- Created by: holly_u
- Created on: 21-02-18 18:36
Divisions of Nervous System
(network of nerves carrying messages from brain&spinal chord to rest of the body)
Central Nervous System Peripheral Nervous System
(Brain and spinal chord) (Rest of the body)
(Involuntary) (Voluntary e.g cycling )
(increases activity-fight or flight) (conserves activity by decreasing)
Neuron= cell that recieves information and transmits it to other cells
Action potential= electrical impulse travels through a neuron
processes information taken from senses. Found in skin, ears, tongue...
Only from body to brain (unipolar)
carry messages from one part of CNS to another. Connect sensory and motor neurons (multipolar)
Only in brain and spinal chord.
carry signals from CNS helping glands, muscles etc to function (multipolar, can send and recieve)
Motor neuron forms synapses which release neurotransmitters to muscles to trigger movement
BARREL ON END
Process of transmitting messages from neuron to neuron
The synapse= the specialised 'gap' between neurons
neurotransmitters= chemicals that bind to specialist receptor cells e.g Serotonin
1) an electrical impulse in the pre-synaptic neuron causes neurtransmitters to be released from vesicles
2) the neurotransmitters diffuse across the synapse and bind to receptor cells of the post-synaptic neuron
3) This causes the post-synaptic neuron to convert them to an electrical impulse
EXCITATION- e.g noradrenaline 'on-switches' they increase likelihood an excitatory signal is sent which then is more likely to fire a neuron
INHIBITION- e.g serotonin and GABA 'off switches' decrease likelihood a neuron will fire, responsible for calming body and inducing sleep
Abnormal levels of neurotransmitters linked to mental illness e.g depression. Drugs prove this
System of glands which release hormones into the bloodstream to produce physiological responses.
- Pituitary gland 'master gland'. - Stimulates adrenal glands to produce cortisol
- Adrenal gland- Part of the fight or flight response. Facilitates release of adrenaline
- Testes- produces testosterone causes development of male features and sex drive
- Ovaries- produce oestrogen and progesterone which prepares womb for pregnancy
- Pancreas- secretes insulin, responsible for blood sugar levels
Fight or Flight Response
The Sympathetic branch of the autonomic system generates a response/ reflex to fear.
1) Hypothalamus detects a stressor in the environment
2) Sends a message to the adrenal gland (adrenal medulla)
3) which triggers release of adrenaline to endocrine system and noradrenaline in the brain
4) causes: slowed digestion, increased heart rate, muscle tension, pupil dilation, sweat production
- Other forms of response e.g women 'tend and befriend' due to oxytocin. evolutionary to care for children
- reductionist. reduces complex human behaviour down, too simplistic
+ Research can be scientific as hormone levels can be measured
Localisation of function
Localisation of function= different parts of the brain are responsible for different behaviours
Contralateral brain= the hemispheres of the brain control opposite sides of the body
Hemispheric lateralisation= division of functions between the two hemispheres.
Phineas Gage- accident occured where an iron rod entered his skull through his eye socket. He recovered well but psychologically was different. He used vulgar language, aggressive and suspected to have molested a child.
Support for localisation of function
LEFT HEMISPHERE= language processing and speech production. Broca's and Wernicke's area
RIGHT HEMISPHERE= Spatial relationships and recognising emotions
Frontal Lobe in BOTH hemispheres as each responsible for movement of each side
Responsible for voluntary movements e.g writing
Parietal Lobe in BOTH hemispheres as both require senses
Responsible for perceiving touch using pressure, pain, temperature
THE VISUAL CORTEX
Occipital Lobe in BOTH hemispheres as require vision for both
Responsible for visual info recieved from eyes.
Contains different areas processing different info e.g colour, shape or movement
Brain process visual info by:
Light hitting the photoreceptors in the eye causing nerve impulses to travel down optic nerve to brain, recieved by thalamus which transmits to visual cortex
Research- Area V1. No vision but 'blindsight' can obtain spatial info. So concious & unconcious sight.
Motor Centres Continued
Temporal lobe in BOTH hemispheres as both need hearing
Function is to hear and process information (intensity, duration, tone)
Sound waves enter Cochlea, they're convertedto nerve impulses and travel via auditory nerve to brain stem which transfers to thalamus and finally auditory cortex.
