An impulse moves from one neuron to another across a small space called

 An impulse moves from one neuron to another across a small space called synapse.

A nerve impulse is transmitted via electrical stimulus (within the cell) and chemical signal (between cells). Two neurons (or neuron with effector cell) communicate one to another by a structure called synapse. Synapse is actually a little space between the end of the axon and dendrite of another cell (but without material continuity between both cells). The axon releases chemical molecules called neurotransmitters, which then attach to receptors in the membrane of the following cell.

The answer for the above question is a synapse. it is a small space in which an impulse travels to move from one neuron to another. An impulse travels from one neuron to another by release and diffusion of chemicals referred to as the neurotransmitters across the synapse (a small gap between neurons). When an impulse reaches an end of a neuron, the impulse opens ion pores in the axon terminal which allows calcium ions to enter and trigger the release of neurotransmitter by the vesicles. 

The type of rock she find is a sediment rock