When a neuron gets excited from a neighboring cell (from neurotransmitters) it gets 'leaky' to certain ions like sodium, potassium, calcium and chloride - and in doing so its state of electrical excitability changes. If it changes by just the right amount then special proteins called 'voltage-gated ion channels' will open allowing a huge influx of even more ions (usually sodium) causing a wave of electrical charge to flow away from the cell body down its axon to its axon terminal - where it will then release its neurotransmitters.
A neuron generates generates a nerve impulse at a region just off the cell body called the axon hillock. That nerve impulse travels away from the cell body down the length of the axon by jumping from node to node in a process called saltatory conduction.
The axons
axon
The dendrites portion of a neuron will generate a potential.
Axon hillock
Well, for starters, membrane potential is a separation of charges across the membrane. So i think what you mean is "generating the action potential in a neuron". So in that case The substance that plays a major role in generating an action potential is Sodium (Na+). However, if you really mean membrane potential, there is only two substances associated with that and those are sodium (Na+) and potassium (K+).However, in truth, the generation of an action potential depends on the ligand and its receptor.
Axon
A neuron will generate action potential when it is stimulated by a neurotransmitter.
sodium
The resting and action potentials depend on the balance of charges of the area outside the neuron and inside the neuron. A resting potential is when the neuron is more negatively (approximately -70mv) charged than the area outside the neuron. The action potential occurs when sodium ions rush into the neuron, causing the polarity to be reversed. When there is no difference in charge between the area inside the neuron and the area outside the neuron, no action potentials can be started by that neuron.
the dendrites are
it is often termed the action neuron because it tells the muscles what to do or how to react.
Sensory neuron
An action potential in the neuron