bio psycho Flashcards
The nervous system
- Network of cells in the human body
- Electrical and chemical signals
Endocrine
- Based on hormones
Nervous system has two functions
- To collect process respond to information in the environment
- To co-ordinate the working of different organs and cells in the body
The nervous system is divided into two subsystems
- Central nervous system
- Peripheral nervous system
The CNS
- Brain is divided into two hemispheres
- Spinal cord is an extension of the brain.
- Passes messages to and from the brain and connects to the PNS
Peripheral nervous system
- Autonomic nervous system- vital functions in the body eg breathing
- Somatic nervous system- -muscle movement and receiving info from sensory receptors
Types of neurons
- Sensory
- Relay
- Motor
Structure of neuron
- Cell body includes a nucleus- genetic material
- Dendrites- branchlike structure, carries nerve impulses towards cell body
- Axon- carries the impulse away from the cell body
- Axon is covered in a fatty layer of the myelin sheath – protects and spends up transmission
- Nodes of Ranvier speed up transmissions by forcing it to jump across the gap along the axon
- End of axon is terminal button communicate with the next neuron – synapse.
Location
- Motor maybe be in CNS or the PNS
- Sensory neurons are located outside the CNS in the PNS in clusters known as ganglia
- Relay found in the brain and the visual system
electric impulse
Electrical transmission- the firing of a neuron
Neuron in a resting stare- negatively charged
Neuron is activated the inside of the cell becomes positively charged for a split second causing an action potential.
This creates an electrical impulse
Synaptic transmission
Chemical transmission
Neuron communicates within groups known as neural networks
Each neuron is separated by a gap called synapse
Signals within neurons are transmitted electrically
Signals between neurons are transmitted chemically across the synapse
When the electrical impulse reaches the end of the neuron the presynaptic terminal it triggers the release of neurotransmitters from tiny sacs called synaptic vesicles.
Neurotransmitters
Chemicals diffuse across the synapse to the next neuron.
Once a neurotransmitter crosses the gap it is taken up by a postsynaptic receptors site on the dendrites of the next neuron
The chemical message is converted back into an electrical impulse
One way only
Neurotransmitters are released from the presynaptic neuron terminal and received by the postsynaptic neuron.
Neurotransmitter has it own specific molecular structure that fits perfectly into the post synaptic receptor sites.
Neurotransmitter- special function
Excitation and inhibition
Neurotransmitters have either an excitatory or inhibitory effect.
Serotonin- inhibition in the receiving neuron results in the neuron becoming more negatively charged and less likely to fire
Adrenaline- excitation of the post synaptic neuron by increasing its positive charge and making it more likely to fire.
Summation
Whether a postsynaptic neuron fire is decided by the process of summation
If the net effect of the postsynaptic neuron is inhibitory then the postsynaptic neuron is less likely to fire.
If the net effect is excitatory, it is more likely to fire
Therefore, the action potential of the postsynaptic neuron is only triggered if the sum of excitatory and inhibitory signals at any one time reaches the threshold.
Competition between two neurotransmitters
If theres more of one eg excitation and meets the threshold excitation effect faster rate.
Verse visa for inhabitation
Localisation of function
Local vs holistic theory
Broca and Wernicke argued for localisation of function
The idea that different parts of the brain perform different tasks and are involved with a different part of the body
If a certain area of the brain becomes damaged through illness or injury the function associated with that area will also be affected
Hemispheres of the brain
The cerebrum is divided into two halves
Activity on the left hand side of the body is controlled by the right hemisphere
Activity on the right hand side of the body is controlled by the left hemisphere
Eg language is linked with the left hemisphere
structure of the brain
The motor somatosensory visual and auditory centres
The cortex is the outer layer of both hemisphere
The cortex is subdivided into four centres
The frontal lobe the parietal lobe the occipital lobe and the temporal lobe
front of head Auditory broca area motor somatosensory back of head visual wernicke
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where and what do they do?
Each lobe is associated with a different function
Frontal lobe in both- motor area controls voluntary movement in opposite sides of the body damage to this area= loss of control over fine movements
Parietal lobes- somatosensory area where sensory info is represented
Occipital lobe- visual cortex eye sends info-> right visual field left visual cortex verse visa
Temporal lobes- auditory area analyses speech-based information
Languages centres of the brain
Language is only on the left side
Left frontal love- speech production -> broacs areas
Damage- slowed laboriously and lacking in fluency
Understanding speech- it was fluent but meaningless-> Wernicke area
Evidence from brain scans
Strength- supports idea that many everyday brain functions are localised
Brain scans to show how active wernickes area was during a listening task and broca area was active during a reading task.
