Three sodium ions pumped out of neurones for two potassium ions in. This turn the cell more negative than the outside.

Some potassium channels remain open in rest potential, so potassium can diffuse out and increase the negative potential.

When cell menbrame is polarise (-70mv).

The stimulus trigger a sensory neurone action potential. Happens only after potential threshold is reached.

It is a refractory period, where no more action potential can happen till resting potential is a achieved

Is a nerve impluse: sodium ions enter a neurone and deploralise it and diffuse allong the neurone. The diffusion of ions opens more channel- voltage sodium to open

The greater axon diameter high temperatures The presence of myelin.

0- Resting potential(-65mv), is affected by the sodium influx ,caused by a stimulus , make the neurone negative potential to decrease. 1- The potential threshold is reach and sodium channels voltage open and sodium ions diffuse at faster rate.(Deplorisation) 2- The sodium channels voltage make the neurone reach maximum positive potential (40mv). 3- At peak sodium gates close and potassium channels open. 4- The outflux of potassium ions decreases the positive potentai, repolarises the menbrame. 5 - hyper-polarisation happens and potassium channels close . 6'- The potassium-sodim channels brings neurone back to resting potential.

A eltrical potential will only happen if a stimuli is great enough to overcome the potential threshold.

When amout of neurotransmitter biuld enough sufficiently to surpass the threshold and cause a action potential.

Spatial summation when lots of presynaptic neurones are connect to a postsynaptic membrame.Each release neurotransmitter that build till it can trigger a action potential.