Biopsych
Divisions of nervous system
Nervous system divided into:
central nervous system (consists of brain and spinal cord) - where all complex processing of information is done and decisions are made
peripheral nervous system - brings information from senses to CNS and transmits information from CNS to muscles and glands
Central nervous system:
brain
spinal cord
Peripheral nervous system
autonomic nervous system - involuntary/unconscious - responsible for vital functions e.g. heart beat, breathing - transmits information from and to internal body organs
sympathetic - stress response - inhibits functions like digestion - involved in flight or fight response (increase HR/BR etc.)
parasympathetic - rest response - stimulates functions like digestion
somatic nervous system - voluntary/conscious - receives information from sense and transmits it to CNS - transmits information from CNS to movement of muscles
Structure and function of neurones
Sensory neurones: carry signals from receptors to spinal cord and brain
Relay neurones: carry messages from one part of CNS to another
Motor neurones: carry signals from CNS to effectors (muscles/glands)
Stimulus → receptor → sensory → relay → motor → effector → response
Sensory neurones:
found in receptors e.g. eyes
carry nerve impulses to spinal cord/brain
some neurones stop at spinal cord allowing for quick reflexes
Relay neurones:
found between sensory and motor
found in brain and spinal cord
allow sensory and motor neurones to communicate
Motor neurones:
found in CNS
control muscle movements
motor neurones stimulated and release neurotransmitters that bind to receptors on muscles = trigger response = movement
Structure of neurones:
cell body - contains nucleus
dendrites extend from cell body - carry electrical impulses from other neurones towards cell body
axon = extension of neuron - carries impulse away from cell body - covered in myelin sheath (increases speed of impulses)
nodes of ranvier in myelin sheath - nerve impulses ‘jump’ from node to node = speeds up transmission
Synapse:
small gap between neurones
neurotransmitters diffuse across:
electrical impulse trravels along axon
triggers nerve ending of presynaptic neurone to release neurotransmitters
neurotransmitters diffuse across synapse and bind with receptor molecules on membrane of next neurone
receptor molecules on this neurone will only bind to these specific chemicals = stimulates neurone to transmit electrical impulse
neurotransmitter reabsorbed in presynaptic neurone after transmission
summation = whether or not to fire action potential
Function of endocrine system
consists of glands which produce hormones - released into blood stream to target organs which contain receptors for specific hormones
pituitary gland controls release of hormones from all other endocrine glands
hormones and more powerful than neurotransmitters but slower
stress response:
hypothalamus detects danger
sends signal to adrenal gland
adrenaline released
triggers sympathetic branch of ANS
increased HR etc. - fight or flight
Fight or flight response
Adrenaline:
triggers fight or flight:
increased HR - blood supply - vasodilation to major muscle groups e.g. heart, lungs
increased BR - more oxygen for muscles
Localisation of function and hemispheric lateralisation
Brain divided into 2 hemispheres - left and right
left controls right hand side of body and vise versa
Divided into lobes:
Frontal lobe = thought, memory and behaviour
Parietal lobe = language and touch
Temporal lobe = hearing, learning and emotions
Occipital lobe = visual processing
Cerebellum = balance and coordination
Brain stem = breathing, heart rate and temperature
Other important regions:
Motor cortex = responsible for generation of voluntary motor movements - located in frontal lobe, along precentral gyrus
Visual centers = located in occipital lobe. Cortex contains several different areas, each of these areas processes different types of visual information (e.g. colour, shape, movement)
Broca’s area = area is critical for speech production
Wernicke’s area = area of brain involved in understanding language
Somatosensory cortex = detects sensory events arising from different regions of the body. Located in parietal lobe, along postcentral gyrus
Auditory centers = area lies within temporal lobes on both sides of brain - pathway begin in cochlea in inner ear, where sound waves are converted to nerve impulses, which travel via auditory nerve to auditory cortex
Localisation of function = specific functions have specific locations within the brain
AO3
+Brain scan evidence - Peterson used brain scans to demonstrate how Wernicke’s area was active during a listening task and Broca’s area was active during a reading task, suggesting these areas of brain have different functions
+neurosurgical evidence - Freeman developed lobotomy which involved destroying connections in frontal lobe to control aggressive behaviour - today neurosurgery is still used in extreme cases of OCD and depression - Dougherty et al - reported on 44 OCD patients who had undergone a cingulotomy - after 32 weeks, 1/3 had met criteria of successful response to surgery
