What initially causes a nerve impulse?

release of enzymes out of the neuron

movement of chemicals into the dendrites of the neuron

pathogens attacking the dendrites of the neuron

red blood cells bathing the neuron

Pathogens attacking the dendrites of the neuron

Explanation:

Dendrites are the neuron that neuroplasmic extension of the neuron that preceded the cell body. They are several dendrites in most neuron cells while there is one axon. Dendrites have receptors on their ends. When the membrane of the receptors is disturbed (such as by pathogens in this case), an electric impulse is induced due to depolarization of the membrane.