what is biological psychology?
the study of the biology of behaviour. it focuses on the nervous system, hormones and genetics. biological psychology examines the relationship between the mind and body, neural mechanisms and the influence of heredity on behaviour.
what are the basic assumptions of biological psychology?
- thinking and behaviour can be explained in terms of biological factors (all thinking and behaviour is caused by the central nervous system, CNS).
- human genes have evolved over millions of years to adapt behaviour to the environment
- patterns of behaviour can be inherited, therefore, most behaviour will have an adaptive/evolutionary purpose.
why are brains studied in biopsychology?
the brain is the seat of consciousness. the brain is where our decisions originate and where processes that lead to our feelings and memories take place. it is where your self is located.
psychology is the study of the mind (the Greek word psyche means ‘mind’) but neuropsychologists are interested in the brain because it shapes the mind. we know that changes to the brain produces changes in mental state. this can be seen when people take drugs or suffer from brain damage (e.g. a stroke.)
how has brain imaging technology evolved?
brain research used to be limited to examining the dead brains of corpses. this was unhelpful because dead brains liquify within hours. however, since then the invention of brain imaging technology has revolutionised psychological understanding of the brain because now we can study live brains to understand thinking or remembering.
what creatures have a central nervous system (CNS)?
vertebrates.
this is a category that includes humans and all other mammals, reptiles, birds and fish but not (for example) insects.
what is the peripheral nervous system (PNS)?
as well as the CNS. you have other nerves in your body. this is the peripheral nervous system (PNS), which stretches out from your brain and spinal cord into every other part of your body. the peripheral nervous system includes sensory nerves, which carry information back to the brain as sensations (the ‘five senses’) and motor nerves which carry messages from the brain, telling muscles to move and glands to release their hormones.
what are the two hemispheres of the brain linked by?
a bridge of nerve fibres called the corpus callosum. the corpus callous allows the left and right hemispheres to communicate with each other.
what is the left hemisphere of the brain responsible for?
the left hemisphere is responsible for linear thinking mode. this involves:
- right hand control
- writing
- language
- scientific skills
- mathematics
- lists
- logic
what is the right hemisphere of the brain responsible for?
the right hemisphere of the brain is responsible for holistic thinking mode. this includes:
- left hand control
- emotional expression
- spatial awareness
- music
- creativity
- imagination
- dimension
- whole picture things