neural mechanisms of habituation and sensitisation

homosynaptic plasticity

habituation only has an effect at one synapse

motor fatigue hypothesis

theory that decreased response after repeated stimulation was due to muscle fatigue. disproved after administering inhibitor to crabs

sensory adaptation hypothesis

theory that decreased response after repeated stimulation was due to lack of perception by sensory receptors. disproved by finding that photoreceptors and laminar monopolar cells did not stop reacting, but the central nervous system did

biological basis of habituation

synaptic depression takes place, so exitatory drive is lowered and fewer vesicles are released, leading to less neurotransmitter in the synaptic cleft

chemical basis of sensitisation

serotonin released by the interneuron increases presynaptic adenylyl cyclase. this upregulates cyclic AMP, which activates protein kinase A

effects of protein kinase A in sensitisation

inactivation of potassium channels, prolonging action potential. upregulation of calcium channels, causing an influx of calcium, which causes an increase in the vesicle pool and enhances release of neurotransmitter. targets structural CREB, encouraging protein synthesis for new synaptic contacts in the long term