· Low level signals can be amplified by a process called summation. If a low level stimulus is persistent it will generate several successive action potentials in the presynaptic neurone. The release of many vesicles of acetylcholine over a short period of time will enable the postsynaptic generator potentials to combine together to produce an action potential. Summation can also occur when several presynaptic neurones each release small numbers of vesicles into one synapse.
· Acclimatisation- after repeated stimulation a synapse may run out of vesicles containing the transmitter substance. The synapse is said to be fatigued. This means the nervous system no longer responds to the stimulus. It explains why we soon get used to smell or background noise. It may also help to avoid overstimulation of an effector, which could damage it.
· The creation of specific pathways within the nervous system is thought to be the basis of conscious thought and memory
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