Broca's Area- Frontal lobe in LEFT hemisphere. Responsible for speech production
Broca's Aphasia (problem with speech production.)- people can understand & read well but not speak fluently
Leborgne- Epilepsy as a child and lost ability to speak only 'Tan'. After he died post-mortem found lesion in Broca's area
Wernicke's Area- Temporal lobe in LEFT hemisphere. Responsible for understanding language
Wernicke's Aphasia- ability to speak fluently but not understand language
Localisation Brain Function Evaluation
+ Case study support. Phineas Gage. Area damaged responsible for reasoning and control
+ Case study support. Leborge. Epilepsy as a child, lost ability to speal. After death Broca did post mortem and found left hemisphere lesion.
- Case study challenge. E.B. Tumour removed in brain when young in left hemisphere. Lost language but by 17 normal functioning. Right hemisphere took role of left after intensive rehabilitation.
- Challenging research. Lashley. Sliced parts of rats brain after training them to run through maze, they were mostly able to remember route, suggesting brain function is spread out.
Hemispheric Lateralisation = the idea that each side of the brain has different functions. Left is responsible for right and vice versa.
Language centres (Broca's and Wernicke's areas)
Focuses on detail e.g in sight
Facial Recognition- Heller and Levy found 2 photos shown that were split in half (half happy, half neutral) ppts found left photo happier due to brain dominance in right hemisphere.
Spatial relationships- ppts asked to identify small details in pcicture greater activity LEFT. ppts looking at picture as a whole RIGHT hemisphere.
- Case study E.B suggests right capable of language processing as he recovered.
- Lateralisation may change throughout a lifetime. Szaflarski found children more left lateralised but with after 25 more bilateral (both hemispheres).
Two hemispheres connected by Corpus Collosum to allow communication
Patients with epliepsy may get corpus collosum severed to restrict it to one hemisphere. Prevents violent electrical activity.
SPERRY AND GAZZINGA
Patients fixate on dot in centre to create split visual field.
Stimulus (word, picture) presented to left and right visual field then asked to make responses either draw/ verbally say what they saw.
Found Patients could say words flashed to RIGHT (left= Broca's area)
Patients identify face made of fruit flashed to RIGHT (left= detail)
Patients could not say words flashed to LEFT (left= speech production) but could draw
Patients could recognise face in LEFT (right= facial recognition)
Suggesting hemispheres have functional specialisations
Split-Brain Research Evaluation
- Split brain research is methodologically flawed.e.g only 3 participants& Extraneous variables. e.g some had more drug therapy than others,
- Sperry and Gazzinga's research lacked mundane realism. Artificial as they made ppts focus on a dot, wouldn't happen in real life, so difficult to generalise.
+ Split brain research has helped understand the functions of each hemisphere
Brain plasticity= the brains ability to change and adaot to modify it's own function
It occurs at beginning of life (brain organising itself), after injury (compensation) and Adulthood (when something new is learnt)
Positive plasticity- growth of pathways e.g learning new skill
Negative plasticity- destruction of pathways e.g substance abuse
+ Plasticity from life experience. Maguire. Compared MRI scans of 16 male london taxi drivers vs 50 non. Found Hippocampus was larger in taxi drivers. Hippocampul volume correlated to time being taxi driver. Suggests plasticity of hippocampus.
Further research compared to bus drivers found larger hippocampus because bus drivers have fixed routes
+ Kuhn et al found video gaming results in new synaptic connection in brain areas such as planning, navigation and working memory
Functional Recovery After Brain Trauma
Recovery after brain trauma is due to anatomical compensation after intensive rehabilitation. Brain learn to compensate for function lost. Brain is very plastic.
Axon Sprouting- axons connected to damaged areasprout an extra axon which replace destroyed ones. Axon nearby has to do similar job for it to occur
Increased Brain Simulation- if undamaged hemsiphere is stimulated it can compensate by producing neural circuits
Denervation Supersensitivity- axons doing the same job become more aroused to compensate for lost function
Perserverence- if function appears to be lost people don't try to regain function
Animal studies show when monkey loses senses in limb it will not use it.
- animals are less complex than humans, can't generalise.