Long term memory study- semantic and episodic memories reside in different parts of the prefrontal cortex
Counter point
rats brain maze
Removed areas of the cortex 10%-50% in rats that were learning the routes through a maze.
No area was more important than any other area in terms of the rat’s ability to learn the routes.
The process of learning requires every part of the cortex to be confined to a particular area. Suggest higher cog processes eg learning -> holistic
Language localisation question
weakness
Language not just localized to Broca and Wernicke’s areas.
2% of language is completely controlled by broca and wernicke area
fMRI neural processes in the brain can be studied
the language function is distributed for more holistically
language may be organized more holistically in the brain.
Case study evidence
Phineas gage- personality and temperament resides in frontal lobe
weakness
Difficult to make generlisations
Evidence supporting localisation may lack validity, oversimplifying the brain processes
Early studies of brain damage poor controlled and lack of the objectivity.
Hemispheric lateralisation
Localisation and lateralisation
For some functions the localised areas appear in both hemispheres eg vision the visual area is in the left and right occipital lobe.
Left and right hemispheres
Language- two main centres are only in the left hemisphere
Broca and Wernicke’s area are in the left temporal lobe
Language is lateralized
Right hemisphere- contributes to emotional context- synthesizer
Many functions are not lateralised eg vision motor and somatosensory
Motor area- the brain is cross-wired
Right hemisphere controls the left
Left hemisphere controls the right
visual and sound
Vision- each eye received light from the left and right visual fields
The left visual field is connected to the right hemisphere
Right visual field is connected to the left hemisphere
The left visual field in both eyes are connected to the right hemisphere
The right visual field in both eyes are connected to the left hemisphere
Enables the visual area to compare the slightly different perspectives from each eye and aids in depth.
A similar arrangement for auditory input to the auditory area and the disparity from the two inputs help us locate the source of sounds
Lateralisation in the connected brain
Strength research shows in connect brains the two hemisphere processes information differently
PET scans to identity which brain area were active during the visual processing task.
When looking at a photo of a forest the right hemisphere was more active
When looking at a tree the left hemisphere was more active
Suggests lateralisation is a feature of connected brain and split brain
One brain
Limitation idea that the left hemisphere as analyser and the right hemisphere as synthesiser may be wrong
There might be different functions in the right and left hemispheres
But research suggest people don’t have a dominate side of their brain
Analysed brain scans from over 1000 people aged 7-29 and did find people used certain hemispheres for certain tasks eg evidence for lateralisation
No evidence of a dominant side
Notion of right or left brain people is wrong
Lateralisation vs plasticity
Lateralisation- adaptive function
strength- lateralisation is preference but plasticity is more important
Allows an animal to be able to perform two tasks simultaneously with greater efficiency
Chickens with a lateralised brain could find food while looking for predators
Chicken reared in the dark whos brain wasn’t laternalised could not
There is benefit to an induvial for their brain not to be too fixed in structure in case of injury- neural plasticity
Eg damage through illness or trauma- some functions cant be taken over by non specialised areas in the opposite hemisphere
Eg language can switch sides
Lateralized functions are flexible rather than fixed.
Lateralisation is the first preference but plasticity is more important because it deals with brain damage.
Split brain research
Severing the connection between RH and LH
Reduced epilepsy
Seizure brain experience excessive electrical activity
Research
How two separated hemispheres deal with speech and vision
Procedure
11 people
Image projected into ppt RVF processed by the LH
Same or different image in the LVF processed by the RH
Normal brain- info is shared= complete image
Split brain- info not shared
Findings-
object shown to RVF linked to LH ppt descive what they could see
But done on the left there was nothing
Messages from the RH are relayed to the language centres in LH not possible in plsit brain
Couldn’t give verbal labels they could select matching objective with left hand linked to RH
Image shown to LVF was emotional reaction- there was nothing
Conclusion
- show certain functions are lateralised in the brain support the view that the LH is verbal and RH is silent but emotional
Research support
Stregnth- support from more recent split brain research
Split brain ppt perform better than connected controls on certain tasks
Eg faster at identiting the odd one out in an array of similar objects
In normal brain LH better cognitive is watered down by the inferior RH
Support sperry research about how the ledt and right brain are different
Generalisation issues
Weakness- causal relationships are hard to establish
Behaviour in sperry split brain was compred to neurotypical control group
None of the ppt had epilepsy in control
Confounding variable
Any differences may be result of epilepsy raher than split brain
Unique features of split brain ppt cog abilities might be due to their epilepsy.
