biopsychology Flashcards
describe fight or flight
the endocrine system and ANS often work together like in stressful events.
a stressor is perceived so the hypothalamus triggers activity in sympathetic branch of the ANS.
ANS changes from normal resting state (parasympathetic) to physiologically aroused sympathetic state. adrenaline is released from the adrenal medulla into the bloddstream.
this triggers physiological changes like increased heart rate to create physiological arousal needs for fight or flight. its an automatic instant response. once the threat passes then parasympathetic returns body to resting state.
sympathetic - increases heart rate and breathing, dilates pupils, inhibits digestion and saliva production and contracts rectum
parasympathetic - decreases heart rate and breathing rate, constricts pupils, stimulates digestion and saliva production and relaxes rectum.
describe the endocrine system.
the endocrine system works alongside the nervous system to control vital functions. its slower than the nervous system.
glands in the body like the thyroid produce hormones that are secreted into the bloodstream and affect any cells in the body with a receptor for that hormone.
most hormones affect cells in several organs or through the whole body e.g. the thyroid gland produces thyroxine that increases heart rate, metabolic rate and affects growth rates.
the major endocrine gland is pituitary gland, often called the ‘master’ gland as its controls the release of hormones from all endocrine glands in the body.
theres the pituitary, thyroid, parathyroid, adrenals, pancreas, ovaries and testes.
describe the nervous system.
the nervous system has two main functions - to collect, process and repsond to info in the environment and to coordinate the working of different organs and cells in the body.
thers 2 subsystems - central nervous system (CNS) and peripheral nervous sytem (PNS).
the CNS is the brain and spinal cord. the brain is the centre of all conscious awareness. the outer layer (cerebral cortex) is highly developed in humans and distinguisges us from animals. the brain has 2 hempishered and the spinal cord is responsible for reflex actions and passes info to and from the brain and connects nerves to the PNS.
the PNS transmits mesages via neurons to and from the CNS. its sub-divided into the autonomic nervous system (ANS) and the somatic nervous system (SNS). the ANS governs vital functions like breathing (involuntary) and SNS controls muscle movement and receives info from sensory receptors (voluntary).
how does synaptic transmission work
signals transmitted electrically down a neuron but chemically between them - neurotransmitters pass from the presynaptic from synaptic vesicles, across the synapse. it gets received by receptors on the postsynaptic neuron. chemical turns back to electric and transmission repeats.
each neurotransmitter ha sits own special function and has its own specific molecular structure that fits perfectly into post-synaptic receptor site, like a lock and key.
what is inhibitory, excitation and summation?
excitation is when a neurotransmitter increases the positive charge of a presynaptic neuron. it increases the likelihood of a neuron firing and passing on an electrical impulse.
inhibitory is when a neurotransmitter increases the negative charge of the postsynaptic neuron which decreases the likelihood a neuron fires and passes on electrical impulses.
neurotransmitters are either excitatory or inhibitory. e.g. serotonin is a neurotransmitter which causes inhibition and adrenaline (neurotransmitter and hormone) causes excitation.
summation is the process of whether a postsynaptic neuron will fire or not.
excitatory and inhibitory influences get summed - if the net effect on postsynaptic is inhibitory then its less likely to fire. if the net effect is excitatory then its more likely to fire - the inside of a postsynaptic neuron gets positively charged and the electrical impulse travels down a neuron.
therefore the action potential of postsynaptic is only triggered if sum of excitatory and inhibitory signals at any time reaches the threshold.
what is a neurotransmitter?
neurotransmitters are chemicals that diffuse across synapses to the next neuron in the chain.
the neurotransmitter crosses the synapse and is taken up by postsynaptic neuron. chemical message get converted back to an electrical impulse and process of transmission repeats in this neuron.
explain how sensory relay and motor neurons function.
the function of sensory neurons is to send info from the senses to the brain, e.g. if someones digging and hits a rock. the sensory neurons in their hand and arm feel this and send the info to the brain.
relay neurons decide what to do in this situation.
motor neurons control movement by passing info from the brain to the muscles. the brain would pass on the info to stop diggning to the persons arm.
explain all the parts of a neuron.
there is the cell body/ soma.
the nucleus contains genetic material of the cell.
dendrites carry nerve impulses from neighbouring neurons to the cell body.
node of ranvier enhances the electrical signals that travel down the axon.
axon carries impulses from cell body down the length of the neuron.
myelin sheath is fatty layer that protects the axon and speeds up electrical transmissions of impulse.
