A nerve impulse is an electro-chemical signal. Inside the nerve cell or neuron, the impulse is electrical. The neuron has a cell body with dendrites, an axon and an axon terminal at the end of the neuron. When an electrical impulse reaches the end of the neuron, there is a space between the first and the next neuron in a nerve pathway. In order for the impulse to continue on its path, neurotransmitters are released which act like chemical messengers. Once the neurotransmitter is released into the synapse or gap, it will then reach the next neuron and act as a signal which will allow the impulse to continue to be transmitted along the nerve pathway. Exocytosis is needed so that intracellular vesicles in the cytoplasm can fuse to the plasma membrane and release the contents of the vesicle into the extracellular space. The contents of the vesicle are the important neurotransmitters. Neurons can quickly take up extra neurotransmitter molecules as well as parts of the vesicle in order to form new vesicles to send another impulse to other neurons. Exocytosis is a way for cells to secrete useful substances outside of the cell to where they are needed.