Physical Exhaustion- when a function is recovered it requires effort to regain
Stress and Alcohol- affect ability to regain
Age- Marquez de la Plata found brains more plastic when young. After brain trauma older patients (40+) regained less function & more likely to decline after 5 years
Gender- Ratcliffe found out of 325 patients, women performed better on attention and working memory, showing they recover better as more bilateral
Education- Schneider found of 769 patients 24% did not finish school and 1 year after 28% made full recovery. 10% did not finish school, suggesting longer education= better cognitive reserve
- hard to generalise as each case depends on location, extent of damage etc
+ research support - Marquez de la Plata, Ratcliffe, Schneider
Studying the Brain
EEG- a continuous (e.g during sleep) measure of electrical activity using electrodes on scalp. They only measure the area under the electrode. Produces no image. Can detect brain disorders e.g brain disease = slowed activity.
+ provides real-time recording so accuratelt measures
- only detects activity under electrode, poor spatial resolution
ERPs- same procedure as EEG but using stimulus e.g picture. No image
+ good for testing reliability of self report answers- lie detector
- lack accuracy, only measure under electrode
fMRI- measures brain activity while performing a task by looking at changed in blood flow. Active areas have more oxygenated blood. Moving picture 1 second after and 1-2mm accurate
+ non-invasive (not harmful), very accurate
- expensive and requires trained professional
Post-Mortem- a persons body & brain examined after death to see causes of death
+ no discomfort as patient is not alive
- patient has to be dead, retrospective
Biological rhythms- Circadian
Biological rhythms- cyclical changes in the body
Circadian rhythms- rhythms that last for 24 hours
circadian rhythms driven by body clocks (endogenous pacemakers)
Sleep-Wake Cycle- Under homeo-static control (tells us when need for sleep is increasing)
Free Running cycle= maintains 24-25 hour cycle even in absence of external cues
+ Research. Siffre spent 6 months in a cave with no daylight or time. Found his cycle became free running 24-30 hours. He lost track of time. Suggests natural light vital for 24 hour cycle.
- But unnatural conditions in a cave affected results e.g cold cave
- not isolated from artifical light
- Differences in cycle onsets. Duffy found morning people (6am-10pm) and evening people (10am-1am)
Temperature Cycle- highest at 6pm. lowest at 4:30am.
+ Practical applications. Chronotherapeutics- chemotherapy certain times of day. Makes it 5x fewer healthy cells damaged. Aspirin before bed.
Infradian and Ultradian Rhythms
Infradian rhythms- longer than 24 hours e.g Menstrual cycle, Seasonal Affective Disorder
- driven by endrocrine (hormone) system. Exogenous zeitgebers e.g light ad odour (pheremones) affect it.
+ McClinton and Stern. Found when sweat samples of women rubbed onto upper lips other another group of women, 68% responded to it. Those recieved at end of periods shortened. Those recieved at beginning of period lengthened.
Seasonal Affective Disorder (SAD)
- individuals experience extreme depression during winter months & recover in summer
- caused by more melotonin as it's darker,leading to depression
Ultraradian rhythms- less than 24 hours e.g Sleep cycle
Sleep Cycle: REM sleep= deeper sleep. Brain very active & dreaming
NREM= Non-rapid eye movement. 4 stages
+ Dement and Kleitman found ppts all experienced REM sleep, stages of sleep follow patterns and REM had high recall when awake
Endogenous Pacemakers & Zeitgebers
Endogenous pacemakers- internal body clocks that regulate rhythms
SCN is main. When photo receptors in eye pick up light send signals to SCN. This syncs rhythms to outside world e.g morning light waking up.
Also regulates melatonin in the pineal gland (another pacemaker)
In pineal gland, if light sensed melatonin is inhibited -Melatonin induces sleep
Exogenous Zeitgebers- environmental cues that regulate the body clock
Most important is light.
Also social cues e.g meal times, alarm clocks.
When moving through time zones zeitgebers allow body to adjust
+ Campbell and Murphy. Shone light on back of ppts knees when sleeping in a laboratory. Found circadian rhythms disrupted by 3 hours.
+ Burgess. Found esposure to bright light before west-east flight decreased re-adjustment time