axon terminals communicate with the next neuron in the chin across the gap - synapse.
describe plasticity
plasticity is the brains tendency to change/ adapt as a result of experience and new leanring. in infancy the brain has rapid growth of synaptic connections - peaking at 15000 at 2-3 years old, double the amount thats in an adult brain. as we age connections that are rarely used get deleted, but some are also strengthened - synaptic pruning.
new research shows any time in life neural connections can change/ form due to learning/ experience.
describe plasticity - research from maguire, draganski and mechelli
maguire 2000 studied london taxi drivers brains and found more grey matter in the posterior hippocampus than in control gorup. this is the part of the brain linked to spatial and navigational skills. when they were training they took a test called ‘the knowledge’ that tests recall of streets and routes. the longer they were in the job, the more structural differences they had (positive correlation).
draganski 2006 imaged brains of medical students 3 months before and after their final exams. learning induced changes in posterior hippocamous and parietal cortex.
mechelli 2004 found larger parietal cortex in bilinguals than in matched monolinguals.
describe brain recovery after trauma
theres functional recovery which is a form of plasticity. after physical injury/ trauma, unaffected areas of the brain adapt and compensate for the damaged areas. this process can occur quickly after trauma (spontaneous recovery) then slow down after several weeks or months.
after this the patient may need rehabilitative therapy. the brain is able to rewire/ reorganise by forming new synaptic connections near that area of damage.
secondary neural pathways are activated so function continues (Doidge 2007). this process is supported by 3 things:
axonal sprouting - growth of new nerve endings that connect with undamaged nerve cells to form new paths.
reformation of blood vessels.
recruitment of homologous areas - on opposite sides of the brain to perform specific tasks e.g. if brocas got damaged on the left, the right side equivalent carries out function and then it can shift back to left.
what are 3 strengths of plasticity and brain recovery?
one strength is understanding processes in plasticity has contributed to the field of neurohabilitation. after brain injury, spontaneous recovery slows down after a few weeks so physical therapy is needed to maintain improvements (e.g. therapy/electrical stimulation of brain to counter cognitive or motor deficits). shows brain can ‘fix’ itself to a point but needs further intervention to be successful.
another strength is negative plasticity. brains ability to rewire itself can have maladaptive behavioural consequence. prolonged drug use can lead to poorer cognitive functioning and increased risk of dementia later in life (Medina). 60-80% amputees report phantom limb syndrome - continued experience of sensations in missing limb. sensations normally unpleasant, painful and its thought to be due to cortical reorganisation in the somatasensory cortex that occurs from limb loss (ramachandran and hirstein).
last strength is age and plasticity. functional plasticity reduces with age. brain more likely to reorganise in childhood as we are constantly adapting to new experiences or learning. but bezzola 2012 showed 40 hours of golf training produced changes in neural representation of movement in pts 40-60 years. used fMRI and observed reduced motor cortex activity in novice group compared to control. suggests more efficient neural representations after training. shows neural plasticity does continue through lifespan.
describe fMRI
fMRI is functional magnetic resonance imaging. it detects changes in blood oxygenation that occurs due to neural activity in specific areas.
active areas consume more oxygen so to meet this increased demand, blood flow is directed to the active areas - haemodynamic response.
3-d images show which brain areas are active in particular mental processes.
what is a strength of fMRI
a strength is it doesnt rely on using radiation like PET scans. its risk free, non invasive and easy to use. the images have a high resolution to millimetres so gives a clear picture of localisation.
what is a weakness of fMRI
a weakness is its expensive compared to other techniques and only gives a clear image if the person is still. it has poor temporal resolution with a 5 second lag between the image and the actual brain firing. it only measures blood flow so cant see individual neuron activity which means its difficult to see what kind of brain activity is represented.
describe EEG
EEG is electroencephalogram and it measures electrical activity in the brain using electrodes fixed to the individuals scalp with a skull cap.
the scan represents brainwave patterns from the actions of millions of neurons so gives an overral account of brain activity.
we can use it as a diagnostic tool for unusual arrhythmic patterns as they can indicate neurological abnormalities like epilepsy, tumours or sleep disorders.
what is a strength of EEG
a strength is its invaluable in diagnosing conditions like epilepsy. its also contributed to understanding of sleep stages. it also has a high temporal resolution with one millisecond or less.
what is a weakness of EEG
a weakness is the generalised nature of the info received. cant pinpoint the exact source of neural activity and cant distinguish between activities originating in different but adjacent loactions.