-plasticity - when brain damaged through illness/injury a particular function has been lost - rest of brain appears able to reorganise itself in an attempt to recover lost function
-holistic - Lashley removed areas of cortex in rats learning a maze - no area proven to be more important than others and appeared process of learning required every part of cortex
Hemispheric lateralisation = dominance of one hemisphere of brain for particular physical and physiological functions
Split brain research = used to investigate hemispheric lateralisation - used to describe results when corpus callosum connecting 2 hemispheres of brain is severed to some degree so right and left sides of brain are separated and each hemisphere has its own separate perception, concepts and impulses to act - having 2 brains in one body
When split brain patients are shown an image only in left visual field they cannot vocally name what they have seen - as image seen in left visual field is sent only to right side of brain, speech control centre on left side of brain, communication between 2 sides of brain is inhibited so patient cannot say out loud the name of what the right side of brain is seeing
Sperry:
11 individuals with corpus callosum severed to treat epilepsy in quasi experiment
participants perform range of tasks and their performance compared with participants with no interhemispheric disconnection
tasks = presenting information to 1 hemisphere by sending it to only 1 visual field
information shown to 1 hemisphere will only be recalled if shown to same hemisphere again
visual material shown to left hemisphere (right visual field) can be described in speech and writing - if shown to right hemisphere (left visual field) participants will deny seeing anything but are able to pick out correct object with left hand
if 2 figures shown to hemispheres then participants will be able to draw what they have seen in left visual field with left hand (right hemisphere) - however if asked what they have drawn they will you the object they saw in right visual field (left hemisphere)
=lateralisation of function
AO3
+Sperry - high levels of control and clearly demonstrated the lateralisation of function between left and right hemisphere
-Sperry - issues with generalisation - sample so unique and control group doesn’t have epilepsy - also individual differences within the sample disconnect between hemispheres greater - on drugs therapy for longer
+domestic chick - perhaps 2 brains better than 1 - can perform 2 tasks simultaneously e.g. finding food and looking for predators - evolutionary advantage for survival
-JW investigated by Turk et al - developed the capacity to speak out of right hemisphere - can now speak about information presented to left and right side of brain
Plasticity:
The brains ability to change and adapt as a result of experience and new learning
More plasticity in kids as during childhood the brain experiences rapid growth in number of synaptic connections - at 3 years old it has 15000 - twice as many than in an adult
As we age rarely used connections are deleted and frequently used connections are strengthened = cognitive pruning - shows that brain is in a continual state of change as we learn and experience
Can be negative e.g. dementia
AO3
+maguire - studied brains of taxi drivers using MRI - more grey matter in posterior hippocampus than in matched control group - this part of brain associated with development of spatial and navigational skills in human and other animals - cabbies must take a complex test which assesses recall of city streets and possible routes - longer ding job the more pronounced the structural difference
+boyke - new experiences = nerve pathways used frequently develop stronger connections whereas neurones that are rarelt used eventually die - by developing new connections and pruning away weak ones brain is able to adapt to a changing environment - however natural decline in cognitive function with age - boyke found evidence of brain plasticity in 60 year olds taught a new skill (juggling) - found increases in grey matter in visual cortex - although when practicing stopped changes reversed
+kempermann - new neurones in hippocampus in brains of rats housed in complex environments compared to those housed in cages - hippocampus part of brain associated with new memories and ability to navigate from one location to another = enriched environment can alter number of neurones in brain
-rats for animal research - use of animals may not be extrapolated to humans - rats different in physiology to humans and they also have different environments - as a result we need to be more careful when applying these findings to human. Despite this ability to create brain trauma and manipulate variable enable us to monitor the function of brain before and after trauma because we cause it - ethically we couldn’t do this to humans and its unlikely that we would have measured their function before a natural event - suggests cost benefit trade off when carrying out animal research