Ethics
Operation not performed for purpose of research
Took advantage of naturally occurring situation
Not deliberately harmed
Possible that the trauma of the operation meant that the patients didn’t later fully understand the implications of wghat they were agreeing to
Repeating testing over many years- stressful
Negative consequences of their involvement
Plasticity
Brain plasticity
Ability to brain during life
Brain experience rapid growth in synaptic connections- infancy
15,000 2-3 y/o
Twice as many as human brain
Rarely used connections are deleted
Frequently used connections are strengthened
Snaptic pruning
Plasticity- new neural connections reformed in response to new demands on the brain
Research into plasticity
London taxi drivers
More grey matter than matched control group
Part of the brain associated with development of spatial and navifational skills
Complex test call the knowledge which assesses their recall of city street and possible routes
Learning experience alters the structure
Longer taxi drivers more pronounced was the structural difference
Negative plasticity
Limitation- negative beahviour consequences
Evidence brain adaption to prolonged drug use leads to poor cognitive functions in later life increased risk of dementia
60-80% amputees develop phantom limb syndrome
Usually not welcome and due to the reorganisation in the somatosensory cortex
Brain ability to adapt to damage isn’t always beneficial
Age and plasticity
Strength- brain plasticity may be life long ability
Plasticity reduce with age
40 hours of golf training produce changes in the neural representation of movement in ppt aged 40-60
fMRI researcher observed increased motor cortex activity compared to novice golf players in control
more efficient neural representation after training
neural plasticity can continue throughout lifespan
Functional recovery
After brain trauma
The unaffected parts of the brain compensate for other areas that are damaged.
Functional recovery happens after trauma
Process can happen quicker after trauma and slow down after weeks/months
After this the individual may require rehab
What happens in the brain during recovery ?
Brain is able to rewire and reorganise itself by forming new synaptic connections
Secondary neural pathways are active or unmasked to enable function
Supported by evidence:
Axonal spourting- growth of new nerve endings
Denervation supersensitivity- axon that do similar jobs become aroused to a high level
Recruitment of homologous- similar areas on the opposite side of the brain.
Real world application
Strength- contributes to the field of rehab
Understanding helps develop new therapies
Constraint induced movement- move affected arm while the unaffected arm is restrained
Useful as medical professionals know when interventions need to be made
Cognitive reserve
Limitiation- level of education may influence recovery rates
More times people with brain injury had spend in education greater the chances of a disability free recovery
40% achieved DFR with 16 years of education
10% achieved DFR with 12 years of education
People with brain damage with insufficient DFR are less likely to make a full recovery
Sample size
Limitation- strong support for new treatments to aid functional recovery.
Treated stroke patients with stem cells
But only 5 patients
Not generalisable
No control group
It is difficult to match patients in terms of the extent of their neurological damage as individual cases may differ
Therefore lack validity making it hard to draw conclusions
Scanning and other techniques
Functional magnetic resonance imaging fMRI Electroencephalogram EEG Event related potentials ERPs Post mortem examinations
Functional magnetic resonance imaging
fMRI- detect the changes in blood oxygenation and flow in a specific area of the brain
more active- more oxygen
3d images
strength- safest option
no use of radiation
virtually risk free non invasive
produces image- high spatial resolution
limitation
expensive
poor temporal resolution
5 second time lag
Not true moment to moment
Electroencephalogram
EEG measures electrical activity within the brain via electrodes
Overall account of brain activity
Strength
useful in studies of stages of sleep
Random burst of energy easily detected on screens
High temporal
Limitation-
generalise nature of the info received
Not useful for pinpointing the exact source of neural activity
Doesn’t allow to distinguish between activities originating in different but adjacent locations
Event related potentials
ERPs tease and isolate responses
Types of brainwaves triggered by particular event
Strengths
more specific measure of neural processes
Temporal resolution
Used to measure cognitive functions and deficits eg maintenance of working memory
Limitations-
lack of standardisation
Hard to confirm findings
To establish pure data in ERP studies background noise and extraneous material must be completely eliminated
Post mortem examinations
Analysis of a persons brain following their death
Rare disorders or have experienced unusual deficits in cognitive processes or behaviour
Establishing the likely cause of the affliction the person experienced
Strengths-
foundation for early understanding
Broca and Wernicke used it as basis for their research
Used to identity places of damage
Provide useful info
Limitations
Causation is an issue
Damage may not be due to deficits but to unrelated trauma or decay
Ethical issues
