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neuronal communication - the nervous system 5.1.3, types of neurone, the…
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the action potential
2) In order to send a message from A to B we need to open a few sodium channels at position A (disturb the membrane). In other words we need to stimulate the axion at location A
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Sodium ions diffuses in, bringing positive charge with it & the membrane potential increases to +40mV on the inside.
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the refractory period
After an action potential has been generated the membrane needs time to recover (return to resting potential). Until this happens another action potential cannot be sensed.
In fast flying insects their visual neurons recover faster (shorter refractory period), otherwise they would see a moving landscape as a blur.
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3) When +40 mV is reached the sodium channels close (voltage sensitive) & the potassium channels open. K^+ now potassium ions flows out bringing the potential back towards -70mV, this is called repolarisation.
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Hyperpolarisation = cause of the delay in closing the potassium channel a few extra ions diffuse out the membrane than they should, causing a hyper polarisation
