A state where there is no net flow of ions across the membrane.

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Change in the membrane potential of a neuron's plasma membrane.

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Change in membrane potential to a      Change in membrane potential

less negative value inside.                          to a more negative value.

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1.  When the action potential reaches the axon terminus it causes vesicles containing neurotransmitter to fuse with the presynaptic membrane 

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2.  The neurotransmitter diffuses across the synaptic cleft (synapse).

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3.  The neurotransmitter binds to its post synaptic receptor which is a

    ligand gated Na ion channel

 

4.  This causes a conformation change in channel allowing diffusion of Na

    ions into neuron resulting in initial local depolarisation (-70mv to -55mv).

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5.  Sufficient Na movement into neuron depolarises membrane beyond            threshold levels, triggering the opening of voltage gated Na channels

 

6.   This causes a further large rapid depolarisation as more Na diffuses into

    neuron.  (-55mv to +30mv)

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7.   Na channels inactivate then voltage gated K channels open

 

8.   This causing K ions to diffuse out of neuron resulting in repolarisation of membrane (+30mv to -85mv)

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9.   Voltage gated K channels inactivate.

 

10.  Hyperpolarisation results (greater than -70mv) due to too many K ions leaving neuron reducing concentration gradients.

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11. The Na/K pump  restoring the resting membrane potential by re-establishing the correct concentration gradients of Na & K (3 Na out & 2 K in).

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