Functional recovery
Moving functions from a damaged area of the brain after trauma to other undamaged areas e.g. after physical injury, strokes etc. to compensate for those damaged areas
Brain rewires and reorganises itself by forming new synaptic connections, and unmasking secondary neural pathways to enable functioning to continue. Process supported by:
Axon sprouting - new nerve endings grow and connect with undamaged areas
reformation of blood vessels
recruitment of homologous areas - on opposite hemisphere to do specific tasks
AO3
Schneider et al - patients with college education 7 times more likely to be disability free after a moderate to severe traumatic brain injury after a year than those who didn’t finish high school - of 769 studied, 214 achieved disability free after one year - of these 40% had 16+ year education, 10% with less than 12 years
Age differences - functional plasticity reduces with age - however studies have suggested that even abilities commonly thought to be fixed in childhood can still be modified in adults
Tajiri et al - role of stem cells in recovery from brain injury - randomly assign rats to one of 2 groups - 1 group receive transplants of stem cells into region of brain affected by traumatic injury, other group (control) received solution infused into brain containing no stem cells - 3 months after injury brains of stem cell rats showed clear development of neuron like cells in area of injury
Rats for animal research - use of animals may not be extrapolated to humans - rats different in physiology to humans and they also have different environments - as a result we need to be more careful when applying these findings to human - can’t generalise. Despite this ability to create brain trauma and manipulate variable enable us to monitor the function of brain before and after trauma because we cause it - ethically we couldn’t do this to humans and its unlikely that we would have measured their function before a natural event - suggests cost benefit trade off when carrying out animal research
Ways of studying the brain
Post mortem examinations
establish underlying neurobiology of a particular behaviour - e.g. researchers may study a person who displays a rare disorder and have experienced unusual deficits in mental processes or behaviour during their lifetime - when person dies researcher examines brains to look for abnormalities that might explain behaviour not found in controls
e.g. Broca and Tan - displayed speech problems when alive and had a lesion in area of brain known as Broca’s area - important for speech production
AO3
+provides greater understanding of rare afflictions in individuals
-obtaining persons brain, even if they have been the subject of a longitude study, can be very difficult
fMRI
technique for measuring changes in brain activity while a person performs a task
measures changes in blood flow in areas of brain - indicates increased neural activity as increased demand for oxygen
measures using radio waves and magnetic fields
researchers produce maps showing which areas involved in particular mental activity
can be used to identify brain areas where matching pattern of change = these areas activated by stimulus
AO3
+provides detailed knowledge of areas of brain that are active whilst completing tasks
-expensive and requires the patient to stay completely still
EEG
measures electrical activity in brain - graphed over time to produce EEG
can be used to detect various types of brain disorder or to diagnose other disorders that influence brain activity e.g. patients with epilepsy show spikes of electrical activity
AO3
+no intervention necessary and therefore allows for natural measurements of brain activity
-electrodes are not sensitive enough to pick out individual action potentials of single neurones
ERP
a snapshot of EEG - types of brainwave that a triggered by particular events
isolates neural responses - filtering out all extraneous brain activity from original EEG leaving only responses relating to presentation of a specific stimulus or performance of specific task
AO3
+specific measure when compared to fMRIs for cognitive functions and deficits
-difficult to eliminate background noise and extraneous materials to establish pure data
Biological rhythms
Biological rhythms = a biological rhythm is an innate biologically driven behaviour that is periodically repeated
Endogenous pacemakers = biological clocks in brain controlling biological rhythms
Exogenous zeitgebers = external stimuli that help towards regulating biological rhythms to outside world
3 types of biological rhythm:
Circadian - 24 hours periodicity e.g. sleep/wake
SCN located in hypothalamus - regulates sleep/wake cycle as it releases melatonin
In animals pineal gland activates release of melatonin in inverse proportion to light
Ultradian - less than 24 hours periodicity - occur many times during day - sleep cycle
Infradian - more than 24 hours periodicity - longer than a day e.g. menstrual cycle
menstrual cycle generated by hypothalamus and causes fluctuations in hormone level - LH and FSH
AO3